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Establishing highly effective charge transfer channels in carbon nitride (g-C3N4) to enhance its photocatalytic activity is still a challenging issue. Herein, the delaminated 2D Ti3C2 MXene nanosheets were employed to decorate the P-doped tubular g-C3N4 (PTCN) for engineering 1D/2D Schottky heterojunction (PTCN/TC) through electrostatic self-assembly. The optimized PTCN/TC exhibited the highest hydrogen evolution rate (565 μmol/h/g), which was 4.3 and 2.0 -fold higher than pristine bulk g-C3N4 and PTCN, respectively. Such enhancement may be primarily attributed to the phosphorus heteroatom doped and unique structure of 1D/2D g-C3N4/Ti3C2 Schottky heterojunction, enhancing the light-harvesting and charges’ separation. One-dimensional pathway of g-C3N4 tube and built-in electric field of interfacial Schottky effect can significantly facilitate the spatial separation of photogenerated charge carriers, simultaneously inhibit their recombination via Schottky barrier. In this composite, metallic Ti3C2 was served as electrons sink and photons collector. Moreover, ultrathin Ti3C2 flake with exposed terminal metal sites as a co-catalyst exhibited higher photocatalytic reactivity in H2 evolution compared to carbon materials (such as reduced graphene oxide). This work not only proposed the mechanism of tubular g-C3N4/Ti3C2 Schottky junction in photocatalysis, but also provided a feasible way to load ultrathin Ti3C2 as a co-catalyst for designing highly efficient photocatalysts.

Photocatalytic oxidation of toxic pollutants is a proficient technique to solve the problems associated with the treatment of bisphenol-A which is classified as 1B reprotoxic substance. In this paper, Ag2C2O4/Ag@GNS nanocomposite whereas Ag and graphene nanosheets (GNS) used as the charge carriers, which is combined through peroxymonosulfate (PMS) for the removal of bisphenol-A (BiP-A) for the first time. The XRD, UV-DRS, SEM, and TEM studies were performed to confirm the phase structure and the purity. Ag2C2O4/Ag@GNS nanocomposite exhibited superior photocatalytic performance and removal rate when compared with pure Ag2C2O4 and pure GNS. In Ag2C2O4/Ag@GNS photocatalyst, the deposited Ag on the surface of Ag2C2O4 rods effectively formed a metal and semiconductor heterostructure, thus photogenerated charge carriers were separated easily by the surface plasmon resonance effect (SPR) effect of noble Ag. Hence charge carriers lifetime has been extended to a great extent for the better photocatalytic performance. The experimental results confirmed that the O2−, OH, SO4− radicals were played major role in the photolysis process. Furthermore, the effect of the photocatalyst & PMS concentration, pH and co-existing ions towards the BiP-A degradation were studied in detail. According to the mass spectroscopy studies BiP-A pollutant was effectively deteriorated into smaller molecules and CO2, H2O. Furthermore, we have proposed the possible degradation pathway and photocatalytic mechanism for better understanding.

The g-C3N4/BiOI/CdS double Z-scheme heterojunction photocatalyst with I3−/I− redox pairs is prepared using simple calcination, solvothermal, and solution chemical deposition methods. The photocatalyst comprised mesoporous, thin g-C3N4 nanosheets loaded on flower-like microspheres of BiOI with CdS quantum dots. The g-C3N4/BiOI/CdS double Z-scheme heterojunction has abundant active sites and in situ redox I3−/I− mediators and shows quantum size effects, which are all conducive to enhancing the separation of photoinduced charges and increasing the photocatalytic degradation efficiency for bisphenol A, a model pollutant. Specifically, the heterojunction photocatalyst achieves a photocatalytic degradation efficiency for bisphenol A of 98.62% in 120 min and photocatalytic hydrogen production of 863.44 μmol h−1g−1 on exposure to visible light. The excellent visible-light photocatalytic performance is as a result of the Z-scheme heterojunction, which extends absorption to the visible light region, as well as the I3−/I− pairs, which accelerate photoinduced charge carrier transfer and separation, thus dramatically boosting the photocatalytic performance. In addition, the key role of the charge transfer across the indirect Z-scheme heterojunction has been elucidated and the transfer mechanism is confirmed based on the detection of intermediate I3− ions. Thus, this study provides guidelines for the design of indirect Z-scheme heterojunction photocatalysts.

In this work, copper sulfide particles are synthesized with different Co doping concentrations such as 0, 1 and 5% at 80 °C by optimizing synthesis times from 1 to 3 h. Copper sulfide particles possess two structural phases of covellite CuS and digenite Cu9S5. The increase in synthesis time from 1 to 3 h increases the Cu9S5 phase growth and changes the morphology from flower to microsphere. The CuS synthesized with 0, 1 and 5% Co dopant concentrations demonstrate flower consisting of agglomerated nanosheets, microsphere and flower like microsphere. The elemental investigation substantiates Co ions presence in CuS microspheres. The A1g (LO) mode intensity is decreased with increase in Co dopant concentration confirming Co incorporation into CuS microsphere. The CuS synthesized with 0, 1, 5% Co dopants exhibit 322 mV, 305 mV and 289 mV to attain 100 mA/cm2 in 1 M KOH seawater. The CuS synthesized with 5% Co dopant demonstrates higher double layer capacitance (Cdl) of 173.9 mFcm−2 and lower charge transfer resistance (Rct) of 6.07 Ω with 78.84% retention after 10 h continuous stability than that of the other pristine (118.3 mFcm−2, 13.72 Ω) and 1% Co doped CuS microsphere (165.7 mFcm−2, 8.55 Ω) indicating more surface active site and rapid charge carrier transport, respectively.

A kind of CdS/Cd-BiOCl immobilized films photocatalyst was prepared. The optical and physicochemical properties of the CdS/Cd-BiOCl photocatalysts were analysed, and the detailed characterization revealed CdS/Cd-BiOCl films photocatalyst with good charge carrier separation effect. The reusabilities and photocatalytic properties of the samples were studied. The 15%CdS/Cd-BiOCl photocatalyst exhibited superior performance in photocatalytic degradation of tetracycline (TC) and favorable stability under visible light irradiation. As for the photodegradation rate of TC, 15%CdS/Cd-BiOCl exhibited an excellent photodegradation activity, which is 4.06 and 9.53 times higher than that of CdS/Cd and BiOCl, respectively. The results showed that dominant active species are •O2− and •OH radicals during photodegradation. The charge transfer in Z-scheme CdS/Cd-BiOCl films photocatalyst could synchronously generate conduct band (CB) electrons in BiOCl and valence band (VB) holes in CdS, and metal Cd served as electron mediator. This work can be a reference for the design of film photocatalysts and new insight for photodegradating towards contaminants.

