Focus on Advanced Nanomaterials for Energy, Environmental Science and Optoelectronic Devices

Gold nanoparticles (Au-NPs) are readily used nanoparticles which finds applications in fields like biosensors, drug delivery, optical bioimaging and many state of art systems used for detection. In the recent years fiber optic sensors have seen utilization of Au-NPs along with other nanoparticles for implementation of sensors for sensing various biomolecules like cholesterol, glucose, and uric acid. The cancer cells, creatinine and bacteria can also be detected with the fiber optic sensors. Given the significance of Au-NPs in fiber optic sensors, the current work is a review of the synthesis, the common methods used for characterization, and the applications of Au-NPs. It is important to discuss and analyse the work reported in the literature to understand the trend and gaps in developing plasmonic optical fiber sensors.

The design of electrocatalysts with excellent activity and stability for overall water splitting is highly desirable, and remains a challenge. Constructing heterojunctions onto the same substrate is beneficial for the integration of a water-splitting reaction. Herein, self-supported IrNi/Ni(OH)₂@PPy and IrNi/Ni(OH)₂@FeOOH are fabricated by coupling polypyrrole (PPy) and iron oxyhydroxide (FeOOH) on IrNi/Ni(OH)₂ nanosheets array, respectively. Benefiting from the nanosheet structure, composition, and heterogeneous interface, the as-constructed IrNi/Ni(OH)₂@PPy and IrNi/Ni(OH)₂@FeOOH catalysts can efficiently drive the hydrogen evolution reaction and oxygen evolution reaction, respectively. Moreover, the electrolyzer consisting of IrNi/Ni(OH)₂@PPy and IrNi/Ni(OH)₂@FeOOH for water splitting requires only a low cell voltage of 1.49 V to deliver 10 mA cm⁻². This study provides a useful strategy for constructing efficient electrocatalysts by synergistic composition modulation and interface engineering.

Photocatalytic water splitting is a promising method for hydrogen production, and the search for efficient photocatalysts has received extensive attention. Two-dimensional van der Waals (vdW) heterostructures have recently been considered excellent candidates for photocatalytic water splitting. In this work, a BP-MoSe₂ vdW heterostructure composed of a blue phosphorus (BP) and MoSe₂ monolayer was studied as a potential photocatalyst for water splitting using first-principles calculations. The results show that the heterostructure has a type-II band structure, and the band edges straddle water redox potentials under biaxial strains from −3% to 2%, satisfying the requirements for photocatalytic water splitting. In addition, the heterostructure has excellent power conversion efficiency (PCE) and strong optical absorption in both visible light and near-ultraviolet region, indicating that it is a very promising candidate for photocatalytic water splitting. Specifically, the PCE was enhanced to ∼20.2% under a tensile strain of 2%. The Gibbs free energy profiles indicate that BP-MoSe₂ vdW heterostructure exhibits good catalytic performance in hydrogen and oxygen evolution reactions. In particular, high carrier mobility implies that the transfer of carriers to reactive sites is easy, and the recombination probability of photogenerated electron–hole pairs is reduced.

Interface engineering of two-dimensional (2D) materials by conductive polymer modification is one of the valid methods to promote hydrogen evolution reaction (HER) performance. Herein, we report a simple and universal strategy for the synthesis of polypyrrole (PPy) modified Rh metallene (Rh@PPy metallene) towards an efficient pH-universal HER. Due to the unique ultrathin 2D metallene structure and the optimized electronic structure between the metallene-PPy surfaces, the as-prepared Rh@PPy metallene not only exhibits excellent HER activity with low overpotentials of 16, 39 and 42 mV in 0.5 M H₂SO₄, 1 M KOH, and 1 M phosphate buffer solution at current density of 10 mA cm⁻², but also displays outstanding stability and durability. This work provides a well-founded pathway to constructe metallene-organic interfaces for various electrocatalytic applications.

