Visible-light Activity Research Articles

Investigation on visible-light induced photocatalytic activity for pure, Ce:doped TiO2 and B:Ce co-doped TiO2 catalysts

In this study, the photocatalytic activity of pristine and Boron (B) - Cerium (Ce) co-doped titanium dioxide (TiO2) have been investigated towards the degradation of aqueous solution of Methylene Blue (MB) dye under visible light activity. The B:Ce co-doped TiO2 catalyst was successfully prepared by co-precipitation method. The structural, optical, and morphological properties of the synthesized samples were characterized by different techniques. PXRD analysis revealed that the prepared nanoparticles (NPs) have tetragonal crystal structures with an anatase phase. In FESEM analysis, the different morphologies (spherical and nanorod bundles) were observed from the synthesized Pure, Ce:TiO2 and B:Ce co-doped TiO2 NPs. The UV-Vis DRS and PL studies showed that B:Ce doped TiO2 exhibited enhanced visible light absorption activity and less electron-hole pair recombination rate. The findings demonstrated the incorporation of B and Ce ions into the TiO2 lattice, which can increase the absorption region to visible light and prevent the recombination rate of e-/h+ pairs. The results of the photocatalytic experiment show that B-Ce co-doped TiO2 improves photodegradation performance, with 97%, 98.0%, and 99% of the MB dye decomposing within 150 min of illumination under simulated visible light irradiation.

Overcoming small-bandgap charge recombination in visible and NIR-light-driven hydrogen evolution by engineering the polymer photocatalyst structure

Designing an organic polymer photocatalyst for efficient hydrogen evolution with visible and near-infrared (NIR) light activity is still a major challenge. Unlike the common behavior of gradually increasing the charge recombination while shrinking the bandgap, we present here a series of polymer nanoparticles (Pdots) based on ITIC and BTIC units with different π-linkers between the acceptor-donor-acceptor (A-D-A) repeated moieties of the polymer. These polymers act as an efficient single polymer photocatalyst for H2 evolution under both visible and NIR light, without combining or hybridizing with other materials. Importantly, the difluorothiophene (ThF) π-linker facilitates the charge transfer between acceptors of different repeated moieties (A-D-A-(π-Linker)-A-D-A), leading to the enhancement of charge separation between D and A. As a result, the PITIC-ThF Pdots exhibit superior hydrogen evolution rates of 279 µmol/h and 20.5 µmol/h with visible (>420 nm) and NIR (>780 nm) light irradiation, respectively. Furthermore, PITIC-ThF Pdots exhibit a promising apparent quantum yield (AQY) at 700 nm (4.76%).

Visible Light Activation of Gold Nanoparticles Embedded into Titanium Dioxide Surface in Electrospun Polymeric Coatings

This work reports the development of a functional photocatalytic coating based on a combination of polymeric electrospun fibres and nanoparticles that is intended to be activated in the visible light range. In this sense, the resulting fibres can act as an effective matrix for the incorporation of titanium dioxide (TiO2) particles, which are covered by gold nanoparticles (AuNPs), in the outer surface of the metal oxide precursor. In the first step of the process, the optical properties of the nanoparticles were determined by UV-Vis spectroscopy. The extension of the visible absorption can be associated to the localized surface plasmon resonance (LSPR) of the metallic AuNPs. In addition, the resultant particle size distribution and average particle diameter was evaluated by dynamic light scattering (DLS) measurements. Furthermore, the phase composition and porosity of the functional particle powder were analysed by an XRD and N2 adsorption test. In the second step, these synthesized particles have been successfully immobilized into a PAA + β-CD electrospun fibre matrix by using the two different deposition methods of dip-coating and solution-casting, respectively. The morphological characterization of the samples was implemented by means of scanning electron microscopy (SEM), showing uniform and homogeneous, free-beaded fibres with a random distribution of the synthesized particles deposited onto the electrospun fibres. Then, the functional coatings were removed from the substrate, and a thermogravimetric (TGA) analysis was carried out for each sample in order to obtain the precursor mass immobilized in the coating. Once the overall mass of precursor was obtained, the percentage of TiO2 particles and AuNPs in the precursor was calculated by using inductively coupled plasma atomic emission spectrometry (ICP-AES). Finally, the photocatalytic activity of both functional solution and electrospun coatings were evaluated in terms of a gradual degradation of rhodamine B (RhB) dye after continuous exposition to a visible-light lamp.