Recently, fabricating type-II vertical van der Waals (vdWs) heterostructure is a promising material for hydrogen production. The absorption capability, charge density distributions, band alignments and electronic properties of the monolayers and heterostructures are systematically investigated using computational studies. Using ab initio molecular dynamics, binding energy and phonon calculations, the stability of the heterostructures are verified. Both heterostructures are type-II materials, which can increase the separation of charge carriers. Moreover, the charge density difference and the potential drop across the interface of MSe2/BSe creates a high built-in electric field that can prevent the recombination of charge carriers. We found that the visible-light optical properties of both heterostructures are much enhanced with suitable bandgap energy for water splitting. The band alignment suggests that the heterostructures straddle water redox potentials in acid solutions (0

Plasmonic photocatalysis, i.e., photocatalysis with activity under visible-light (vis) irradiation due to plasmonic feature of noble metals (NMs), has been intensively studied as promising method for solar energy conversion. Although various plasmonic photocatalysts have already been investigated, the vis activity is usually low, and thus should be improved for commercial application. Moreover, considering charge carriers’ mechanism, the stability of NMs during long-term irradiation should be also considered. Accordingly, this study has focused on the improvement of photocatalytic activity and stability of gold-modified titania photocatalysts under vis irradiation. Among a few proposed synthesis procedures, modified photodeposition method has resulted in the formation of TiO2/Au/TiO2 composites with high level of photoactivity. Large gold nanoparticles (NPs), formed on large rutile titania particles, are partially covered with fine anatase titania NPs, and thus the interface between titania and gold has been enlarged. Moreover, partial coverage of gold by fine titania NPs hinders gold aggregation, resulting in improved stability of these samples. Action spectrum of 2-propanol oxidation and numerical 3D-FDTD simulations of field distribution have indicated that the enhanced utilization of incident photons is responsible for high activity of TiO2/Au/TiO2 photocatalysts.

Novel black oxygen deficient bismuth oxide (Bi2O3-Bi2O3–x) photocatalytic material is successfully prepared by a two zone temperature controlled muffle furnace method. The lanthanum, cerium and erbium ions are successfully doped into Bi2O3-Bi2O3–x with the average contents of 10.77%, 7.62% and 8.14%, respectively. The results show that a large number of oxygen vacancies existence in Bi2O3-Bi2O3–x. La3+, Ce3+ and Er3+ act as electron acceptors to temporarily trap the photo-generated electrons. The XPS spectrum show Bi-O band in Bi2O3-Bi2O3–x and the O 1s peak of Ce/Bi2O3-Bi2O3–x move toward the direction of low binding energy. These phenomena fully proved that the separation of photogenerated electron-hole pairs will be more effectual, so as to reduce the possibility of charge carrier recombination. The radical scavenging experiments and Electron spin resonance detections confirmed the conduction band of the original Bi2O3 can easily receive photogenerated electrons, while the valence band of the modified Bi2O3-Bi2O3–x tend to accept photogenerated holes and then form the circulation system. Therefore, Ce/Bi2O3-Bi2O3–x can degrade tetracycline hydrochloride up to 90.15%. This research provides some new insights into developing green and recyclable photocatalysts for the remediation of antibiotic contamination.

BiVO4 coupled to N-Doped TiO2 were obtained using the sol gel method assisted by microwave. Double modifications of TiO2 by doping with nitrogen and BiVO4 were induced to improve the UV visible response of TiO2 and improves the separation of generated charge carriers. The structural and morphological analyses support the formation of uniform BiVO4 and N-TiO2 heterostructures, with the surface area significantly increased by approximately 2.5 times in comparison with the bare TiO2. Doping with N and BiVO4 shifted the TiO2 band gap energy from 3.2 eV to around 2.4 eV. The photocatalytic activities of the catalysts were evaluated in the degradation reaction of Rhodamine B and Ofloxacin in aqueous solution. The resulting structures showed superior photocatalytic activity compared to their individual counterparts. More than 98% and 92% of Rhodamine B and Ofloxacin, respectively, could be degraded with the most active BiVO4/N-TiO2 catalyst under visible light radiation. The enhanced photocatalytic activity displayed by the heterostructures could be explained in terms of higher absorption of visible light due to the synergistic effect of N-doping of TiO2 and BiVO4 coupling and improved charge separation due to the formation of an n–n junction at the interface of N-TiO2 and BiVO4 semiconductors. The showed enhance photocatalytic response for the degradation for both pollutants was attributed to electrons and holes from photo-oxidation by ROS, confirmed by carrier scavenger experiments. The separation efficiency of photoinduced charge carriers was further affirmed by photoluminescence and electrochemical studies. The structures were stable even after the third catalytic cycle, indicating their efficiency in potential treatments of pollutants. Finally, based on experimental and test results, a reaction mechanism was proposed.

Organic semiconductors (OSCs) possess diverse chemical structures and tailored optoelectronic properties via simple chemical modifications, so increasing use of them are found in efficient visible-light photocatalysis. However, the weak chemical bonds and the poor charge behavior (e.g., low concentration of free charge carriers, low carrier mobility) intrinsic in them, always incur quite limited stability and efficiency. Therefore, the assembly of them into refined nanostructures or nanocomposites is usually proposed to enhance their optoelectronic properties, as well as the photocatalytic efficiency and reliability. Zero-dimensional (0D) nanoparticles are low in size and hence high specific surface area (SSA); One-dimensional (1D) nanostructures are usually arranged in an orderly long range thus leading to low surface defect density and increased carrier mobility; Two-dimensional (2D) nanostructures are particularly capable of enhancing the photogenerated charge utilization because of their large reaction sites and shortened charge transport length. Furthermore, the building of heterogeneous interfaces in the nanocomposites can effectively facilitate the special charge separation. All these highlight the importance of organic nanostructures in improving the photocatalytic activity and stability. Therefore, organic semiconductor nanostructures (OSNs) have been increasingly used in the photocatalytic water splitting into H2 and O2, CO2 reduction, pollutant decomposition, disinfection, and etc.. In this review, we first examine the important optoelectronic properties of OSNs that govern the photocatalytic processes; we then analyze different classes of OSNs and their mechanistic pathways, with an emphasis on the structure-property relationships; we also introduced various photocatalytic applications of OSNs; we lastly propose the challenges and future outlook in real use.

The random mobility of charge carriers is a main factor causing the low photocatalytic efficiency of g-C3N4. Thus, the controllable migration of charge carriers is a rational strategy to suppress the charge recombination and facilitate charge separation. Herein, an ethylenediamine modified g-C3N4 displays improved photocatalytic activity. The excellent charge separation efficiency is confirmed to be a key factor for the enhancement. The observation from TEM image after photo-deposited Pt nanoparticles and DFT calculations verify the accumulation of electrons on some area of surface. The increased -NH2 groups significantly tune the electronic structure of g-C3N4 after modification. The generation of midgap state also affect the charge separation. Our reports provide a simple method to manage the migration of charge carriers and enables electrons directional transfer, which suppress the recombination and improve the photocatalytic activity.

Two-dimensional (2D) covalent organic framework nanosheets (CONs) are attracting increasing research attention because of their unique properties derived from their ultrathin thickness, high surface-to-volume atomic ratio, and extremely large surface area. 2D CONs can provide high transport pathways for charge carriers (e.g., electrons, holes and ions) through either the conjugated skeletons or the open channels. Therefore, they have shown great potential in energy related applications. In this review, we firstly introduce the recent developments and characteristics of 2D CONs by focusing on the two typical synthetic methods, i.e., top-down and bottom-up methods. Then, the energy-related applications in energy storage and conversion of 2D CONs are summarized. Finally, we give our personal views on the challenges and perspectives for the future research of 2D CONs and their composites.

