Hole Recombination Research Articles

Hollow and heterojunction-structured Janus nanomotors for pyroelectrodynamic and nanozyme-catalyzed tumor therapy

Pyroelectrodynamic therapy (PEDT) has emerged as an attractive therapeutic modality for tumors, but is dramatically discounted by inherent defects of wide band gap, fast electron − hole recombination and low photothermal utilization. Herein, hollow-structured Janus nanoparticles (NPs) are developed to improve tumor accumulation and PEDT generation of reactive oxidative species (ROS) for antitumor treatment. Hollow barium titanate (hBT) NPs were prepared by the template and hydrothermal method for in situ deposition of CuS nanodots and then partially coated with polydopamine (PDA) caps to obtain hBT-CuS@PDA. Finite element analysis reveals that the unique thin shell of hBT benefits transportation of pyroelectrically generated charge carriers through shortening diffusion distance to the interface. The CuS deposition forms heterojunctions with hBT to accelerate electron − hole separation and leads to a larger pyroelectric current. The hollow structure facilitates light absorption and conversion, and the photothermal effect of the half-coated PDA caps generates asymmetric temperature gradient to drive NP locomotion across biological barriers. The in situ generated pyroelectric field selectively affects membrane potential and fluidity of tumor cells to enhance the specific NP internalization. The pyroelectric effect enhances the peroxidase-like activity of CuS nanodots to generate toxic ·OH and the glutathione peroxidase-like activity to inhibit glutathione consumption of ROS. The integration of photothermal, pyroelectric, nanozyme catalysis and self-protrusion effects promotes NP accumulation and penetration throughout tumors to exhibit therapeutic effect at a mild-temperature, reducing the possible high-temperature ablation of normal tissues. The hollow and heterjunction structure generates abundant intracellular ROS and efficient diffusion in tumor tissues to inhibit tumor growth and extend animal survival, offering a safe and effective PEDT strategy.

Facile Synthesis of Bandgap-Engineered N-Doped MgO/g-C3N4 Nanocomposites for Enhanced Sunlight-Driven Photocatalytic Degradation of Organic Dyes

This study tests the theory of using a p-n junction to inhibit the recombination of photo-generated electrons and holes in N-MgO/g-C3N4 for the photocatalytic degradation of methylene blue (MB) dye. While the use of n-type semiconductor junctions with g-C3N4 for bandgap narrowing is well-studied in dye degradation, this research explores the innovative application of nitrogen (N)-doped MgO to create a p-type junction with n-type g-C3N4. The N-MgO/g-C3N4 nanocomposites were designed and synthesized to leverage both the bandgap narrowing effect and the formation of a p-n junction. The results demonstrate that these nanocomposites can effectively degrade MB dye under sunlight, achieving over 90% degradation efficiency with a bandgap of 2.63 eV. Under high pH conditions, the degradation efficiency further increased to 94%. The enhanced photocatalytic activity of the N-MgO/g-C3N4 composite is attributed to the formation of a heterojunction, which facilitates efficient separation and transmission of photo-induced charge carriers. This study discusses the detailed mechanism of this enhanced activity, emphasizing the role of the p-n junction in promoting effective charge separation and transfer, thereby improving the photocatalytic performance under sunlight.

Adsorption‐photocatalysis for methylene blue dye removal by novel Fe‐MOFs through defect engineering