Novel copper vanadium oxide/g-C3N4 nano-composites for optoelectronic and biosensing properties

This study investigates into the synthesis, characterization, and multifaceted analysis of a composite material comprised of copper vanadium oxide (CVO) and graphitic Carbon Nitride g-C3N4 (GCN). The fabrication of the composite was achieved through wet-chemical method followed by annealing at 600 °C for 3 h, ensuring controlled composition and structure. The characterization process encompassed X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible spectroscopy, unveiling the composite's crystalline structure, novel nano-rod morphology with decorated flakes, and UV–visible light activation capability. The obtained band gap of approximately 2.7 eV signified the composite's optical properties. Electrochemical analysis, including cyclic voltammetry (CV), highlighted the composite's robust biosensing attributes, particularly in response to ascorbic acid. The conducting and metallic characteristics of the composite enhanced its reactivity, promising applications in biosensors and energy storage devices. This comprehensive investigation elucidates the multifaceted potential of the CVO/GCN nano-composite across diverse optoelectronic realms.

Construction of NiS/MnCdS S-scheme heterojunction for efficient photocatalytic overall water splitting: Regulation of surface sulfur vacancy and energy band structure

The overall water splitting based on specific photocatalysts is one of the ultimate ways to solve the energy and environmental crisis facing humanity. Sulfide photocatalysts have greater potential in photocatalytic production of solar fuel. However, due to its easy photocorrosion phenomenon, it not effectively driving the water oxidation semi-reaction to produce oxygen, so how to use sulfide photocatalyst to decompose pure water to achieve stoichiometric reaction of H2/O2 production remains a quite challenging task. Herein, sulfur vacancies-rich MnCdS nanoparticles were modified with NiS nanosheets through the hydrothermal derivation method. Different concentration gradients of sulfur-vacancy in MnCdS nanoparticles (MnCdS-Vs-X) with tunable band structures were successful prepared by regulating the concentration of hydrazine hydrate, thus improves the efficiency of light energy utilization and charge separation and the existence of S defects was verified by transmission electron microscopy (TEM) and electron paramagnetic resonance (EPR). The density function theory (DFT) calculation bears out that the draw into of S vacancy adjusted the band structure of MnCdS. Moreover, the successful construction of an S-scheme heterojunction between NiS and MnCdS-Vs-3 has been strongly demonstrated by in-situ XPS and UPS, which promoted interfacial charge separation and further improved the photocatalytic hydrogen evolution efficiency. The as-obtained S-scheme 20 %NiS/MnCdS-Vs-3 heterojunction exhibit excellent visible-light H2 production activity of 4099.55 μmol g−1h−1, 6.75 times higher than pure MnCdS. Most importantly, the excellent and stable photocatalytic overall water splitting activity of H2-509.70 μmol g-1h−1/O2-254.90 μmol g-1h−1 were obtained over 20 % NiS/MnCdS-Vs-3, which further demonstrates the application value of NiS/MnCdS-Vs-3 photocatalysts. This work proposes new ideas for the application of S-vacancies and S-scheme heterojunction in addressing the stability issues associated with sulfide-based photocatalysts in photocatalytic water splitting.

A photoelectrochemical aptasensing platform assembled at the heterojunction interface of Cu3BiS3 sensitized CuV2O6 for bisphenol A.

