Search Results (96)

The rapid advancement of micro/nano-electromechanical systems (MEMS/NEMS) and precision manufacturing has fundamentally challenged traditional friction theories at the nanoscale. Classical continuum models fail to capture energy dissipation mechanisms at the atomic level, which are influenced by interfacial phenomena such as electron transfer, charge redistribution, and energy level realignment. Density functional theory (DFT), renowned for its accurate description of ground-state properties in many-electron systems, has emerged as a key tool for uncovering quantized friction mechanisms. By quantifying potential energy surface (PES) fluctuations, the evolution of interfacial charge density, and dynamic electronic band structures, DFT establishes a universal correlation between frictional dissipation and electronic behavior, transcending the limitations of conventional models in explaining stick–slip motion, superlubricity, and non-Amonton effects. Research breakthroughs in the application of DFT include characterizing frictional chemical potentials, designing heterojunction-based superlubricity, elucidating strain/load modulation mechanisms, and resolving electronic energy dissipation pathways. However, these advances remain scattered across interdisciplinary studies. This article systematically summarizes methodological innovations and cutting-edge applications of DFT in computational tribology, with the aim of constructing a unified framework for carrying out the “electronic structure–energy dissipation–frictional response” predictions. It provides a state of the art of using DFT to help design high-performance lubricants and actively control interfacial friction. Full article

Room-temperature (RT) gas sensors for nitrogen dioxide (NO₂) detection face persistent challenges, including reliance on high operating temperatures and inefficient charge carrier utilization under UV activation. To address these limitations, we engineered a p-n nano-heterojunction (NHJ) gas sensor by integrating p-type nickel oxide (NiO) nanoparticles onto n-type zinc oxide (ZnO) nanorods. This architecture leverages UV-driven carrier generation and interfacial electric fields at the NHJ to suppress recombination, enabling unprecedented RT performance. By optimizing thermal annealing conditions, we achieved a well-defined heterojunction with uniform NiO distribution on the top of the ZnO nanorods, validated through electron microscopy and X-ray photoelectron spectroscopy. The resulting sensor exhibits a 5.4-fold higher normalized response to 50 ppm NO₂ under 365 nm UV illumination compared to pristine ZnO, alongside rapid recovery and stable cyclability. The synergistic combination of UV-assisted carrier generation and heterojunction-driven interfacial modulation offers a promising direction for next-generation RT gas sensors aimed at environmental monitoring. Full article

This investigation aims to evaluate the biocompatibility and assess the cytotoxicity of synthesized ZnO/Ag heterojunction nanorods with commercially available root canal sealers in India. Among the commercially available root canal sealers, zinc oxide (ZnO) eugenol-based sealers are widely utilized as per Grossmann’s requirements. However, these ZnO eugenol-based sealers often experience solubility issues and tissue reactions in contact with periapical tissues. To overcome the inexplicable reactivity of ZnO eugenol-based sealers, nano ZnO and nano ZnO/Ag heterojunction materials have been developed via a wet-chemical approach and studied to assess their biocompatibility and cytotoxicity. The findings of our study revealed that nano ZnO/Ag heterojunction material possesses a higher degree of biocompatibility and low cytotoxicity as compared to conventional ZnO eugenol-based sealers, attributed to its high surface-to-volume ratio, the enhanced penetration of nanosized sealers into dentinal tubules, and the synergistic spillover sensitization effect of nano ZnO combined with Ag nanoclusters. From this comparative evaluation of root canal sealers, the usage of nano ZnO/Ag heterojunction materials was found to be significantly advantageous over commercial zinc oxide eugenol-based sealers and may find profound usage with a long shelf-life. Full article

