Search Results (38)

Conjugated microporous polymers (CMP) are advanced photocatalytic systems for degrading organic dyes. However, their potential and efficiency are often limited by rapid electron–hole pair (e⁻/h⁺) recombination. To overcome this limitation, this study proposes a strategy that involves designing a Mott–Schottky heterojunction and integrating graphene sheets with a near-zero bandgap into the CMP-1 framework, resulting in a non-covalent graphene/CMP (GCMP) heterojunction composite. GCMP serves two main functions: physical adsorption and photocatalytic absorption that uses visible light energy to trigger and degrade the organic dye. GCMP effectively degraded four dyes with both anionic and cationic properties (Rhodamine B; Nile Blue; Congo Red; and Orange II), demonstrating stable recyclability without losing its effectiveness. When exposed to visible light, GCMP generates reactive oxygen species (ROS), primarily singlet oxygen (¹O₂), and superoxide radicals (^•O₂), degrading the dye molecules. These findings highlight GCMP’s potential for real-world applications, offering a metal-free, cost-effective, and environmentally friendly solution for wastewater treatment. Full article

With the intensification of the energy crisis and the growing concern over environmental pollution, particularly the discharge of organic dye pollutants in industrial wastewater, photocatalytic degradation of these contaminants using solar energy has emerged as an effective, eco-friendly solution. In this study, we successfully synthesized 2D/2D g-C₃N₄/BiOI p-n heterojunctions via a simple precipitation method and a high-temperature calcination method. The unique 2D structures of g-C₃N₄ nanosheets (NSs) and BiOI NSs, coupled with the synergistic effect between the two materials, significantly enhanced the photocatalytic degradation performance of the heterojunctions under simulated sunlight. The band structures, as determined by Tauc curves, Mott–Schottky curves and XPS-VB analysis, revealed a Z-scheme charge transfer mechanism that efficiently reduced charge carrier recombination and improved electron–hole separation. The photocatalytic activity of 2D/2D g-C₃N₄/BiOI p-n heterojunctions for rhodamine B (Rh B) degradation reached 99.7% efficiency within 60 min, a 2.37-fold and 1.27-fold improvement over pristine BiOI NSs and g-C₃N₄ NSs, respectively. Furthermore, the heterojunction exhibited excellent recyclability stability, with the degradation efficiency decreasing by only 1.2% after five cycles. Radical scavenging experiments confirmed the involvement of superoxide radicals (∙O₂⁻) and hydroxyl radicals (∙OH) as the primary reactive species in the degradation process. This work highlights the potential of 2D/2D g-C₃N₄/BiOI p-n heterojunctions for efficient photocatalytic applications in environmental remediation. Full article

With the abuse of antibiotics, its pollution poses an increasing threat to the environment and human health. Effective degradation of organic pollutants in water bodies is urgent. Compared to traditional treatment methods, advanced oxidation processes that have developed rapidly in recent years are more environmentally friendly, efficient and applicable to a wider range of organic compounds. FeWO₄ was used in this study as the iron-based semiconductor material to modify and optimize the material design. Fe₃O₄/FeWO₄ composites were prepared by a two-step hydrothermal method. The crystal structure, surface morphology, electrochemical properties and separability of the composite semiconductor were analyzed by XRD, XPS, UV-vis, SEM, EDS and Mott-Schottky. The results showed that, when the initial contaminant concentration was 30 mg/L, the initial solution pH was 4, the dosage of the catalyst was 25 mg and the dosage of hydrogen peroxide was 30 μL, the degradation efficiency of tetracycline hydrochloride (TCH) could reach 91% within 60 min, which was significantly improved compared to the performance of the single semiconductors Fe₃O₄ and FeWO₄. In addition, the catalyst prepared in this experiment can be easily recovered by magnetic separation technology in practical application, which will not affect the turbidity of water while reducing the cost of catalyst separation and recovery. Full article