The nonradiative recombination of charge carriers at the hole transport layer (HTL)/perovskite interface generally induces remarkable performance loss of the inverted two-dimensional perovskite solar cells (2D PSCs). Herein, a cross-linkable small molecule of 2-mercaptoimidazole (2-MI) was introduced into the nickel oxide (NiOx)/2D perovskite interface. Experiments have confirmed the formation of Ni-N covalent bond by N atom in the 2-MI and Ni in the NiOx and the coordinating between S atom of 2-MI and under-coordinated Pb2+ near to the NiOx/perovskite interface, which contributes to creating a cross-linking between NiOx/perovskite interface to restrain charge carrier recombination and enhance the extraction of hole carriers at the interface. Besides, the 2-MI modification layer is also beneficial for promoting the crystallinity of 2D perovskite. Consequently, the inverted 2D PSCs with 2-MI modification achieved the best power conversion efficiency of 15%. This paves a route to acquire highly efficient 2D PSCs by constructing a cross-linking at the NiOx HTL/2D perovskite interface.

In this perspective, we have highlighted the current literature and explained the synthesis, structure, morphology, modification strategies, and photocatalytic applications of emerging BiPO4-based photocatalysts. Since BiPO4 is a large bandgap photocatalyst, it uses UV light for the excitation of electrons, and also, the recombination of charge carriers is an issue in BiPO4. Various novel modification strategies of BiPO4 photocatalysts viz. defect modifications, heterojunction formation, phase-junctions, surface plasmon resonance, Schottky junction have been successfully proposed and highlighted. These modifications enhance the light absorption and inhibit the recombination of charge carriers BiPO4 photocatalyst. Finally, future aspects for further research on BiPO4-based photocatalysts are also explored. It expects that BiPO4-based photocatalysts represent a promising strategy for developing practical photocatalysts for energy and environmental remediation applications.

Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity. Devices based on two-dimensional (2D) transition metal dichalcogenides can exhibit picosecond photoresponse speed. However, 2D materials naturally have low absorption, and when increasing thickness to gain higher responsivity, the response time usually slows to nanoseconds, limiting their photodetection performance. Here, by taking time-resolved photocurrent measurements, we demonstrated that graphene/MoTe2 van der Waals heterojunctions realize a fast 10 ps photoresponse time owing to the reduced average photocurrent drift time in the heterojunction, which is fundamentally distinct from traditional Dirac semimetal photodetectors such as graphene or Cd3As2 and implies a photodetection bandwidth as wide as 100 GHz. Furthermore, we found that an additional charge carrier transport channel provided by graphene can effectively decrease the photocurrent recombination loss to the entire device, preserving a high responsivity in the near-infrared region. Our study provides a deeper understanding of the ultrafast electrical response in van der Waals heterojunctions and offers a promising approach for the realization of photodetectors with both high responsivity and ultrafast electrical response.

Nanocrystalline copper ferrite shows distinct photocatalytic properties, but it suffers from a high recombination rate of photogenerated electrons (e−) and holes (h+) due to its narrow bandgap. Herein, Al3+ doping is shown to reduce the (e−/h+) recombination rate and improve the charge carriers’ availability in doped CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles produced by a solid-state, mechanochemical process. CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles exhibit the growth of a nanocrystalline cubic spinel lattice when annealed at 1000 °C. The lattice parameter is reduced by Al3+ doping due to the smaller ionic radius of Al3+ ions substituting bigger Fe3+ ions. However, a higher degree of sintering and greater crystallite size are observed for Al3+ doped samples. The surface morphology and topography also reveal an increase in the particle size, but significantly narrow size distribution and greater homogeneity. The effect of Al3+ doping on the optical properties of CuFe2−xAlxO4 (0 ≤ x ≤ 1) nanoparticles is demonstrated by a decrease in the photoluminescence signal that is attributed to the lower rate of (e−/h+) recombination. Thus, Al3+ doping increases transition time and improves the availability of charge carriers for potential photocatalytic applications.

The vast majority of high-performance perovskite solar cells (PSCs) are based on a formamidinium lead iodide (FAPbI3)-dominant composition. Nevertheless, the FA-based perovskite films suffer from undesirable phase transition and defects-induced non-ideal interfacial recombination, which significantly induces energy loss and hinders the improvement of device performance. Herein, we employed 4-fluorophenylmethylammonium iodide (F-PMAI) to modulate surface structure and energy level alignment of the FA-based perovskite films. The superior optoelectronic films were obtained with reduced trap density, pure α-phase FAPbI3 and favorable energy band bending. The lifetime of photogenerated charge carriers increased from 489.3 ns to 1010.6 ns, and a more “p-type” perovskite film was obtained by the post-treatment with F-PMAI. Following this strategy, we demonstrated an improved power conversion efficiency of 22.59% for the FA-based PSCs with an open-circuit voltage loss of 399 mV.

SUMMARYRuddlesden-Popper (RP) perovskites are two-dimensional semiconductors for high performance devices. In this work, we report a long in-plane charge carrier diffusion length in 2D RP perovskite single crystals probed by scanning photocurrent microscopy. Carrier diffusion lengths of 7~14 µm are observed when the number of PbI6-2 octahedrons between organic spacers increases from 1 to 3. By detailed light intensity and electric field-dependent photocurrent measurements, we attribute the observed long diffusion length to the dominating dissociated free carrier transport. This is further validated by time-resolved photoluminescence measurements where the decay lifetime increases in the presence of an electric field. From our experiments, we conclude that the in-plane transport in RP perovskites is efficient because of the partial free carrier generation overcoming strong excitonic effects. Our results suggest that semiconducting devices fabricated from RP perovskite single crystals can be as efficient as their 3D counterparts.

Metal halide perovskite-based solar cells (PSCs) have rapidly-increased power conversion efficiency (PCE) exceeding 25% but poor stability especially under ultraviolet (UV) light. Meanwhile, non-radiative recombination caused by diverse defects in perovskite absorbers and related interfaces is one of the major factors confining further development of PSCs. In this study, we systematically investigate the role of 2-(2-hydroxy-5-methylphenyl)benzotriazole (UVP) additive in perovskite layers. By adjusting the amount of doped UVP, the quality of perovskite absorbers is significantly improved with enlarged grains, longer lifetime and diffusion length of charge carriers. Furthermore, UVP not only reduces defects for less non-radiative recombination, but also matches energy level alignment for efficient interfacial charge extraction. X-ray photoelectron spectroscopy confirms that N-donor of UVP molecule coordinates with undercoordinated Pb2+ on the surface. Interestingly, UVP incorporated in PbI2 protects the perovskite by absorbing UV through the opening and closing of the chelating ring. Eventually, the UVP treated PSCs obtain a champion PCE of 22.46% with remarkably enhanced UV stability, retaining over 90% of initial PCE after 60 mW/cm2 strong UV irradiation for 9 h while the control maintaining only 74%. These results demonstrate a promising strategy fabricating passivated and UV-resistant perovskite materials simultaneously for efficient and stable perovskite photovoltaics.