Heterostructure BiVO₄/Bi₂O₃ nanocomposites with enhanced visible light activity are effectively synthesized through an easiest and single step hydrothermal route, using bismuth subnitrate and ammonium meta-vanadate as main raw materials in existence of citric acid. The phase and surface structure, topography and optical properties of synthesized composites are characterized by XRD, SEM, EDX, FTIR, UV–Visible and PL spectroscopy. It was found that 5%BiVO₄/Bi₂O₃ (BOBV-5) nanocomposite exhibit excellent photocatalytic performance for rhodamine B dye degradation and tetracyclic under irradiation of visible light as compared to single component i.e. BiVO₄. The increased photocatalytic activity should be ascribed for making p–n heterojunction among p-type Bi₂O₃ and n-type BiVO₄. This p–n heterojunction successfully reduce the recombination of photogenerated charge carriers. Furthermore, the BOBV-5 novel photocatalyst shows good stability in constructive five cycles and photocatalytic activity is best for conquering photo corrosion of a photocatalysts. To explain charge migration route, whole photocatalytic mechanism was described in terms of energy band structures. Furthermore, the present work is helpful effort for design of new visible light photocatalytic materials with heterojunction structures.

Thermally oxidized MWCNTs (OMWCNTs) are fabricated by a thermal treatment of MWCNTs at 500 °C for 3 h in an oxygen-containing atmosphere. The oxygen content of OMWCNTs increases from 1.9 wt% for MWCNTs to 8.3 wt%. And the BET specific surface area of OMWCNTs enhances from 254.2 m² g⁻¹ for MWCNTs to 496.1 m² g⁻¹. The Fe₂O₃/OMWCNTs nanocomposite is prepared by a hydrothermal method. Electrochemical measurements show that Fe₂O₃/OMWCNTs still keeps a highly reversible specific capacity of 653.6 mA h g⁻¹ after 200 cycles at 0.5 A g⁻¹, which shows an obviously higher capacity than the sum of that of single Fe₂O₃ and OMWCNTs. The OMWCNTs not only buffer the volume changes of Fe₂O₃ nanoparticles but also provide high-speed electronic transmission channels in the charge–discharge process. The thermal oxidation method of OMWCNTs avoids using strong corrosive acids such as nitric acid and sulfuric acid, which has the advantages of safety, environmental protection, macroscopic preparation, etc.

Self-sufficient power sources provide a promising application of abundant electronic devices utilized in detection of ambient properties. Recently, triboelectric nanogenerators (TENGs) have been widely investigated to broaden the self-powered systems by converting the ambient mechanical agitations into electrical voltage and current. Graphene oxide (GO), not only for sensing applications but also as a brilliant energy-related nanomaterial, provides a wide range of controllable bandgap energies, as well as facile synthesis route. In this study, GO-based self-powered photodetectors have been fabricated by conflating the photosensitivity and triboelectric characteristics of freestanding GO paper. In this regard, photodetection via TENGs has been investigated in two forms of active and passive circuits for ultraviolet (UV) and visible illumination. The photodetector responsivity upon UV enhanced from 0.011 mA W⁻¹ for conventional GO-photoresistors up to 13.41 mA W⁻¹ by active photodetection setup. Moreover, applying the active-TENG improved the efficiency from 0.25% (in passive TENG) to 4.21%. Our findings demonstrate that active TENGs might enable materials with insignificant optical response to represent considerably higher light-sensitivity by means of synergizing the effect of TENG output changes with opto-electronical properties of desired layers.

Solar-driven photoelectrochemical (PEC) water splitting for hydrogen generation is regarded as a sustainable strategy to relieve fossil resource issue. However, its PEC conversion efficiency still suffers from the low light absorption and high electron–hole recombination. Herein, we report 1D/2D hierarchical heterostructured photoelectrode constructed by ordered ZnO nanorod array and intimately attached ultra-thin Hematene (thickness of monolayer: 1–2 nm) for effective PEC water oxidation with visible light irradiation. The onset potential of Hematene/ZnO NRs photoanode (0.28 V versus RHE) for PEC water oxidation has an obvious negative shift compared with that of ZnO NRs (0.32 V versus RHE) indicating the enhanced PEC kinetics. Furthermore, reduced charge transport resistance (18.82 KΩ cm⁻²), a high carrier density of 9.03 × 10¹⁸ cm⁻³ and the resulting significantly enhanced incident photon-to-current efficiency enhancement compared with ZnO NRs photoanode were obtained for Hematene/ZnO NRs photoanode. All these were ascribed to the formation of large built-in electric field which was arising from the charge redistribution at the ZnO and Hematene interface, and the band alignment engineering between the components. In summary, such interfacial engineering may inspire the future development of 1D/2D hierarchical heterostructured photoanodes in the field of PEC water splitting.

