Visible light driven photo-degradation of Congo red by TiO2ZnO/Ag: DFT approach on synergetic effect on band gap energy

Solvothermal synthesis of 3D rod-shaped Ti/Al/Cr nano-oxide for photodegradation of wastewater micropollutants under sunlight: a green way to achieve SDG:6

Waterbodies are day-by-day polluted by the various colored micropollutants, e.g., azo dyes enriched (carcinogenic, non-biodegradable) colored wastewater from textile industries. Water pollution has become a serious global issue as ~ 25% of health diseases are prompted by pollution as reported by WHO. Around 1 billion people will face water scarcity by 2025 and this water crisis is also a prime focus to the UNs' sustainable development goal 6 (SDG6: clean water and sanitation). To prevent the water pollution caused by micropollutants, a mesoporous, 3D rod-like nano-oxide Ti/Al/Cr (abbreviated as TAC) has been synthesized via the solvothermal method. TAC degraded all classes of azo dyes (mono, di, tri, etc.) with > 90% efficiency under renewable energy source solar irradiation within the pH range 2-11. The detailed study was done on the photodegradation of carcinogenic di-azo dye Congo red (CR) which is banned in many countries. TAC showed 90.64 ± 2% degradation efficiency for CR at pH 7. The proposed photodegradation mechanism of CR was confirmed by the high-resolution liquid chromatography-mass spectroscopy (HRLC-MS) analysis obeying the Pirkanniemi path. The photodegradation obeyed the pseudo-1st-order kinetics and was reusable up to successive 5 cycles which can be an efficient tool to meet the UNs' SDG:6.

Rapid synthesis of ZnO nanoparticles via gliding arc discharge: unveiling the impact of discharge time on particle properties and photocatalytic performance

Herein, we present a novel approach for the synthesis of ZnO nanoparticles (ZnO NPs) using a non-thermal plasma source generated by the gliding arc discharge-air system. The effect of discharge time on the physical and optical properties, as well as the photocatalytic performance of the as-fabricated ZnO NPs, was investigated. The characterization techniques revealed that the as-synthesized ZnO exhibit hexagonal Wurtzite structure, with a wide energy gap and peak intensities of UV-vis absorption with longer discharge times. A decrease in particle size from 29 to 25 nm was also observed with increasing discharge time, while all samples were thermally stable between 25 and 700 °C. The photocatalytic performance of the ZnO NPs was evaluated by degrading Congo Red (CR) dye with a concentration of 20 ppm under sunlight at a dose of 1 mg/mL. The as-synthesized ZnO NPs revealed exceptional photocatalytic performance by degrading ~ 97% of CR dye after irradiation for 150 min. This work presents an easy and simple method for synthesizing NPs in a short time and pave the way for other potential ideas on the application of plasma gliding arc discharge.

Density functional theory for doped TiO2: current research strategies and advancements

Since the inception of the density functional theory (DFT) by Hohenberg and Kohn in 1964, it rapidly became an indispensable theoretical tool across various disciplines, such as chemistry, biology, and materials science, among others. This theory has ushered in a new era of computational research, paving the way for substantial advancements in fundamental understanding. Today, DFT is routinely employed for a diverse range of applications, such as probing new material properties and providing a profound understanding of the mechanisms underlying physical, chemical, and biological processes. Even after decades of active utilization, the improvement of DFT principles has never been slowed down, meaning that more accurate theoretical results are continuously generated with time. This work highlights the latest achievements acquired by DFT in the specific research field, namely the theoretical investigations of doped TiO2systems, which have not been comprehensively reviewed and summarized yet. Successful progress in this niche is currently hard to imagine without the support by DFT. It can accurately reveal new TiO2properties after introducing the desired dopant and help to find the optimal system design for a specific application prior to proceeding to more time-consuming and expensive experimental research. Hence, by evaluating a selection of the most recent research studies, we aim to highlight the pertinent aspects of DFT as they relate to the study of doped TiO2systems. We also aim to shed light on the strengths and weaknesses of DFT and present the primary strategies employed thus far to predict the properties of various doped TiO2systems reliably.

