Search Results (55)

A facile and versatile strategy to obtain NPs@ZnAlO nanocomposite materials, comprising controlled-size nanoparticles (NPs) within a ZnAlO matrix is reported. The mono-(Au, Ni) and bimetallic (Ni-Au) NPs serving as an active phase were prepared by the polyol-alkaline method, while the ZnAlO support was obtained via the thermal decomposition of its corresponding layered double hydroxide (LDH) precursors. X-ray diffraction (XRD) patterns confirmed the successful fabrication of the nanocomposites, including the synthesis of the metallic NPs, the formation of LDH-like structure, and the subsequent transformation to ZnO phase upon LDH calcination. The obtained nanostructures confirmed the nanoplate-like morphology inherited from the original LDH precursors, which tended to aggregate after the addition of gold NPs. According to the UV-Vis spectroscopy, loading NPs onto the ZnAlO support enhanced the light absorption and reduced the band gap energy. ATR-DRIFT spectroscopy, H₂-TPR measurements, and XPS analysis provided information about the functional groups, surface composition, and reducibility of the materials. The catalytic performance of the developed nanostructures was evaluated by the photodegradation of bisphenol A (BPA), under simulated solar irradiation. The conversion of BPA over the bimetallic Ni-Au@ZnAlO reached up to 95% after 180 min of irradiation, exceeding the monometallic Ni@ZnAlO and Au@ZnAlO catalysts. Its enhanced activity was correlated with good dispersion of the bimetals, narrower band gap, and efficient charge carrier separation of the photo-induced e⁻/h⁺ pairs. Full article

Z-scheme Zn₃In₂S₆/NiFe₂O₄ nanocomposites were prepared by electrospinning and hydrothermal methods, and their photocathodic protection performance was studied on 304 SS and Q235 CS in NaCl solution (3.5 wt.%). The two-dimensional Zn₃In₂S₆ loaded on the one-dimensional NiFe₂O₄ resulted in faster electron migration and enhanced light absorption capability. Moreover, it had been observed through electrochemical testing that the assembly of Zn₃In₂S₆/NiFe₂O₄ heterojunctions improves the efficacy of photocathodic protection. Following illumination, the self-corrosion potentials of 304 SS and Q235 CS coupled with Zn₃In₂S₆/NiFe₂O₄ nanocomposites decreased by 1040 mV and 560 mV, and the photoinduced current densities were 1.2 times and 3.9 times greater than the value of Zn₃In₂S₆. Furthermore, the mechanism of enhanced photocathodic protection performance for Zn₃In₂S₆/NiFe₂O₄ heterojunctions was systematically discussed. XPS and ESR analysis indicated that Zn₃In₂S₆/NiFe₂O₄ composites follow the Z-scheme electron migration path and retain the stronger reduction and oxidation capacity of Zn₃In₂S₆/NiFe₂O₄. Therefore, the Z-scheme heterostructures are responsible for the realization of cathodic protection for carbon steel. Full article

The efficient separation of photo-generated electrons and holes is significantly importance for enhancing photocatalytic performance. However, there are few reports on precisely constructing interfaces within a single nanocrystal to investigate the mechanism of photoinduced carrier transfer. In this study, nanorod heterodimer-structured CuS/Zn_xCd_1−xS heteronanocrystals (CuS/ZnCdS HNCs) were successfully synthesized as a typical model to explore the photoinduced carrier dynamics in the photocatalytic hydrogen evolution reaction (HER). The CuS/ZnCdS HNCs exhibited a photocatalytic hydrogen evolution activity of 146 mmol h⁻¹ g⁻¹ under visible light irradiation, which is higher than most reported values. Moreover, after 15 h of hydrogen production cycling tests, we found that the material maintained high hydrogen production performance, indicating excellent stability. The CuS/ZnCdS HNCs achieved an apparent quantum yield (AQY) of 69.2% at 380 nm, which is the highest value reported so far for ZnCdS- or CuS-based photocatalysts. The remarkable activity and stability of the CuS/ZnCdS HNCs were attributed to the strong internal electric field (IEF) and Z-scheme mechanism, which facilitate efficient charge separation, as demonstrated by in situ X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analyses. This discovery provides a new approach for constructing Z-scheme heterogeneous copper-based nanocomposites within nanocrystals and offers guidance for improving photocatalytic activity. Full article

