Next Article in Journal
Strong Radiative Cooling Coating Containing In Situ Grown TiO2/CNT Hybrids and Polyacrylic Acid Matrix
Previous Article in Journal
The Effect of Crevice Structure on Corrosion Behavior of P110 Carbon Steel in a Carbonated Simulated Concrete Environment
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Coatings
Volume 15
Issue 8
10.3390/coatings15080920
coatings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Grain Boundary Regulation in Aggregated States of MnOx Nanofibres and the Photoelectric Properties of Their Nanocomposites Across a Broadband Light Spectrum

by
Xingfa Ma
1,*,
Xintao Zhang
1,
Mingjun Gao
1,
Ruifen Hu
2,
You Wang
2 and
Guang Li
2
1
School of Environmental and Material Engineering, Centre of Advanced Functional Materials, Yantai University, Yantai 264005, China
2
National Laboratory of Industrial Control Technology, Institute of Cyber-Systems and Control, Zhejiang University, Hangzhou 310027, China
*
Author to whom correspondence should be addressed.
Coatings 2025, 15(8), 920; https://doi.org/10.3390/coatings15080920
Submission received: 13 July 2025 / Revised: 3 August 2025 / Accepted: 4 August 2025 / Published: 6 August 2025
(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)
Browse Figures
Review Reports Versions Notes

Abstract

Improving charge transport in the aggregated state of nanocomposites is challenging due to the large number of defects present at grain boundaries. To enhance the charge transfer and photogenerated carrier extraction of MnOx nanofibers, a MnOx/GO (graphene oxide) nanocomposite was prepared. The effects of GO content and bias on the optoelectronic properties were studied. Representative light sources at 405, 650, 780, 808, 980, and 1064 nm were used to examine the photoelectric signals. The results indicate that the MnOx/GO nanocomposites have photocurrent switching behaviours from the visible region to the NIR (near-infrared) when the amount of GO added is optimised. It was also found that even with zero bias and storage of the nanocomposite sample at room temperature for over 8 years, a good photoelectric signal could still be extracted. This demonstrates that the MnOx/GO nanocomposites present a strong built-in electric field that drives the directional motion of photogenerated carriers, avoids the photogenerated carrier recombination, and reflect a good photophysical stability. The strength of the built-in electric field is strongly affected by the component ratios of the resulting nanocomposite. The formation of the built-in electric field results from interfacial charge transfer in the nanocomposite. Modulating the charge behaviour of nanocomposites can significantly improve the physicochemical properties of materials when excited by light with different wavelengths and can be used in multidisciplinary applications. Since the recombination of photogenerated electron–hole pairs is the key bottleneck in multidisciplinary fields, this study provides a simple, low-cost method of tailoring defects at grain boundaries in the aggregated state of nanocomposites. These results can be used as a reference for multidisciplinary fields with low energy consumption.

1. Introduction

Due to the significant development of various battery and energy storage technologies, manganese dioxide (MnO2) and its nanocomposites have received considerable attention, particularly in the field of supercapacitors [1,2,3,4,5,6,7,8,9,10,11,12,13] and various battery applications [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41]. Other applications include membrane fuel cells [42], oxygen evolution [43], seawater electrolysis [44], electrochromic devices [45], the treatment of organic pollutants using photocatalysis [46], CO2 capture [47], CO2 photoreduction [48], chemical and biosensors [49,50,51,52], oil–water separation [53], catalysis [54,55], U(VI) electrosorption [56], the removal of toxic industrial dyes [57], and more.
Analysing the above-mentioned literature, it was found that most of the literature focuses on the area of multiple batteries and energy storage devices. These studies cover almost the entire field of batteries, including Zn-ion batteries, lithium-ion batteries, lithium–sulphur batteries, sodium-ion batteries, and supercapacitors. Despite the fast and reversible oxidation-reduction process of MnO2, its low cost, versatility, and environmental friendliness, poor electrical conductivity greatly limits its energy storage performance. Therefore, enhancing the electrical conductivity of MnO2 materials is a key improving the overall performance of nanocomposites [1,2,3,4,5,6,7,10,14,24,27,29,30,34,35,39,42,50,56,57]. Other measures such as Ni doping [3,6], iron doping [20,34], transition metal doping [44], a designed hierarchical structure [5], interface coupling [7,25], intercalation [17,19], nanocomposites [18,40,53,57], and oxygen vacancy tailoring [21,43,51], are also widely utilised to enhance the physical and chemical properties of MnO2-based composites.
A clear understanding of the mechanism of action is important for enhancing the comprehensive performance of MnO2-based nanomaterials. Due to the diversity of nanocomposite interfaces, defects and other factors, studying and gaining a deep insight into the physical mechanism is still an important area of current research. Jhanka and co-workers [1] investigated the charge storage kinetics of the MnO2/reduced graphene oxide nanocomposite. Ze and colleagues [9] deciphered the charge storage of metal cations and protons. Xu and colleagues [33] studied the sodium storage mechanism. Xue and co-workers [37] introduced Mn2+/MnO2 conversion through redox mediation. Wu and colleagues [41] elucidated the charge storage mechanism. Dhanusha and colleagues [58] enhanced the near-resonant two-photon absorption of α-MnO2 nanowires, and so on.
One of the most commonly used routes for composite design is enhancing the comprehensive performance of MnO2 through interfacial interactions in nanocomposites. Among the many potential components, graphene is an attractive choice due to its high electrical conductivity and carrier mobility. Compared with MnO2 materials, graphene and its modification product have a more wider range of applications in energy conversion and storage [59,60], supercapacitors [61,62,63,64,65], alkaline hydrogen evolution [66], energy and photonics applications [67], sensing [68], the electrochemical hydrogen uptake and release [69], photocatalytic activity and photothermal effect [70,71], and so on. Therefore, MnO2 materials that incorporate graphene and its derivatives are expected to exhibit synergistic or complementary behaviour. MnO2 and GO exhibit strong interfacial interactions due to the presence of the abundance of chemically reactive groups on their surfaces.
In the materials fields, interfaces play a non-negligible influence on the properties of nanocomposites. Good interface contacts not only have a significant impact on the performance of devices (often, it may be said that the interface is the device, as note in the Nobel Lecture in Physics) [72], but are also important for the performance of nanocomposites and multidisciplinary applications. There are various types of interface, including interfaces between components and phases, dimensional interfaces and grain boundaries. Grain boundaries are more complex. On the one hand, they are irregularly shaped and not flat in most cases, which leads to poor interface contact and uneven gaps in the nanocomposite. On the other hand, they contain a large number of defects and impurity aggregation sites. This is unfavourable for charge transport. From a broad perspective, the strength of interfacial interactions determines not only the design of structural composites, but also the design of functional composites.
Heterojunctions occupy an important place in the field of composites. Heterostructures are widely used in photodetectors, solar cells, photothermal, photocatalytic processes, nanocomposites, and so on. The applications of heterostructures in optoelectronic devices mainly refer to solar cells and photodetectors. In photodetector applications, high-quality films and good interfacial contacts are extremely important, as are advanced processing techniques and equipment. Compared to the photocatalysis field, only a limited number of material systems can fulfil these requirements. Promising material systems in the fields of photodetectors include metal dichalcogenides [73,74,75,76], graphene heterostructures [77,78], phosphorus heterostructures [79,80,81], perovskites [82], 2D semimetals [83], AlGaN heterojunctions [84], GaN [85,86], hexagonal boron nitride heterostructures [87], and so on [88]. To construct a high-quality heterostructure and its associated device, epitaxial film growth generally requires expensive instrumentation and strict processing techniques. Integrating electron and hole transport layers improves the separation and transfer of photogenerated electrons and holes, avoiding their recombination. Reducing the dark current is an important way to improve light detection sensitivity. Preparing high-performance photodetectors requires integrating advanced materials with excellent properties and superior processing techniques. As it is difficult for us to follow these research directions, we can only conduct some complementary research from multidisciplinary fields, combining this with our own professional foundation and other material systems. As optoelectronic materials are a very broad field, complementary content from multidisciplinary fields also has good scientific reference value.
Otherwise, current techniques can characterise the physical properties of individual nanostructures (such as nanofibre, nanorod, nanobelt, nanotube, etc.), but these techniques are often time-consuming and costly. Nanocomposite applications are typically found in an aggregated state, so studying the physical properties of nanocomposites in this state is particularly important. The most notable feature of the aggregated state of nanocomposites is the large number of grain boundaries present. These defects can significantly impact the photophysical properties. This study is based on defect passivation in nanocomposites and the modulation of grain boundaries in the aggregated state of oxide nanowires [89], with the aim of improving their photophysical properties. Over 10 years of research investigations has shown that obtaining the photoelectric signal of MnO2 nanowires is very difficult. In our previous publications [90,91], the adsorption of heavy metal ions onto one-dimensional manganese dioxide with different morphologies was compared [90]. Based on the QCM (quartz crystal microbalance) device’s high sensitivity to adsorption properties, the selectivity of low-dimensional MnO2 to dimethyl methylphosphonate was tailored using a nanocomposite [91]. In this study, we would report on the photoelectric properties of MnO2 nanofiber aggregation in broadband spectrum range, achieved by regulating grain boundaries through the interfacial interaction of the nanocomposite. To the best of our knowledge, this has rarely been reported. We hope that this study will serve as a reference for multidisciplinary fields and the interaction between light and matter.