Persistent reactive azo dyes released from textile finishing are a serious threat to water systems, but effective methods using sunlight to break them down are still limited. Everzol Yellow 3RS (EY-3RS) is particularly recalcitrant: past studies have relied almost exclusively on physical adsorption onto natural or modified clays and zeolites, and no photocatalytic pathway employing engineered nanomaterials has been documented to date. This study reports the synthesis, characterization, and performance of a visible-active ternary nanocomposite, Cu₄O₃/ZrO₂/TiO₂, prepared hydrothermally alongside its binary (Cu₄O₃/ZrO₂) and rutile TiO₂ counterparts. XRD, FT-IR, SEM-EDX, UV-Vis, and PL analyses confirm a heterostructured architecture with a narrowed optical bandgap of 2.91 eV, efficient charge separation, and a mesoporous nanosphere-in-matrix morphology. Photocatalytic tests conducted under midsummer sunlight reveal that the ternary catalyst removes 91.41% of 40 ppm EY-3RS within 100 min, markedly surpassing the binary catalyst (86.65%) and TiO₂ (81.48%). Activity trends persist across a wide range of operational variables, including dye concentrations (20–100 ppm), catalyst dosages (10–40 mg), pH levels (3–11), and irradiation times (up to 100 min). The material retains ≈ 93% of its initial efficiency after four consecutive cycles, evidencing good reusability. This work introduces the first nanophotocatalytic strategy for EY-3RS degradation and underscores the promise of multi-oxide heterojunctions for solar-driven remediation of colored effluents. Full article

Due to its persistence and potential negative effects on ecosystems and human health, microplastic pollution in aquatic environments has become a major worldwide concern. Photocatalytic degradation is a sustainable manner to degrade microplastics to non-toxic by-products. In this review, comprehensive discussion focuses on the synergistic effects of various photocatalytic materials including TiO₂, ZnO, WO₃, graphene oxide, and metal–organic frameworks for producing heterojunctions and involving multidimensional nanostructures. Such mechanisms can include the generation of reactive oxygen species and polymer chain scission, which can lead to microplastic breakdown and mineralization. The advancements of material modifications in the (nano)structure of photocatalysts, doping, and heterojunction formation methods to promote UV and visible light-driven photocatalytic activity is discussed in this paper. Reactor designs, operational parameters, and scalability for practical applications are also reviewed. Photocatalytic systems have shown a lot of development but are hampered by shortcomings which include a lack of complete mineralization and production of intermediary secondary products; variability in performance due to the fluctuation in the intensity of solar light, limited UV light, and environmental conditions such as weather and the diurnal cycle. Future research involving multifunctional, environmentally benign photocatalytic techniques—e.g., doped composites or composite-based catalysts that involve adsorption, photocatalysis, and magnetic retrieval—are proposed to focus on the mechanism of utilizing light effectively and the environmental safety, which are necessary for successful operational and industrial-scale remediation. Full article

Nano-titanium dioxide (TiO₂) is currently the most widely studied photocatalyst. However, its rapid recombination of photogenerated carriers and narrow range of light absorption have limited its development. Crystal form regulation and polymer modification are important means for improving the photocatalytic activity of single-phase materials. In this paper, TiO₂ materials of different crystal forms were prepared by changing the synthesis conditions, and they were compounded with trimesoyl chloride–melamine polymers (TMPs) by the hydrothermal synthesis method. Then, their photocatalytic performance was evaluated by degrading methylene blue (MB) under visible light. The mechanisms of influence of TiO₂ crystal form on the photocatalytic activity of TiO₂-TMP were explored by combining characterization and theoretical calculation. The results showed that the TiO₂ crystal form, through interface interaction, the built-in electric field intensity of the heterojunction, and active sites, affected the interface charge separation and transfer, thereby influencing the photocatalytic activity of TiO₂-TMP. In the 4T-TMP photocatalytic system, the degradation rate of MB was the highest. These studies provide theoretical support for understanding the structure–property relationship of the interfacial electronic coupling between TiO₂ crystal forms and TMP, as well as for developing more efficient catalysts for pollutant degradation. Full article