The interaction between the sensitive interfaces of photoelectrochemical (PEC) semiconductor nanomaterials and microscopic matter creates endless potential for the efficient detection of endocrine disruptor. Thiswork presents the development of a high-efficiency PEC aptasensor for bisphenol A (BPA) monitoring based on Cu3BiS3 sensitized CuV2O6 nanocomposites with exceptional visible-light PEC activity. We implemented the integration of Cu3BiS3 nanosheet photosensitizer to sensitize the CuV2O6 nanowire structure that was synthesized utilizing a facile hydrothermal approach. The band gap alignment between Cu3BiS3 and CuV2O6 facilitated enduring PEC response yielding an efficient interfacial structure. The surface of the CuV2O6/Cu3BiS3 electrode was modified with BPA aptamer, enabling specific binding with BPA and precise quantification of its content. The developed aptamer sensors possess a wide detection range of5.00 × 10-1 to 5.00 × 104 ng/mL, and a low detection limit of 1.60 × 10-1 ng/mL (at S/N = 3). After undergoing 20 testing cycles and enduring long-term storage, the sensor maintained its stability and showcased excellent repeatability and reproducibility. This study presents a promising methodology for the detection of BPA in environmental settings.

The visible optical driving N-S co-doped La2Ti2O7 activated peroxydisulfate for carbamazepine removal: Mechanism and performance

Carbamazepine (CBZ) as an “emerging pollutant”, which poses a threat to human health. Photocatalytic activation of peroxydisulfate (PDS)-based advanced oxidation processes (AOPs) can deep oxidation of CBZ pollutants through the generation of free radicals with high redox potential. However, most of common photocatalysts only have a narrow band gap, which limits their application under visible light. In order to broaden the band gap of photocatalysis, herein we report the N-S co-doping in La2Ti2O7 (N-S LTO) is viable, and then evaluate the visible light activation of PDS to remove the pollutants of CBZ. Compared with pure LTO and N or S mono-doped LTO, the degradation efficiency of CBZ in N-S LTO/PDS/Vis system was 2.18, 1.45, and 1.41 times improved, respectively, under the visible light irradiation condition. Furthermore, the mechanism of CBZ degradation under N-S LTO/PDS/Vis processes was explored and revealed that the HO• and SO4•− were the main substances for the breakage of CBZ molecules. The further physicochemical characterization of samples convinced the active sites in N-S LTO for PDS motivation and oxidation processes with the best separation and migration ability of carriers than other samples. Finally, combined with density functional theory (DFT) calculations, the detailed degradation pathways of CBZ were proposed. This work not only provides insight into the construction of photocatalysts with co-doping for PDS activation, but also brings an inspiration of CBZ degradation in water treatment.

High-efficiency and conveniently recyclable g-C3N4/diatomite/calcium alginate composite gel bead photocatalysts

Graphitic carbon nitride (g-C3N4) is considered an encouraging photocatalyst with visible light activity. However, the utilization of g-C3N4 nanosheets in powdered form in wastewater treatment presents difficulties in the recovery and recycling of photocatalysts. Consequently, supported g-C3N4 photocatalysts have been developed for practical applications. In the present work, a novel, conveniently recyclable composite gel bead photocatalyst, comprised of g-C3N4/diatomite/calcium alginate, has been fabricated using a dropwise addition strategy. The systematic investigation of photocatalytic activity and photochemical stability of the composite gel beads was conducted through the degradation of methylene blue (MB) under visible light exposure (λ > 420 nm). As a result, g-C3N4/diatomite/calcium alginate gel beads show a high photocatalytic effectiveness of 95% when MB solution is disintegrated at 120 minutes.

Automotive Technology Revolutionized Restorative Dentistry Discovery of Alpha-diketone/Amine Catalyst: Part II -Reflections on Photopolymerization from Conception to Development of Composite Resin and Activator Light.