AbstractIn recent years, metal–organic frameworks (MOFs) have attracted much attention in environmental pollution control. However, most MOFs still have problems such as low utilization of visible light and easy recombination of photogenerated electrons and holes. In this study, novel defective Fe‐MOFs with appropriate structural defects were prepared by solvothermal method and used to remove methylene blue (MB) in aqueous phase through adsorption and photocatalysis. Defective Fe‐MOFs have Fe content as high as 10.31% with specific surface area of 40.95 m2/g, which is beneficial for both dye adsorption and photocatalytic process. Defective Fe‐MOFs have spindle‐like structures with sizes ranging from 40 nm to 100 nm and an average size of 69.1 nm, as well as some irregularly shaped nanoparticles. Irregular stacking of these two kinds of structure makes Fe‐MOFs appropriate structural defects, large specific surface area, and mesoporous structure. Kinetics and isotherms of dye adsorption process are consistent with pseudo‐first‐order kinetic model and Freundlich isotherm model, respectively. Defective Fe‐MOFs can absorb MB dye rapidly, reaching adsorption equilibrium within 60 min. Dye adsorption process is endothermic, spontaneous, and entropy‐increasing process. After 180 min visible light illumination, dye photocatalytic efficiency of the defective Fe‐MOFs reaches 97.56% in the condition of MB concentration as high as 30 mg/L. Consequently, defective Fe‐MOFs with appropriate structural defects, porous structure, high Fe‐O content, and strong electron‐donating amino groups have huge potential applications in removing organic dyes from the aqueous solution by a green and environmentally friendly way due to their high dye adsorption and dye photocatalytic activity.

Biomass-derived activated carbon/cerium oxide nanocomposite as adsorptive photocatalyst for effective removal of carcinogenic dye

Semiconductor-based photocatalysts offer potential solutions for carcinogenic dye-related issues in water under light irradiation. However, their efficiency is affected by the recombination of photoelectrons and holes. The present study focuses on synthesizing biomass-derived activated carbon (AC), Cerium Oxide (CeO2), and AC/CeO2 (ACO) nanocomposites for toxic dye degradation. The physicochemical properties of samples were analyzed by XRD, SEM, EDX, TEM, UV–visible, Raman, XPS, and PL analysis. The photocatalytic performance of AC, CeO2, and ACO nanocomposites was evaluated under dark and light conditions for the removal of carcinogenic Rhodamine B (RhB). ACO nanocomposites exhibited adsorptive-photocatalytic performance, displaying unique adsorption and photocatalytic degradation rates due to their synergistic combination. Remarkably, the ACO-4 composite showed lower recombination of e−/h+ pairs, thereby exhibiting superior photocatalytic activity compared to other samples. The degradation rate constant under light was 0.1815 min⁻¹ with a half-life time of 3.81 min, whereas in dark, it was 0.0665 min⁻¹ with a half-life time of 10.42 min.

Programmed Charge Transfer in Conjugated Polymers with Pendant Benzothiadiazole Acceptor for Simultaneous Photocatalytic H2O2 Production and Organic Synthesis.

While being important candidate for heterogeneous photocatalyst, conjugated polymer typically exhibits random charge transfers between the alternating donor and acceptor units, which severely limits its catalytic efficiency. Herein, inspired by natural photosystem, the concept of guiding the charge migration to specific reaction sites is employed to significantly boost photocatalytic performance of linear conjugated polymers (LCPs) with pendant functional groups via creating programmed charge-transfer channels from the backbone to its pendant moiety. The pendant benzothiadiazole, as revealed in both in situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations, can act as electron "reservoir" that aggregates electrons at the active sites. Moreover, the presence of charge-transfer channels, evidenced by transient absorption spectroscopy (TAS), accelerates the electron transfer, preventing the recombination of electrons and holes. As a result, in this elaborately-designed architecture, the photogenerated electron can move smoothly towards the reduction sites, facilitating the reduction of O2 into H2O2, while remaining holes are directed to oxidation centers, simultaneously oxidizing furfuryl alcohol to furoic acid. The optimized photocatalyst LCP-BT demonstrates a competitive catalytic performance with H2O2 productivity of 868.3 μmol L-1 h-1 (9.8 times higher than conventional random charge-transfer polymer LCP-1) and furfuryl alcohol conversion over 95% after 6 h.