One of the most fascinating aspects of condensed matter is its ability to conduct electricity, which is particularly pronounced in conventional metals such as copper or silver. Such behavior stems from a strong tendency of valence electrons to delocalize in a periodic potential created by ions in the crystal lattice of a given material. In many advanced materials, however, this basic delocalization process of the valence electrons competes with various processes that tend to localize these very same valence electrons, thus driving the insulating behavior. The two such most important processes are the Mott localization, driven by strong correlation effects among the valence electrons, and the Anderson localization, driven by the interaction of the valence electrons with a strong disorder potential. These two localization processes are almost exclusively considered separately from both an experimental and a theoretical standpoint. Here, we offer an overview of our long-standing research on selected organic conductors and manganites, that clearly show the presence of both these localization processes. We discuss these results within existing theories of Mott–Anderson localization and argue that such behavior could be a common feature of many advanced materials. Full article

The organic–inorganic composites F70-TiO₂, based on fullerene with carboxyl group derivatives and TiO₂ semiconductor, have been designed and constructed to become an optical-functional photocatalyst via the facile sol–gel method. The composite photocatalyst obtained shows excellent photocatalytic activity for the high-efficiency conversion of benzylamine (BA) to N-benzylidene benzylamine (NBBA) with air pressure at a normal temperature under visible light irradiation. By optimizing the composition, the composites with the 1:15 mass ratio of F70 and TiO₂, denoted as F70-TiO₂(1:15), demonstrated the highest reaction efficiency for benzylamine (>98% conversion) to N-benzylidene benzylamine (>93% selectivity) in this study. However, pure TiO₂ and fullerene derivatives (F70) exhibit decreased conversion (56.3% and 89.7%, respectively) and selectivity (83.8% and 86.0%, respectively). The UV–vis diffuse reflectance spectra (DRS) and Mott–Schottky experiment’s results indicate that the introduction of fullerene derivatives into anatase TiO₂ would greatly broaden the visible light response range and adjust the energy band positions of the composites, enhancing the sunlight utilization and promoting the photogenerated charge (e⁻-h⁺) separation and transfer. Specifically, a series of results on the in situ EPR tests and the photo-electrophysical experiment indicate that the separated charges from the hybrid could effectively activate benzylamine and O₂ to accelerate the formation of active intermediates, and then couple with free BA molecules to form the desired production of N-BBA. The effective combination, on a molecular scale, between fullerene and titanium dioxide has provided a profound understanding of the photocatalysis mechanism. This work elaborates and makes clear the relationship between the structure and the performance of functional photocatalysts. Full article

Photochemical hydrogen evolution and the degradation of synthetic dyes in water are the two key ways to unravel the issues associated with the energy and environmental sectors for sustainability. The present work deals with the use of a deep eutectic solvent for the synthesis of Ni₃V₂O₈/N-doped reduced graphene oxide (NiV/NR hybrid). The NiV/NR hybrid, NRGO, and NiV were characterized using XRD, SEM, TEM, UV-DRS, XPS, and other photo-electrochemical techniques. The NiV/NR hybrid exhibited high efficiency towards light-driven hydrogen evolution (12,546 µmol)) compared to pristine NiV (6453 µmol) and NRGO (1935 µmol). Among the various sacrificial agents examined, TEOA showed better activity in H₂ evolution. The photocatalytic degradation of anionic (Methyl orange; MO) and cationic dyes (crystal violet; CV) were evaluated and the reaction conditions were carefully optimized to attain the utmost efficiency. The efficiency of the NiV/NR hybrid was higher under visible light irradiation than UV light and able to degrade 94.6 and 96.7% of MO and CV, respectively. The results of the simultaneous degradation of dyes and total organic carbon (TOC) removal were good. Based on the obtained bandgap and Mott–Schottky plots, the mechanism of photocatalysis in the NiV/NR hybrid is discussed in detail. The reusability and stability of the NiV/NR hybrid in both H₂ evolution experiments and degradation studies are excellent. The fabricated NiV/NR hybrid material could be used for multiple applications in energy and environmental applications. Full article

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

Semiconductor quantum dots of the A₂B₆ group and organic semiconductors have been widely studied and applied in optoelectronics. This study aims to combine CdTe quantum dots and perylene-based dye molecules into advanced nanostructure system targeting to improve their functional properties. In such systems, new electronic states, a mixture of Wannier–Mott excitons with charge-transfer excitons, have appeared at the interface of CdTe quantum dots and the perylene dye. The nature of such new states has been analyzed by absorption and photoluminescence spectroscopy with picosecond time resolution. Furthermore, aggregation of perylene dye on the CdTe has been elucidated, and contribution of Förster resonant energy transfer has been observed between aggregated forms of the dye and CdTe quantum dots in the hybrid CdTe-perylene nanostructures. The studied nanostructures have strongly quenched emission of quantum dots enabling potential application of such systems in dissociative sensing. Full article