Development of transistors for advanced low noise amplifiers requires better understanding of mechanisms governing the charge carrier transport in correlation with the noise performance. In this paper, we report on study of the carrier velocity in InGaAs/InP high-electron-mobility transistors (HEMTs) found via geometrical magnetoresistance in the wide range of the drain fields, up to 2 kV/cm, at cryogenic temperature of 2 K. We observed, for the first time experimentally, the velocity peaks with peak velocity and corresponding field decreasing significantly with the transverse field. The low-field mobility and peak velocity are found to be up to 65000 cm2/Vs and 1.2x106 cm/s, respectively. Extrapolations to the lower transverse fields show that the peak velocity can be as high as 2.7x107 cm/s. The corresponding intrinsic transit frequency can be up to 172 GHz at the gate length of 250 nm. We demonstrated, for the first time, that the low-field mobility and peak velocity reveal opposite dependencies on the transverse field, indicating the difference in carrier transport mechanisms dominating at low- and high-fields. Therefore, the peak velocity is an appropriate parameter for characterization and development of the low noise HEMTs, complementary to the low-field mobility. The results of the research clarify the ways of the further development of the HEMTs for advanced applications.

Photocatalytic (PC) / Photoelectrochemical (PEC) water splitting under solar light irradiation is considered as a prospective technique to support the sustainable and renewable H2 economy and to reach the ultime goal of carbon neutral. TiO2 based photocatalysts with high chemical stability and excellent photocatalytic properties have great potential for solar-to-H2 conversion. To conquer the challenges of the large band-gap and rapid recombination of photo generated electron-holepairs in TiO2, non-metal doping turns out to be economic, facile, and effective on boosting the visible light activity. The localized defect states such as oxygen vacancy and Ti3+ generated by non-metal doping are located in the band-gap of TiO2, which result in the reduction of band-gap, thus a red-shift of the absorption edge. The hetero doping atoms such as B3+, I7+, S4+/S6+, P5+ can also act as electron donors or trap sites which facilitate the charge carrier separation and suppress the recombination of electron-hole pairs. In this comprehensive review, we present the most recent advances on non-metal doped TiO2 photocatalysts in terms of fundamental aspects, origin of visible light activity and the PC / PEC behaviours for water splitting. In particular, the characteristics of different non-metal elements (N, C, B, S, P, Halogens) as dopants are discussed in details focusing on the synthesis approaches, characterization as well as the efficiency of PC and PEC water splitting. The present review aims at guiding the readers who want quick access to helpful information about how to efficiently improve the performance of photocatalysts by simple doping strategies and could stimulate new intuitive into the new doping strategies.

The rapid recombination of photoinduced charge carriers and low selectivity are still challenges for the CO2 photoreduction. Herein, we proposed that ZIF-67-derived Co3O4 hollow polyhedrons (CoHP) were embedded into NaCl-template-assisted synthesized 3D graphitic carbon nitride (NCN), subsequently, loading Ag by photo-deposition as efficient composites (CoHP@NCN@Ag) for CO2 photoreduction. This integration simultaneously constructs two heterojunctions: p-n junction between Co3O4 and g-C3N4 and metal-semiconductor junction between Ag and g-C3N4, in which Co3O4 and Ag serve as hole (h+) trapping sites and electron (e-) sinks, respectively, achieving spatial separation of charge carriers. The donor-acceptor structure design of NCN realize a good photogenerated e--h+ separation efficiency. The mesoporous structure of hollow Co3O4 facilitate gas-diffusion efficiency, light scattering and harvesting. And the introduction of plasmonic Ag further strengthens the light-harvesting and charge migration. Benefiting from the rational design, the optimized ternary heterostructures exhibit a high CO2-CO yield (562 μmol g-1), which is about 4-fold as high as that of the NCN (151 μmol g-1). Moreover, the conjectural mechanism was systematically summarized. We hope this study provides a promising strategy for designing efficient g-C3N4 systems for the CO2 photoreduction.

Numerous approaches have been used to modify graphitic carbon nitride (g-C3N4) for improving its photocatalytic activity. In this study, we demonstrated a facial post-calcination method for modified graphitic carbon nitride (g-C3N4-Ar/Air) to direct tuning band structure, i.e., bandgap and positions of conduction band (CB)/valence band (VB), through the control of atmospheric condition without involving any additional elements or metals or semiconductors. The synthesized g-C3N4-Ar/Air could efficiently degrade sulfamethazine (SMT) under simulated solar light, i.e., 99.0% removal of SMT with rate constant k1 = 2.696 h−1 within 1.5 h (4.9 times than pristine g-C3N4). Material characterizations indicated that the damaged/partial-collapsed structure and decreased nanosheet-interlayer distance for g-C3N4-Ar/Air resulted in the shift of band structure due to the denser stacking of pristine g-C3N4 through oxidative exfoliation and planarization by air calcination. In addition, the bandgap of g-C3N4-Ar/Air was slightly shrunk from 2.82 eV (pristine g-C3N4) to 2.79 eV, and the CB was significantly upshifted from -0.44 eV (pristine g-C3N4) to -0.81 eV, suggesting the powerful ability for donating the electrons for O2 to form •O2−. Fukui index (f –) based on theoretical calculation indicated that the sites of SMT molecule with high values, i.e., N9, C4 and C6, preferred to be attacked by •O2− and •OH, which is confirmed by the intermediates’ analysis. The tuning method for graphitic carbon nitride provides a simple approach to regulate the charge carrier lifetime then facilitate the utilization efficiency of solar light, which exhibits great potential in efficient removal of emerging organic contaminants from wastewater.

In this study, we demonstrate for the first time the construction of a ternary BiVO4/FeVO4/Cu2O nanorod array (NRA) photoelectrode via seed-assisted refluxing, hydrothermal and successive ionic-layer adsorption and reaction (SILAR) method and its photoelectrochemical (PEC) water oxidation performance. The energy band structures of the BiVO4, FeVO4 and Cu2O show that two type-II band alignments with a ladder-like structure are formed in the constructed ternary BiVO4/FeVO4/Cu2O NRA photoelectrode, enabling the photoelectrode to display substantially enhanced PEC performance. The constructed ternary photoelectrode loaded with the optimized Cu2O nanoparticles achieves a zero-bias photocurrent density of 50 μA cm−2, 5 times higher than that of the pure BiVO4 NRA photoelectrode. The measurements of optical property reveal that the constructed BiVO4/FeVO4/Cu2O nanorod arrays (NRAs) demonstrate improved light absorption capability. The electrochemical impedance and photoluminescence measurements confirm that the charge carriers of the BiVO4/FeVO4/Cu2O heterojunction NRAs are transferred and separated effectively. The substantially boosted PEC water oxidation activity of the constructed ternary BiVO4/FeVO4/Cu2O heterojunction NRA photoelectrode is ascribed to the improved light harvesting and effective charge separation.