Surface modification of TiO2 photoanode in dye-sensitized solar cells using reduced graphene oxide: A computational and experimental study

This study investigated the modification of TiO2 photoanodes using reduced graphene oxide (rGO) to enhance electron transport channels and prevent recombination processes, thereby improving the photovoltaic performance. Through the ultraviolet (UV)-assisted photoreduction of GO on TiO2 coated on a fluoride tin oxide substrate (FTO|TiO2), we demonstrated the successful integration of rGO. This was evidenced by the increased Csp2 content observed during X-ray photoelectron spectroscopy and reduced photogenerated electron–hole recombination observed during photoluminescence spectroscopy. The incorporation of rGO significantly improved the photocurrent density and power conversion efficiency (PCE). A 12 % increase was observed in the PCE, which reached 8.5 % when the UV irradiation time was optimized from 10 to 15 min compared with the 7.57 % in the standard cell (rGO-0 min). Electrochemical impedance spectroscopy confirmed that the optimized rGO content enhanced the electron lifetime and recombination resistance, attributable to the high conductivity and large specific surface area of rGO. DFT simulation further elucidated how improved charge separation and transport mechanisms of TiO2–rGO heterojunction. This study highlights the potential of TiO2–rGO materials as promising electrodes for improving the efficiency, capacity, and stability of dye-sensitized solar cells.

Visible light sensitive BiVO4–TiO2 nanocomposites for photocatalytic dye degradation

Abstract The hydrothermal approach was used to prepare visible light active BiVO4–TiO2 nanosheet composites in varying molar ratios. The photoluminescence (PL) spectrum, X-ray photoelectron spectroscopy (XPS), UV-Visible Diffuse Reflectance Spectroscopy (DRS), Transmission electroscopy (TEM), Brunauer-Emmett-Teller (BET) and field emission scanning electron microscopy (FESEM), were used to analyze the photocatalysts and composites. Photocatalytic activity of BiVO4–TiO2 composites was investigated by decolorizing methylene blue. Out of four different molar ratio BiVO4–TiO2 composites with a molar ratio of 3:1 BiVO4 TiO2 composite showed enhanced photocatalytic activity which is further proved by photoluminescence investigation of coumarin and Scavenger test. The DRS of BiVO4 TiO2 composite showed red shift in optical absorption. The enhanced photocatalytic activity is due to minimizing electron hole recombination by making composite with TiO2.

Synergistic effect of FeOOH cocatalyst and Al2O3 passivation layer on BiVO4 photoanode for enhanced photoelectrochemical water oxidation

BiVO4 is one of the most attractive photoanodes for water oxidation due to its 2.4 eV narrow band gap, suitable band edge position, good stability in aqueous solution, low cost and non-toxicity. However, due to some inherent disadvantages such as low carrier mobility, severe charge recombination and slow water oxidation kinetics, the actual BiVO4 photocurrent density is often lower than the theoretical value of 7.5 mA cm−2. In this paper, BiVO4 was modified by alkali-treated Al2O3 passivation layer and FeOOH, and the photocurrent density of BiVO4 reached an astonishing 3.8 mA cm−2 at 1.23 VRHE, and the ABPE (applied bias photon-to-current efficiency) was close to 1 %. The detailed structural characterization and electrochemical test show that Al2O3 prepared by ALD (atomic layer deposition) can play a role in passivation of BiVO4 surface state after alkali treatment, inhibit electron hole recombination on BiVO4 surface, and accelerate hole transfer. As a hole storage layer and catalyst layer, FeOOH promoted the interfacial hole transfer, increased the active sites at the electrode electrolyte interface, and significantly increased the water oxidation activity. This work provides a novel method to enhance the performance of water electrolysis by using ALD to assist passivation of bismuth vanadate photoanode surface states.

A Facile Microwave-Promoted Formation of Highly Photoresponsive Au-Decorated TiO2 Nanorods for the Enhanced Photo-Degradation of Methylene Blue.