2. Materials and Methods

2.1. Materials

Potassium permanganate (AR), Yantai Sanhe Chemical Reagent Co., Ltd. (Yantai, China). Manganese sulphate (AR), Tianjin Komeo Chemical Reagent Development Centre (Tianjin, China). Imported graphite, 325 mesh (purity 99.8%). Concentrated sulfuric acid (AR) and concentrated nitric acid (AR) are commercially available.

2.2. Preparation of Graphene Oxide

Graphene oxide (GO) synthesised is shown in our previous reference [92]. The concentration of GO is about 6.5 mg/mL in this study.

2.3. Preparation of the MnO2 Nanofiber and Its Nanocomposites

The preparation of the MnO2 nanofiber can be seen in our previous study [91]. Manganese sulphate was oxidised with potassium permanganate using a hydrothermal method. The synthesis conditions were 160 °C for 8–12 h. The MnO2 nanowires were obtained after washing with water and drying at room temperature.
Several 300 mL glass containers were each filled with 0.5 g of MnO2 nanowires and 50 mL of water. Then, 5, 10, 30, 50, and 60 mL of GO solution (with a concentration of approximately 6.5 mg/mL) were added to the respective containers and sonicated for 10–15 min. The obtained nanocomposites were labelled MnO2/GO (5), MnO2/GO (10), MnO2/GO (30), MnO2/GO (50), and MnO2/GO (60) respectively.

2.4. Characterisation of SEM, XPS, UV-Vis-NIR, XRD and Raman

The characterisation of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis-NIR (UV-VIS-NIR spectrophotometer), XRD (X-ray powder diffraction), and Raman were shown in our previous reference [89]. The instrument used was a JSM-6700F (Japan Electronics Co., Ltd., Tokyo, Japan). UV-Vis-NIR was carried out with a TU-1810 spectrophotometer (Beijing Puxi General Instrument Co., Ltd., Beijing, China). XPS was performed with ESCALAB 250 produced by ThermoFisher SCIENTIFIC (East Grinstead, West Sussex, UK). The Raman spectra were determined using a PHS-3C confocal Raman spectrometer (HORIBA, Kyoto, Japan). The XRD experiment was taken with XRD-7000 from SHIMADZU (Shimadzu, Kyoto, Japan), respectively. In order to eliminate the interference of nuclear electric effect, the resulting nanocomposites were coated on the aluminium foil during SEM sampling.

2.5. Optoelectronic Signal Measurement of the MnO2/GO Nanocomposite Aggregation States to the Light Sources with Different Wavelengths

The MnO2/GO nanocomposite suspension was coated onto the Au gap electrodes on a flexible PET (polyethylene terephthalate) film. The structure of the electrodes is shown in Scheme 1. The measurement of photoconductive signals to the visible light (25 W) or 405 nm, 650 nm (5, 10, 50 and 100 mW), and 780, 808, 980, and 1064 nm NIR (10, 50, 100 and 200 mW) was similar to our previous references [89]. Biases of 0, 1 V, 4 V, 5 V, 6 V, −1, −4, −5. −6 V DC were applied.