In this study, we detailed the fabrication and characterization of photovoltaic structures based on PTB7:ICBA (1:1, wt.%) bulk-heterojunction on optical glass substrates by spin-coating. Some samples were deposited on a flat substrate, and others were placed on a patterned substrate obtained by nano-imprinting lithography; the induced effects were analyzed. We demonstrated that using a patterned substrate enhanced the maximum output power, primarily because the short-circuit current density increased. This can be considered a direct consequence of reduced optical reflection and improved optical absorption. The topological parameters evaluated by atomic force microscopy, namely, the root mean square, Skewness, and Kurtosis, had small values of around 2 nm and 1 nm, respectively. This proves that the mixture of a conductive polymer and a fullerene derivative creates a thin film network with a high flatness degree. The samples discussed in this paper were fabricated and characterized in air; we can admit that the results are encouraging, but further optimization is needed. Full article

Ammonia (NH₃) is a common agricultural gas, and its accurate detection is critical to agricultural production. In this study, nano-CuO/CeO₂ composites were prepared to achieve a wide range of ammonia detection at room temperature. Characterization data verified the composite heterojunction structure of CuO/CeO₂, which demonstrates an outstanding large specific surface area for ammonia detection. It provides more active sites for NH₃ molecules, which brings a very high response to ammonia (70.3% @100 ppm NH₃), a large detection range (0.5–200 ppm NH₃), and a fast response/recovery time (13 s/17 s @20 ppm NH₃). Systematic testing showed that the nano-CuO/CeO₂ composites also exhibit excellent extended-term stability and selectivity. Further studies showed that the p-n heterojunction structure of CuO/CeO₂ allowed the composite to retain its gas-sensitive properties to ammonia, in addition to the improved ammonia-detection range of the composite based on the synergistic effect of these two materials. The mechanism of CuO/CeO₂ heterojunction nanocomposites towards ammonia detection was also elucidated from a microscopic perspective at the molecular level. Finally, a triboelectric nanogenerator (TENG) that can be driven by wind power has been prepared, upon which the feasibility of the combination of the TENG and the ammonia sensor to realize environmental monitoring was investigated. Full article

The use of fibers or fabrics as frameworks for loading photocatalysts is beneficial in solving the problems of photocatalytic nanomaterials, which tend to agglomerate and are difficult to recycle. In this study, Bi₂WO₆/CFb and Bi₂WO₆/Bi₂S₃/CFb photocatalytic fibers rich in oxygen vacancies were prepared using carbon fibers as the framework by the crystal seed attachment method and in situ growth method by using the self-polymerization and strong adhesion properties of dopamine. The results of SEM, TEM and XRD tests showed that Bi₂WO₆ and Bi₂WO₆/Bi₂S₃ nanosheets were uniformly and completely encapsulated on the surface of the carbon fibers. The results of XPS and EPR tests showed that Bi₂WO₆ nanosheets were rich in oxygen vacancies. The PL, transient photocurrent responses and EIS results showed that the introduction of Bi₂S₃ significantly improved the migration efficiency of the photogenerated carriers of Bi₂WO₆/Bi₂S₃/CFb, which effectively hindered the recombination of photogenerated electron–hole pairs. By conducting degradation experiments on p-nitrophenol and analyzing the bandgap structure, it was postulated that the heterojunction structure of Bi₂WO₆/Bi₂S₃/CFb in the Bi₂WO₆/Bi₂S₃ material was not Type-II but Z-scheme. As analyzed by the active species assay, the active species that played a major role in the degradation process were O₂⁻ and h⁺. The incorporation of a small amount of Bi₂S₃ resulted in enhanced photocatalytic degradation activity of Bi₂WO₆/Bi₂S₃/CFb toward tetracycline hydrochloride compared to Bi₂WO₆/CFb. The excellent photocatalytic performance of Bi₂WO₆/Bi₂S₃/CFb photocatalytic fibers can be attributed to the rapid transmission and separation performance and the high oxidation and reduction capacities of photogenerated electron–hole pairs formed by direct Z-scheme heterojunctions. Full article