Simultaneous recognition of dopamine and uric acid in real samples through highly sensitive new electrode fabricated using ZnO/carbon quantum dots: bio-imaging and theoretical studies

Dopamine (DA) and uric acid (UA), which are vital components in human metabolism, cause several health problems if they are present in altered concentrations; thus, the determination of DA and UA is essential in real samples using selective sensors. In the present study, graphite carbon paste electrodes (CPE) were fabricated using ZnO/carbon quantum dots (ZnO/CQDs) and employed as electrochemical sensors for the detection of DA and UA. These electrodes were fully characterized via different analytical techniques (XRD, SEM, TEM, XPS, and EDS). The electrochemical responses from the modified electrodes were evaluated using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. The results showed that the present electrode has exhibited high sensitivity towards DA, recognizing even at low concentrations (0.12 μM), and no inference was observed in the presence of UA. The ZnO/CQD electrode was applied for the simultaneous detection of co-existing DA and UA in real human urine samples and the peak potential separation between DA and UA was found to be greatly associated with the synergistic effect originated from ZnO and CQDs. The limit of detection (LOD) of the electrode was analyzed, and compared with other commercially available electrodes. Thus, the ZnO/CQD electrode was used to detect DA and UA in real samples, such as Saccharomyces cerevisiae cells.

Direction of theoretical and experimental investigation into the mechanism of n-HA/Si-PA-SC@Ag as a bio-based heterogeneous catalyst in the reduction reactions

In the present study, a natural-based heterogeneous catalyst is synthesized. For this purpose, nano-hydroxyapatite (n-HA) is prepared, silica-modified and functionalized with phthalimide. Finally, Ag²⁺ was immobilized onto n-HA/Si-PA-SC and reduced to Ag nanoparticles by Bellis perennis flowers extract. n-HA/Si-PA-SC@Ag characterized by TGA, FTIR, SEM/EDX, XRD, TEM, BET and ICP-AES techniques. Moreover, metal-ligand interactions in n-HA/Si-PA-SC@Ag complex models were assessed to make a quantitative representation for the immobilization behavior of Ag NPs on the surface of n-HA/Si-PA-SC through quantum chemistry computations. Furthermore, the performance of n-HA/Si-PA-SC@Ag was studied in the nitroarene, methylene blue and congo red reductions. Finally, the recyclability study as well as Ag-leaching verified that, n-HA/Si-PA-SC@Ag was stable and reused-up to four times without losing its activity.

Efficient Degradation of Congo Red in Water by UV-Vis Driven CoMoO4/PDS Photo-Fenton System

In order to improve the catalytic activity of cobalt molybdate (CoMoO₄), a PDS-activated and UV-vis assisted system was constructed. CoMoO₄ was prepared by coprecipitation and calcination, and characterized by XRD, FTIR, Raman, SEM, TEM, XPS, TGA Zeta potential, BET, and UV-Vis DRS. The results showed that the morphology of the CoMoO₄ nanolumps consisted of stacked nanosheets. XRD indicated the monoclinic structures with C2/m (C³_2h, #12) space group, which belong to α-CoMoO₄, and both Co²⁺ and Mo⁶⁺ ions occupy distorted octahedral sites. The pH of the isoelectric point (pHIEP) of CMO-8 at pH = 4.88 and the band gap of CoMoO₄ was 1.92 eV. The catalytic activity of CoMoO₄ was evaluated by photo-Fenton degradation of Congo red (CR). The catalytic performance was affected by calcination temperature, catalyst dosage, PDS dosage, and pH. Under the best conditions (0.8 g/L CMO-8, PDS 1 mL), the degradation efficiency of CR was 96.972%. The excellent catalytic activity of CoMoO₄ was attributed to the synergistic effect of photo catalysis and CoMoO₄-activated PDS degradation. The capture experiments and the ESR showed that superoxide radical (·O₂^-), singlet oxygen (¹O₂), hole (h⁺), sulfate (SO₄^-·), and hydroxyl (·OH^-) were the main free radicals leading to the degradation of CR. The results can provide valuable information and support for the design and application of high-efficiency transition metal oxide catalysts.

Critical role of tetracycline's self-promotion effects in its visible-light driven photocatalytic degradation over ZnO nanorods

Zinc oxide (ZnO), which is widely applied for ultraviolet-light driven photocatalysis, has no activity in visible-light photocatalytic process due to its large band gap of ∼3.2 eV. Herein, however, we demonstrated the multiple self-promotion effects of tetracycline as band adjuster, photo-sensitizer, and charge transfer promoter for ZnO nanorods, realizing its visible-light photocatalytic degradation with an excellent removal efficiency up to 91.1% within only 2 h. Besides, the influence of complex realistic factors on this unique process was evaluated together with tests with realistic water matrices. Furthermore, the active species and degradation products were identified. Both acute and developmental toxicities were found to be reduced as the degradation proceeds. These results pave the path for the brand-new self-driven visible-light photocatalysis.