3. Results and Discussion

We have attempted to construct a MnO2 nanofiber chemical sensor due to the simplicity of its preparation, the abundance of resources, its low cost, its environmental friendliness, and its good redox characteristics. However, acquiring electrical response signals based on gap electrodes is very difficult. After several years of failed attempts, a QCM chemical sensor was constructed based on the adsorption response signals [91]. Since MnO2 nanofibers have excellent adsorption properties for VOCs (organic volatiles), the selectivity was adjusted by modifying the MnO2 nanofibers with ZnO. Meanwhile, the absorption in the visible region and near-infrared region was considered; it is expected to be well utilised in a wide spectral range. However, characterising its optoelectronic signal remains very challenging after several years of attempts. The main reason for this is the large number of grain boundary defects, which affect charge transport. Therefore, passivating the grain boundary defects in the MnO2 nanofibers is expected to produce a good photophysical signal.
There are many ways to passivate the defects in materials, and passivating the defects of MnO2 nanofibers using graphene oxide should be simple and cost-effective. Graphene oxide is well known for have many defects, such as -COOH, -OH, and epoxide groups, which can easily capture photogenerated carriers. Combining MnO2 and GO components is expected to achieve mutual defect passivation to enable photogenerated charge extraction.
Based on the optoelectronic signals, the SEM image of the representative MnO2/GO nanocomposite is shown in Figure 1.
Figure 1 shows a clear MnO2 nanofiber embedded in a GO film. The nanofibres are very long, several μm in length. These nanofibers are corrected by the GO film, which improves the charge transfer between the MnO2 nanowires. The GO film is also clear, and tightly bonds to the nanowire of MnO2. GO films have good electrical conductivity. This morphology therefore helps to improve the photogenerated charge transport at the grain boundaries of the MnO2 nanowires.
The XRD results of the representative MnO2/GO nanocomposite are shown in Figure 2. The UV-Vis-NIR of the representative MnO2/GO nanocomposite are shown in Figure 3.
As shown in Figure 2, the diffraction peaks at 12.30°, 18.00°, 25.10°, 28.70°, 36.5°, 37.40°, 41.83°, 47.17°, 49.84°, 52.50°, 56.05°, 60.14°, and 69.38° correspond to the peaks of (110), (200), (220), (310), (400), (211), (301), (510), (411), (440), (600), (521), and (541) planes of the MnO2 (PDF# 44-0141), respectively. Otherwise, the strength of the diffraction peaks at 12.30°, 18.00°, and 28.70° is much higher than that of other diffraction peaks. This indicates that some crystal faces grow preferentially during the growth of nanowires. Therefore, the MnO2/GO nanocomposite contains MnO2 component.
As can be seen in Figure 3, the absorption band edge of the representative MnO2/GO nanocomposite is found to be over 1100 nm. This indicates that the resulting nanocomposites absorb light in the visible and near-infrared regions. Here, the absorption band edge is for reference purposes only. Subsequent acquisition of photoelectric signals will provide further support for this absorption result in the visible and near-infrared regions.
Defects and interfaces in materials play an important role in acquiring optoelectronic signals. Compared with graphene, graphene oxide has a large number of chemical groups containing the element oxygen. The introduction of these groups has several advantages: (1) the introduction of a bandgap; (2) the ability to form films easily; and (3) the increase in the interfacial interaction between MnO2 and GO. However, the biggest shortcoming is the ease with which photogenerated carriers are captured and the difficulty of detecting photoelectric signals. For this reason, Raman characterisation was selected for the study of defects in representative samples. The results are shown in Figure 4.
As can be seen in Figure 4, the D band (1326.74 cm−1) and G (1582.84 cm−1) band of graphene oxide are clearly visible. The D and G peaks have comparable intensity, which indicates that the graphene oxide in the nanocomposite contains a large number of defects. Otherwise, the D band is very broad. This indicates the presence of multiple types of defects. Typical defects in graphene oxide include the -COOH, -OH, and epoxide groups. These groups tend to localise charge and hinder charge delocalisation and transport.
Since the resulting nanocomposite absorbs light in the visible region and the near-infrared range, the optoelectronic signal of the MnO2/GO nanocomposite in aggregation states in response to the visible light and the 808 nm NIR light have been examined. When the GO addition is low, e.g., 5 mL, it is difficult to obtain a photoelectric signal. Similarly, the photoelectric signal is also difficult to detect when the GO addition is high. Only when GO is added in the right amount, a clear photoelectric signal can be detected. Representative results for the MnO2/GO (10) nanocomposite are shown in Figure 5. This indicates that the MnO2 and GO component can passivate each other’s defects and promote the extraction of photogenerated charges by adjusting the nanocomposite’s component ratios.
As shown in Figure 5, the aggregation states of the resulting MnO2/GO nanocomposite showed good photocurrent response signals to the representative light sources, such as the visible light and the 808 nm light source.
The dependence of optoelectronic signals on the power of the representative light source (808 nm light source) was also studied. The results are shown in Figure 6.
Figure 6 shows that the optoelectronic signals of the resulting nanocomposite depend heavily on the power of the 808 nm light source. As the incident light power decreases, the photoelectric signal decreases significantly. However, it still exhibits a good optoelectronic signal with a 5 mW 808 nm light source excitation.
After storing the resulting nanocomposites at room temperature for over eight years, the nanocomposite sample was coated on the Au gap electrodes again and its photocurrent response to several light sources was examined. The results are shown in Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14, Figure 15, Figure 16 and Figure 17.
Figure 7 and Figure 8 show the effect of different biases on the photocurrent signals of the MnO2/GO (10) nanocomposite aggregation states. Even when no bias is applied, a good photoelectric signal can still be obtained. As the current is generated as a result of the directional motion of carriers in the presence of an external bias or built-in electric field, this indicates the presence of a built-in electric field in the nanocomposite driving the transport of photogenerated charges. When a positive bias is applied, the current polarity reverses as the bias increases. Similarly, when a negative bias is applied, the current polarity also reverses. As the external bias is in the opposite direction to the built-in electric field, as shown in Figure 7 and Figure 8, it is estimated that the built-in electric field lies within the 5–6 V range. This field is the result of charge transfer at the interface between the MnO2 and GO component.
Increasing the amount of GO added, when a positive bias is applied, the current polarity similarly reverses as the bias increases. The same occurs when a negative bias is applied. It is estimated that the built-in electric field lies within the 4–5 V range for the MnO2/GO (30) nanocomposite aggregation states. These are shown in Figure 9 and Figure 10. As can be seen, adjusting the component ratio affects charge transfer between the interfaces, thereby changing the strength of the built-in electric field.
Figure 11, Figure 12 and Figure 13 demonstrate that appropriately increasing the amount of GO added substantially improves the photocurrent performance against representative light sources. Regarding excitation by light sources at 50 mW 405, 650, 780, 808, and 980 nm, the order of their photoelectric responsiveness is as follows: 808 nm > 780 nm > 980 nm, 650 nm > 780 nm > 405 nm. For an 808 nm light source radiation, a clear two-stage response with a different ratio is observed. The first stage responds quickly, while the second stage responds slowly. The fast response corresponds to the photoelectric effect of the nanocomposite, while the slow response corresponds to the photothermoelectric effect of the nanocomposite. This indicates that the material has more defects and that the photothermoelectric effect is unavoidable.
To enable a clear comparison of the results shown in Figure 11, Figure 12 and Figure 13, the key data from these figures has been summarised in Table 1.
As shown in Table 1, appropriately increasing the amount of graphene oxide in the nanocomposite significantly improves its response speed, recovery speed, and the ratio of on/off.
The dependence of optoelectronic signals on the power of the 808 and 980 nm light sources is shown in Figure 14, Figure 15, Figure 16 and Figure 17.
As Figure 14, Figure 15, Figure 16 and Figure 17 show, there is a positive correlation between the photoelectric signal and the incident light power. The resulting nanocomposites still have good photoelectric signals for 5 mW 808 nm and 980 nm light sources, and their photoelectric sensitivity increases significantly with an appropriate increase in GO addition. Therefore, optimising the amount of GO added would improve the extraction of photogenerated charges. This is closely related to the material’s defects and defect passivation. It also highlights the importance of interfacial interactions and defect passivation in nanocomposite design.
To further explore the physical mechanism of the nanocomposite, the XPS of a typical nanocomposite sample was carried out. The results are shown in Figure 18.
As shown in Figure 18, in the XPS curve of Mn 2p, 642.2 eV corresponds to Mn4+ 2p3/2, 653.6 eV corresponds to Mn4+ 2p1/2, 643.4 eV corresponds to Mn3+ 2p3/2, 654.7 eV corresponds to Mn3+ 2p1/2. 645.2 eV belongs to the satellite peak [1,6].
In the XPS curve of O1s, 529.6 eV belongs to Mn-O-Mn, 530.1 eV, 530.8 eV, 531.5 eV correspond to different oxygen defects, such as oxygen vacancy, 532.2 eV, 532.9 eV correspond to -OH. Since graphene oxide contains a variety of oxygen-containing groups, differences in chemical environments lead to some changes in binding energy of O1s.
In the XPS curve of C1s, 284.0 eV, 284.7 eV correspond to C=C/C-C, 285.3 eV, 286.3 eV, 287.0 eV, 287.9 eV correspond to C-O, C=O, O-C=O, 291.0 eV, 293.5 eV belong to K+ 2p. The presence of K+ is a consequence of the raw material potassium permanganate used. K+ can be adsorbed on the surface of the material or intercalated in the nanocomposite. It is difficult to be washed away. K+ is a difficult impurity to remove in the synthesis of nanocomposites. Since graphene oxide contains a variety of oxygen-containing groups, differences in chemical environments also lead to some changes in the binding energy of C1s.
As shown in Figure 18, the nanocomposites contain trivalent and tetravalent Mn, which exhibits redox characteristics. The mutual shift in valence states leads to a change in the Mn-O chemical bonding, resulting in the production of oxygen vacancies. XPS of O1s also further confirms the presence of oxygen vacancies. The presence of oxygen vacancies improves charge transport and photogenerated electron extraction. As can be seen, the two types of defect-rich material exhibit improved charge transport and photogenerated electron extraction due to charge transfer between interfaces, which leads to the mutual passivation of defects. This could inspire the development of other nanocomposite systems with mutual defect passivation to enhance synergy and complementarity between materials, improving their photophysical properties. Additionally, the resulting nanocomposites present valence heterojunctions as well as component heterojunctions. The synergy of multiple heterojunctions is important for improving the extraction of optoelectronic signals.
Graphene is well known for its high carrier mobility and good conductivity, but it has low light absorption and is a zero-bandgap material. Graphene oxide, on the other hand, has a band gap whose width depends on its degree of oxidation. Compared with graphene, graphene oxide has reduced conductivity and carrier mobility. According to reference [8], the band gap of MnO2 is approximately 0.25 eV. Therefore, light absorption in the visible and near-infrared (NIR) regions mainly depends on the MnO2 nanofibre component of the MnO2/GO nanocomposite. Graphene oxide also contributes to light absorption. Under visible and near-infrared irradiation, electrons are excited from the valence level of MnO2 to the conductive level and then transferred to the conductive level of graphene oxide. The holes in the graphene oxide valence band were transferred to the MnO2 valence band. Consequently, an efficient charge transfer channel exists between the two components of the MnOx/GO nanocomposite. Charge transfer between the interfaces of the MnO2/GO nanocomposite forms an internal electric field that drives the directed motion of photo-generated carriers, thereby exhibiting photoelectric response characteristics. Graphene oxide acts as a bridge role between the grain boundaries of the MnOx nanofibres. Consequently, adding graphene oxide to the nanocomposite improves the extraction of photo-generated charges and prevents recombination.
Avoiding photogenerated carrier recombination and enhancing charge extraction properties have important applications in multidisciplinary fields [93]. As the recombination of photogenerated electron–hole pairs has been a key bottleneck in multidisciplinary fields for several decades, this study focused on regulating grain boundaries and studying the aggregate state of nanocomposites to improve the extraction of photogenerated charges in broadband spectrum range. This study provides a useful reference for multidisciplinary fields. This research will expand multidisciplinary applications and the study of interactions between light and matter. This is one of the most important aspects of material research.

4. Conclusions

In summary, the optimised MnO2/GO nanocomposite was obtained by passivating the grain boundary defects, which improved photogenerated charge extraction and transport. The resulting nanocomposite shows good photoelectric response in the visible light region and near-infrared (NIR) ranges. It also exhibits good photophysical stability. The photocurrent signals can still be extracted when a 0 V bias is applied. This believes that the interactions between the interfaces of nanocomposite produce a built-in electric field that avoids the recombination of photogenerated charges. The strength of the built-in electric field is affected by the component ratios of the resulting nanocomposite, which further supports the idea that interactions between the component interfaces lead to its formation. The resulting nanocomposites present valence heterojunctions in addition to component heterojunctions. The synergy between multiple heterojunctions and oxygen vacancies is crucial for improving the extraction of optoelectronic signals. This provides a reference for grain boundary regulation and suppression of photogenerated carrier recombination. Modulation of grain boundaries and photophysical properties will always be significant for aggregate state studies of nanocomposites.

Author Contributions

Conceptualisation, methodology, investigation, writing—original draft preparation, writing—review and editing, funding acquisition, resources, investigation, X.M.; investigation, X.Z., M.G., R.H. and Y.W.; resources, G.L.; all authors analysed the data; all authors discussed the results of the paper. All authors have read and agreed to the published version of the manuscript.

Funding

This project was supported by the Natural Science Foundation of Shandong Province (project no. ZR2013EMM008).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author.