The integration of noble metal nanoparticles (NPs) effectively modifies the electronic properties of semiconductor photocatalysts, leading to improved charge separation and enhanced photocatalytic performance. TiO2 nanorods decorated with Au NPs were successfully synthesized using a cost-effective, rapid microwave-assisted method in H2O2 and HF media for methylene blue (MB) degradation under visible light illumination. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, and UV-vis spectroscopy were employed to characterize the structures, morphologies, compositions, and photoelectronic properties of the as-synthesized materials. The fusing of Au NPs effectively alters the electronic structure of TiO2, enhancing the charge separation efficiency and improved electrical conductivity. The HF treatment promotes the exposure of the highly reactive (001) and (101) crystalline facets. The improved photocatalytic activity of Au/TiO2, achieving 97% efficiency, is attributed to the surface plasmon resonance (SPR) effect of the Au NPs and the presence of oxygen vacancies. The photodegradation of MB using the TiO2/Au photocatalysts follows pseudo-first-order kinetics, highlighting the enhanced catalytic efficiency of the synthesized nanostructures. The exceptional properties of the binary Au/TiO2 photocatalysts, including the SPR effect, exposed crystallographic faces, and efficient charge carrier separation through a decrease in the recombination of electrons and holes, contribute to the photocatalytic degradation of MB.

Hole Polaron-Mediated Suppression of Electron-Hole Recombination Triggers Efficient Photocatalytic Nitrogen Fixation.

In the pursuit of successful photocatalytic transformations, challenges persist due to limitations in charge carrier utilization and transfer efficiency, which stemming from rapid recombination. Overcoming these limitations necessitates the exploration of novel mechanisms that enhance the effective separation of photogenerated electron-hole pairs. Herein, deviating from the conventional approach of enhancing carrier migration to separate photogenerated charges and extend their lifetime, the proposal is to directly prevent the recombination of photogenerated electrons and holes by forming hole polarons. Specifically, disordered pores are introduced on the surface of KTaO3 ultrathin sheets, and the clear-cut evidences in electron paramagnetic resonance, photoluminescence, and ultrafast spectroscopy unambiguously confirm the enhanced carrier-phonon coupling, which results in the formation of hole polarons to impede the recombination of photogenerated electron-hole pairs. Taking the challenging nitrogen oxidation reaction as an example, it is found that the hole polarons in atomic-disordered pore KTaO3 ultrathin nanosheets trigger outstanding photo-oxidation performance of nitrogen (N2)to nitrate, with a nitrate-producing rate of 2.1 mg g-1 h-1. This scenario is undoubtedly applicable to a wide variety of photocatalytic reactions due to the common challenge of charge carrier recombination in all photocatalytic processes, manifesting broad implications for promoting photocatalysis performance.

Modification of opto‐electrical behavior of polyvinyl chloride by infusion of SrTiO3 nanofiller synthesized via green route

AbstractEnhancing the opto‐electrical properties of polymer is crucial for optoelectronic devices. This study emphasis the synthesis of strontium titanate (SrTiO3) nanoparticles using a green sol–gel method and incorporates them into polyvinyl chloride (PVC) to create nanocomposite films via solution casting. The structural, optical, thermal, and electrical properties of PVC with SrTiO3 at concentrations of 1, 3, and 5 wt.% were examined. Better crystallinity was obtained with filler incorporation. Fourier transform infrared shows the physical interaction between nanofiller and the matrix. SEM results suggested that SrTiO3 nanofiller are well distributed in PVC surface. UV–Vis spectroscopy was used to study optical behavior of the nanocomposites. Optical bandgap energy decreased from 3.2 to 2.5 eV with increased concentration of SrTiO3 in PVC matrix. Photoluminescence results show the reduction of electron hole recombination rate. The integration of SrTiO3 nanofiller into the PVC matrix improved the thermal stability, dielectric constant, and the overall performance of the prepared nanocomposite films, making them suitable for high‐temperature optoelectronic and energy storage applications. The green synthesis of SrTiO3 nanofiller also ensures the environmental benefits, high purity, and homogeneity, leading to consistent enhancements in the PVC/SrTiO3 composites. These improvements highlight their potential for advanced optoelectronic devices requiring efficient and durable materials.