Rapid heat loss and fast charge carrier recombination constitute two crucial issues that hinder the development of efficient solar energy utilization and conversion over the semiconductor in a photothermal catalytic system. Inspired by energy production from waste water, we designed an advanced 3D C@TiO2 multishell nanoframe (MNF) photocatalyst. Its unique structural features of heat confinement and vibrant photocarrier kinetics lead to excellent photo-thermal conversion for synchronous superior photocatalytic H2 evolution (503 μmol g-1 h-1) and 98.2% RhB removal without the use of any co-catalyst and sacrificial reagent under simulated sunlight irradiation (AM 1.5G). Mechanism exploration reveals that the difference between the inner and outer gas pressure formed inside C@TiO2 precursor facilitates the selective cleavage of outer TiO2 layers at selected temperatures during calcination. Synergistic effects between residual carbon core and multi-shelled TiO2 framework endow C@TiO2 MNF with excellent heat confinement and vibrant photocarrier kinetics. Such MNF photo-thermocatalyst concept provides a novel strategy for effective utilization of solar energy, and this work may open a novel avenue towards advanced nanostructures for efficient waste-to-energy conversion.

Because of its superior safety and excellent processability, solid polymer electrolytes (SPEs) have attracted widespread attention. In lithium based batteries, SPEs have great prospects in replacing leaky and flammable liquid electrolytes. However, the low ionic conductivity of SPEs cannot meet the requirements of high energy density systems, which is also an important obstacle to its practical application. In this respect, escalating charge carriers (i.e. Li+) and Li+ transport paths are two major aspects of improving the ionic conductivity of SPEs. This article reviews recent advances from the two perspectives, and the underlying mechanism of these proposed strategies is discussed, including increasing the Li+ number and optimizing the Li+ transport paths through increasing the types and shortening the distance of Li+ transport path. It is hoped that this article can enlighten profound thinking and open up new ways to improve the ionic conductivity of SPEs.

Molybdenum disulfide (MoS2) with low cost, high activity and high earth abundance has been found to be a promising catalyst for the hydrogen evolution reaction (HER), but its catalytic activity is considerably limited due to its inert basal planes. Here, through the combination of theory and experiment, we propose that doping Ni in MoS2 as catalyst can make it have excellent catalytic activity in different reaction systems. In the EY/TEOA system, the maximum hydrogen production rate of EY/Ni-Mo-S is 2.72 times higher than that of pure EY, which confirms the strong hydrogen evolution activity of Ni-Mo-S nanosheets as catalysts. In the lactic acid and Na2S/Na2SO3 systems, when Ni-Mo-S is used as co-catalyst to compound with ZnIn2S4 (termed as Ni-Mo-S/ZnIn2S4), the maximum hydrogen evolution rates in the two systems are 5.28 and 2.33 times higher than those of pure ZnIn2S4, respectively. The difference in HER enhancement is because different systems lead to different sources of protons, thus affecting hydrogen evolution activity. Theoretically, we further demonstrate that the Ni-Mo-S nanosheets have a narrower band gap than MoS2, which is conducive to the rapid transfer of charge carriers and thus result in multi-photocatalytic reaction systems with excellent activity. The proposed atomic doping strategy provides a simple and promising approach for the design of photocatalysts with high activity and stability in multi-reaction systems.

Despite the rapid development of power conversion efficiency (PCE) for halide perovskite solar cells (PSCs), the lattice strain engineering in perovskite thin films has been rarely probed in recent years. Herein, a strain compensation by homogeneous crystallization in perovskite films is achieved with the aid of precursor aging in the mixed-cation perovskite of Cs0.05(FA0.83MA0.17)Pb(I0.90Br0.10)3 with near 20% PCE in inverted devices. The homogeneous crystallization releases the residual tensile stress and induces more compressive stress at the edges of perovskite films, thus elongating the carrier lifetime and reducing the trap-assisted carrier recombination. The high dependence on the perovskite components in strain engineering strategy was systematically revealed, wherein MAPbI3 and Cs0.05(FA0.83MA0.17)PbI3 film showed an increased compressive strain and FAPbI3 film showed adverse tensile strain after aging. The density functional theory (DFT) calculations are further performed to reveal the change of electronic features. The precursor aging-induced strain modulation was correlated with a systematic characterization of the charge carrier transport and recombination dynamics in the mixed-cation perovskite films. We believe that this facile approach provides a novel strain engineering strategy for PSCs technology.

The recombination of charge carriers arriving from the random charge movement in semiconductor photocatalysts greatly limits the practical application of solar-driven H2 evolution. The design of photocatalytic systems with spatially oriented charge-transfer is a promising route to achieve high charge-separation efficiency for photocatalysts. Herein, novel sea-urchin-like ReS2 nanosheet/TiO2 nanoparticle heterojunctions (SURTHs) are constructed. The unique sea-urchin-like structure endows the ReS2 cocatalyst with an unusual charge edge-collection effect, which leads to a significant acceleration of charge separation and transfer, as evidenced by the well-designed selective photodeposition of Pt quantum dots in SURTHs. The markedly improved charge transfer capacity contributes to a high photocatalytic H2 evolution rate of 3.71 mmol h−1 g−1 for SURTHs (an apparent quantum efficiency (AQE) of 16.09%), up to 231.9 times by contrast with that of P25 TiO2. This work would provide a new platform for designing the high-efficiency cocatalyst/photocatalyst system with excellent charge transfer capacity. This work was funded by the China Postdoctoral Science Foundation (pre-station, No. 2019TQ0050), Applied Basic Research Program of Sichuan Province (No. 2020YJ0068), the China Postdoctoral Science Foundation (No. 2020M673186), National Natural Science Foundation of China (No. 22002014), the Applied Basic Research Program of Sichuan Province (No. 2020ZYD014). Thanks for the technical help from Sichuan Province Key Laboratory of Display Science and Technology, State Key Laboratory of Electronic Thin Films and Integrated Devices. Dr. Xiao Luo acknowledges financial support from the National Natural Science Foundation of China (No. 21903084) and Applied Basic Research Program of Sichuan Province (No. 2021YJ0408). Dr. Qing Liu acknowledges financial support from the National Natural Science Foundation of China (No. 52002051) and the Fundamental Research Funds for the Central Universities, SCUT (No. ZYGX2020J009).

In the work, CdSxSe1-x/N-GQDs composites were fabricated via a simple one-step hydrothermal process and their tunable composition, structure and photoelectric properties were characterized by various techniques. The photoelectric properties of CdSxSe1-x/N-GQDs could be adjusted by different Se/S ratios and tunable band-gaps. CdSxSe1-x/N-GQDs composites reached the optimal photocurrent response and the lowest interfacial impedance at the Se/S ratio of 0.75:0.25. Mott-Schottky plots and LSV spectra showed that the n-type CdS0.25Se0.75/N-GQDs presented a higher carrier density under light illumination. The excellent properties of the composites could be attributed to the mechanism involved in the excitation and electron-transfer process. On one hand, the band-gap of CdS0.25Se0.75/N-GQDs was narrowed, and more electrons were excited by the lower band-gap energy to promote a superior electron separation and transportation. On the other hand, N-GQDs acted as charge carriers and conductive way providers for electron-transfer instead of electron-hole recombination in the composites.