Acknowledgments

Thanks to You Wang and Guang Li of Zhejiang University for the fabrication of several electrodes and for checking the English in the paper. SEM was carried out by Fang Tian, Raman spectra were measured by Weiwei Wang, at the Structural Composition Testing Center, School of Chemistry and Chemical Engineering, Shandong University. XPS was performed by Hechun Jiang, State Key Laboratory of Crystalline Materials, Shandong University.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Jhankal, D.; Khan, M.S.; Shakya, P.; Bhardwaj, N.; Yadav, B.; Jhankalc, K.K.; Sachdev, K. Charge storage kinetics of in-terconnected MnO2 nano-needles/reduced graphene oxide composite for high energy density quasi-solid-state sodiumion asymmetric supercapacitor. Energy Adv. 2024, 3, 191. [Google Scholar] [CrossRef]
  2. Zhang, S.; Wang, Z.; Yang, S.; Hao, D.; Yu, S.; Wu, Q. Chitosan modified graphene oxide with MnO2 deposition for high energy density flexible supercapacitors. Int. J. Biol. Macromol. 2024, 259, 129223. [Google Scholar] [CrossRef]
  3. Raskar, N.; Dake, D.; Mane, V.; Sonpir, R.; Vasundhara, M.; Asokan, K.; Deshpande, U.; Venkatesh, R.; Mote, V.; Dole, B. Designing reduced graphene oxide decorated Ni doped δ-MnO2 nanocomposites for supercapacitor applications. Mater. Sci. Semicond. Process. 2024, 178, 108451. [Google Scholar] [CrossRef]
  4. Fu, X.-Y.; Shu, R.-Y.; Ma, C.-J.; Jiang, H.-B.; Yao, M.-N. Graphene oxide assisted-MnO2 nanoparticles enhanced laser-induced graphene based electrodes for supercapacitor application. Electrochim. Acta 2024, 481, 143987. [Google Scholar] [CrossRef]
  5. Guo, Y.; Chen, J.; Liang, Z.; Su, X.; Sun, M.; Tang, J.; Li, Z.; Dang, D.; Yu, L. Hierarchical porous MnO2/3D graphene oxide/carbon cloth used as practical mass-loading supercapacitor electrodes. J. Alloys Compd. 2024, 1010, 177125. [Google Scholar] [CrossRef]
  6. Tan, B.; Chen, N.; Gao, X.; Huang, L.; Tan, L.; Feng, H. High performance 2.4 V aqueous asymmetric supercapacitors based on a cathode material of Ni-doped MnO2/reduced graphene oxide nanocomposite. J. Energy Storage 2025, 118, 116339. [Google Scholar] [CrossRef]
  7. Chen, Y.; Zhang, J.; Li, M.; Yang, C.; Zhang, L.; Wang, C.; Lu, H. Strong interface coupling and few-crystalline MnO2/Reduced graphene oxide composites for supercapacitors with high cycle stability. Electrochim. Acta 2018, 292, 115–124. [Google Scholar] [CrossRef]
  8. Liu, J.; Bao, J.; Zhang, X.; Gao, Y.; Zhang, Y.; Liu, L.; Cao, Z. MnO2-based materials for supercapacitor electrodes: Challenges, strategies and prospects. RSC Adv. 2022, 12, 35556–35578. [Google Scholar] [CrossRef]
  9. Ze, H.; Fan, X.-T.; Yang, Z.-L.; Ding, X.; A, Y.-L.; Wen, X.; Zhang, Y.; Oropeza, F.E.; Zhang, K.H.L.; Gu, Y.; et al. Deciphering the Competitive Charge Storage Chemistry of Metal Cations and Protons in Aqueous MnO2-Based Supercapacitors. J. Am. Chem. Soc. 2025, 147, 9620–9628. [Google Scholar] [CrossRef]
  10. Sun, J.; Li, S.; Li, Y.; Zhang, X.; Yang, Z. High-Performance Flexible Asymmetric Supercapacitor Based on Nanostructured MnO2 and Bi2O3 Decorated 3D Carbon Nanotube Sponge in an Aqueous Gel-Electrolyte. ACS Appl. Energy Mater. 2024, 7, 7450–7458. [Google Scholar] [CrossRef]
  11. Ding, Y.; Wang, L.; Yang, L.; Li, X.; Fang, H.; Peng, J.; Qian, D.; Xu, Z.; Guan, Y.; Li, J.; et al. Laser Patterned In-Plane Asymmetric MXene//LIG@MnO Microsupercapacitor for Self-Powered Pressure Detection Systems. ACS Appl. Mater. Interfaces 2025, 17, 21713–21724. [Google Scholar] [CrossRef]
  12. Shahidi, S.; Kalaoglu, F.; Naji, L.; Rahmanian, A.; Mongkholrattanasit, R. MnO2/Ni-Cu-Plated Polyester Fabric as a Free-Standing Electrode in Supercapacitor Applications. ACS Omega 2025, 10, 7091–7101. [Google Scholar] [CrossRef]
  13. Yadav, A.A.; Hunge, Y.M.; Majumder, S.; Islam, M.M.; Sakurai, T. Solar-Powered Supercapacitors: A Review and Outlook on Next-Generation Sustainable Energy Storage Solutions. Energy Fuels 2025, 39, 12323–12366. [Google Scholar] [CrossRef]
  14. Pang, N.; Wang, M.; Wang, X.; Xiong, D.; Xu, S.; Lu, X.; Wang, L.; Jiang, L.; Chu, P.K. Graphene-oxide-modified MnO2 composite electrode for high-performance flexible quasi-solid-state zinc-ion batteries. Mater. Sci. Eng. B 2023, 299, 116981. [Google Scholar] [CrossRef]
  15. Inigo Antony, M.; Punnakkal, N.; Vyshnav Vinod, M.; Krishnendu, S.D.; Satheesh Babu, T.G.; Suneesh, P.V. MnO2 nanowires modified reduced graphene oxide thick film cathode for aqueous zinc-ion prismatic battery. J. Energy Storage 2024, 103, 114283. [Google Scholar] [CrossRef]
  16. Wang, C.; Liu, H.; Han, L.; Zhang, J.; Liu, R.; Kong, F. Reduced graphene oxide modified ɛ-MnO2 nanoflowers cathode with oxygen vacancy for advanced rechargeable aqueous zinc-ion batteries. Mater. Res. Bull. 2025, 191, 113543. [Google Scholar] [CrossRef]
  17. Ma, W.; Jin, Y.; Wan, W.; Sun, D.; Jia, L.; Gong, D.; Tu, Y.; Zhou, W.; Chai, H. C3N4 Preintercalation of α-MnO2 Nanotubes with Expanded Interlayer Spacing for High-Performance Aqueous Zn-Ion Batteries. ACS Appl. Nano Mater. 2025, 8, 9427–9436. [Google Scholar] [CrossRef]
  18. Chahartagh, N.M.; Aghdam, A.M.; Namvar, S.; Ajdari, F.B.; Ershadi, M.; Jafari, M. Conductive Polymer Designed of Binder-Free Polypyrrole-MnO2/Ti3C2 for Oxidative Stable Aqueous Zinc-Ion Batteries. ACS Appl. Energy Mater. 2025, 8, 2720–2732. [Google Scholar] [CrossRef]
  19. Zhong, S.; Xin, Y.; Mo, L.; He, B.; Zhang, F.; Zhao, C.; Hu, L.; Tian, H. Intercalation and Interface Engineering of Layered MnO2 Cathodes toward High-Performance Aqueous Zinc-Ion Batteries. J. Phys. Chem. C 2025, 129, 6684–6696. [Google Scholar] [CrossRef]
  20. Jiang, S.; Tian, S.; Zhang, S.; Fang, L.; Wang, Z.; Nie, P.; Han, W.; Xue, X.; Zhao, C.; Lu, M.; et al. Iron-Doped Nanorods of MnO2 For Applications in Zinc-Ion Batteries. ACS Appl. Nano Mater. 2024, 7, 27648–27655. [Google Scholar] [CrossRef]
  21. Chen, X.; Xu, Z.; Guo, S.; Sun, B.; Li, Q.; Meng, Q.; Wei, F.; Qi, J.; Sui, Y.; Cao, P. Oxygen Vacancy-Rich Cobalt-Doped MnO2 Nanorods for Zn Ion Batteries. ACS Appl. Mater. Interfaces 2025, 17, 12074–12084. [Google Scholar] [CrossRef] [PubMed]
  22. Chen, R.; Tian, W.; He, H.; Fu, X.; Sun, Q.; Wang, R.; Zhao, X.; Zhang, X.; Zhu, Y.; Zheng, Z.; et al. Peanut Shell-Derived Carbon Microsheet@MnO2 Nanoparticles Composite for Ultra Long-Cycling Aqueous Zinc-Ion Batteries. Langmuir 2025, 41, 10282–10291. [Google Scholar] [CrossRef]
  23. Hwang, T.; Bergschneider, M.; Kong, F.; Cho, K. Reaction Mechanisms and Improvement of α-MnO2 Cathode in Aqueous Zn-Ion Battery. Chem. Mater. 2025, 37, 1244–1254. [Google Scholar] [CrossRef]
