Search Results (54)

In this study, we present bi-layered hydrogel systems that incorporate different sizes and shapes of gold nanoparticles (nanospheres and nanorods) for potential use in areas such as photoactuators, soft robotics, artificial muscles, drug delivery and tissue engineering. The synthesized nano Au-PNiPAAm/PVA bi-layered hydrogel nanocomposites provide the unique ability to exhibit controlled motion upon light exposure, indicating that the above systems possess the capability of photo–thermal energy conversion. The chosen synthesis approach is a combination of chemical production of gold nanoparticles (AuNPs) followed by gamma radiation formation of crosslinked polymer networks around them, as the final step, which also allows for sterilization in a single technological step. According to the TEM analysis, the gold nanospheres (AuNSs) with mean diameters of around 17 and 30 nm, as well as nanorods (AuNRs) with an aspect ratio of around 4.5, were synthesized and used as nanofillers in the formation of nanocomposites. Their stability within the polymer matrix was confirmed by UV–Vis spectral studies, by the presence of local surface plasmon resonance (LSPR) bands, typical for nanoparticles of various shapes and sizes. Morphological studies (FE-SEM) of hydrogels revealed the formation of a porous structure with PNiPAAm hydrogel as an active layer and PVA hydrogel as a passive layer, as well as a stable interfacial layer with a thickness of around 80 μm. The synthesized bi-layered photoactuators showed a photo–thermal response upon exposure to irradiation of green lasers and lamps that simulate sunlight, resulting in bending motion. This bending response reveals the huge potential of the obtained materials as soft actuators, which are more flexible than rigid systems, making them effective for specific applications where controlled movement and flexibility are essential. Full article

In this work, we have reported a simple synthesis method for a hollow porous organic nanosphere-supported ZnO composite photocatalyst (HPON@ZnO) through a combination of a hyper-crosslinking-mediated self-assembly method and a “ship-in-bottle” strategy. The obtained HPON@ZnO possesses a large specific surface area and hierarchically porous structures, which exhibited exceptionally high catalytic activity in the adsorption and degradation of crystal violet, with the reaction proceeding under mild conditions. Additionally, the catalyst demonstrated degradation activity towards other dyes and featured a good stability and recyclability. This simple strategy provides a new approach for the large-scale synthesis of efficient heterogeneous photocatalysts, and offers an effective dye wastewater treatment technique. Full article

This study presents an effective method to remove organic dyes from wastewater, using a composite of few-layered porous (FLP) Ti₃C₂T_x MXene and polythiophene (PTh) nanospheres. The FLP MXene, which was pre-synthesized by a series of intercalation, heat-induced TiO₂ formation, and its selective etching, was combined with PTh nanospheres via a simple solution method. The composite effectively removed various organic dyes, but its efficiency was altered depending on the type of dye. Particularly, the removal efficiency of methylene blue reached 91.3% and 97.8% after irradiation for 10 min and 1 h, respectively. The high dye removal efficiency was attributed to the large surface area (32.01 m²/g) of the composite, strong electrostatic interaction between the composite and dye molecules, and active photodegradation process. The strong electrostatic interaction and large surface area could facilitate the adsorption of dye molecules, while photocatalytic activity further enhance dye removal under light. These results are indicative that the PTh/FLP MXene composite may be a promising material for environmental remediation through synergistic processes of adsorption and photocatalysis. Full article

In this article, Pt-Sn_xO_y hybrid nanoparticles encaged in porous silica nanospheres (Pt-Sn_xO_y@PSNs) were prepared by using 1-dodecanethiol (C₁₂-SH) as a coordination agent to confine Pt and Sn ions in a microemulsion system, which is formed by cetyltrimethylammonium bromide (CTAB) and C₁₂-SH as co-surfactants in water. Compared with Pt@PSNs, when different molar ratios of Sn_xO_y were introduced into Pt@PSNs to form Pt-Sn_xO_y@PSNs, the catalytic efficiency of 4-nitrophenol (4-NP) reduction with NaBH₄ can be significantly enhanced. At molar ratios of 4-NP/Pt of 150/1, the 4-NP conversion reached 100% over Pt-Sn_xO_y@PSNs with Pt/Sn molar ratios of 1/0.75 in 8 min. This catalytic performance showed a slight decrease after six reaction cycles. This enhanced catalytic efficiency can be ascribed to the synergistic effect between Pt and Sn_xO_y, and the protection of porous silica nanostructures can effectively improve the stability of the catalyst. Full article