Two-dimensional carbon nitride (2D-C3N4) nanosheets are promising materials in photocatalytic water splitting, but still suffer from easy agglomeration and fast photogenerated electron–hole pairs recombination. To tackle this issue, herein, a hierarchical Nb2O5/2D-C3N4 heterostructure is precisely constructed and the built-in electric field between Nb2O5 and 2D-C3N4 can provide the driving force to separate/transfer the charge carriers efficiently. Moreover, the strongly Lewis acidic Nb2O5 can adsorb TEOA molecules on its surface at locally high concentrations to facilitate the oxidation reaction kinetics under irradiation, resulting in efficient photogenerated electrons-holes separation and exceptional photocatalytic hydrogen evolution. As expected, the champion Nb2O5/2D-C3N4 heterostructure achieves an exceptional H2 evolution rate of 31.6 mmol g–1 h−1, which is 213.6 times and 4.3 times higher than that of pristine Nb2O5 and 2D-C3N4, respectively. Moreover, the champion heterostructure possesses a high apparent quantum efficiency (AQE) of 45.08% at λ = 405 nm and superior cycling stability. Furthermore, a possible photocatalytic mechanism of the energy band alignment at the hetero-interface is proposed based on the systematical characterizations accompanied by density functional theory (DFT) calculations. This work paves the way for the precise construction of a high-quality heterostructured photocatalyst with efficient charge separation to boost hydrogen production.

To obtain a high-performance heterogeneous photo-catalyst, herein, the hetero-structured ZnIn2S4-NiO@MOF (ZNM) nano-sheets are designed and prepared by partial pyrolysis of nickel-based MOFs (Ni-MOF) combined with the low-temperature solvo-thermal method. The results indicate that the NiO nanoparticles, produced by partial pyrolysis of the Ni-MOF, have a high density of the surface active sites with limited aggregation, which act as a co-catalyst to capture photo-induced charge carriers. In addition, the morphology and structure of Ni-MOF nano-sheets were preserved in ZNM, which is beneficial to the reduction of the conduction barrier for the photo generated electron-hole pairs. With the synergetic advantages of co-catalyst and unique two-dimensional hetero-structure, ZNM nano-sheets exhibited significantly improved activity for photo-catalytic hydrogen production.

The galvanomagnetic properties (magnetoresistivity and Hall Effect) and resistivity at temperatures from 2 K to 300 K in magnetic fields of up to 9 T as well as optical characteristics (real and imaginary parts of the complex permittivity, optical conductivity, and reflectivity) at room temperature were studied. It was shown that the temperature dependence of the electrical resistivity has a “metallic” type and is quadratic at low temperatures (< 60 K) that can be caused by the “electron-phonon-surface” interference scattering mechanism in WTe2. Whereas an applied magnetic field induces a minimum in the temperature dependence of the resistivity at low temperatures, that shifts to higher temperature with increasing field, one of the possible explanation of which is the transition from high to weak effective magnetic fields. The magnetoresistivity increases with the magnetic field according to the quadratic law, reaching 1750% at 2 K, which is due to the compensation of charge carriers in WTe2. Hall Effect studies showed that the majority charge carriers are electrons with the concentration 1019 cm-3 and the mobility 7500 cm2/V•s at 2 K. At the same time optical investigations did not reveal the features characteristic of metals. The optical conductivity spectrum is a broad band centered at 3.4 eV, formed by interband transitions. The presence of peaks in the infrared region indicates the formation of low-energy gaps in the band spectrum of WTe2. The obtained data on the real and imaginary parts of the complex permittivity also evidence the absence of a contribution from free carriers up to 0.2 eV. The optical characteristics are shown to be in good agreement with the data on electronic transport properties. The revealed features are a manifestation of the topological nature of the material.

Cationic surfactants (CS) pillared Ti3C2 composites (Ti3C2/CS) were prepared by a facile electrostatic assembly method, which have large interlayer spacing and slight N-doping. In hybrid magnesium-lithium batteries (HMLBs), the Ti3C2/CS composites exhibit excellent performance by utilizing both Li+ and Mg2+ as charge carriers. Among these composites, the Ti3C2/CTAB (CTC) electrode displays a reversible capacity of 115.9 and 60 mAh g-1 in APC/LiCl (APCL) and APC electrolytes at 0.1 A g-1, and it also exhibits excellent high rate performance and ultralong cycle performance. It is verified that CS is vital to significantly improve the diffusion kinetics of Mg2+ on the electrode surface. The CS can act as the conductive “bridge” which connects different Ti3C2 layers and the interlayer pillar which expands the interlayer distance. In addition, the N element in CS is effective in neutralizing electronegativity and enhancing electrical conductivity for the CTC electrode. The electrode design strategy can adapt to the synthesis of cathode materials with high rate capability in HMLBs.

A few compositions of the system Sr2Mn1-xSnxO4 (x = 0.0, 0.3, 0.5) were synthesized in the air by the solid-state ceramic route. A change in the sign (positive to negative) of the permittivity above a particular temperature (TC) is observed at all the measured frequencies. The negative permittivity was analyzed by the Drude-Lorentz model. It was found that negative permittivity is caused by the plasma oscillations of thermally excited free charge carriers. Analysis of XPS spectra confirmed the presence of mixed-valence states of both Mn (Mn4+ and Mn3+) and Sn (Sn4+ and Sn2+) ions. The UV–vis.-IR spectroscopy results indicated generation of a large number of defect states in the forbidden bandgap region of Sr2MnO4 on the substitution of Sn at Mn site. Synthesized samples are promising metamaterials for radio frequency (10 Hz -2 MHz) region applications due to the high-temperature plasmonic behavior.

Photocatalytic water splitting for hydrogen production is an important strategy to achieve clean energy development. In this report, a novel three-dimensional (3D) hierarchical hollow tubular g-C3N4/ZnIn2S4 nanosheets (HTCN/ZIS) type-Ⅱ heterojunction photocatalyst was successfully prepared and applied for photocatalytic hydrogen production under visible light irradiation. The experimental results reveal that the optimal proportion of HTCN/ZIS with the remarkable photocatalytic H2 evolution rate of 20738 μmol h−1 g−1 was obtained. The main reasons for the improvement of hydrogen production activity are as follows: (i) this unique tubular hollow structure can effectively enhances the light capturing ability by the multiple light scattering/reflection of incident light in the inner cavity; (ii) the shorten the phase plane transmission distance could reduce the path of charge transfer; (iii) the surface coated a large number of scaly ZnIn2S4 nanosheets can provide abundant reactive sites. Combining the various characterization tests, the enhanced spatial segregation of charge carriers could owning to the intimately interfacial contact and well-matched band gaps structure between g-C3N4 and ZnIn2S4 through the type-II heterojunction. This work provides a new prospect for the construction of a novel 3D hierarchical type-II heterojunction photocatalyst for highly efficient photocatalytic hydrogen production.

Heterojunction engineering has been regarded as a promising strategy to sufficiently utilizing photogenerated charge carriers, thus benefiting the improvement of photocatalytic performance. Herein, Ag3PO4/WO3 S-scheme heterojunction was synthesized via a simple deposition-precipitation process, and its photocatalytic activity was evaluated by monitoring water splitting and pollutant degradation under visible light. As a result, Ag3PO4/WO3 with optimized ratio photocatalyst showed enhanced photocatalytic activity in oxygen production (306.6 μmol·L-1·h-1) relative to pure Ag3PO4 (204.4 μmol·L-1·h-1). Additionally, it also exhibits rapid toxicity elimination efficiency over hexavalent chromium ions (Cr6+) and ciprofloxacin (CIP) with degrading rate of 72% and 83% within 30 min, respectively. According to a series characterization, a possible S-scheme photocatalytic mechanism of Ag3PO4/WO3 was demonstrated in detail, which endowed the heterojunction with strong redox abilities to provide powerful diving force towards the photocatalytic reaction. This work presents an innovative perspective to construct Ag3PO4-based S-scheme heterojunctions for boosting photocatalytic performance for various applications.