Enhancing the performance of organic solar cells (OSCs) is essential for achieving sustainability in energy production. This study presents an innovative strategy that involves fine-tuning the thickness of the bulk heterojunction (BHJ) photoactive layer at the nanoscale to improve efficiency. The organic blend D18:L8-BO is utilized to capture a wide range of photons while addressing the challenge of minimizing optical losses from low-energy photons. The research incorporates SnO₂ and ZnO as electron transport layers (ETLs), with PMMA functioning as a hole transport layer (HTL). A comprehensive analysis of photon absorption, charge carrier generation, localized energy fluctuations, and thermal stability reveals their critical role in enhancing the efficiency of D18:L8-BO active films. Notably, introducing SnO₂ as an ETL significantly decreased losses and modified localized energy, achieving an impressive efficiency of 19.85% at an optimized blend thickness of 50 nm with low voltage loss (ΔV_oc) of 0.4 V within a J_sc of 28 mA cm⁻² by performing an optoelectronic simulation employing “Oghma-Nano 8.1.015” software. In addition, the SnO₂-based structure conserved 88% of the PCE at 350 K compared to room temperature PCE, which describes the high thermal stability of this structure. These results demonstrate the potential of this methodology in improving the performance of OSCs. Full article

Photodegradation of antibiotics based on photocatalytic semiconductors is a promising option to alleviate water pollution. Despite its limitations, TiO₂-based photocatalysts are still the most widely studied materials for pollutant degradation. In this work, a pomegranate-like g-C₃N₄/C/TiO₂ nano-heterojunction was constructed using the hydrothermal–calcination method, consisting of interconnected small crystals with a dense structure and closely contacted interface. Low-crystallized carbon filled the gap between TiO₂ and g-C₃N₄, forming a large interface. The local in-plane heterostructures generated by C/g-C₃N₄ are further improved for carrier transport. As expected, the optimal sample calcined at 300 °C (GTC-300) efficiently eliminated tetracycline hydrochloride (TC-HCl, 20 mg L⁻¹), achieving a removal rate of up to 92.9% within 40 min under full-spectrum irradiation and 87.8% within 60 min under the visible spectrum (λ > 400 nm). The electron mediator, low-crystallized carbon, successfully promoted the formation of new internal electric fields via the widespread heterojunction interface, which accelerated the separation and migration of photogenerated carriers between g-C₃N₄ and TiO₂. These results confirm that the g-C₃N₄/C/TiO₂ nano-heterojunction exhibited outstanding photodegradation performance of TC-HCl. The electron mediator shows great potential in promoting carrier transfer and enhancing photocatalytic performance of heterogeneous photocatalysts in water treatment. Full article

This study investigates the effects of varying indium tin oxide (ITO) layer thicknesses and the patterning of the ITO layer on the growth of metallic gold (Au) nano- and microstructures on titanium dioxide (TiO₂) templates. The ITO-TiO₂ heterojunction serves to collect photogenerated electrons in the ITO sublayer, facilitating their transport to the pattern edges and concentrating photocatalytic activity at these edges. Six template types were fabricated on glass substrates, with systematic variations in ITO thickness (0, 3, 6, 10, and 30 nm) and different ITO patterning methods (either continuous or patterned with the TiO₂ layer). Photocatalytic gold growth was carried out on each of the substrates, and morphological analysis was conducted using scanning electron microscopy (SEM). Results showed that a 6 nm ITO layer beneath a 70 nm TiO₂ layer yielded the most uniform gold lines, characterized by 3D flower-shaped structures and enhanced edge growth. Conductance measurements indicated a value of 23 mS, suggesting potential applications in bio-inspired electronics. These findings provide insights into optimizing gold structure growth for advanced neuromorphic devices. Full article