  24. Zhong, S.; Xin, Y.; Lei, M.; Cai, S.; Zhao, C.; Zhang, H.; Tian, H. Scalable Production of MnO2/Carbon Composites via a Simple One Step Precipitation Method for Aqueous Zn-Ion Batteries. Energy Fuels 2025, 39, 12254–12263. [Google Scholar] [CrossRef]
  25. Lai, G.; Hu, X.; Liang, S.; Yang, Y.; Elsharkawy, E.R.; Mersal, G.A.M.; Lu, B.; El-Bahy, Z.M.; Liu, Y.; Zhou, J. Synergistic Electro-Chemo-Structural Interface Engineering for Stable Aqueous Zn-MnO2 Batteries. ACS Energy Lett. 2025, 10, 3437–3444. [Google Scholar] [CrossRef]
  26. Chakraborty, A.; Ghosh, A.; Paul, A.; Murmu, N.C.; Samanta, P.; Kuila, T. Tuning MnO2: A Nernstian-Type Electrode Material as a Substitute for Bare Zinc Foil for Triggering the Performance of ZHS. ACS Appl. Energy Mater. 2024, 7, 10428–10440. [Google Scholar] [CrossRef]
  27. Pradhan, S.; Ahirrao, D.J.; Jha, N. Sustainable Hydrothermal Synthesis of Reduced Graphene Oxide Wrapped on α-MnO2 Nanorod Cathode for Zinc-Ion Batteries. Adv. Sustain. Syst. 2024, 8, 2400362. [Google Scholar] [CrossRef]
  28. Yi, X.; Song, Y.; He, D.; Li, W.; Pan, A.; Han, C. Constructing a high-performance bifunctional MnO2-based electrocatalyst towards applications in rechargeable zinc–air batteries. J. Mater. Chem. A 2024, 12, 29355–29382. [Google Scholar] [CrossRef]
  29. Chuong, Y.K.N.; Van Thang, V.; Vuong, T.T.T.; Vu, P.T.; Phung, T.V.B.; Nguyen, L.P.; Le, P.M.L. MnO2-Decorated Graphene Oxide Nanosheet Composites as Promising Electrode Materials for Lithium-Ion Battery Energy Storage Applications. RSC Adv. 2025, 15, 16015–16027. [Google Scholar] [CrossRef]
  30. Wang, N.; Peng, S.; Chen, X.; Wang, J.; Wang, C.; Qi, X.; Dai, S.; Yan, S. Construction of Ultrathin MnO2 Decorated Graphene/Carbon Nanotube Nanocomposites as Efficient Sulfur Hosts for High-Performance Lithium–Sulfur Batteries. RSC Adv. 2019, 9, 6346–6355. [Google Scholar] [CrossRef]
  31. Jee, W.; Sokol, A.A.; Xu, C.; Camino, B.; Zhang, X.; Woodley, S.M. Discharging of Ramsdellite MnO2 Cathode in a Lithium-Ion Battery. Chem. Mater. 2024, 36, 8737–8752. [Google Scholar] [CrossRef]
  32. Xu, Y.; Qian, K.; Deng, Y.; Liu, Z.; Chen, Z. Green and Sustainable Recovery of MnO2 from Alkaline Batteries for High-Performance Lithium Manganese Oxide Cathode. Energy Fuels 2024, 38, 21601–21606. [Google Scholar] [CrossRef]
  33. Xu, W.; Jiang, L.; Li, Y.; Zhang, J.; Huang, Q.; Yao, J.; Xiao, S.; Lei, C. Sodium Storage Performance and Mechanism of MnO2 with Different Phase Structures (α, β, γ, δ) as Anode Materials for Sodium Ion Batteries. ACS Appl. Mater. Interfaces 2024, 16, 61877–61887. [Google Scholar] [CrossRef]
  34. Raskar, N.D.; Dake, D.V.; Mane, V.A.; Sonpir, R.B.; Khawal, H.A.; Mote, V.D.; Vasundhara, M.; Asokan, K.; Gattu, K.P.; Dole, B.N. Nanoengineered Reduced Graphene Oxide-Fe Doped α-MnO2: A Multifunctional Smart Material for Energy Storage and Environmental Remediation. J. Energy Storage 2024, 86, 111206. [Google Scholar] [CrossRef]
  35. Rosaiah, P.; Divya, P.; Prakash, N.G.; Dhananjaya, M.; Sambasivam, S.; Al-Asbahi, B.A.; Shaik, D.P.; Ko, T.J. Ultra-long MnO2 nanowire-entrenched reduced graphene oxide composite electrodes for energy storage. Diam. Relat. Mater. 2023, 133, 109709. [Google Scholar] [CrossRef]
  36. Zhang, Y.; Xu, H.; Ebaid, M.S.; Zhang, X.; Jiang, K.; Zhang, X.; Guo, Z.; Xu, B. Advances in layer manganese dioxide for energy conversion and storage: Mechanisms, strategies and prospects. Chem. Sci. 2025, 16, 9092. [Google Scholar] [CrossRef]
  37. Xue, X.; Li, Y. Advancing Mn2+/MnO2 Conversion Chemistry through Redox Mediation: Mechanistic Insights and Outlook. ACS Energy Lett. 2025, 10, 3275–3286. [Google Scholar] [CrossRef]
  38. Xu, D.; Sheng, Q.; Chen, A.; Chen, L.; Zhang, Y.; Zhu, C.; Chen, J.; Chen, S.; Hu, C. MnO2 Microspheres as Self-Degraded Templates to Fabricate Hollow Urchin-Like Polyaniline Microspheres for Electrochemical Energy Storage. ACS Appl. Polym. Mater. 2025, 7, 3544–3554. [Google Scholar] [CrossRef]
  39. Wu, H.; Jiang, L.; Liu, J.; Jin, Y.; Dong, S.; Shi, X.; Yuan, Y.; Bai, W.; Wu, S. MnO2 Nanoflakes Anchored on N-Doped Carbon Nanotubes for Lithium Storage. ACS Appl. Nano Mater. 2025, 8, 7630–7641. [Google Scholar] [CrossRef]
  40. Xu, D.; Gu, Y.; Chen, L.; Zhang, Y.; You, F.; Chen, S.; Hu, C.; Huang, H.; Chen, J. MnO2 Nanosheets on TiO2 Tetragonal Prism Nanoarrays as Electrode Materials for Electrochemical Energy Storage. ACS Appl. Nano Mater. 2024, 7, 22997–23007. [Google Scholar] [CrossRef]
  41. Wu, L.; Li, Z.; Xiang, Y.; Dong, W.; Wu, H.; Xu, Y.; Ling, Z.; Chae, M.S.; Sharon, D.; Shpigel, N.; et al. Unraveling the Charge Storage Mechanism of β-MnO2 in Aqueous Zinc Electrolytes. ACS Energy Lett. 2024, 9, 5801–5809. [Google Scholar] [CrossRef]
  42. Ahmed, M.; Ahmad, S.; Nawaz, T.; Ali Durrani, M.; Ali, A.; Saher, S.; Khan, M.A.Z.; Egilmez, M.; Samreen, A.; Mustafa, F. Performance evaluation of graphene oxide-MnO2 nanocomposite for alkaline membrane fuel cell. Electrochem. Sci. Adv. 2022, 2, e2100085. [Google Scholar] [CrossRef]
  43. Xu, Z.; Zhong, M.; Li, S.; Chen, Y.; Li, P.; Fan, Z.; Liu, P.; Wang, D.; Zhang, Z. One-Step Hydrothermal Method Realizing Oxygen Vacancy Construction and P Doping of MnO2 to Optimize Its Oxygen Evolution Performance. Inorg. Chem. 2025, 64, 5029–5037. [Google Scholar] [CrossRef]
  44. Wang, L.; Wang, Y.; Zhou, L.; Liu, J.-Y.; Wu, Z. Manipulating d-Electronic States via Transition Metal Doping in MnO2 to Boost Direct Seawater Electrolysis. ACS Sustain. Chem. Eng. 2024, 12, 13907–13917. [Google Scholar] [CrossRef]
  45. Lou, J.; Zhu, X.; Li, T.; Yang, X.; Ma, D.; Zhu, L.; Wang, J. Preparation and Electrochromic Properties of MnO2/PPy Composite Films with Coral-like Structures. ACS Appl. Mater. Interfaces 2024, 16, 36942–36952. [Google Scholar] [CrossRef]
  46. Wang, F.; Xie, J.; Zhang, S.; Huang, C. Superior Performance of the δ-MnO2 Ultrathin Nanoflower for Photocatalytic HCHO Oxidation. Inorg. Chem. 2025, 64, 6275–6285. [Google Scholar] [CrossRef]
  47. Aquatar, O.; Bhatia, U.; Rayalu, S.S.; Krupadam, R.J. Reduced graphene oxide-MnO2 nanocomposite for CO2 capture from flue gases at elevated temperatures. Sci. Total Environ. 2022, 816, 151522. [Google Scholar] [CrossRef]
  48. Wang, Q.; Liang, S.; Liu, J.; Xie, Y.; Pang, Q.; Liu, Z.; Chen, Y. Activating Mn Sites on MnO2 Hollow Spheres for CO2 Photoreduction. ACS Appl. Nano Mater. 2025, 8, 6575–6582. [Google Scholar] [CrossRef]
  49. Aktürk, M.; Dursun, Z. A novel composite electrode based on graphene oxide/MnO2:h-MoO3 particles for square wave voltammetric determination of acetaminophen. Electroanalysis 2024, 36, e202400042. [Google Scholar] [CrossRef]