Sunlit photocatalytic degradation of organic pollutant by NiCr2O4/Bi2S3/Cr2S3 tracheid skeleton nanocomposite: Mechanism, pathway, reactive sites, genotoxicity and byproduct toxicity evaluation

In this study, 3D C₂S₃ (CS) and 2D Bi₂S₃ (BS) modified NiCr₂O₄ nanocomposite (NCO-BS-CS NCs) was prepared by sonochemical assisted co-precipitation method for the enhanced photocatalytic activity. Here, NCO-BS-CS NCs showed band gap energy of 2.23 eV and the PL intensity of NCO-BS-CS NCs was lower than NCO, BS, and CS NPs. Thus, the results indicate the fabricated NCO-BS-CS NCs enhance the charge segregation and lower in recombination rate. NCO-BS-CS NCs showed enhanced photodegradation of methyl orange (MO) (95%) and congo red (CR) (99.7%) respectively. The total organic compound (TOC) analysis shows the complete mineralization of about 91 and 98% for MO and CR respectively. Furthermore, the Fukui function was used for the prediction of reactive sites in the photodegradation pathway of MO and CR by NCs. ECOSAR program was done to determine the toxicity of the intermediate and the results conclude that the degraded product shows nontoxic to the environmental organism (fish, daphnia, and algae). Thus, the fabricated NCO-BS-CS NCs can be used for the remediation of toxic organic pollutants from the waste water by photocatalytic degradation.

Crystal Plane Impact of ZnFe2O4-Ag Nanoparticles Influencing Photocatalytical and Antibacterial Properties: Experimental and Theoretical Studies

This paper describes the crystal interphase impact of ZnFe₂O₄-Ag in the photodegradation of Rhodamine B. Prepared ZnFe₂O₄ nanoparticles (NPs) were deposited with Ag NPs to offer ZnFe₂O₄-Ag (0-2.5%). An X-ray diffraction peak corresponding to the Ag NPs was detected if the particle content reached about 2.0%, observing multiple crystalline interphases in HR-TEM. Magnetic saturation (Ms) was increased ∼160% times for ZnFe₂O₄-Ag (7.25 to 18.71 emu/g) and ZnFe₂O₄ (9.62 to 25.09 emu/g) if the temperature is lowered from 298 to 5.0 K; while for Fe₃O₄ (91.09 to 96.19 emu/g), the Ms increment was just about 5.6%. After analyzing the DFT-Density of State, a decrease of bandgap energy for ZnFe₂O₄-Ag₆ from the influence of the size of Ag cluster was seen. Quantum yield (Φ) was 0.60 for ZnFe₂O₄, 0.25 for ZnFe₂O₄-Ag (1.0%), 0.70 for ZnFe₂O₄-Ag (1.5%), 0.66 for ZnFe₂O₄-Ag (2.0%), and 0.66 for ZnFe₂O₄-Ag (2.5%), showing that the disposition of Ag NPs (1.5-2.5%) increases the Φ to >0.60. The samples were used to photo-oxidize RhB under visible light assisted by photopowered Langmuir adsorption. The degradation follows first-order kinetics (k = 5.5 × 10^-3 min^-1), resulting in a greater k = 2.0 × 10^-3 min^-1 for ZnFe₂O₄-Ag than for ZnFe₂O₄ (or Fe₃O₄, k = 1.1 × 10^-3 min^-1). DFT-total energy was used to analyze the intermediates formed from the RhB oxidation. Finally, the ZnFe₂O₄-Ag exhibits good antibacterial behavior because of the presence of Zn and the Ag components.