Photo-controlled fluorescent switching is of great utility in fluorescence sensors, reversible data storage, and logic circuit, based on their modifiable emission intensity and spectra. In this work, a novel photo-controlled reversible fluorescent switching system was constructed based on photochromic diarylethene (DT) molecular modified fluorescent carbon dots (CDs). The fluorescent CDs acted as fluorescent donors and the photochromic diarylethene molecular functioned as acceptors in this fluorescent switching system. The fluorescence modulation efficiency of the fluorescent switching was determined to be 97.1%. The result was attributable to Förster resonance energy transfer between the CDs and the diarylethene molecular. The fluorescent switching could undergo 20 cycles without significant decay.

The layered hybrid double perovskites emerged as excellent semiconductor materials owing to their environment compatibility and stability. However, these materials are weakly luminescent, and their photoluminescence (PL) properties can be modulated via doping. While Mn²⁺ doping in perovskites is well known, but to the best of our knowledge the doping of Mn²⁺ in layered double perovskites (LDPs) is yet to be explored. Herein, for the first time, we demonstrate the doping of Mn²⁺ in hybrid inorganic-organic two-dimensional (2D) LDPs, (BA)₄AgBiBr₈ (BA = n-butyl amine) via a simple solid-state mechanochemical route. The powder x-ray diffraction pattern, and electron paramagnetic resonance analysis confirm the successful incorporation of Mn²⁺ ions inside (BA)₄AgBiBr₈ lattice. The Mn²⁺ doped 2D LDP shows energy transfer from host excitons to d-electrons of Mn²⁺ ions, which results in red-shifted broad Mn²⁺ emission band centered at 625 nm, attributed to the spin-forbidden⁴T₁ to ⁶A₁ internal transition. This work opens up new possibilities to dope metal ions in 2D LDPs to tune the optical as well as magnetic properties.

In this paper, we have developed a ‘phosphine-free’ method for synthesising copper telluride nanocrystals using diphenyl ditelluride as an air-stable tellurium source. The diphenyl ditelluride is shown to have optimal reactivity for the colloidal synthesis of Cu₂Te, allowing optimal control over the phase and morphology. Using this unexplored Te precursor for copper telluride synthesis, 1D nanorods of hexagonal phase (Cu₂Te) were synthesised at a moderate temperature of 180 °C. The precise control over key parameters for this system results in Cu_2−xTe nanocrystals forming with varied shapes (1D nanorods and 2D nanoplates), sizes, and crystal phases (hexagonal Cu₂Te and orthorhombic Cu_1.43Te).

Aqueous zinc-ion batteries (ZIBs) is a potential energy storage system due to its advantages of low cost, good safety, and high theoretical capacity (820 mAh g⁻¹). However, the lack of cathode materials with long cycle stability severely restricts the development of ZIBs. In this paper, V₂O₅/ NaV₆O₁₅ nanocomposites are synthesized by molten salt method in one step and used as cathode material for ZIBs, which have good electrochemical performances. The specific capacity of the materials remain 160 mAh g⁻¹ when the current density is 0.5 A g⁻¹ after 1000 cycles, and the capacity retention rate is 102.03% when the current density is 5 A g⁻¹ for 1000 cycles. This is mainly due to the large number of active sites generated by crystal defects and the synergistic interaction between the dual-phase materials, which reduces the stress of ions inserted/extracted during the Zn²⁺ storage process and improves the electrochemical performance.

Two-dimensional (2D) cobalt zeolitic imidazolate frameworks (ZIF-67) have attracted significant research interests to synthesize cobalt and nitrogen co-doped carbon-based (Co–N–C) catalyst for oxygen reduction reaction (ORR). However, most of the current synthetic approaches of 2D ZIF-67 are energy-intensive, environmentally hazardous and low-yield. Herein, a feasible and efficient ‘morphology-retaining method via a high-pressure vapor-solid reaction’ are reported to synthesize 2D ZIF-67 nanosheets by using 2D cobalt carbonate hydroxide template. In the strategy, the high-pressure vapor caused by sublimation of 2-Melm and the pores formed from effusion of CO₂ during transformation ensure the complete transformation from 2D template to 2D ZIF-67. The corresponding 2D Co–N–C catalyst exhibits comparable ORR electrocatalytic activity and better stability than Pt/C in alkaline media. The present method is expected to offer a feasible and universal way to efficiently synthesize 2D M–N–C catalysts.