A full account of the preceded early research tribulation that led to the development of the first visible light activated composite resin and the first visible light activator source is documented. The events took place over four years since early 1974 when a raw industrial composite resin that was radiolucent, stiff paste, universal optically opaque white color, polymerized by exposure to a prototype visible light for 120 seconds was given to developed. Four years later, the developed restorative composite resin ended up as a radiopaque, optically translucent, universal color with an additional three shades that possessed the biologic, esthetic, mechanical and physical characteristics with proven efficacy be used for esthetic zone. This conservative account of early development of a technology that must count as one of a small number of inventions during the seventies, over the years has revolutionized restorative dental practice. We were privileged and very lucky to be associated with developmental stages, stumbling blocks, and final success of the first LC Composite resin that ignited the thought process worldwide and laid the foundation for modern esthetic restoratives practiced today.

Synthesis of TiO2/Fe2O3 Nanocomposites as Photocatalyst for Methyl Orange Degradation

Fe2O3/TiO2 composites were successfully synthesized using the sol-gel method. The photocatalytic performance of prepared nanocomposites to degrade methyl orange under UV light irradiation was systematically investigated. The Fe2O3 added and calcination temperature were varied to study their effect on psychochemical properties. Further, to study the effect of psychochemical properties of the prepared nanocomposites on photocatalytic activity, X-ray diffraction (XRD), and scanning electron microscope Energy Dispersive X-ray spectroscopy (SEM-EDS) characterization were conducted. The visible light active Fe2O3 photocatalyst managed to decrease the bandgap energy of the prepared composites from 3.32 eV to 1.95 eV. This decrease in the band gap energy led to the composite being more active under visible light and less active under UV light irradiation. A composite with 6% Fe2O3 content exhibits the smallest degradation efficiency of 14% in 180 min, while the pure TiO2 nanoparticles are 94%. The results in this study provided important implications for further research on the preparation of composite TiO2 with Fe2O3 co-catalyst showing a promising route for improving the visible light activity of photocatalysts.

A step-scheme mechanism in a NiO/CdS heterojunction nanoarray for visible light-activated gas sensing at room temperature

A novel step-scheme NiO/CdS heterojunction nanoarray sensor was constructed in situ on a commercial alumina flat surface to detect triethylamine under visible light activation.

Structure, Optics, Visible Light and Photocatalytic Activity of Pure and Pd Doped Tungsten Trioxide Nanoparticles Synthetized by the Microwave Irradiation Method

Structure, Optics, Visible Light and Photocatalytic Activity of Pure and Pd Doped Tungsten Trioxide Nanoparticles Synthetized by the Microwave Irradiation Method

Controllable synthesis of vertically aligned WO3 nanoplate arrays on stainless steel for improved visible-light photoelectrocatalytic activity

Vertically aligned WO3 nanoplate films were synthesized on stainless steel (SS) via a simple hydrothermal method.

Controlled synthesis of 2D-2D conductive metal-organic framework/g-C3N4 heterojunctions for efficient photocatalytic hydrogen evolution.

Designing photocatalysts with efficient charge separation and electron transport capabilities to achieve efficient visible-driven hydrogen production remains a challenge. Herein, 2D-2D conductive metal-organic framework/g-C3N4 heterojunctions were successfully prepared by an in situ assembly. Compared to pristine g-C3N4, the ratio-optimized Ni-CAT-1/g-C3N4 exhibits approximately 3.6 times higher visible-light H2 production activity, reaching 14 mmol g-1. Through investigations using time-resolved photoluminescence, surface photovoltage, and wavelength-dependent photocurrent action spectroscopies, it is determined that the improved photocatalytic performance is attributed to enhanced charge transfer and separation, specifically the efficient transfer of excited high-energy-level electrons from g-C3N4 to Ni-CAT in the heterojunctions. Furthermore, the high electrical conductivity of Ni-CAT enables rapid electron transport, contributing to the overall enhanced performance. This work provides a feasible strategy to construct efficient dimension-matched g-C3N4-based heterojunction photocatalysts with high-efficiency charge separation for solar-driven H2 production.

Enhanced photocatalytic performance of SnS2 under visible light irradiation: strategies and future perspectives.