Green synthesis of P − ZrO2CeO2ZnO nanoparticles using leaf extracts of Flacourtia indica and their application for the photocatalytic degradation of a model toxic dye, Congo red

In the present work P−ZrO2CeO2ZnO nanoparticles were synthesised for the first time using phytochemical extracts from Flacourtia indica leaves and applied in the photocatalytic degradation of Congo Red in the presence of Light Emitting Diode warm white light. The photocatalytic degradation was optimized with respect to P−ZrO2CeO2ZnO nanoparticle dosage, initial Congo Red concentration, and degradation time. The optimum conditions for P−ZrO2CeO2ZnO nanoparticle synthesis was pH 9, leaves extracts of F. indica dosage 4 g 100 mL⁻¹, Zirconia, Cerium and Zinc metal ion concentration 0.05 mg/L and metal ion to plant volume ratio of 1:4. The leaves extract dosage, pH and metal concentration had the most significant effects on the synthesis of the nanoparticles. The nanoparticles followed type III physisorption adsorption isotherms with surface area of 0.4593 m³g⁻¹, pore size of 6.80 nm, pore volume 0.000734 cmg−13 and average nanoparticle size 0.255 nm. A degradation efficiency of 86% was achieved and the optimum degradation conditions were 0.05 g/L of P−ZrO2CeO2ZnO nanoparticle dosage, 10 mg/L initial Congo red concentration, and 250 minutes irradiation time. Data from kinetic studies showed that the degradation followed pseudo first order kinetics at low concentration, with a rate constant of 0.069 min⁻¹. The superoxide, h+ holes and light were the main determinants of the reaction mechanisms for the degradation of Congo Red. The investigation outcomes demonstrated that P−ZrO2CeO2ZnO nanoparticles offer a high potential for photocatalytic degradation of Congo Red.

•

The most significant factors on P−ZrO2CeO2ZnO nanoparticles synthesis were plant leaves dosage, pH and initial metal concentration.

•

The nanoparticles exhibited high catalytic activity towards photocatalytic degradation of Congo red.

•

Superoxide, h+ holes and light were the main determinants of the photocatalytic degradation mechanisms.

A sustainable and green chlorophyll/TiO2:W composite supported on recycled plastic bottle caps for the complete removal of Rhodamine B contaminant from drinking water

This investigation reports the photocatalytic performance of the tungsten doped titania (TiO₂:W or TW) with and without coating of chlorophyll (Chl) for the removal of the RhB dye from the drinking water. These particles were also supported on recycled plastic bottle caps (Bcap) to form other photocatalytic composites (TW/Bcap and TW + Chl/Bcap). The SEM images demonstrated that the TW particles without Chl had irregular shapes and sizes of 0.8-12 μm. The TW particles coated by the Chl presented shapes of quasi-rounded grains and smaller particle sizes of 0.8-1.8 μm. The photocatalytyic experiments showed that the photocatalyst powders containing Chl removed completely the RhB dye from the water after 2h under UV-VIS light, while the photocatalyst without Chl removed a maximum of 95% of the RhB. Interestingly, the TW/Bcap and TW + Chl/Bcap composites removed 94-100% of the RhB after 2h. Those ones removed such dye by photocatalysis and by physical adsorption at the same time (as confirmed by the absorbance and FTIR measurements), therefore, the removal of RhB was still very high. Scavenger experiments were also achieved and found that the •OH radicals are the main oxidizing species generated by the photocatalysts with and without Chl. The •O₂^- radicals and holes (h⁺) were the secondary oxidizing species. The presence of the chlorophyll on the photocatalyst increased in general the light absorption and the photocurrent. Overall, our work demonstrated that making composites with recycled plastic bottle caps is a feasible alternative to remove dyes from contaminated drinking water with high efficiency and low cost.

Solar-Energy-Driven Cu-ZnO/TiO2 Nanocomposite Photocatalyst for the Rapid Degradation of Congo Red Azo Dye

This study effectively demonstrates the sonochemical synthesis of visible-light-responsive Cu-ZnO/TiO2 ternary Z-scheme heterojunction nanocomposite photocatalyst. The as-prepared photocatalyst was comprehensively characterized by techniques including high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray analysis (EDX) and elemental dot mapping, X-ray diffraction (XRD), UV-Vis-diffuse reflectance spectroscopy (UV-Vis-DRS), Brunauer–Emmett–Teller (BET) surface area, and Fourier-transform infrared spectroscopy (FTIR). The photocatalytic activity of the Cu-ZnO/TiO2 nanocomposite photocatalyst was assessed for the degradation of Congo red (CR), an azo dye, under direct sunlight. The pseudo-first-order rate constant for CR degradation was found to be 0.09 min−1. The outcome implies that the synthesised nanocomposite photocatalyst demonstrates excellent photocatalytic activity under direct sunlight as 98% degradation of CR dye was achieved in approximately 20 min using the Cu-ZnO/TiO2 nanocomposite photocatalyst. Furthermore, its high recoverability and reusability of five times indicate its excellent catalytic potential.