In this work, the optical and electronic characteristics of MoS₂(n,n) and MoSe₂(n,n) nanotubes and 1D van der Waals nanoheterostructures based on them are determined from first principles. It is shown that with an increase in the diameters of MoS₂(n,n) and MoSe₂(n,n) nanotubes, their bandgaps increase (in MoS₂(n,n), the gap varies from 0.27 eV to 1.321 eV, and in MoSe₂(n,n) from 0.153 eV to 1.216 eV). It was found that with an increase in the diameter of the nanotubes, the static permittivity decreases; van der Waals nanostructures of MoS₂(8,8)@MoSe₂(16,16) and MoS₂(6,6)@MoSe₂(14,14) consisting of coaxially compound MoS₂(8,8) and MoSe₂(16,16), MoS₂(6,6) and MoSe₂(14,14), respectively, have high static dielectric permittivitiesof 6. 5367 and 3.0756. Such nanoheterostructures offer potential for developing various nanoelectronic devices due to the possibility of effective interaction with an electric field. Studies revealed that the van der Waals nanostructures MoSe₂(6,6)@MoS₂(14,14) and MoSe₂(8,8)@MoS₂(16,16) exhibit a semiconductor nature with bandgap widths of 0.174 eV and 0.53 eV, respectively, and MoS₂(6,6)@MoSe₂(14,14) and MoS₂(8,8)@MoSe₂(16,16) exhibit metallic properties. Stepped areas of Coulomb origin with a constant period at a voltage of 0.448 V appear on the current–voltage characteristic of the van der Waals nanoheterodevices. It is found that MoSe₂(6,6)@MoS₂(14,14) and MoSe₂(8,8)@MoS₂(16,16) nanodevices transmit electric current preferentially in the forward direction due to the formation of a nanoheterojunction between semiconductor nanotubes with different forbidden band values. The fundamental regularities obtained during the study can be useful for the further development of electronic components of nano- and microelectronics. Full article

Ultraviolet (UV) photodetectors (PDs) are characterized by wide wavelength selectivity and strong anti-interference capability. The focus of research is not only limited to the adjustment of the structure composition, but it also delves deeper into its working mechanism and performance optimization. In this study, a heterojunction self-powered photodetector with a unique honeycomb structure was successfully constructed by combining the advantages of two semiconductor materials, zinc oxide (ZnO) and nickel oxide (NiO), using magnetron sputtering and hydrothermal synthesis. The detector has high responsivity, high detectivity and favorable spectral selectivity under UV irradiation. The nearly 10-fold increase in responsivity and detectivity of the detector with the introduction of the honeycomb structure under zero-bias conditions is attributed to the macroporous structure of the ZnO honeycomb nano-mesh, which increases the surface active sites and facilitates the enhancement of light trapping. This study provides significant value to the field of UV detection by improving detector performance through structural optimization. Full article

Imidacloprid (IMI), a widely used neonicotinoid pesticide, has led to significant water contamination due to excessive use. As a result, there is an urgent need for effective and straightforward methods to remove IMI residues from water. Photocatalytic technology, an integral part of advanced oxidation processes, is particularly promising due to its renewability, high catalytic efficiency, fast degradation ratio, and cost-effectiveness. This review systematically examines recent progress in the photocatalytic degradation of imidacloprid in aqueous solutions using various solid catalysts. It provides a comparative analysis of key factors affecting catalytic performance, such as catalyst synthesis methods, reaction times, catalyst loading, and IMI concentrations. Among the solid catalysts studied, nano-ZnO achieved a higher degradation rate of IMI in a shorter period and with a reduced catalyst dosage, reaching approximately 95% degradation efficiency within one hour. Additionally, this review explores the types of heterojunctions formed by the catalysts and elucidates the mechanisms involved in the photocatalytic degradation of IMI. In conclusion, this review offers a comprehensive evaluation of solid catalysts for the photocatalytic removal of IMI from water, serving as an important reference for developing innovative catalysts aimed at eliminating organic pollutants from aquatic environments. Full article