Tin(II) sulfide (SnS2) has emerged as a promising candidate for visible light photocatalytic materials. As a member of the transition metal dichalcogenides (TMDs) family, SnS2 features a band gap of approximately 2.20 eV and a layered structure, rendering it suitable for visible light activation with a high specific surface area. However, the application of SnS2 as a visible light photocatalyst still requires improvement, particularly in addressing the high recombination of electrons and holes, as well as the poor selectivity inherent in its perfect crystal structure. Therefore, ongoing research focuses on strategies to enhance the photocatalytic performance of SnS2. In this comprehensive review, we analyze recent advances and promising strategies for improving the photocatalytic performance of SnS2. Various successful approaches have been reported, including controlling the reactive facets of SnS2, inducing defects in the crystal structure, manipulating morphologies, depositing noble metals, and forming heterostructures. We provide a detailed understanding of these phenomena and the preparation techniques involved, as well as future considerations for exploring new science in SnS2 photocatalysis and optimizing performance.

Non-metallic nitrogen-doped graphene quantum dots coupled with g-C3N4 achieve efficient photocatalytic performance

Photocatalysis has been prominently featured as a promising technology for solving environmental problems and energy crises. The incorporation of supported non-metallic cocatalysts is paramount in significantly augmenting the efficiency and performance of semiconductor photocatalysis. N-GQD/CN was successfully prepared and showed excellent performance in terms of light-absorbing capacity, carrier separation efficiency and visible-light driving. The findings underscore the exceptional photocatalytic prowess of the 0.02 wt.% N-GQD/CN composites, particularly in the degradation of RhB, HCl-TC, and BPA under visible light irradiation. The 0.02 wt.% N-GQD/CN composite could eliminate 91.2 % RhB in 90 min, remove 72.4 % of the HCl-TC in 180 min, and degrade 47.9 % of the BPA in 4 h. All of the activities of the 0.02 wt.% N-GQD/CN was superior to that of the monomer g-CN. This elevated photocatalytic performance can be predominantly attributed to the N-GQDs acting as co-catalysts. These N-GQDs possess substantial specific surface areas, effectively enhancing light absorption and facilitating synergistic interactions with g-CN nanosheets. Exploring the utility of N-GQD/CN using ionic interference and pH photocatalysis experiments. The present work provides a rational strategy for designing 0D/2D photocatalysts with improved visible light activity for environmental applications.

Preparation and photocatalytic performance of nanosheet BiOClxBryI1-x-y with high visible light activity by one-pot solvothermal method

A ternary solid solution (BiOClxBryI1-x-y) was constructed in this work to improve the photocatalytic activity of BiOX (X = Cl, Br, I). Compared with BiOCl and BiOBr, the optical absorption properties of BiOClxBryI1-x-y in the visible light region have been enhanced due to their narrower band gap. This enhancement could be attributed to the modulation of electronic structure originated from the coupling of Cl, Br and I. Additionally, the separation of photogenerated carriers has been enhanced, and the active species, h+ and •O2–, contributed more to the photocatalytic performance due to the positions of VB and CB. The pseudo-first-order rate constant of the optimal sample BiOCl0.6Br0.2I0.2 was 14 times higher than that of BiOCl in photodegradation of RhB and 4 times higher in the case of tetracycline.

One-pot synthesis and immobilization of urea-derived graphitic carbon nitride onto ceramic foams for visible-light photocatalytic wet peroxide oxidation in water treatment