Zn/Pt dual-site single-atom driven difunctional superimposition-augmented sonosensitizer for sonodynamic therapy boosted ferroptosis of cancer

Sonodynamic therapy (SDT) as a non-invasive antitumor strategy has been widely concerned. However, the rapid electron (e-) and hole (h+) recombination of traditional inorganic semiconductor sonosensitizers under ultrasonic (US) stimulation greatly limits the production of reactive oxygen species (ROS). Herein, we report a unique Zn/Pt dual-site single-atom driven difunctional superimposition-augmented TiO2-based sonosensitizer (Zn/Pt SATs). Initially, we verify through theoretical calculation that the strongly coupled Zn and Pt atoms can assist electron excitation at the atomic level by increasing electron conductivity and excitation efficiency under US, respectively, thus effectively improving the yield of ROS. Additionally, Zn/Pt SATs can significantly enhance ferroptosis by producing more ROS and sonoexcited holes under US stimuli. Therefore, the establishment of dual-site single-atom system represents an innovative strategy to enhance SDT in cancer model of female mice and provides a typical example for the development of inorganic sonosensitizer in the field of antitumor therapy.

Cu-doped Bi2S3 nanorod films via chemical synthesis for improved photoelectrochemical water splitting

Bismuth sulfide (Bi2S3) is a promising photoelectrochemical (PEC) material due to its favorable optoelectronic properties. However, its overall PEC performance is limited by slow charge transport and high electron–hole recombination at the Bi2S3-electrolyte interface. In this study, we have intentionally introduced Cu into Bi2S3 photoelectrodes to enhance both their physical properties and PEC performance. Cu-doping concentrations ranging from 0 to 8.4 at.% were incorporated into Bi2S3 films synthesized via chemical bath deposition followed by annealing. The undoped Bi2S3 photoelectrodes exhibited nanorods with lengths of 50–100 nm, a direct bandgap of 1.26 eV, and a photocurrent density of 4.7 mA/cm2 at 1.5 V vs Hg/HgO. As the Cu-doping concentration increased from 1.0 to 4.4 at.%, the nanorod length extended to 200–400 nm, with a corresponding increase in density, leading to an enhanced photocurrent density of 6.8 mA/cm2. However, further increasing the Cu-doping concentration to 8.4 at.% resulted in a reduction in film thickness, nanorod density, and a decrease in photocurrent to 6.0 mA/cm2. These results demonstrate that Cu-doping in Bi2S3 significantly increases nanorod density and improves both the physical and PEC properties, offering a promising approach for developing more efficient PEC water-splitting devices.

Enhanced Gas-Phase pollutant removal using Pt nanoparticle-modified exfoliated carbon nitride photocatalysts under UV and visible light

Platinum nanoparticles (Pt NPs) have been prepared by the organometallic approach on the surface of exfoliated graphitic carbon nitride (exf-g-CN) with different metal loadings. Multi-technique characterization shows a good dispersion of Pt NPs on the surface of exf-g-CN with a narrow size distribution between 1.7–2.2 nm and a BET area of about 120 m2/g. The Pt NPs are mainly composed of platinum metal with a minor contribution of oxidic surface species. The effect of UV-A and Vis light of different wavelengths on the photocatalytic performance is investigated. The as-prepared hybrid materials show excellent photocatalytic activity for the decontamination of air from volatile organic compounds (VOCs, in particular trichloroethylene, C2HCl3) under low power visible light irradiation. The conversion value reaches a maximum close to 85 % at 405 nm Vis light for 0.5 wt.% Pt loading. At this level of Pt content, electron and hole recombination rates are suppressed according to photoluminescence analysis. Photonic efficiencies of around 0.3 % were achieved under Vis light. The optimised material shows high stability from 2,500 min of operation. XPS analysis suggests the crucial role of Pt/Pt2+ and chlorine species detected on used samples in the reaction rate and stability of the material.