Here, cobalt-doped copper bismuth oxide (Co-CuBi2O4) was synthesized via a facile hydrothermal method for photoelectrocatalytic (PEC) hydrogen production. The results disclosed that the 5% Co-doped CuBi2O4 has better PEC activity which is ∼3 fold higher than pristine CuBi2O4. The doping of cobalt in CuBi2O4 improves the interfacial charge transfer at an electrode/electrolyte interface and reduces the recombination rate of photogenerated electron-hole pairs. This higher performed 5% Co-doped CuBi2O4 photocathode further modified with TiO2-P25 to form a Co-CuBi2O4/TiO2 p‐n heterojunction. This Co-CuBi2O4/TiO2 photocathode displayed a photocurrent density of 330 μA cm−2 at +0.5 V vs. RHE which was ∼2 fold higher than Co-CuBi2O4. Because this p-n junction affords inner electric field in the space charge region that helps for further minimization of electron-hole recombination, which facilitate efficient charge separation and transport thereby enhance the PEC water reduction.

Suppressing the nonradiative recombination in the bulk and surface of perovskite film is highly desired to improve the power conversion efficiency (PCE) and stability of halide perovskite solar cells (PSCs). In this study, a benzotriazole derivative (6-chloro-1-hydroxybenzotriazole, Cl-HOBT) is applied to improve the crystallinity and reduce the trap density of methylammonium lead iodide (MAPbI3) perovskite film. Meanwhile, incorporation of Cl-HOBT elongates the photoluminescence carrier lifetime and charge-recombination lifetime, implying the trap-assisted nonradiative recombination is greatly suppressed. Besides, the improved energy level alignment and enhanced built-in potential are conducive to the charge carrier separation and transfer process with Cl-HOBT. Consequently, a PCE of 20.27% and an open-circuit voltage (Voc) of 1.09 V are achieved for the inverted MAPbI3 PSCs, along with an 85% maintaining of the initial PCE under stored at relative humidity of 20% for 500 h. Furthermore, the existence of Cl-HOBT could inhibit the formation of Pb0 defect under prolonged UV illumination to retard the degradation of perovskite film. It is believed that this study paves a novel path for the realization of high-efficiency PSCs with UV-stability.

Surface ligand engineering is of great importance for the preparation of one-dimensional (1D) CsPbBr3 nanowires for high-performance photodetectors. The traditional long-chain terminated ligands such as oleylamine/oleic acid (C18) used in the preparation of CsPbBr3 nanowires will form an electrically insulating layer on the surface of the nanowires, which hinders the effective transport of charge carriers in optoelectronic devices. In this paper, short-chain ligands, including dodecylamine/dodecanoic acid (C12), octylamine/octanoic acid (C8) and hexylamine/hexanoic acid (C6), are introduced to partially replace long-chain ligands (C18) to successfully prepare various CsPbBr3 nanowires via a solvothermal method. Microstructure characterization indicates that the four kinds of nanowires before/after surface ligand engineering, which are named as C18-CsPbBr3, C12/18-CsPbBr3, C8/18-CsPbBr3 and C6/18-CsPbBr3, all have high aspect ratio and purity. As compared with CsPbBr3 with long-chain terminated ligands, the C8/18-CsPbBr3 and C6/18-CsPbBr3 nanowires with shorter chain ligands exhibit superior photoluminescence (PL) performance and stability under adverse conditions such as ultraviolet irradiation and high temperature. The constructed photodetectors based on C8/18-CsPbBr3 and C6/18-CsPbBr3 nanowires have shown improved performances. This work provides a new idea for the preparation of CsPbBr3 nanowires with high optical properties, stability and charge transport, and the prepared CsPbBr3 nanowires have potential application prospects in optoelectronic devices.

Taking advantage of the superflat surface of ultrananocrystalline diamond (UNCD), highly precise UNCD nanowire (NW) arrays were fabricated to develop high-performance UV photodetectors. The large surface-to-volume ratio of a nanowire significantly increases the number of surface trap states, and the reduced dimensionality effectively confines the active area of the charge carrier and shortens the transit time, which results in an enhanced photoconductivity and response speed. In this paper, the zero-biased UV photodetectors based on nitrogen-incorporated ultrananocrystalline diamond nanowire arrays have been demonstrated and characterized. The estimated responsivity was 2.0 A/W for 350 nm incident light when the device operated at room temperature. The UVA and UVB photocurrent signals from this visible blind photodetector were well defined with a rise and decay time of less than 1 s.

Thin-film of Mn-doped iron disulfide (FeS2) has been prepared using the thermal evaporation method. This work reports the Hall measurements, temperature and light intensity-dependent photoconductivity, electrical transport mechanism, and photodetection properties of Mn-doped FeS2 thin film. The transient photoconductivity measurements of p-type Mn-doped FeS2 thin film show a consistent dependence upon temperature and light intensity. Charge transport mechanism was illustrated using different models. In region-I (303–393 ​K) deposited film followed the thermally activated transport mechanism. Nearest neighbour hopping (NNH) transport mechanism was followed by region-II (274–293 ​K), and Mott's variable range hopping (VRH) mechanism was dominant in region-III (108–273 ​K). The fabricated device resulted in higher photoconductivity due to collecting charge carriers through electrodes under light illumination. The results also revealed that Mn-doped thin film possessed good photoresponsivity (∼19 ​mA/W) as well as photo-detectivity (∼3.4 ​× ​1012 Jones) due to the occupation of localized states formed by Mn-doping. Light intensity-dependent photodetection properties suggested the potential for real-time photodetection applications.

The design and scale-up of carbon nanotube (CNT)-based thermoelectric (TE) modules is limited by the low structural similarity between p-type enhancers and n-dopants. This study was aimed at investigating the organic TE properties of polyazacycloalkane/CNT TE films prepared using the drop casting method and the effect of Cu ion doping that can coordinate with its organic ligands. The Seebeck coefficient of cyclen-doped CNTs was −43.3 μV K−1 at 345 K but reduced to 41.6 μV K−1 after adding Cu ions. Cu ion addition switched the charge carrier type of the composite film from electrons to holes owing to cyclen complexation with Cu ions, resulting in a neutral molecular state with suppressed electron donation of the dopant molecules. Notably, conventional approaches cannot maintain sufficient power characteristics owing to the reduced electrical conduction induced by structural defects in the nanotubes. However, herein, an output power exceeding 200 μW m−1 K−2 was obtained, which was 2–5 times higher than that of existing carrier-switchable CNTs. For a typical TE module consisting of five pairs of p-type (Cu(II)-cyclen/CNT)-n-type (cyclen/CNT) junctions, the generated TE voltage and power, depending on the temperature gradient, were similar to the theoretical values. Under optimized conditions, a maximum output power of 1.36 μW was achieved at a temperature difference of 75 K, which is higher than that of previously reported carrier-switchable CNT-based TE modules that used oil-based dopants, whereas we used optimal water-soluble dopants. The proposed approach can help simplify the path from material preparation to module fabrication.