In Silico Screening of Semi-Synthesized Compounds as Potential Inhibitors for SARS-CoV-2 Papain-like Protease: Pharmacophoric Features, Molecular Docking, ADMET, Toxicity and DFT Studies

Papain-like protease is an essential enzyme in the proteolytic processing required for the replication of SARS-CoV-2. Accordingly, such an enzyme is an important target for the development of anti-SARS-CoV-2 agents which may reduce the mortality associated with outbreaks of SARS-CoV-2. A set of 69 semi-synthesized molecules that exhibited the structural features of SARS-CoV-2 papain-like protease inhibitors (PLPI) were docked against the coronavirus papain-like protease (PLpro) enzyme (PDB ID: (4OW0). Docking studies showed that derivatives 34 and 58 were better than the co-crystallized ligand while derivatives 17, 28, 31, 40, 41, 43, 47, 54, and 65 exhibited good binding modes and binding free energies. The pharmacokinetic profiling study was conducted according to the four principles of the Lipinski rules and excluded derivative 31. Furthermore, ADMET and toxicity studies showed that derivatives 28, 34, and 47 have the potential to be drugs and have been demonstrated as safe when assessed via seven toxicity models. Finally, comparing the molecular orbital energies and the molecular electrostatic potential maps of 28, 34, and 47 against the co-crystallized ligand in a DFT study indicated that 28 is the most promising candidate to interact with the target receptor (PLpro).

A novel approach in revealing mechanisms and particular step predictors of pH dependent tartrazine catalytic degradation in presence of Oxone®

The degradation of tartrazine in the presence of cobalt activated Oxone® (potassium peroxymonosulfate) was investigated at different initial pH values. Aluminum pillared clay had the role of a support for catalytically active cobalt oxide species. The degradation of tartrazine and the formation of a mixture of degradation products were monitored using the Ultraviolet-Visible (UV-Vis) spectroscopy and gas chromatography-mass spectrometry (GC-MS). The exact qualitative composition of this mixture and the determination of the most probable mechanism of degradation (the primary goal) were obtained using GC-MS. Besides, the main reaction pathway (reaction with SO₄˙- radical anion) and secondary pathways were proposed depending on the pH value. At pH = 6 the reaction with HO˙ radical was proposed. At pH = 11 decarboxilation was suggested as the first step of the secondary proposed reaction pathway. The combination of results acquired from the deconvolution of UV-Vis spectra and the theoretical UV-Vis spectra of degradation products, whose occurrence was predicted by quantum-chemical calculations, was proven to be beneficial for the identification of tartrazine degradation products and for defining UV-Vis predictors of particular degradation steps. An additional contribution of this paper, from the reactivity aspect, was the establishment of the critical structural demand for the radical degradation of any diazo compound. The existence of a hydrogen atom bound to a diazo group was found to be the essential prerequisite for the radical cleavage of diazo compounds.

Adsorption Behavior of Congo Red onto Barium-Doped ZnO Nanoparticles: Correlation between Experimental Results and DFT Calculations

Ba-loaded ZnO nanoparticles (Ba/ZnO) were obtained by the co-precipitation process and employed as a sorbent for Congo Red (C₃₂H₂₂N₆Na₂O₆S₂) dye (CR). Physicochemical parameters such as particle size, pH, and contact time were checked to characterize the adsorption process. The maximum adsorption capacity of Ba/ZnO NPs for CR (1614.26 mg/g) proves its potential utility in the elimination of CR dye from wastewater. The adsorption mechanism was studied via infrared spectroscopy and density functional theory calculations. The geometrical parameters and electronic properties of the CR-Ba/ZnO complex, particularly the interaction energy, the density of states, and the charge transfer, highlighted the Ba-ion mediation in the chemical bond formation between CR and the surface. The interaction between CR and Ba-doped ZnO has found to show strong chemisorption with charge transfer between the SO₃^- group and adsorbed Ba²⁺ ion on the surface.