The electronic nose is an increasingly useful tool in many fields and applications. Our thermal electronic nose approach, based on nanostructured metal oxide chemiresistors in a thermal gradient, has the advantage of being tiny and therefore integrable in portable and wearable devices. Obviously, a wise choice of the nanomaterial is crucial for the device’s performance and should therefore be carefully considered. Here we show how the addition of different amounts of Au (between 1 and 5 wt%) on Cu₂O–SnO₂ nanospheres affects the thermal electronic nose performance. Interestingly, the best performance is not achieved with the material offering the highest intrinsic selectivity. This confirms the importance of specific studies, since the performance of chemoresistive gas sensors does not linearly affect the performance of the electronic nose. By optimizing the amount of Au, the device achieved a perfect classification of the tested gases (acetone, ethanol, and toluene) and a good concentration estimation (with a mean absolute percentage error around 16%). These performances, combined with potentially smaller dimensions of less than 0.5 mm², make this thermal electronic nose an ideal candidate for numerous applications, such as in the agri-food, environmental, and biomedical sectors. Full article

Hydrogel nanocomposites that respond to external stimuli and possess switchable electrical properties are considered as emerging materials with potential uses in electrical, electrochemical, and biological devices. This work reports the synthesis and characterization of thermo-responsive and electroconductive hydrogel nanocomposites based on poly(N-isopropylacrylamide) (PNiPAAm) and gold nanoparticles (nanospheres—AuNPs and nanorods—AuNRs) using two different synthetic techniques. Method I involved γ-irradiation-induced crosslinking of a polymer matrix (hydrogel), followed by radiolytic in situ formation of gold nanoparticles, while Method II included the chemical synthesis of nanoparticles, followed by radiolytic formation of a polymer matrix around the gold nanoparticles. UV–Vis spectral studies revealed the presence of local surface plasmon resonance (LSPR) bands characteristic of nanoparticles of different shapes, confirming their formation and stability inside the polymer matrix. Morphological, structural, and physicochemical analyses indicated the existence of a stable porous polymer matrix, the formation of nanoparticles with a face-centered cubic structure, increased swelling capacity, and a slightly higher volume phase transition temperature (VPTT) for the hydrogel nanocomposites. Comparative electrochemical impedance spectroscopy (EIS) showed an increase in conductivity for the nano Au-PNiPAAm hydrogel nanocomposites compared to the PNiPAAm hydrogel, with a considerable rise detected above the VPTT. By reverting to room temperature, the conductivity decreased, indicating that the investigated hydrogel nanocomposites exhibited a remarkable reversible “on–off” thermo-switchable mechanism. The highest conductivity was observed for the sample with rod-shaped gold nanoparticles. The research findings, which include optical, structural, morphological, and physicochemical characterization, evaluation of the efficiency of the chosen synthesis methods, and conductivity testing, provide a starting point for future research on the given nanocomposite materials with integrated multifunctionality. Full article

Zn–air batteries (ZABs) are a promising technology; however, their commercialization is limited by challenges, including those occurring in the electrolyte, and thus, gel polymer electrolytes (GPEs) and hydrogels have emerged as substitutes for traditional aqueous electrolytes. In this work, PVA/PAA membranes were synthesized by the solvent casting method and soaked in 6 M KOH to act as GPEs. The thickness of the membrane was modified (50, 100, and 150 μm), and after determining the best thickness, the membrane was modified with synthesized SiO₂ nanospheres and multi-walled carbon nanotubes (CNTs). SEM micrographs revealed that the CNTs displayed lengths of tens of micrometers, having a narrow diameter (95 ± 7 nm). In addition, SEM revealed that the SiO₂ nanospheres had homogeneous shapes with sizes of 110 ± 10 nm. Physicochemical experiments revealed that SiO₂ incorporation at 5 wt.% increased the water uptake of the PVA/PAA membrane from 465% to 525% and the ionic conductivity to 170 mS cm⁻¹. The further addition of 0.5 wt.% CNTs did not impact the water uptake but it promoted a porous structure, increasing the power density and the stability, showing three-times-higher rechargeability than the ZAB operated with the PVA/PAA GPE. Full article

The chemical tolerance of ketoenamine covalent organic frameworks (COFs) is excellent; however, the tight crystal structure and low surface area limit their applications in the field of catalysis. In this work, a porous single-atom iron catalyst (FeSAC) with a core–shell structure and high surface area was synthesized by using Schiff base COF nanospheres as the core and ketoenamine COF nanosheets growth on the surfaces. Surface defects were created using sodium cyanoborohydride etching treatment to increase specific surface area. The dye degradation experiments by peroxymonosulfate (PMS) catalyzed by the FeSAC proved that methylene blue can be degraded with a degradation rate constant of 0.125 min⁻¹ under the conditions of 0.1 g L⁻¹ catalyst dosage and 0.05 g L⁻¹ peroxymonosulfate. The FeSAC/PMS system effectively degrades various pollutants in the pH range of 4–10 with over 80% efficiency for four cycles and can be recovered by soaking in iron salt solution. Free radical quenching experiments confirmed that singlet oxygen and superoxide radicals are the main active species for catalysis. Full article