Anodic titania nanotubes (TiO₂-NT) are very promising for use in photocatalysis and photovoltaics due to their developed surface, symmetrical structure and conductive properties, which, moreover, makes them a convenient matrix for creating various nanocomposites. Herein we propose a new facile way of synthesizing symmetrical TiO₂-NT followed by a modification with barium titanate (BaTiO₃) nanoparticles, combining the advantages of electrochemical oxidation and hydrothermal synthesis. The electrophysical and optoelectronic properties of the formed nanocomposites have been studied. An asymmetry of the current–voltage characteristics was revealed. It is shown that during the barium titanate deposition, a symmetry-breaking nanoheterojunction TiO₂/BaTiO₃ is formed. Using EPR spectroscopy, paramagnetic defects (titanium, barium and oxygen vacancies) in the samples were determined. It was observed for the first time that upon illumination of titania nanotubes modified with BaTiO₃, the asymmetrical separation of photoexcited charge carriers (electrons and holes) between TiO₂-NT and BaTiO₃ occurs, followed by the capture of electrons and holes by defects. As a result, the photoinduced charge accumulates on the defects. Full article

Photoanisotropic materials, in particular azodyes and azopolymers, have attracted significant research interest in the last decades. This is due to their applications in polarization holography and 4G optics, enabling polarization-selective diffractive optical elements with unique properties, including circular polarization beam-splitters, polarization-selective bifocal lenses, and many others. Numerous methods have been applied to increase the photoinduced birefringence of these materials, and as a result, to obtain polarization holographic elements with a high diffraction efficiency. Recently, a new approach has emerged that has been extensively studied by many research groups, namely doping azobenzene-containing materials with nanoparticles with various compositions, sizes, and morphologies. The resulting nanocomposites have shown significant enhancement in their photoanisotropic response, including increased photoinduced birefringence, leading to a higher diffraction efficiency and a larger surface relief modulation in the case of polarization holographic recordings. This review aims to cover the most important achievements in this new but fast-growing field of research and to present an extensive comparative analysis of the result, reported by many research groups during the last two decades. Different hypotheses to explain the mechanism of photoanisotropy enhancement in these nanocomposites are also discussed. Finally, we present our vision for the future development of this scientific field and outline its potential applications in advanced photonics technologies. Full article

The characteristics of the surface and interface of nanocomposites are important for exerting multi-functional properties and widening interdisciplinary applications. These properties are mainly depending on the electronic structures of materials. Some key factors, such as the surface, interface, grain boundaries, and defects take vital roles in the contribution of desired properties. Due to the excellent sensitivity of the QCM (quartz crystal microbalance) device, the surface and interface features of the nanocomposite were studied with the aid of the gas-response of the sensors (Sensor’s Gas-Sensitivity) in this work. To make full use of the visible light and part of NIR, a ZnO/MnS_x nanocomposite was constructed using hydrothermal synthesis for narrowing the bandgap width of wide bandgap materials. The results indicated that the absorbance of the resulting nanocomposite was extended to part of the NIR range due to the introduction of impurity level or defect level, although ZnO and MnS belonged to wide bandgap semiconductor materials. To explore the physical mechanism of light activities, the photoconductive responses to weak visible light (650 nm, etc.) and NIR (near-infrared) (808 nm, 980 nm, and 1064 nm, etc.) were studied based on interdigital electrodes of Au on flexible PET (polyethylene terephthalate) film substrate with the casting method. The results showed that the on/off ratio of ZnO/MnS_x nanocomposite to weak visible light and part of NIR light were changed by about one to five orders of magnitude, with changes varying with the amount of MnS_x nanoparticle loading due to defect-assisted photoconductive behavior. It illustrated that the ZnO/MnS_x nanocomposite easily produced photo-induced free charges, effectively avoiding the recombination of electrons/holes because of the formation of strong built-in electrical fields. To examine the surface and interface properties of nanocomposites, chemical prototype sensor arrays were constructed based on ZnO, ZnO/MnS_x nanocomposite, and QCM arrays. The adsorption response behaviors of the sensor arrays to some typical volatile compounds were examined under a similar micro-environment. The results exhibited that in comparison to ZnO nanosheets, the ZnO nanosheets/MnS_x nanocomposite increased adsorption properties to some typical organic volatile compounds significantly. It would have good potential applications in photo-catalysts, self-cleaning films, multi-functional coatings, and organic pollutants treatment (VOCs) of environmental fields for sustainable development. It provided some reference value to explore the physical mechanism of materials physics and photophysics for photo-active functional nanocomposites. Full article