The MnO/C composites were obtained by co-precipitation method, which used Mn₃O₄ nanomaterials as precursors and dopamine solution after ultrasonic mixing and calcination under N₂ atmosphere at different temperatures. By studying the difference of MnO/C nanomaterials formed at different temperatures, it was found that with the increase of calcination temperature, the materials appear obvious agglomeration. The optimal calcination temperature is 400 °C, and the resulting MnO/C is a uniformly dispersed slender nanowire structure. The specific capacitance of MnO/C nanowires can reach 356 F g⁻¹ at 1 A g⁻¹. In the meantime, the initial capacitance of MnO/C nanowires remains 106% after 5000 cycles. Moreover, the asymmetric supercapacitor was installed, which displays a tremendous energy density of 30.944 Wh kg⁻¹ along with a high power density of 10 kW kg⁻¹. The composite material reveals a promising prospect in the application of supercapacitors.

We report the fabrication of binder-free, low-cost and efficient hybrid supercapacitive electrode based on the hexagonal phase of two-dimensional MoS₂ nanoworms reinforced with molybdenum nitride nanoflakes deposited on stainless steel (SS) substrate using reactive magnetron sputtering technique. The hybrid nanostructured MoS₂–Mo₂N/SS thin film working electrode delivers a high gravimetric capacitance (351.62 F g⁻¹ at 0.25 mA cm⁻²) investigated in 1 M Na₂SO₄ aqueous solution. The physisorption/intercalation of sodium (Na⁺) ions in electroactive sites of MoS₂–Mo₂N composite ensures remarkable electrochemical performance. The deposited porous nanostructure with good electrical conductivity and better adhesion with the current collector demonstrates a high-energy density of 82.53 Wh kg⁻¹ in addition to a high-power density of 24.98 kW kg⁻¹. Further, excellent capacitance retention of 93.62% after 4000 galvanostatic charge–discharge cycles elucidated it as a promising candidate for realizing high-performance supercapacitor applications.

The averaged power conversion efficiency of polyelectrolytes (P3CT-Na) based MAPbI₃ solar cells can be increased from 14.94% to 17.46% with a wetting method before the spin-coating process of MAPbI₃ precursor solutions. The effects of the wetting process on the surface, structural, optical and excitonic properties of MAPbI₃ thin films are investigated by using the atomic-force microscopic images, x-ray diffraction patterns, transmittance spectra, photoluminescence spectra and Raman scattering spectra. The experimental results show that the wetting process of MAPbI₃ precursor solution on top of the P3CT-Na/ITO/glass substrate can be used to manipulate the molecular packing structure of the P3CT-Na thin film, which determines the formation of MAPbI₃ thin films.

All inorganic perovskite nanocrystals CsPbX₃(X = Cl, Br, I) are the great potential candidates for the application of high-performance light emitting diodes (LED) due to their high Photoluminescence Quantum Yield (PLQY), high defect tolerance, narrow full-width half-maximum and tunable wavelength of 410–700 nm. However, the application of red-emitting (630–650 nm) CsPbBr_xI_3-x nanocrystals are perplexed by phase segregation due to the composition of mixed halides and the difference in halide ion mobility. Herein, we provide an effective strategy to suppressing the migration of Br/I ions through Ni²⁺ doping via a facile Hot-Injection method and the PLQY was improved as well. DFT calculations show that the introduction of Ni²⁺ causes a slight contraction of the host crystal structure, which improves the bond energy between Pb and halides and reduces the level of surface defects. Therefore, the phase stability is improved by Ni²⁺ doping because the phase segregation caused by ion migration in the mixed phase is effectively inhibited. Meanwhile, the non-radiative recombination in the exciton transition process is reduced and the PLQY is improved. What’s more, benefiting from the suppressed ion migration and enhanced PLQY, we combine the Ni²⁺-doped CsPbBr_xI_3-x nanocrystals with different Br/I ratios and YAG: Ce³⁺ phosphors as color conversion layers to fabricate high efficiency WLED. When the ratio of Br/I is 9:11, WLED has a color coordinate of (0.3621, 0.3458), the color temperature of 4336 K and presents a high luminous efficiency of 113.20 lm W⁻¹, color rendering index of 94.9 under the driving current of 20 mA and exhibits excellent stability, which shows great potential in the application of LED.