A straightforward one-pot in-situ method was employed to successfully obtain urea-derived graphitic carbon nitride (CN) deposited onto a macro-reticulated ceramic alumina-based foam (AF). The resulting CN-coated foams (CN-F) were characterized by different techniques (SEM, N2 adsorption, DRUV–vis, fluorescence spectroscopy), revealing that CN-F structures have visible light absorption and distinctive photoluminescence properties. Moreover, these CN-F materials were investigated for the first time in water treatment, specifically for the degradation of the antibiotic sulfamethoxazole (SMX) in aqueous solutions under visible-LED irradiation and continuous flow mode with total recirculation. The photocatalytic activity of different CN-F was investigated using various CN loads, without or with addition of H2O2 (i.e. Photocatalysis – PC or photocatalytic wet peroxide oxidation – PCWPO, respectively), at different pH (5.0 – 8.5) and a tentative reaction mechanism was described. Thus CN-F with 13.5 mgCN·gAF−1 performed better than with other loads in PCWPO, as demonstrated by a higher conversion of H2O2 and SMX into reaction by-products (short-chain acids and inorganic ions belonging to organic N- or S-containing species). This photocatalyst also succeeded when tested in continuous dead-end mode operation with SMX in ultrapure water or a mixture of 6 pharmaceutical substances (500 ppb each) spiked in a natural river water sample, demonstrating an excellent visible-light PCWPO activity preventing fouling over the catalyst, achieving lower phytotoxicity for the treated water and showing a prolonged stability under 72 h, without CN detachment or any loss of material.

Assembling Ag@CuO/UiO-66-NH2 nanocomposites for efficient photocatalytic degradation of xylene.

Achieving efficient and stable photocatalytic degradation of xylene hinges on the advancement of photocatalytic materials with outstanding visible light activity. This low-carbon strategy serves as a promising solution to combat air pollution effectively. In this study, we synthesized a Z-scheme heterojunction Ag@CuO/UiO-66-NH2 nanocomposite by hydrothermal method to investigate its photodegradation properties for xylene gas under visible light conditions. XRD, XPS, SEM, FTIR, and UV-vis analyses were employed to confirm the presence of the Z-scheme heterojunction. The CuO/UiO-66-NH2 (CuU-2) composite has high photocatalytic activity, which is 2.37 times that of the original UiO-66-NH2. The incorporation of Z-scheme heterojunction facilitates efficient charge transfer and separation, leading to a substantial enhancement in photocatalytic activity. The Ag@CuO/UiO-66-NH2 (Ag-1@CuU) composite has the highest photocatalytic activity with a degradation efficiency of 84.12%, which is 3.36 times and 1.41 times that of UiO-66-NH2 and CuO/UiO-66-NH2, respectively. The silver cocatalyst improves the absorption capacity of the composite material to visible light, makes the ultraviolet visible absorption edge redshift, and significantly improves the photocatalytic performance. This study introduces a novel approach for xylene gas degradation and offers a versatile strategy for designing and synthesizing metal-organic framework (MOF)-based photocatalysts with exceptional performance.

Noble metal-free 0D-1D CoOx/Mn0.3Cd0.7S nanocomposites for efficient visible-light hydrogen production

Here, a series of MnxCd1-xS sosoloid composite photocatalysts with visible-light activity were first prepared by a solvothermal process. The element ratio of Cd2+ to Mn2+ was optimized to be Mn0.3Cd0.7S in MnxCd1-xS sosoloid on account of its photocatalytic activity for H2 evolution from H2O in response to visible light excitation. And on this basis, the CoOx nanopariticles were loaded on the surface of Mn0.3Cd0.7S sosoloid composite to obtain a binary p-n heterojunction of CoOx/Mn0.3Cd0.7S composite through a facile impregnation process and a high temperature sintering procedure. Benefitting from the synergistic effect of the built-in electric field, binary p-n heterojunction structure, and rearrange of the Fermi level equilibrium, the as-synthesized CoOx/Mn0.3Cd0.7S composite presents a highly enhanced photocatalytic activity for hydrogen production from H2O in response to visible light excitation, which is demonstrated to be 53.4 and 4.0 times higher than that of the primitive CdS and Mn0.3Cd0.7S, respectively. Furthermore, after 4 times circles of photocatalytic H2 production tests, the CoOx/Mn0.3Cd0.7S composite still keeps 92.0 % of the original photocatalytic activity. Considering its reasonable photochemistry stability and excellent photocatalytic activity for hydrogen evolution from H2O under with visible light excitation, the as-synthesized CoOx/Mn0.3Cd0.7S composite has potential applications in solar hydrogen production areas.