Hollow porous AuAg nanospheres (AuAg HPNSs) were obtained through a simple solvothermal synthesis, complemented by a dealloying strategy. The hollow interior, open pore voids, and integral interconnected skeleton shell in AuAg HPNSs are beneficial for providing sufficient electrolyte diffusion and contacts, abundant active sites, and efficient electron transport. This specific structure and the favorable alloy synergism contribute to the superior electrocatalytic activity toward dopamine (DA) and acetaminophen (AC). AuAg HPNSs show high sensitivity, good selectivity, excellent sensing durability, and outstanding repeatability for amperometric assays of AC and DA. In particular, the AuAg-based sensors achieve effective ultrasensitive simultaneous analyses of AC and DA, exhibiting the characteristics of the wide linear range and low detection limit. With their prominent electrocatalytic activity and simple preparation methods, AuAg HPNSs present broad application prospects for constructing a highly responsive electrochemical sensing system. Full article

Silicon (Si) shows great potential as an anode material for lithium-ion batteries. However, it experiences significant expansion in volume as it undergoes the charging and discharging cycles, presenting challenges for practical implementation. Nanostructured Si has emerged as a viable solution to address these challenges. However, it requires a complex preparation process and high costs. In order to explore the above problems, this study devised an innovative approach to create Si/C composite anodes: micron-porous silicon (p-Si) was synthesized at low cost at a lower silver ion concentration, and then porous silicon-coated carbon (p-Si@C) composites were prepared by compositing nanohollow carbon spheres with porous silicon, which had good electrochemical properties. The initial coulombic efficiency of the composite was 76.51%. After undergoing 250 cycles at a current density of 0.2 A·g⁻¹, the composites exhibited a capacity of 1008.84 mAh·g⁻¹. Even when subjected to a current density of 1 A·g⁻¹, the composites sustained a discharge capacity of 485.93 mAh·g⁻¹ even after completing 1000 cycles. The employment of micron-structured p-Si improves cycling stability, which is primarily due to the porous space it provides. This porous structure helps alleviate the mechanical stress caused by volume expansion and prevents Si particles from detaching from the electrodes. The increased surface area facilitates a longer pathway for lithium-ion transport, thereby encouraging a more even distribution of lithium ions and mitigating the localized expansion of Si particles during cycling. Additionally, when Si particles expand, the hollow carbon nanospheres are capable of absorbing the resulting stress, thus preventing the electrode from cracking. The as-prepared p-Si utilizing metal-assisted chemical etching holds promising prospects as an anode material for lithium-ion batteries. Full article

Currently, new clean energy storage technology must be effective, affordable, and ecologically friendly so as to meet the diverse and sustainable needs of the energy supply. In this work, NiCo-LDH containing intercalated EG was successfully prepared within 210 s using an ultrafast microwave radiation technique. Subsequently, a series of characterization and systematic electrochemical tests were conducted to analyze the composition, structure, and energy storage mechanism of the NiCo-LDH material. The Ni:Co ratio of 5:5 results in the highest capacitance value of 2156 F/g at 1 A/g and an outstanding rate performance of 86.8% capacity retention rate at 10 A/g. The results demonstrated that the unique porous structure of NiCo-LDH and large layer spacing were conducive to more electrochemical reactions. Additionally, an electrochemical test was carried out on the NiCo-LDH as a hybrid supercapacitor electrode material, with NiCo-LDH-5:5 serving as the positive electrode and activated carbon as the negative electrode, the asymmetric supercapacitor can achieve a maximum energy density of 82.5 Wh kg⁻¹ and power density of 8000 W kg⁻¹. The NiCo-LDH-5:5//AC hybrid supercapacitors own 81.5% cycle stability and 100% coulombic efficiency after 6000 cycles at 10 A/g. Full article