Metal sulfides are often used as cathode materials for lithium-ion batteries (LIBs) owing to their high theoretical specific capacity; however, excessively fast capacity decay during charging/discharging and rapid shedding during cycling limits their practical application in batteries. In this study, we proposed a strategy using plasma treatment combined with the solvothermal method to prepare cobalt sulfide (Co_1−xS)-carbon nanofibers (CNFs) composite. The plasma treatment could introduce oxygen-containing polar groups and defects, which could improve the hydrophilicity of the CNFs for the growth of the Co_1−xS, thereby increasing the specific capacity of the composite electrode. The results show that the composite electrode present a high discharge specific capacity (839 mAh g⁻¹ at a current density of 100 mA g⁻¹) and good cycle stability (the capacity retention rate almost 100% at 2000 mA g⁻¹ after 500 cycles), attributing to the high conductivity of the CNFs. This study proves the application of plasma treatment and simple vulcanization method in high-performance LIBs.

Magnetic force microscopy (MFM) is utilized to characterize the magnetic moment in nanostructured plant leaf-derived graphene quantum dot clusters (GQDCs). The MFM signal reveals that the magnetic response of the GQDCs depends on the height and width of the GQDCs. However, individual GQDs, and smaller clusters with widths of less than 20 nm, have not shown any observable magnetic signal. Importantly, experimental analyses suggest that the magnetic signal of GQDCs distributed in a plane can be effectively detected at room temperature. These results could pave the way for future graphene-based magnetic storage media and spin manipulation quantum devices.

Zinc oxide (ZnO) nanorod thin films were prepared by CBD onto glass and FTO/glass substrates. Silver (Ag) nanoparticles were synthesized on the surface of the prepared ZnO nanorod thin films using electrochemical methods. The scanning electron microscopy images of the Ag/ZnO/glass core/shell nanostructure confirmed that the average particles size is 20 nm while it was 41 nm for Ag NPs that synthesized onto ZnO/FTO NRs. The photocatalytic activity of the prepared Ag/ZnO core/shell nanostructure was studied by analyzing the degradation of methylene blue (MB) dye under visible light. Various pH values (6 and 10) and exposure time (30–240) min were controlled to investigate the photocatalytic activity of as-prepared Ag/ZnO core/shell nanostructure and that annealed at 200 °C and 300 °C for 1 h. It was observed that when the pH was 6, the degradation rate increased with the annealing temperature and irradiation time reaching 51% at the annealing temperature of 300 °C and exposure time of 240 min. In other hands, when the pH was 10, and the sample was annealed at 200 °C, it showed a good degradation rate of 100% at the irradiation time of 90 min. By contrast, the sample annealed at 300 °C required 180 min to degrade the MB dye completely. The photoelectrochemical cell measurement based on photocurrent density revealed a slight response to light. Cycle voltammetry (CV) measurement was conducted, and the CV curves of the Ag/ZnO core/shell electrodes indicated nonfaradaic and pseudocapacitance behavior. The electrodes showed nearly rectangular CV curves, which indicated the dominance of the nonfaradaic capacitance behavior. The specific capacitance of the electrodes remained at approximately 99%. Mott–Schottky analysis revealed that the semiconductor was an n-type with dependence on flat band potential V_FB deviation in the negative direction.

Here, a relative simpler and lower cost method, ion beam sputtering deposition was applied to fabricate diluted magnetic Mn_xGe_1−x quantum dots (QDs). The effects of Ge–Mn co-deposition amount on the morphology and crystallization of Mn_0.03Ge_0.97 QDs were investigated systematically by employing the atomic force microscopy and Raman spectroscopy techniques. It can be seen that the morphology, density, and crystallinity of Mn_0.03Ge_0.97 QDs exhibit unique evolution processes with the increase of Ge–Mn co-sputtering amount. The optimal deposition amount for realizing well size-uniform, large-aspect-ratio, and high-density QDs is also determined. The unique evolution route of diluted magnetic semiconductor QDs and the amount of co-sputtering are also discussed sufficiently.