  50. Liu, Y.; Zhao, W.; Gao, Y.; Zhuo, Q.; Chu, T.; Huang, W.; Zheng, Y.; Li, Y. In situ green synthesis of the nanocomposites of MnO2/graphene as an oxidase mimic for sensitive colorimetric and electrochemical dual-mode biosensing. RSC Adv. 2023, 13, 31067. [Google Scholar] [CrossRef]
  51. Rehman, S.U.; Lin, Y.; Wu, H. Oxygen-Deficient Fluorescent λ-MnO2 Nanosheets for Selective Detection of Chloramphenicol. ACS Appl. Nano Mater. 2025, 8, 10306–10314. [Google Scholar] [CrossRef]
  52. Shahid, M.; Rizvi, S.N.B.; Afzal, A. Tailoring Surface and Electrochemical Properties: Effect of Acid, Silane, and Epoxy Functionalization on γ-MnO2 Electrodes for L-Glutamine Detection. Ind. Eng. Chem. Res. 2025, 64, 13730–13740. [Google Scholar] [CrossRef]
  53. Zhu, J.; Yang, F.; Jiang, C.; Li, Z.; Zhou, Y.; Li, X. Multifunctional Superhydrophobic Sponge In Situ Anchoring of AgMnO2 via Polydopamine Activation for Efficient Oil−Water Separation, Photothermal Conversion and Antibacterial Applications. ACS Appl. Mater. Interfaces 2025, 17, 30327–30339. [Google Scholar] [CrossRef]
  54. Song, H.; Xu, L.; Chen, M.; Cui, Y.; Wu, C.; Qiu, J.; Xu, L.; Cheng, G.; Hu, X. Recent progresses in the synthesis of MnO2 nanowire and its application in environmental catalysis. RSC Adv. 2021, 11, 35494. [Google Scholar] [CrossRef]
  55. Zhao, S.; Ji, Z.; Hao, L.; Wang, Z.; Li, J.; Cheng, F.; Hussain, M.; Liu, J. Electron-Enriched Pt Induced by MnO2 Structural Variation Achieving Low-Alkalinity Methanol Electrooxidation. ACS Appl. Energy Mater. 2025, 8, 6595–6604. [Google Scholar] [CrossRef]
  56. Liu, D.; Zhou, L.; Liu, Y.; Xia, C.; Ouyang, J.; Adesina, A.A. Electrodeposition fabrication of graphene oxide/α-MnO2/polyaniline hierarchical porous electrodes with large hybrid specific capacitance for efficient U(VI) electrosorption. J. Environ. Chem. Eng. 2024, 12, 113450. [Google Scholar] [CrossRef]
  57. Rajendiran, R.; Patchaiyappan, A.; Harisingh, S.; Balla, P.; Paari, A.; Ponnala, B.; Perupogu, V.; Lassi, U.; Seelam, P.K. Synergistic effects of graphene oxide grafted chitosan & decorated MnO2 nanorods composite materials application in efficient removal of toxic industrial dyes. J. Water Process. Eng. 2022, 47, 102704. [Google Scholar] [CrossRef]
  58. Dhanusha, A.; Sabari Girisun, T.C. Improved near-resonant two photon absorption of α-MnO2 nanowires surface functionalized reduced graphene oxide sheets. Colloids Surf. A Physicochem. Eng. Asp. 2024, 697, 134395. [Google Scholar] [CrossRef]
  59. Jha, B.K.; Yoon, J.-C.; Jang, J.-H. 3D Graphene for Energy Technologies: Chemical Strategies and Industrial Challenges. Acc. Mater. Res. 2025, 6, 799–813. [Google Scholar] [CrossRef]
  60. Bongu, C.S.; Tasleem, S.; Krishnan, M.R.; Alsharaeh, E.H. Graphene-based 2D materials for rechargeable batteries and hydrogen production and storage: A critical review. Sustain. Energy Fuels 2024, 8, 4039–4070. [Google Scholar] [CrossRef]
  61. Sui, H.; Van Toan, N.; Ono, T. Density effects of vertical graphene nanowalls on supercapacitor performance. Mater. Adv. 2022, 3, 5406–5417. [Google Scholar] [CrossRef]
  62. Yu, X.; Qin, X.; Zhao, Z.; Liu, S.; Zhang, R.; Liu, L. Nitrogen-Doped Carbon Nanospheres Dispersed within Graphene Oxide to Fabricate Composite Fibers for High Performance Flexible Supercapacitors. ACS Appl. Nano Mater. 2025, 8, 1935–1943. [Google Scholar] [CrossRef]
  63. Yan, H.; Ding, Y.; Lin, S.; Li, J.; Zhao, Y.; Lin, Z.; Zhang, J.; Bai, J.; Hu, X.; Bai, H. Structural Supercapacitors Based on Graphene Composite Film Electrodes. ACS Appl. Energy Mater. 2025, 8, 8981–8991. [Google Scholar] [CrossRef]
  64. Pathak, M.; Jeong, S.M.; Rout, C.S. Graphene hybrids for supercapacitor applications. Chem. Commun. 2025, 61, 8803–8829. [Google Scholar] [CrossRef] [PubMed]
  65. Jung, H.Y.; Kim, S.I.; Kim, J.; Kim, Y.J.; Hong, H.; Yun, J.; Ryu, W. MnO2-decorated highly porous 3D-printed graphene supercapacitors for photosynthetic power systems. J. Mater. Chem. A 2023, 11, 20608–20622. [Google Scholar] [CrossRef]
  66. George, S.; Sasidharan, S.; Shafna, M.A.; Anil, A.; Suresh, G.; Ratheesh, A.; Shibli, S.M.A. Triggering Redox Active Sites Through Electronic Structure Modulation in rGO Encapsulated Mixed Transition Metal Oxides Hybrid for Alkaline Hydrogen Evolution. ACS Appl. Mater. Interfaces 2024, 16, 40948–40963. [Google Scholar] [CrossRef]
  67. Levchenko, I.; Baranov, O.; Riccardi, C.; Roman, H.E.; Cvelbar, U.; Ivanova, E.P.; Mohandas, M.; Ščajev, P.; Malinauskas, T.; Xu, S.; et al. Nanoengineered Carbon-Based Interfaces for Advanced Energy and Photonics Applications: A Recent Progress and Innovations. Adv. Mater. Interfaces 2022, 10, 2201739. [Google Scholar] [CrossRef]
  68. Aftab, S.; Koyyada, G.; Mukhtar, M.; Kabir, F.; Nazir, G.; Memon, S.A.; Aslam, M.; Assiri, M.A.; Kim, J.H. Laser-Induced Graphene for Advanced Sensing: Comprehensive Review of Applications. ACS Sensors 2024, 9, 4536–4554. [Google Scholar] [CrossRef] [PubMed]
  69. Boateng, E.; McGuire, C.; Xu, R.; Jiang, D.-T.; Chen, A. Effects of Heteroatom Doping on the Electrochemical Hydrogen Uptake and Release of Pd-Decorated Reduced Graphene Oxide. ACS Appl. Mater. Interfaces 2024, 16, 47703–47712. [Google Scholar] [CrossRef]
  70. Zhou, B.; Cai, Z.; Wen, J.; Liu, H. Engineering Thermally Reduced Graphene Oxide for Synchronously Enhancing Photocatalytic Activity and Photothermal Effect. ACS Appl. Bio Mater. 2024, 7, 6249–6260. [Google Scholar] [CrossRef]
  71. Adfar, Q.; Hussain, S.; Maktedar, S.S. Insights into energy and environmental sustainability through photoactive graphene-based advanced materials: Perspectives and promises. New J. Chem. 2025, 49, 2511–2650. [Google Scholar] [CrossRef]
  72. Kroemer, H. Nobel Lecture: Quasielectric fields and band offsets: Teaching electrons new tricks. Rev. Mod. Phys. 2001, 73, 783–793. [Google Scholar] [CrossRef]
  73. Liu, S.; Qin, K.; Yang, J.; Hu, T.; Luo, H.; Wu, J.; Zhen, C.; Li, T.; Ding, F.; Wang, X.; et al. Direct orientational-epitaxy of wafer-scale 2D van der Waals heterostructures of metal dichalcogenides. Natl. Sci. Rev. 2025, 12, nwaf119. [Google Scholar] [CrossRef] [PubMed]
  74. Das, S.; Dey, T.; Mandal, D.; Ray, S.K.; Banerji, P.; Chandra, A.; Basori, R. Plasmon-sensitized SiNWs/SnS2 heterostructures for high-sensitivity photodetector devices. J. Appl. Phys. 2025, 137, 233103. [Google Scholar] [CrossRef]
  75. Zheng, B.; Wang, B.; Wang, Y.; Li, Y.; Wang, H.; Liu, Y.; Xu, Z.; Wu, G.; Sun, X.; Zhu, C. Epitaxial Growth of SnS2/WS2-WSe2 Bilayer P-N Hybridized Heterojunctions for Multifunctional Optoelectronic Devices. ACS Appl. Mater. Interfaces 2025, 17, 19987–19995. [Google Scholar] [CrossRef]