SiO₂ has a much higher theoretical specific capacity (1965 mAh g⁻¹) than graphite, making it a promising anode material for lithium-ion batteries, but its low conductivity and volume expansion problems need to be improved urgently. In this work, pompon mum-like SiO₂/C nanospheres with the sandwich and porous nanostructure were obtained by using dendritic fibrous nano silica (DFNS) and glucose as matrix and carbon source, respectively, through hydrothermal, carbonization and etching operations. The influence of SiO₂ content and porous structure on its electrochemical performance was discussed in detail. The final results showed that the C/DFNS-6 with a SiO₂ content of 6 wt% exhibits the best electrochemical performance as a negative electrode material for lithium-ion batteries due to its optimal specific surface area, porosity, and appropriate SiO₂ content. C/DFNS-6 displays a high specific reversible capacity of 986 mAh g⁻¹ at 0.2 A g⁻¹ after 200 cycles, and 529 mAh g⁻¹ at a high current density (1.0 A g⁻¹) after 300 cycles. It also has excellent rate capability, with a reversible capacity that rises from 599 mAh g⁻¹ to 1066 mAh g⁻¹ when the current density drops from 4.0 A g⁻¹ to 0.2 A g⁻¹. These SiO₂/C specific pompon mum-like nanospheres with excellent electrochemical performance have great research significance in the field of lithium-ion batteries. Full article

Sugar industries generate substantial quantities of waste biomass after the extraction of sugar water from sugarcane stems, while biomass-derived porous carbon has currently received huge research attention for its sustainable application in energy storage systems. Hence, we have investigated waste sugarcane bagasse (WSB) as a cheap and potential source of porous carbon for supercapacitors. The electrochemical capacitive performance of WSB-derived carbon was further enhanced through hybridization with silicon dioxide (SiO₂) as a cost-effective pseudocapacitance material. Porous WSB-C/SiO₂ nanocomposites were prepared via the in situ pyrolysis of tetraethyl orthosilicate (TEOS)-modified WSB biomass. The morphological analysis confirms the pyrolytic growth of SiO₂ nanospheres on WSB-C. The electrochemical performance of WSB-C/SiO₂ nanocomposites was optimized by varying the SiO₂ content, using two different electrolytes. The capacitance of activated WSB-C was remarkably enhanced upon hybridization with SiO₂, while the nanocomposite electrode demonstrated superior specific capacitance in 6 M KOH electrolyte compared to neutral Na₂SO₄ electrolyte. A maximum specific capacitance of 362.3 F/g at 0.25 A/g was achieved for the WSB-C/SiO₂ 105 nanocomposite. The capacitance retention was slightly lower in nanocomposite electrodes (91.7–86.9%) than in pure WSB-C (97.4%) but still satisfactory. A symmetric WSB-C/SiO₂ 105//WSB-C/SiO₂ 105 supercapacitor was fabricated and achieved an energy density of 50.3 Wh kg⁻¹ at a power density of 250 W kg⁻¹, which is substantially higher than the WSB-C//WSB-C supercapacitor (22.1 Wh kg⁻¹). Full article

Optimized sustainable procedures in both acidic and basic conditions are considered to meet some of the current environmental challenges of the scientific community. In this paper, the successful syntheses of two classes of indium-based silica nanomaterials are reported. Both procedures were conceived to enhance the sustainability of the synthesis methods and promote their preparations at room temperature while avoiding the hydrothermal treatment under static conditions at 100 °C. A fast, room-temperature synthesis of porous nanospheres was conceived together with an “acid-free” procedure for SBA-15-like materials. Moreover, the isomorphic substitution of silicon with indium was achieved. All the materials were deeply characterized to probe their structural, textural and morphological properties (e.g., transmission electron microscopy, N₂ physisorption, ss MAS NMR of ²⁹Si). The high specific surface area and the mesoporosity were always preserved even under the mild reaction conditions employed. The honeycomb structure and the spherical morphology of SBA-15-like materials and nanospheres, respectively, were also observed. The insertion of indium was confirmed via X-ray photoelectron spectroscopy (XPS) investigations. Full article

Benefiting from their high surface areas, excellent conductivity, and environmental-friendliness, porous carbon nanospheres (PCSs) are of particular attraction for the anodes of lithium-ion batteries (LIBs). However, the regulation of carbon nanospheres with controlled pore distribution and graphitization for delivering high Li⁺ storage behavior is still under investigation. Here, we provide a facile approach to obtain PCSs with different microstructures via modulating the carbonization temperatures. With the processing temperature of 850 °C, the optimized PCSs exhibit an increased surface area, electrical conductivity, and enhanced specific capacity (202 mA h g⁻¹ at 2 A g⁻¹) compared to the PCSs carbonized at lower temperatures. Additionally, PCSs 850 provide excellent cyclability with a capacity retention of 83% for 500 cycles. Such work can pave a new pathway to achieve carbon nanospheres with excellent performances in LIBs. Full article