A series of Yttrium (Y)-doped Bi₂MoO₆ composites with calcined mussel shell powder (CMS) as supports were synthesized using a solvothermal method. The as-prepared samples were analyzed using multiple techniques to investigate their microscopic morphology, composition structure, and optical properties. The photocatalytic performance of the as-prepared samples was assessed via examining their capacity to degrade Rhodamine B (RhB) under visible-light irradiation. The photocatalytic data showed that the Y-doped Bi₂MoO₆/CMS composites exhibited better photocatalytic activity compared to pure Bi₂MoO₆ and undoped Bi₂MoO₆/CMS samples. Among the samples, the 0.5%Y-doped Bi₂MoO₆/CMS (0.5%Y-BC) showed the highest photocatalytic activity, achieving a maximum degradation rate of 99.7% within 60 min. This could be attributed to highly reactive sites due to Y doping, a narrower band gap, and a lower recombination rate of photoinduced electron–hole pairs. Additionally, the 0.5%Y-BC photocatalyst exhibited excellent stability and reusability properties even after four cycles, making it suitable for practical applications. The findings provided a feasible synthesis of nanocomposite photocatalysts with outstanding properties for organic pollutant removal from the solution system. Full article

CdS@ZnS core shell nanocomposites were prepared by a one-pot hydrothermal route. The morphology of the composite was tuned by simply changing the Zn²⁺ precursor concentration. To characterize the samples prepared, various techniques were employed, including XRD, FESEM, TEM, XPS and UV-vis DRS. The band gaps of CdS and ZnS were measured to be 2.26 and 3.32 eV, respectively. Compared with pure CdS, the CdS@ZnS samples exhibited a slight blue shift, which indicated an increased band gap of 2.29 eV. The CdS@ZnS core shell composites exhibited efficient photocatalytic performance for H₂ generation under simulated sunlight illumination in contrast to pure CdS and ZnS. Additionally, an optimized H₂ generation rate (14.44 mmol·h⁻¹·g⁻¹_cat) was acquired at CdS@ZnS-2, which was approximately 4.6 times greater than that of pure CdS (3.12 mmol·h⁻¹·g⁻¹_cat). Moreover, CdS@ZnS heterojunction also showed good photocatalytic stability. The process of charge separation over the photocatalysts was investigated using photoelectrochemical analysis. The findings indicate that the CdS@ZnS nanocomposite has efficient charge separation efficiency. The higher H₂ generation activity and stability for CdS@ZnS photocatalysts can be attributed to the intimate interface in the CdS@ZnS core–shell structure, which promoted the light absorption intensity and photoinduced charge separation efficiency. It is expected that this study will offer valuable insights into the development of efficient core shell composite photocatalysts. Full article

In recent years, ZnO/Co₃O₄ nanoparticles (NPs) have been reflected as typical of the most promising photocatalysts utilized in the field of photocatalysis for potentially solving energy shortages and environmental remediation. In this work, a novel ZnO/Co₃O₄ NP photocatalyst was fabricated and utilized for photocatalytic hydrogen evolution with visible light activity. ZnO/Co₃O₄ NPs display an improved photocatalytic hydrogen production rate of 3963 μmol/g through a five-hour test under visible light activity. This is much better than their single components. Hence, bare ZnO NPs loaded with 20 wt% Co₃O₄ NPs present optimum efficiency of hydrogen evolution (793.2 μmol/g/h) with 10 vol% triethanolamine (TEOA), which is 11.8 times that of pristine ZnO NPs. An achievable mechanism for improved photocatalysis is endowed in terms of the composite that promotes the operative separation rate of charge carriers that are produced by visible light irradiation. This study yields a potential process for the future, proposing economical, high-function nanocomposites for hydrogen evolution with visible light activity. Full article