  76. Kumar, A.; Chakkar, A.G.; Das, C.; Kumar, P.; Sahu, S.; Saliba, M.; Kumar, M. Self-Powered Broadband Photodetectors Based on WS2-Anchored MoS2 with Enhanced Responsivity and Detectivity. Small 2025, 21, 2502900. [Google Scholar] [CrossRef]
  77. Cheng, Y.; Lin, X.; Wang, C.; Zhang, Z.; Wang, C.; Geng, L.; Suo, P.; Du, J.; Ma, G. Revealing a Nonlinear Photocurrent in the Graphene/MoS2 Heterostructure via Terahertz Emission Spectroscopy. J. Phys. Chem. Lett. 2025, 16, 2654–2660. [Google Scholar] [CrossRef]
  78. Ghopry, S.; Shultz, A.; Alamri, M.; Alzahrani, S.; Wu, J. Enhanced Photoresponse in Intermingled WS2 and MoS2 Nanodiscs on Graphene Heterostructure Nanohybrids. Adv. Mater. Interfaces 2025, 12, 2500087. [Google Scholar] [CrossRef]
  79. Wang, L.; Li, S.; Zhang, L. Ultrafast charge transfer in two-dimensional black phosphorus/SiS van der Waals heterostructure for photoconversion. J. Appl. Phys. 2025, 137, 195304. [Google Scholar] [CrossRef]
  80. Ghafary, Z.; Hallaj, R.; Salimi, A.; Akhtari, K. Two-Dimensional Graphdiyne-Black Phosphorus van der Waals Heterostructure: A Versatile Platform for Broadband Photodetection from UV to IR. ACS Appl. Nano Mater. 2025, 8, 7719–7735. [Google Scholar] [CrossRef]
  81. Mazzotti, A.; Durante, O.; De Stefano, S.; Viscardi, L.; Pelella, A.; Kharsah, O.; Daniel, L.; Sleziona, S.; Schleberger, M.; Di Bartolomeo, A. BP/MoS2 Van Der Waals Heterojunctions for Self-Powered Photoconduction. Adv. Opt. Mater. 2025, 13, 2500811. [Google Scholar] [CrossRef]
  82. Du, Y.; Yang, J.; Lv, Z.; Zhai, Y.; Yi, Z.; Xie, Y.; Zheng, M.; Ma, X.; Gong, G.; Wang, Y. Integration of Perovskite/Low-Dimensional Material Heterostructures for Optoelectronics and Artificial Visual Systems. Adv. Funct. Mater. 2025, 2500953. [Google Scholar] [CrossRef]
  83. Li, X.; Liu, K.; Wu, D.; Lin, P.; Shi, Z.; Li, X.; Zeng, L.; Chai, Y.; Lau, S.P.; Tsang, Y.H. Van Der Waals Hybrid Integration of 2D Semimetals for Broadband Photodetection. Adv. Mater. 2025, e2415717. [Google Scholar] [CrossRef]
  84. Lv, Z.; Peng, Z.; Yin, Y.; Liu, K.; Yang, S.; Wang, G.; Jiang, H. Epitaxial strain reconfiguration of AlGaN multiple heterojunctions for high-responsivity high-speed UV detection. Appl. Phys. Lett. 2025, 126, 242106. [Google Scholar] [CrossRef]
  85. Lin, Y.; Miao, X.; Zhang, Y.; Li, L.; Yang, J.; Lei, H.; Pan, Y. Surface Argon Plasma Treatment Enabled Broadband Optoelectronic Synapses Based on Large-Scale Epitaxial GaSe/GaN Heterojunctions. ACS Appl. Mater. Interfaces 2025, 17, 14257–14268. [Google Scholar] [CrossRef] [PubMed]
  86. Yao, L.; Yun, J.; Zhao, H.; Zhang, L.; Ma, Y.; Kang, P.; Yan, J.; Zhao, W.; Zhang, Z. Design and analysis of monolayer GaN-boron phosphide lateral heterostructures for ultraviolet photodetection and rectification. Appl. Surf. Sci. 2025, 688, 162428. [Google Scholar] [CrossRef]
  87. Kim, J.; Moon, S.; Im, S.; Song, J.; Ji, C.; Pak, S.; Kim, J.K. The heterostructure of hexagonal boron nitride with wurtzite III-nitrides for optoelectronic and electronic applications. J. Appl. Phys. 2025, 137, 210902. [Google Scholar] [CrossRef]
  88. Ahn, J.; Yeon, E.; Hwang, D.K. Recent Progress in 2D Heterostructures for High-Performance Photodetectors and Their Applications. Adv. Opt. Mater. 2025, 13, 2403412. [Google Scholar] [CrossRef]
  89. Ma, X.; Li, C.; Zhang, X.; Gao, M.; Wang, Y.; Li, G. Interface Optimisation of the Fe2O3/C3N4 Heterojunction with Metal Nanoparticles and Their Negative and Positive Photoelectric Responses in a Broadband Light Spectrum Range. Coatings 2024, 14, 1595. [Google Scholar] [CrossRef]
  90. Ma, X.F.; Gao, M.J.; He, X.C.; Li, G. Controlled Morphology of One-Dimensional Manganese Dioxide with Dramatic Enhancing Removal Efficiency to Heavy Metal Ions in Aqueous Solution. Mater. Sci. Forum 2011, 688, 23–30. [Google Scholar] [CrossRef]
  91. Pei, Z.; Ma, X.; Ding, P.; Zhang, W.; Luo, Z.; Li, G. Study of a QCM Dimethyl Methylphosphonate Sensor Based on a ZnO-Modified Nanowire-Structured Manganese Dioxide Film. Sensors 2010, 10, 8275–8290. [Google Scholar] [CrossRef]
  92. Lv, S.S.; Bian, L.; Qiu, J.X.; Zhang, X.T.; Gao, M.J.; He, X.C.; Ma, X.F.; Li, G. Surface Modification of Graphene Oxide with Pyrene Derivatives and their Photo-Switching Behaviors. Mater. Sci. Forum 2017, 898, 1739–1748. [Google Scholar] [CrossRef]
  93. Talebian-Kiakalaieh, A.; Hashem, E.M.; Guo, M.; Ran, J.; Qiao, S. Single Atom Extracting Photoexcited Holes for Key Photocatalytic Reactions. Adv. Energy Mater. 2025, e2501945. [Google Scholar] [CrossRef]
Coatings 15 00920 sch001
Scheme 1. The structure of the Au electrodes on polymer film substrate.
Scheme 1. The structure of the Au electrodes on polymer film substrate.
Coatings 15 00920 sch001
Coatings 15 00920 g001
Figure 1. The SEM images of the representative MnO2/GO (10) nanocomposite (the scale bar is 1 μm).
Figure 1. The SEM images of the representative MnO2/GO (10) nanocomposite (the scale bar is 1 μm).
Coatings 15 00920 g001
Coatings 15 00920 g002
Figure 2. The XRD results of the representative MnO2/GO (50) nanocomposite.
Figure 2. The XRD results of the representative MnO2/GO (50) nanocomposite.
Coatings 15 00920 g002
Coatings 15 00920 g003
Figure 3. The UV-Vis-NIR curve of the representative MnO2/GO (10) nanocomposite.
Figure 3. The UV-Vis-NIR curve of the representative MnO2/GO (10) nanocomposite.
Coatings 15 00920 g003
Coatings 15 00920 g004
Figure 4. The Raman of the representative MnO2/GO (10) nanocomposite.
Figure 4. The Raman of the representative MnO2/GO (10) nanocomposite.
Coatings 15 00920 g004
Coatings 15 00920 g005
Figure 5. The photocurrent response of MnO2/GO (10) nanocomposite ((A): 25 W visible light; (B): 200 mW 808 nm) (with 1 V bias applied).
Figure 5. The photocurrent response of MnO2/GO (10) nanocomposite ((A): 25 W visible light; (B): 200 mW 808 nm) (with 1 V bias applied).
Coatings 15 00920 g005
Coatings 15 00920 g006
Figure 6. The dependence of optoelectronic signals on the power of the representative light source (808 nm light source) (1 V bias applied).
Figure 6. The dependence of optoelectronic signals on the power of the representative light source (808 nm light source) (1 V bias applied).
Coatings 15 00920 g006
Coatings 15 00920 g007
Figure 7. The comparative optoelectronic signals of MnO2/GO (10) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (0, 1, 4, 5, 6 V bias applied).
Figure 7. The comparative optoelectronic signals of MnO2/GO (10) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (0, 1, 4, 5, 6 V bias applied).