Efficacy and reusability of mixed-phase TiO2-ZnO nanocomposites for the removal of estrogenic effects of 17β-Estradiol and 17α-Ethinylestradiol from water

Photocatalytic removal of estrogenic compounds (ECs), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) were assessed using a TiO₂-ZnO nanocomposite (NC) over a range of initial EC concentration (C_o; 10 mg/L - 0.05 mg/L). Photocatalytic removal was evaluated under UV and visible irradiation using 10 mg/L NC over 240 min duration. After 240 min, analysis using GCxGC TOF MS revealed 100% transformation at C_o ≤ 1 mg/L and ≥25% transformation at C_o ≤ 10 mg/L under visible irradiation. Degradation was accompanied by breakdown of the fused ring structure of E2, generating smaller molecular weight by-products which were subsequently mineralized as revealed through TOC removal. With UV photocatalysis, ~30% and ~20% mineralization was attained for E2 and EE2, respectively, for C_o of 10 mg/L. Under visible irradiation, ~25% and ~10% mineralization was achieved for E2 and EE2, respectively. Estrogenicity variation was estimated using the E-screen assay conducted with estrogen receptor-positive MCF-7 breast cancer cells. Complete removal of estrogenicity of ECs was confirmed after 240 min of photocatalysis under UV and visible irradiation. FTIR spectroscopy-based analysis of the NC after E2 photocatalysis revealed the presence of sorbed organics. Desorption, followed by GC × GC TOF-MS analysis revealed these organics as by-products of photocatalysis. Desorption of sorbed organics followed by recalcination at 600 °C for 1 h regenerated the active sites on the NC, enabling its efficient reuse for 3 cycles under visible irradiation without loss in activity.

Enhancement of photocatalytic degradation of Malachite Green using iron doped titanium dioxide loaded on oil palm empty fruit bunch-derived activated carbon

Iron-doped titanium dioxide loaded on activated carbon (Fe-TiO₂/AC) was successfully synthesized from oil palm empty fruit bunch (OPEFB) using sol-gel method. The properties of the synthesized pure TiO₂, Fe-doped TiO₂, AC, TiO₂/AC and Fe-TiO₂/AC were examined by various techniques such as field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and nitrogen adsorption-desorption analyses at 77 K. FE-SEM revealed that Fe-doped TiO₂ particles were dispersed homogeneously on the AC surface. FT-IR demonstrated high surface hydroxylation after Fe doping on TiO₂ and UV-Vis DRS showed that Fe-TiO₂/AC had the lowest band gap energy. Catalytic performance results proved that Fe dopants could restrict the recombination rate of hole and electron pairs, whereas AC support improved the Malachite Green (MG) adsorption sites and active sites of the hybrid catalyst. Photocatalytic degradation of 100 mg/L MG in the presence of 1.0 g/L 15 wt% Fe-TiO₂ incorporated with 25 wt% AC, initial solution pH of 4 and 3 mM H₂O₂ could achieve the highest removal efficiency of 97% after 45 min light irradiation. This work demonstrates a promising approach to synthesis an inexpensive and efficient Fe-TiO₂/AC for the photocatalytic degradation of organic dye.

Biosynthesis of zinc oxide nanoparticles using leaf extracts of Alchornea laxiflora and its tyrosinase inhibition and catalytic studies

Zinc oxide nanoparticles (ZnO-NPs) were synthesized using a simple, low cost and safe method involving aqueous leaf extracts of Alchornea laxiflora and a zinc precursor salt. The nanoparticles were characterized by ultraviolet-visible (UV-vis), Fourier transform (FT-IR) spectroscopy, Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Scanning electron microscope (SEM). They were evaluated for their potentials as tyrosinase inhibitors and as catalysts in the degradation of Congo red dye. The UV-vis spectra gave characteristic surface Plasmon bands within the range 276-456 nm. The band gap energies of the ZnO-NPs were of the range, 2.50-3.67 ev. The SEM results showed average sizes of 29 nm and 38 nm for particles obtained using 1 mL and 2 mL of the plant extracts respectively. EDX plot showed the elemental compositions of the nanoparticles with zinc and oxygen being pronounced. The ZnO nanoparticles exhibited good photocatalytic efficiency of 87 % degradation of Congo red (CR) dye molecules in 60 min, They also showed good anti-tyrosinase ability with an IC50 of 66.28 μg/mL. Overall the biogenic ZnO nanoparticles are promising materials for dual applications as photocatalysts in the degradation of Congo red dye and as tyrosinase inhibitors.

Construction of Ag-modified TiO2/ZnO heterojunction nanotree arrays with superior photocatalytic and photoelectrochemical properties

The work involves the preparation of TiO₂/ZnO heterojunction nanotree arrays by a three-step: hydrothermal, sol–gel, and secondary hydrothermal method, and then modification of Ag quantum dots (QDs).