Photocatalyst performance is often limited by the poor separation and rapid recombination of photoinduced charge carriers. A nanoheterojunction structure can facilitate the separation of charge carrier, increase their lifetime, and induce photocatalytic activity. In this study, CeO₂@ZnO nanocomposites were produced by pyrolyzing Ce@Zn metal–organic frameworks prepared from cerium and zinc nitrate precursors. The effects of the Zn:Ce ratio on the microstructure, morphology, and optical properties of the nanocomposites were studied. In addition, the photocatalytic activity of the nanocomposites under light irradiation was assessed using rhodamine B as a model pollutant, and a mechanism for photodegradation was proposed. With the increase in the Zn:Ce ratio, the particle size decreased, and surface area increased. Furthermore, transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed the formation of a heterojunction interface, which enhanced photocarrier separation. The prepared photocatalysts show a higher photocatalytic activity than CeO₂@ZnO nanocomposites previously reported in the literature. The proposed synthetic method is simple and may produce highly active photocatalysts for environmental remediation. Full article

The development of a highly efficient, visible-light responsive catalyst for environment purification has been a long-standing exploit, with obstacles to overcome, including inefficient capture of near-infrared photons, undesirable recombination of photo-generated carriers, and insufficient accessible reaction sites. Hence, novel carbon quantum dots (CQDs) modified PbBiO₂I photocatalyst were synthesized for the first time through an in-situ ionic liquid-induced method. The bridging function of 1-butyl-3-methylimidazolium iodide ([Bmim]I) guarantees the even dispersion of CQDs around PbBiO₂I surface, for synchronically overcoming the above drawbacks and markedly promoting the degradation efficiency of organic contaminants: (i) CQDs decoration harness solar photons in the near-infrared region; (ii) particular delocalized conjugated construction of CQDs strength via the utilization of photo-induced carriers; (iii) π–π interactions increase the contact between catalyst and organic molecules. Benefiting from these distinguished features, the optimized CQDs/PbBiO₂I nanocomposite displays significantly enhanced photocatalytic performance towards the elimination of rhodamine B and ciprofloxacin under visible/near-infrared light irradiation. The spin-trapping ESR analysis demonstrates that CQDs modification can boost the concentration of reactive oxygen species (O₂^•−). Combined with radicals trapping tests, valence-band spectra, and Mott–Schottky results, a possible photocatalytic mechanism is proposed. This work establishes a significant milestone in constructing CQDs-modified, bismuth-based catalysts for solar energy conversion applications. Full article

Removing organic pollutants, textile dyes, and pharmaceutical wastes from the water bodies has become an essential requirement for a safe environment. Therefore, the present study aimed to prepare semiconductor zinc oxide nanoparticles (ZnO NPs) and plasmonic Ag-supported ZnO nanocomposite (ZnO–Ag) using an environmentally friendly bio-approach as an alternative to hazardous synthesis approaches. ZnO NPs and ZnO–Ag nanocomposite were characterized by using UV–Vis diffuse reflectance spectroscopy (UV–DRS) (the Ag-supported ZnO nanocomposite exhibited an absorption band between 450–550 nm, attributed to the Ag NPs surface plasmon resonance (SPR)), Photoluminescence (PL) spectral investigation, which revealed the PL emission intensity of ZnO–Ag NPs was lower than pure ZnO NPs, describing an extended electron-hole pair (e--h+) lifespan of photogenerated charge carriers, Fourier transform infrared spectroscopy (FTIR), FT-Raman, and X-ray diffraction (XRD) analyses were deduced. In addition, energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were performed and further ascertained the successful biosynthesis and thermally stable ZnO Nps and ZnO–Ag nanocomposite. The as-prepared ZnO–Ag nanocomposite displayed increased photocatalytic characteristics due to the decline in the bandgap energy from 3.02 eV (ZnO NPs) to 2.90 eV (ZnO–Ag nanocomposite). The photocatalytic activity of the developed nanocomposite for the degradation of methylene blue (MB) dye, a primary textile industry released water-pollutant, was conducted under UV light irradiation. Meanwhile, the maximum % degradation of MB dye molecules was attained by 98.0 % after 60 min exposure of UV-light irradiation. Increased photocatalytic activity of ZnO–Ag nanocomposites and a faster rate of MB degradation were achieved by the deposition of plasmonic Ag NPs and the surface plasmon resonance (SPR) effect possessed by Ag NPs. The primary oxidative route that resulted in MB degradation was the production of hydroxyl radicals (OH^•). The SPR effect of the photocatalyst induced the synergistic enhancement of the optical response and separation of the photo-induced charge carriers. The combined study gives comprehensive information and directions for future research on noble metal-modified nanocatalysts for direct applications in the photocatalytic degradation of textile and organic wastes in water. Full article