Tetraalkynylporphyrin-mediated covalent assembly of gold nanoclusters for targeted tumor fluorescence imaging and enhanced photodynamic therapy.

A covalent assembly strategy was developed to construct agold nanocluster-based nano-assembly (AuNCNA) in a controllable manner, using Au8 nanocluster as node and 5,10,15,20-tetra(4-alkynylphenyl)porphine (TEPP) as ligand. Subsequently, the tripeptide arginine glycine aspartic acid (RGD) peptide is further modified via clicking reaction to build a multi-functional nanoplatform (AuNCNA@RGD) that can integrate the targeted fluorescence imaging and efficient photodynamic therapy (PDT). The strong interregulation of Au8 nanocluster and TEPP results in AuNCNA@RGD exhibiting three distinct advantages: (i) TEPP plays an important role in stabilizing the Au8 nanocluster and keeping the active site fixed within the framework, thereby enhancing stability of Au8 nanocluster; (ii) Au8 nanocluster possess adjustable energy level, which can accelerate the transfer of photogenerated charge and prevent the recombination of electrons and holes, thus improving thephotosensitivity of TEPP for PDT; (iii) AuNCNA exhibits bright fluorescence emission that facilitates RGD-assisted targeted tumor imaging. This work expands the construction method of AuNC assembly, and this assembly method is versatile and can flexibly transform different organic ligands to construct various AuNC-based functional nanomaterials.

Adjusting the Covalency of Metal-Oxygen Bonds in CuBi2O4 by Zn Cation Doping to Achieve Highly Efficient Photocathodes.

Zn doped CuBi2O4 photocathodes are prepared by using a low-cost solution-based spray pyrolysis method. The doping of Zn in CuBi2O4 promotes the separation and migration of carriers and effectively increases the carrier density. Compared with CuBi2O4 alone, the photoelectrochemical activity of the Zn doped CuBi2O4 photoelectrode is improved with the photocurrent density of -0.56 mA/cm2 at 0.4 V vs. RHE. This improvement is due to the lower electronegativity of Zn, which leads to the covalent increase of Cu-O and Bi-O bonds in CuBi2O4, which limits the recombination of photogenerated electrons and holes and improves charge separation and transport. This study presents an innovative approach to enhance the charge separation efficiencies of photocathodes by implementing element doping strategies, which may contribute to further research on photocatalytic water splitting.

Plasmonic ZnO-Au Nanocomposites: A Synergistic Approach to Enhanced Photocatalytic Activity through Nonthermal Plasma-Assisted Synthesis

A novel and efficient method for synthesizing Au-decorated ZnO nanoparticles (NPs) with enhanced photocatalytic activity is presented. The synthesis involves a two-step process: hydrothermal preparation of ZnO NPs followed by nonthermal plasma-assisted deposition of Au nanoparticles on their surface. Comprehensive characterization of the ZnO and ZnO–Au NPs was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Optical properties were evaluated via UV-Vis absorption and fluorescence measurements. The synthesized ZnO NPs displayed a hexagonal wurtzite structure, and the successful deposition of Au NPs was confirmed by TEM and XPS analysis, along with Raman and fluorescence data showing the quenching effect caused by Au. The incorporation of Au nanoparticles led to the appearance of localized surface plasmon resonance (LSPR) at 540 nm, enhancing visible light absorption and improving photocatalytic performance. Notably, the methylene blue (MB) degradation efficiency increased from 78% with pure ZnO NPs to 91.6% with ZnO–Au NPs under UV-Vis irradiation, demonstrating superior photocatalytic activity. This study introduces a simple and scalable method for synthesizing plasmonic ZnO-Au hybrid nanomaterials using plasma technology and highlights the critical role of Au NPs in enhancing photocatalytic performance by reducing electron–hole recombination.