The families of organic charge-transfer salts $\kappa$-(BEDT-TTF)${}_{2}X$ and $\kappa$-(BETS)${}_{2}X$, where BEDT-TTF and BETS stand for the organic donor molecules C${}_{10}$H${}_8$S${}_8$ and C${}_{10}$H${}_8$S${}_4$Se${}_4$, respectively, and X for an inorganic electron acceptor, have been proven to serve as a powerful playground for the investigation of the physics of frustrated Mott insulators. These materials have been ascribed a model character, since the dimerization of the organic molecules allows to map these materials onto a single band Hubbard model, in which the dimers reside on an anisotropic triangular lattice. By changing the inorganic unit X or applying physical pressure, the correlation strength and anisotropy of the triangular lattice can be varied. This has led to the discovery of a variety of exotic phenomena, including quantum-spin liquid states, a plethora of long-range magnetic orders in proximity to a Mott metal-insulator transition, and unconventional superconductivity. While many of these phenomena can be described within this effective one-band Hubbard model on a triangular lattice, it has become evident in recent years that this simplified description is insufficient to capture all observed magnetic and electronic properties. The ingredients for generalized models that are relevant include, but are not limited to, spin-orbit coupling, intra-dimer charge and spin degrees of freedom, electron-lattice coupling, as well as disorder effects. Here, we review selected theoretical and experimental discoveries that clearly demonstrate the relevance thereof. At the same time, we outline that these aspects are not only relevant to this class of organic charge-transfer salts, but are also receiving increasing attention in other classes of inorganic strongly correlated electron systems. This reinforces the model character that the $\kappa$-phase organic charge-transfer salts have for understanding and discovering novel phenomena in strongly correlated electron systems from a theoretical and experimental point of view. Full article

The metal–insulator transition in the organic quasi-two-dimensional metal κ-(BEDT-TTF)₂Hg(SCN)₂Br at T_MI ≈ 90 K has been investigated. The crystal structure changes during this transition from monoclinic above T_MI to triclinic below T_MI. A theoretical study suggested that this phase transition should be of the metal-to-metal type and brings about a substantial change of the Fermi surface. Apparently, the electronic system in the triclinic phase is unstable toward a Mott insulating state, leading to the growth of the resistance when the temperature drops below T_MI ≈ 90 K. The application of external pressure suppresses the Mott transition and restores the metallic electronic structure of the triclinic phase. The observed quantum oscillations of the magnetoresistance are in good agreement with the calculated Fermi surface for the triclinic phase, providing a plausible explanation for the puzzling behavior of κ-(BEDT-TTF)₂Hg(SCN)₂Br as a function of temperature and pressure around 100 K. The present study points out interesting differences in the structural and physical behaviors of the two room temperature isostructural salts of κ-(BEDT-TTF)₂Hg(SCN)₂X with X = Br, Cl. Full article

P-n heterojunction-structured CuFe₂O₄/MgFe₂O₄ hollow spheres with a diameter of 250 nm were synthesized using a template-free solvothermal method, and time-dependent morphological studies were carried out to investigate the hollow formation mechanism. The CuFe₂O₄/MgFe₂O₄ with a molar ratio of 1:2 (Cu:Mg) had the highest degradation efficiency with the model organic dye Acid Orange 7, with a degradation rate of 91.96% over 60 min. The synthesized CuFe₂O₄/MgFe₂O₄ nanocomposites were characterized by XRD, TEM, HRTEM, UV-vis spectroscopy, Mott–Schottky, and EIS. Due to the synthesis of the p-n heterojunction, CuFe₂O₄/MgFe₂O₄ has efficient photogenerated carriers, and the hollow structure has a higher specific surface area and stronger adsorption capacity, which is significantly better than that of CuFe₂O₄ and MgFe₂O₄ in terms of photocatalytic performance. The outstanding performance shows that the p-n heterostructure of CuFe₂O₄/MgFe₂O₄ has potential for application in wastewater degradation. Full article