Quantum confinement of the charge carriers of graphene is an effective way to engineer its properties. This is commonly realized through physical edges that are associated with the deterioration of mobility and strong suppression of plasmon resonances. Here, we demonstrate a simple, large-area, edge-free nanostructuring technique, based on amplifying random nanoscale structural corrugations to a level where they efficiently confine charge carriers, without inducing significant inter-valley scattering. This soft confinement allows the low-loss lateral ultra-confinement of graphene plasmons, scaling up their resonance frequency from the native terahertz to the commercially relevant visible range. Visible graphene plasmons localized into nanocorrugations mediate much stronger light–matter interactions (Raman enhancement) than previously achieved with graphene, enabling the detection of specific molecules from femtomolar solutions or ambient air. Moreover, nanocorrugated graphene sheets also support propagating visible plasmon modes, as revealed by scanning near-field optical microscopy observation of their interference patterns. A scalable soft nanoengineering technique enables the realization of visible plasmons in corrugated graphene.

New ternary PVA/POPDA-GO-ZnO nanocomposite has been synthesized for electrical applications, using several facile synthesis-steps. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared (FT-IR) used to characterize the structural properties, and the capacitance data to determine the dielectric constant (ɛ'), dissipation factor (ɛ''), and A.C. electrical conductivity (σa.c) in the frequency range (1 – 5 MHz). The structural exams proved the formation of crystalline ternary PVA/POPDA-GO-ZnO nanocomposite. The prepared PVA/POPDA-GO-ZnO film shows an enhanced electrical properties comparing with PVA film, the highest dielectric constant (ɛ') and A.C. electrical conductivity (σa.c) recorded to the ternary PVA/POPDA-GO-ZnO nanocomposite (1.62348), (3.29*10-5 S/m) at the frequency (1 MHz) and (5 MHz) respectively, while at the frequency (5 MHz) achieved the lowest dissipation factor (ɛ'') (0.46369). This improvement is due to the GO nanosheets and ZnO nanoparticles which effectively enhancing the transfer ability of charge carriers and the surface area of the ternary nanocomposite, the adding of crystalline POPDA polymer improves the electrical conductivity of the PVA matrix polymer. The electrical properties effectively depend on the frequency of applied electric field.

Multiwall carbon nanotubes (MWCNTs) modified n- type Ni:Bismuth Vanadate photoanode has been prepared and investigated for solar energy induced water splitting for hydrogen generation. 0.5 wt% MWCNTs modified Ni:BiVO4 (M3) sample displayed the best response in comparison to the other samples. Electrochemical impedance spectroscopy (EIS) analysis indicates reduced charge transfer resistance and enhanced photoresponse at electrode/electrolyte interface. The calculated flat band potential, photocurrent density and applied bias photon to current conversion efficiency also support the augmentation in photoresponse. Thus, characteristics of MWCNTs has been demonstrated clearly which would support PEC efficiency as well as separation of charge carriers.

In this article, we introduce a double-gate nanotube tunneling field-effect transistor with high scalability based on the Si/Ge heterostructure. Our device includes two Ge source regions which are covered by the gate metal to facilitate line tunneling in these regions. The tunneling charge carriers flow toward the drain region through two n⁻ Si channel regions. The manufacturing process of the proposed transistor is fully compatible with CMOS technology. The performance of the device is investigated by employing a numerical simulator which is calibrated to experimental data. We achieved a remarkable switching performance including a minimum subthreshold swing (SS) of 10 mV/dec, an I $_{{on}}$ / I $_{{off}}$ ratio of 3.92 x 10⁷, an on-state current of 52.19 μA/μm, and a drain-induced barrier lowering of 45 mV/V for the device; moreover, the ambipolar conduction completely vanished.

The polycrystalline ceramic (Sm0.75Bi0.25FeO3)0.5 (BaTiO3)0.5 (SF-BT) is synthesized by high temperature solid state reaction method at an optimized temperature 1250 °C. The sample is investigated for its multifunctionality by analyzing its structural and electrical properties. The room temperature XRD pattern confirms the single phase compound in the tetragonal symmetry. The symmetry of the compound have been verified by commercially available software POWD. Complex impedance studies confirm the grain contribution to the electrical properties in the material. It reveals semiconducting behaviour of the material and transport phenomena is due to short range mobility of charge carriers. The relaxation mechanism in the sample is due to the short-range mobility of charge carriers.

Abundant heat is generated in household, industry and natural processes, and the majority of the heat is dissipated to environment as waste heat owing to the low heat utilization efficiency. Hence, to harvest waste heat is of great significance for the sustainable development. Among the heat-harvesting technologies including organic Rankine cycles, thermo-osmotic energy conversion and thermoelectric generators (TEGs), TEGs that can directly convert heat into electricity is the only feasible technology to harvest the low-grade heat that has a temperature below 200 oC and is about 2/3 of the total waste heat. The operational principle of TEGs is the Seebeck effect of electronic thermoelectric (TE) materials such as semiconductors or semimetals. Recently, ionic conductors, such as liquid ionic conductors and gel ionic conductors, emerged as the next-generation TE materials mainly due to their high thermopower. Their thermopower can be higher than that of the electronic TE materials by 2-3 orders in magnitude. In addition, they usually have a low thermal conductivity. Because the charge carriers in ionic conductors are cations and anions, the principle for the ionic thermopower and ionic TE conversion devices are notably different from the electronic counterparts. Very exciting progress has been made on the ionic TE materials and devices. This article provides a review on the ionic TE materials, including the thermopower mechanism, TE properties, and applications.

The photoelectrochemical (PEC) process is one of the most promising techniques for converting solar energy directly into clean fuels and for environmental remediation applications. One-dimensional (1D) TiO2 nanostructure arrays are extensively studied morphologies for a wide range of catalytic processes, including photocatalysis (PC) and PEC reactions for water splitting. In this study, a well-aligned spaced TiO2 nanorod (TNR) arrays were uniformly grown on a fluorine-doped tin oxide (FTO) substrate, and thermal exfoliation of the TNRs, which appeared as small islands, was investigated. The calcination time, which ranged from 1 to 5 h at 400 °C, had a significant impact on the agglomerated TNRs islands, which tended to be uniformly exfoliated as spaced nanorods and eventually improved the PEC performance. The regularly arranged spaced nanorods allow for the efficient transfer of internal charge carriers within the TNRs. Furthermore, the heterojunction formation with NiCo2S4 via the successive ionic layer adsorption and reaction (SILAR) method, substantially improve PEC performance, owing to reduced charge carrier recombination at the interface of the heterojunction. The Mott–Schottky analysis strongly supports the improved charge carrier density at the heterojunction interface. The improved life time of the charge carriers was investigated by comparing the time-resolved photoluminescence spectra for the TiO2/NiCo2S4 heterojunction with pristine TNRs, which was eventually confirmed by incident photon-to-current efficiency analysis.