A Review: Recent Advances of Piezoelectric Photocatalysis in the Environmental Fields.

Piezoelectric photocatalysis can effectively suppress the recombination of electron holes during the course of photocatalysis, which has been widely applied in environmental and energy catalysis. Its advantage is that when the piezoelectric effect happens, a built-in electric field is formed inside the catalyst, which improves the separation efficiency of photogenerated charge carriers and obtains more excellent photocatalytic performance. The efficient conversion of mechanical energy to chemical energy can be realized through the synergistic effect of the piezoelectric effect, and photocatalysis is greatly significant in solving the energy crisis and providing environmental protection. Therefore, we organized a more complete review to better understand the mechanism and system of piezoelectric photocatalysis. We briefly introduce the principle of the piezoelectric effect, the existing types of piezoelectric photocatalysts, the practical application scenarios, and the future challenges and feasible methods to improve catalytic efficiency. The purpose of this review is to help us broaden the idea of designing piezoelectric photocatalysts, clarify the future research direction, and put it into more fields of environmental protection and energy reuse.

Pressure-controlled luminescence in fast-response barium fluoride crystals

Cross-luminescence (CL) in a barium fluoride (BaF2) scintillator arising from the recombination of a valence band electron and a core band hole results in a fast picosecond decay time. However, the CL emission wavelength in the vacuum ultraviolet region is difficult to detect, and intrinsically intense and slow nanosecond self-trapped exciton (STE) luminescence occurs. Herein, we report a redshift in the CL emission wavelength with high-pressure application. The wavelength of the CL emission shifted from 221 nm to 240 nm when 5.0 GPa was applied via a sapphire anvil cell. Increasing the pressure decreases the core-valence bandgap due to the downward expansion of the valence band, resulting in a decrease in the valence band minimum. The onset of a phase transition from a cubic crystal structure to an orthorhombic crystal structure at 3.7 GPa inhibited the recombination of conduction band electrons and self-trapped holes, leading to the disappearance of the STE emission. Manipulating the band structure of BaF2 by high-pressure application enables control of its luminescence emission, providing a pathway toward solving the problems inherent in this leading fast-response scintillator.

Phyto-mediated synthesis of ZnO nanoparticles and their sunlight-driven photocatalytic degradation of cationic and anionic dyes

Abstract In this study, zinc oxide-based nanocatalysts were biosynthesized using Ocimum basilicum (OB) and Olea africana (OA) leaf aqueous extracts, termed OB-ZnO and OA-ZnO, as a simple, affordable, and environmentally friendly approach. Their characteristics and efficacy in photodegrading cationic dyes (crystal violet and methylene blue) and anionic dyes (methyl orange and naphthol blue black) were investigated. The catalyst’s properties were analyzed using various techniques, including Fourier transform infrared, X-ray diffraction, photoluminescence, thermogravimetric analysis, UV-Vis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller. Analysis revealed pure products having a hexagonal wurtzite structure, crystallite sizes of 15.04 and 21.46 nm, surface areas of 23.65 and 7.97 m2/g, particle sizes of 35 and 170 nm with spherical (uniform) and oval-like (non-uniform) shapes, and optical bandgaps of 3.15 and 3.05 eV, respectively. Photocatalytic applications under sunlight indicated excellent activity of both catalysts against targeted cationic and anionic dyes. Most notably, even though OA-ZnO has a lower surface area than OB-ZnO, it demonstrated greater efficiency. The variation in effectiveness is explained by the lower bandgap value of OA-ZnO and its ability to reduce electron–hole recombination due to its larger crystal size, which accelerates the degradation process. Additionally, both catalysts exhibited high stability after being used four times.