Photocatalytic hydrogen production joined with simultaneous organic compound removal is a potential but challenging approach for both environmental modification and reusable energy generation. In this study, we designed a nanocomposite method for the fabrication of MoS₂/Co₃O₄ heterojunction with an extremely productive photocatalytic capability. The as-fabricated MoS₂/Co₃O₄ nanocomposites displayed greatly enhanced the hydrogen production (3825 μmol/g/h) and methyl violet dye (MV) contaminant removal (apparent kinetic constant of 0.038 min⁻¹) activity. The nanocomposites’ structures had a better specific surface area, numerous active sites, and enhanced the transport ability of charge carriers to promote the photocatalytic activity. The increase in Co₃O₄ improved the visible-light absorption efficiency and narrowed energy bandgap and served as a highway for charge carriers to facilitate the transfer and separation and inhibit the combination of photoinduced charge carriers. The migration route of the photoexcited charges, the formation pathway, and the function of various reactive oxygen species (such as O²⁻ and •OH) are discussed. The optimized energy band structure and high electron transfer rate of the S-scheme heterojunction nanocomposite promotes the evolution of H₂ and the removal of pollutants, which shows an excellent potential in a stable and efficient photocatalytic hydrogen evolution and environment remediation. Full article

The contamination of organic dye molecules in aquatic environments caused by the effluents released from vast industrial establishments has been a matter of serious concern in recent years, owing to their strong non-biodegradable nature and acute toxicity. Semiconductor-mediated visible-light-driven photocatalytic-dye detoxification is considered as a sustainable technique because it abundantly utilizes the available solar energy and releases environmentally friendly chemicals such as H₂O as byproducts. Adequate textural and microstructural properties, an extended visible-light response, pronounced isolation and transfer of photoinduced charge carriers, and facile magnetic-separation characteristics make spinel-ferrite-decorated graphene or its analogues’ (GO/rGO) nanocomposites (MFGNs) a versatile photocatalytic system for the efficacious detoxification of dyes. Therefore, this review article emphasizes their exceptional photodegradation performance in terms of systematic studies of the above-mentioned features, after a brief description of the synthesis protocols. The mechanism of the photodetoxification of dyes over MFGNs is precisely demonstrated in three different sections based on their redox abilities. The kinetics of the MFGN-driven photodecomposition of dyes are then highlighted. We discuss the role of different parameters such as pH, temperature, catalyst dose, and dye concentration in augmented photocatalytic-dye-degradation reactions. Finally, the emerging challenges that act as hurdles in achieving superior photocatalytic-dye-detoxification performance are addressed, along with the conclusion. We then propose some possible future research directions in order to overcome these challenges, for impressively accomplishing the photodegradation of organic dyes. Full article

Combining steady-state photoluminescence and transient absorption (TA) spectroscopy, we have investigated the photoinduced charge transfer dynamics between lead-free Mn-doped Cs₂NaIn_0.75Bi_0.25Cl₆ double perovskite (DP) nanocrystals (NCs) and conjugated poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). Upon ultraviolet-A excitation, the photoinduced absorption feature of DP NCs/MDMO-PPV nanocomposites disappeared, and the stimulated emission weakened in the TA spectrum. This was due to charge transfer from the MDMO-PPV polymers to DP NCs. Upon a higher photon-energy ultraviolet-C excitation, stimulated emission and photoinduced absorption features vanished, indicating there existed a reversible charge transfer from DP NCs to MDMO-PPV polymers. Reversible charge transfer of Mn-doped DP NCs/MDMO-PPV nanocomposites was tuned by varying the excitation photon-energy. The manipulation of reversible charge transfer dynamics in the perovskite-polymer nanocomposites opens a new avenue for optical and optoelectronic applications. Full article