Photocatalytic hydrogen production using stable metal-organic frameworks (MOFs), especially the titanium-based MOFs (Ti-MOFs) as photocatalysts is one of the most promising solutions to solve the energy crisis. However, due to the high reactivity and harsh synthetic conditions, only a limited number of Ti-MOFs have been reported so far. Herein, we synthesized a new amino-functionalized Ti-MOFs, named NH₂-ZSTU-2 (ZSTU stands for Zhejiang Sci-Tech University), for photocatalytic hydrogen production under visible light irradiation. The NH₂-ZSTU-2 was synthesized by a facile solvothermal method, composed of 2,4,6-tri(4-carboxyphenylphenyl)-aniline (NH₂-BTB) triangular linker and infinite Ti-oxo chains. The structure and photoelectrochemical properties of NH₂-ZSTU-2 were fully studied by powder X-ray diffraction, scanning electron microscope, nitro sorption isotherms, solid-state diffuse reflectance absorption spectra, and Mott–Schottky measurements, etc., which conclude that NH₂-ZSTU-2 was favorable for photocatalytic hydrogen production. Benefitting from those structural features, NH₂-ZSTU-2 showed steady hydrogen production rate under visible light irradiation with average photocatalytic H₂ yields of 431.45 μmol·g⁻¹·h⁻¹ with triethanolamine and Pt as sacrificial agent and cocatalyst, respectively, which is almost 2.5 times higher than that of its counterpart ZSTU-2. The stability and proposed photocatalysis mechanism were also discussed. This work paves the way to design Ti-MOFs for photocatalysis. Full article

In this paper we critically discuss several examples of two-dimensional electronic systems displaying interaction-driven metal-insulator transitions of the Mott (or Wigner–Mott) type, including dilute two-dimension electron gases (2DEG) in semiconductors, Mott organic materials, as well as the recently discovered transition-metal dichalcogenide (TMD) moiré bilayers. Remarkably similar behavior is found in all these systems, which is starting to paint a robust picture of Mott criticality. Most notable, on the metallic side a resistivity maximum is observed whose temperature scale vanishes at the transition. We compare the available experimental data on these systems to three existing theoretical scenarios: spinon theory, Dynamical Mean Field Theory (DMFT) and percolation theory. We show that the DMFT and percolation pictures for Mott criticality can be distinguished by studying the origins of the resistivity maxima using an analysis of the dielectric response. Full article

Three bismuth silicate-based photocatalysts (composites of Bi₂SiO₅ and Bi₁₂SiO₂₀) prepared via the hydro-/solvothermal approach were studied using electrochemical methods. The characteristic parameters of semiconductors, such as flat band potential, donor density, and mobility of their charge carriers, were obtained and compared with the materials’ photocatalytic activity. An attempt was made to study the effect of solution components on the semiconductor/liquid interface (SLI). In particular, the Mott–Schottky characterization was made in a common model electrolyte (Na₂SO₄) and with the addition of glycerol as a model organic compound for photocatalysis. Thus, a medium close to those in photocatalytic experiments was simulated, at least within the limits allowed by electrochemical measurements. Zeta-potential measurements and electrochemical impedance spectroscopy were used to reveal the processes taking place at the SLI. It was found that the medium in which measurements were carried out dramatically impacted the results. The flat band potential values (E_fb) obtained via the Mott–Schottky technique were shown to differ significantly depending on the solution used in the experiment, which is explained by different processes taking place at the SLI. A strong influence of specific adsorption of commonly used sulfate ions and neutral molecules on the measured values of E_fb was shown. Full article

We investigate the carrier concentration dependent Seebeck coefficient in Gaussian disordered organic semiconductors (GD-OSs) for thermoelectric device applications. Based on the variable-range hopping (VRH) theory, a general model predicting the Seebeck effect is developed to reveal the thermoelectric properties in GD-OSs. The proposed model could interpret the experimental data on carrier concentration- and temperature-dependence of the Seebeck coefficient, including various kinds of conducting polymer film and small molecule based field-effect transistors (FETs). Compared with the conventional Mott’s VRH and mobility edge model, our model has a much better description of the relationship between the Seebeck coefficient and conductivity. The model could deepen our insight into charge transport in organic semiconductors and provide instructions for the optimization of thermoelectric device performance in a disordered system. Full article