Coatings 15 00920 g007
Coatings 15 00920 g008
Figure 8. The comparative optoelectronic signals of MnO2/GO (10) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (−1, −4, −5, −6 V bias applied).
Figure 8. The comparative optoelectronic signals of MnO2/GO (10) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (−1, −4, −5, −6 V bias applied).
Coatings 15 00920 g008
Coatings 15 00920 g009
Figure 9. The comparative optoelectronic signals of MnO2/GO (30) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (0, 1, 4, 5, 6 V bias applied).
Figure 9. The comparative optoelectronic signals of MnO2/GO (30) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (0, 1, 4, 5, 6 V bias applied).
Coatings 15 00920 g009
Coatings 15 00920 g010
Figure 10. The comparative optoelectronic signals of MnO2/GO (30) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (−4, −5 V bias applied).
Figure 10. The comparative optoelectronic signals of MnO2/GO (30) nanocomposite aggregation states with Au electrodes on the PET film to 200 mW 808 nm light sources (−4, −5 V bias applied).
Coatings 15 00920 g010
Coatings 15 00920 g011
Figure 11. The comparative optoelectronic signals of MnO2/GO (10, 30) nanocomposite aggregation states with Au electrodes on the PET film to 50 mW 405, 650, 780 nm light sources ((A): 405 nm; (B): 650 nm; (C): 780 nm) (0 V bias applied).
Figure 11. The comparative optoelectronic signals of MnO2/GO (10, 30) nanocomposite aggregation states with Au electrodes on the PET film to 50 mW 405, 650, 780 nm light sources ((A): 405 nm; (B): 650 nm; (C): 780 nm) (0 V bias applied).
Coatings 15 00920 g011
Coatings 15 00920 g012
Figure 12. The comparative optoelectronic signals of MnO2/GO (10, 30) nanocomposite aggregation states with Au electrodes on the PET film to 50 mW 780, 808, 980 nm and 20 mW 1064 light sources ((A): 780 nm; (B): 808 nm; (C): 980 nm; (D): 1064 nm) (0 V bias applied).
Figure 12. The comparative optoelectronic signals of MnO2/GO (10, 30) nanocomposite aggregation states with Au electrodes on the PET film to 50 mW 780, 808, 980 nm and 20 mW 1064 light sources ((A): 780 nm; (B): 808 nm; (C): 980 nm; (D): 1064 nm) (0 V bias applied).
Coatings 15 00920 g012
Coatings 15 00920 g013
Figure 13. The comparative optoelectronic signals of MnO2/GO (30) nanocomposite aggregation states with Au electrodes on the PET film to 50 mW 405, 650, 780, 808, 980 nm light sources (0 V bias applied).
Figure 13. The comparative optoelectronic signals of MnO2/GO (30) nanocomposite aggregation states with Au electrodes on the PET film to 50 mW 405, 650, 780, 808, 980 nm light sources (0 V bias applied).
Coatings 15 00920 g013
Coatings 15 00920 g014
Figure 14. The dependence of optoelectronic signals on the power of 808 nm light source for MnO2/GO (10) nanocomposite aggregation states (0 V bias applied).
Figure 14. The dependence of optoelectronic signals on the power of 808 nm light source for MnO2/GO (10) nanocomposite aggregation states (0 V bias applied).
Coatings 15 00920 g014
Coatings 15 00920 g015
Figure 15. The dependence of optoelectronic signals on the power of 980 nm light source for MnO2/GO (10) nanocomposite aggregation states (0 V bias applied).
Figure 15. The dependence of optoelectronic signals on the power of 980 nm light source for MnO2/GO (10) nanocomposite aggregation states (0 V bias applied).
Coatings 15 00920 g015
Coatings 15 00920 g016
Figure 16. The dependence of optoelectronic signals on the power of 808 nm light source for MnO2/GO (30) nanocomposite aggregation states (0 V bias applied).
Figure 16. The dependence of optoelectronic signals on the power of 808 nm light source for MnO2/GO (30) nanocomposite aggregation states (0 V bias applied).
Coatings 15 00920 g016
Coatings 15 00920 g017
Figure 17. The dependence of optoelectronic signals on the power of 980 nm light source for MnO2/GO (30) nanocomposite aggregation states (0 V bias applied).
Figure 17. The dependence of optoelectronic signals on the power of 980 nm light source for MnO2/GO (30) nanocomposite aggregation states (0 V bias applied).
Coatings 15 00920 g017
Coatings 15 00920 g018
Figure 18. The XPS results of the representative MnO2/GO (10) nanocomposite.
Figure 18. The XPS results of the representative MnO2/GO (10) nanocomposite.
Coatings 15 00920 g018
Table 1. The comparative photocurrent response results of the MnOx/GO (10, 30) nanocomposite aggregation states with Au gap electrodes and PET film to some representative light sources (0 V bias applied).
Table 1. The comparative photocurrent response results of the MnOx/GO (10, 30) nanocomposite aggregation states with Au gap electrodes and PET film to some representative light sources (0 V bias applied).
Excitation Light Wavelength (nm)SampleResponse Time (s)Recovery Time (s) Ratio of on/off
50 mW, 405 nmMnOx/GO (10)59.8127.51.08
50 mW, 405 nmMnOx/GO (30)31.855.61.23
50 mW, 650 nmMnOx/GO (10)103.7111.21.09
50 mW, 650 nmMnOx/GO (30)4.243.91.29
50 mW, 780 nmMnOx/GO (10)59.783.61.07
50 mW, 780 nmMnOx/GO (30)11.736.01.18
50 mW, 808 nmMnOx/GO (10)87.4151.31.09
50 mW, 808 nmMnOx/GO (30)59.428.01.27
50 mW, 980 nmMnOx/GO (10)59.4123.31.04
50 mW, 980 nmMnOx/GO (30)23.839.71.07
20 mW, 1064 nmMnOx/GO (10)83.6103.71.05
20 mW, 1064 nmMnOx/GO (30)39.759.81.21
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Ma, X.; Zhang, X.; Gao, M.; Hu, R.; Wang, Y.; Li, G. Grain Boundary Regulation in Aggregated States of MnOx Nanofibres and the Photoelectric Properties of Their Nanocomposites Across a Broadband Light Spectrum. Coatings 2025, 15, 920. https://doi.org/10.3390/coatings15080920

AMA Style

Ma X, Zhang X, Gao M, Hu R, Wang Y, Li G. Grain Boundary Regulation in Aggregated States of MnOx Nanofibres and the Photoelectric Properties of Their Nanocomposites Across a Broadband Light Spectrum. Coatings. 2025; 15(8):920. https://doi.org/10.3390/coatings15080920

Chicago/Turabian Style

Ma, Xingfa, Xintao Zhang, Mingjun Gao, Ruifen Hu, You Wang, and Guang Li. 2025. "Grain Boundary Regulation in Aggregated States of MnOx Nanofibres and the Photoelectric Properties of Their Nanocomposites Across a Broadband Light Spectrum" Coatings 15, no. 8: 920. https://doi.org/10.3390/coatings15080920

APA Style

Ma, X., Zhang, X., Gao, M., Hu, R., Wang, Y., & Li, G. (2025). Grain Boundary Regulation in Aggregated States of MnOx Nanofibres and the Photoelectric Properties of Their Nanocomposites Across a Broadband Light Spectrum. Coatings, 15(8), 920. https://doi.org/10.3390/coatings15080920

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop