Blue Shift Of Absorption Edge Research Articles

Sulfonic grafted graphitic-like carbon nitride for the improved photocatalytic production of benzaldehyde in water

This work reports the modification of graphitic carbon nitride (CN) through sulfonation (SCN) as an enhanced strategy for photocatalytic activity during the oxidation of benzyl alcohol to benzaldehyde. CN was prepared from melamine and functionalized with -SO3H groups using different doses of chlorosulfonic acid. The textural, structural, morphological, chemical, and optical properties of the prepared samples were characterized by diverse techniques. The increase in the doping dose produced, a decrease in surface area, a blue-shifted absorption edge under irradiation, and a decrease in the recombination charges. The -SO3H improved the kinetics of benzyl alcohol oxidation (BA) in aqueous solution and raised the selectivity to benzaldehyde (BD). An optimum dosage of precursor led to an SCN sample with the highest removal rate and selectivity. This optimized sample was selected for the study of the reactive oxidant species involved during the photocatalytic process, suggesting that the species with the highest contribution during BA oxidation was the superoxide radical, especially in terms of selectivity for the aldehyde formation. This work examples the modification of carbon nitride to enhance the production of an aldehyde with interest in the industry under a sustainable scheme that involves the transformation of light into chemical energy in aqueous solution.

Strain effect on the electronic and optical properties of anisotropic Au2Te monolayer

In this article, the strain effect on the electronic and optical properties of Au2Te monolayer is investigated based on first-principles calculations. The band gap responds monotonically to uniaxial strain, and it increases (decreases) from 1.13 (1.51) eV to 1.45 (1.13) eV for applying strain along the x (y) direction from -5% to +5%. The band gap varies in a parabolic trend for the applied biaxial strain, and both compressive and stretch strains increase the band gap. The indirect bandgap characteristic of Au2Te monolayer is maintained under both uniaxial and biaxial strains. In addition, the light absorption edge blueshift (redshift) with the increasing (decreasing) strain-induced band gap. Notably, the optical response is more sensitive to biaxial strain than uniaxial strain. These tunable properties endow the anisotropic Au2Te monolayer as a promising 2D semiconductor for anisotropic optoelectronic devices.

Effect of gallium and strontium salts on the characteristics and biological applications of Sr and Ga-modified titanate nanotubes

In this work, we report the synthesis of Na-TiNTs sodium titanate nanotubes prepared by the hydrothermal method in a highly alkaline subsequently modified by the substitution of Na+ ions present in the walls of the nanotubes by ions of Sr2+ and Ga3+ revealing the presence of phases such as SrOH2 and α-GaOOH through the analysis by X-ray diffraction. Raman spectroscopy showed the characteristic peaks of the vibrational modes of the titanate nanotube structure. UV–Vis analysis revealed a blueshift of absorption edge that leads to an increase in the bandgap with the insertion of Sr and Ga ions. The ion exchange causes a decrease in the Urbach energy, which suggests a certain attenuation in the concentration of structural defects.Through the SEM images it is observed the cluster of interwoven nanotubes it self is characteristic of titanate nanotubes and, the elemental mapping shows the complete efficiency of the reaction process of sodium ion exchange by strontium and gallium in the Sr-TiNT and Ga-TiNT samples respectively, showing the environment of the chemical composition of the surface with the presence of chemical elements such as Sr, Ga. The Na-TiNT, Sr-TiNT, and Ga-TiNT nanotubes did not show direct antibacterial activity against the tested strains. The Na, Ga, and Sr TiNTs of the ampicillin antibiotic exhibited significant values against the microorganism S. aureus 10 compared to the control antibiotic, thereby reducing its inhibitory concentration. The same was observed for gentamicin. The Na-TiNT, in combination with gentamicin, displayed a reduction in inhibitory concentration compared to the control for P. aeruginosa 24. In E. coli 06, the Na, Sr, and Ga TiNTs showed a reduction in concentration when combined with gentamicin, indicating a potential synergistic effect.

Molecular engineering of novel dithiophene-fused hole-transporting materials for highly efficient perovskite solar cells

Understanding the relationship between structure and property of hole-transporting materials (HTMs) plays an important role in developing highly efficient perovskite solar cells (PSCs). Herein, we report a density functional theory study (DFT) combined with Marcus theory on the structural, electronic, optical, electrochemical and hole-transporting properties of designed molecules. The calculated results demonstrate that extending π-conjugation of the center by replacing CDT with IDT can lower the HOMO level, increase Stokes shift, enhance the solubility, strengthen the defect passivation ability and improve the hole mobility of molecules. The HOMO and LUMO energy alignments of the designed molecules properly match with the VBM and CBM of conventional perovskite CH3NH3PbI3 or mixed perovskite (FAPbI3)0.85(CH3NH3PbBr3)0.15, respectively. The introduction of electron-accepting groups in the π-linker results in the blue-shift of absorption edge into the UV region, which has no competition with the absorption of perovskites. Besides possessing lower HOMO levels, better solubilities and spectral properties, three designed molecules para-IDT-CN (1.76 × 10−1 cm2 V−1 s−1), meta-IDT-O (2.09 × 10−2 cm2 V−1 s−1) and meta-IDT-CN (7.53 × 10−3 cm2 V−1 s−1) exhibit higher hole mobility than the reported HTMs CDT (4.15 × 10−3 cm2 V−1 s−1) and CDT-CN (1.15 × 10−3 cm2 V−1 s−1), which ensure that these novel molecules have potentials to be efficient HTMs in the application of PSCs.

Structural characteristics and effective two photon absorption induced optical limiting behavior of Co2+ doped monoclinic LaPO4 nanostructures

The Nonlinear optical limiting properties of pure and Co2+ doped monoclinic LaPO4 nanostructures synthesized by co-precipitation technique is reported. The Structural confirmation of Co2+ doped LaPO4 nanostructures is studied by X-ray diffraction (XRD) and Raman spectra. The replacement of larger La3+ ion by smaller Co2+ ion is confirmed by the shift of XRD and Raman scattering lines. X ray photoelectron spectroscopy (XPS) survey spectrum of 0.3 % Co2+ doped sample confirms the presence of lanthanum (La). Phosphor (P), oxygen (O) and Cobalt (Co) elements. Transmission electron microscopy (TEM) image portrays the formation of nearly mono-dispersed spherical particle with diameter of 48 nm. The absorption spectra reveals a blue shift in absorption edge with additional peak at 580 nm upon Co2+ doping. Photoluminescence emission spectra shows blue green emission with major peak at 440 nm. Open aperture (OA) Z-scan technique excited at 532 nm with a nanopulsed Nd: YAG laser revealed pure and Co2+ doped LaPO4 exhibits reverse saturable absorption ascribed due to two photon absorption (2PA). Intensity dependent OA measurements shows that the nonlinear absorption coefficient remains constant with varying input on-axis intensity, ensuring genuine 2PA for pure sample. While for Co doped sample, the nonlinear absorption coefficient varies with input on-axis intensity, assuring the occurrence of sequential 2PA. Co doped samples exhibit enhanced nonlinear absorption due to synergistic influence of Co2+ in LaPO4 crystal structure. Optical limiting action induced by 2PA in LaPO4 with lower onset limiting ensures the potentiality of the chosen material for photonic applications.

Determination of optical constants and band gap variation of Zn0.98-xCu0.02MgxO thin films

Cu doped ZnO (ZnCuO) is a very important candidate for electronic applications, since it has been shown that it possesses p–type conductivity. In order to broaden its applications, it is crucial to tune optical and electronic properties. In this study, by doping ZnCuO with magnesium, variation of refractive index, extinction coefficient, and band gap of thin films were investigated. Optical constants were evaluated using a transmittance model which is derived from Fresnel equations. Refractive indices of thin films were expressed as a dispersion relation in a polynomial form, while extinction coefficients were modelled as a convolution by Lorentzian curves. It was observed that magnesium doping decreased the refractive index and also caused a blue shift in absorption edge which is a clear indicator of band gap widening.

Molecular weight and linking position (2,7 vs 3,6) effects on electrochromic properties of alternating carbazole-EDOT copolymers obtained by direct (hetero) arylation polymerization

Two carbazole-EDOT electrochromic conjugated polymers (ECPs), namely P(2,7-Cbz-E)-HW and P(3,6-Cbz-E) have been developed by direct (hetero)arylation polymerization (DHAP). The effects of molecular weight and linked position on electrochromic properties for the above ECPs were investigated in detail. The 2,7-linked high molecular weight ECPs of P(2,7-Cbz-E)-HW exhibited excellent optical contrast and electrochemical stability. Meanwhile, both P(2,7-Cbz-E)-LW and P(2,7-Cbz-E)-HW performed short response times at 450 nm (<1 s) and P(2,7-Cbz-E)-LW showed outstanding coloration efficiency (up to 370 cm2 C−1 at 450 nm). However, 3,6-linked ECPs of P(3,6-Cbz-E), whose conjugation are sort of interruption, resulted in a low molecular weight and presented a highly blue-shifted absorption edge and unsatisfactory electrochromic performance compared with 2,7-linked ECPs. Further, flexible and patterned electrochromic devices (ECDs) were presented employing 2,7-linked ECPs, which achieved a reversible color change between yellow and dark blue with acceptable optical contrast (26% for P(2,7-Cbz-E)-LW and 32% for P(2,7-Cbz-E)-HW both at 605 nm). The research indicates that the molecular weight and linked position are crucial to achieve high-performance electrochromism, which provides guidance for designing ECPs and flexible ECDs.

Synthesis and Optical Properties of Ag–Ga–S Quantum Dots

Ag–Ga–S quantum dots (QDs) are obtained by colloidal synthesis in aqueous solutions with glutathione ligands at mild conditions. The QDs can be assigned to metastable orthorhombic, rhombohedral, or rocksalt‐type phases, assuming a significant internal pressure within crystallites, while the conventional tetragonal AgGaS2 phase is less likely formed. Similarly to these metastable phases, the QDs reveal a relatively narrow indirect bandgap contrary to the wide and direct bandgap of tetragonal AgGaS2. Size‐selected fractions of the colloidal solutions are separated by repeated centrifuging with addition of 2‐propanol. The QD size is evaluated from atomic force microscopy, while the crystallite size determined using the Scherrer formula is underestimated. X‐ray photoemission spectroscopy reveals that the QD composition changes from nearly stoichiometric for the fraction with the largest QDs toward Ag deficient and S rich for smaller QDs. The synthesized QDs are characterized by the absorption edge blueshift with decreasing QD size. A blueshift of the photoluminescence (PL) peak with decreasing QD size is observed as well as a nonmonotonous size dependence of the PL intensity. Raman spectra of the Ag–Ga–S QDs are discussed compared to those of bulk crystals and a strong contribution of surface phonons is revealed.

Synthesis of α-Bismuth oxide nanoparticles, spectral characterization and their photocatalytic activity

α-Bismuth oxide nanoparticles (α-BiNPs) were synthesized using oxalic acid as a reducing agent. Synthesized nanoparticles were characterized by Ultraviolet-Visible spectroscopy (UV Vis-DRS), Photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermo gravimetric-Differential Thermal analysis (TG-DTA), and High-Resolution Transmission electron microscopy (HR-TEM) coupled with selected area electron diffraction (SAED) pattern. The UV–DRS spectrum reveals the blue shift of absorption edge and the bandgap energy. The XRD pattern revealed the crystalline nature of the synthesized α-BiNPs. The decomposition of the samples was analyzed by TG-DTA analysis. The HR-TEM morphology confirms that the nanoparticles are in an irregular shape. The FT-IR spectrum confirms the Bi-O bond in α-BiNPs. The α-BiNPs exhibit 87 and 84% of photocatalytic activity against MB and CV. Therefore, the synthesized α-BiNPs can be used as a photocatalyst for environmental applications.

Effect of glutathione capping on the antibacterial activity of tin doped ZnO nanoparticles

In the present study, we first synthesized pristine ZnO and Sn doped ZnO nanoparticles (NPs) then capped the synthesized NPs by Glutathione at different capping concentrations. The structural, morphological, and optical properties of synthesized NPs was examined by x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), UV–visible, and energy resolved photoluminescence spectroscopy. The XRD analysis confirmed the formation of wurtzite crystal structure of ZnO nano-crystallites while TEM micrographs showed the formation of dendrite nanostructure at higher capping concentration of glutathione in Sn doped ZnO NPS. Strong absorption band around 2525 cm−1 in the IR spectrum indicates the presence of S–H stretching vibration of glutathione which has been disappeared in glutathione capped ZnO NPs. Blue shift in absorption edge was observed in glutathione capped ZnO NPs as compared to uncapped NPs. Moreover, the synthesized NPs showed excellent response against both Gram positive bacteria (Streptococcus sp. & Staphylococcus sp.) and Gram negative (E. coli & Klebsiella sp.) bacteria. Maximum zone of inhibition has been observed with glutathione capped Sn doped ZnO nanostructures. Hence, it can be concluded from the present investigation that the optimization of capping concentration will be very beneficial to exploit Sn doped ZnO semiconductor nanostructures as a coating material for different chemotherapeutic drugs.

Enhancement of optical limiting performance in nanocrystalline La3+ doped ZnO film

Zn1-xLaxO nanofilms were prepared on the glass substrate at 723K using the chemical spray pyrolysis technique. All deposits are hexagonal wurtzite structures with intense plane along the (101) plane. The films doped with 3% La3+ ion showed the least crystalline size with maximum dislocation density. The surface morphology of the deposits changed from fibrous to needles like structure with increased dopant concentration. Both red and blue shifts of absorption edge were noticed as a function of dopant in highly transparent deposited films. A systematic variation of the extinction coefficient and the refractive index was noticed with the incorporation of La3+ in the deposits. Various defects oriented in the films were confirmed by photoluminescence spectra. However, white light emission was found for 4% doped film. Third-order nonlinear optical absorption coefficient (β), susceptibility (χ3) and refractive index (n2) values are 15 × 10−1cm/W, 6.11 × 10−4esu, and −0.34 × 10−5cm2/W, respectively for 3% doped film. It was noticed that Zn0.97La0.03O nanofilm is a more suitable optical limiter application.

To study the photoluminescence properties of CdS/PVK Nanocomposites

In optoelectronic applications Cadmium Sulfide have very good substance. Which creates interest to describe its optical studies in nanoscale range? Presently photoluminescence of CdS/PVK nanocomposites have been reported. Chemical method is used to prepare the composites and characterized them XRD, UV-Visible absorption and study their photoluminescence. The study of XRD indicates CdS nanocrystals formation having cubic zinc blend crystal structure, with three peaks of planes are respectively 111, 220, and 311. Size of particle is calculated using DebyScherrer’s technique. It has obtained within 3 to 12 nm. Results from XRD shows that when CdS concentration is increases in PVK the particle size also increases. The optical absorption spectra of the nanocomposites show blue shifted absorption edge which show increased band gap because of quantum confinement effect. Absorption side is shifted on larger wave length shows reducing the band gap with increasing CdS concentration, which indicates increase in particle size. The wavelength of 400 nm is incident on PVK, photoluminescence (PL) exhibit single peak on 451 nanometer and covers spectral range from 400 to 600 nm. The CdS nanocrystals give single peak at 530 nm when excited separately by 400 nm. In CdS/PVK nanocomposites two PL peaks are obtained, first peak due to PVK near 450 nm and second peak due to CdS near 530 nm.PL intensity decreases with increasing concentration of CdS in PVK.

Dominance of c-axis orientation on the carrier transport properties of Sn doped ZnO thin films

Sol-gel derived pure and Tin (Sn) doped ZnO thin films were deposited on the glass substrate by cost-effective spin-coating method. The influence of Sn incorporation on the structural, morphological, optical, and electrical properties of ZnO films was investigated by varying Sn concentration. X-ray diffraction reveals the hexagonal crystal structure with a preferential orientation of the crystallites along c-axis in ZnO film after doping with Sn. The transparency of ZnO thin film in the visible region is increased significantly from 72% to 93% after Sn incorporation into the ZnO matrix. The grain size of the film decreased from 27 nm to 20 nm after doping with Sn. The widening of optical band gap from 3.23 to 3.29 eV i.e., a blue shift of absorption edge with Sn doping is attributed to a combination of the Burstein-Moss effect and electron-impurity scattering. Urbach energy values have shown that Sn dopant decreases the width of the band tail of localized states. The electrical properties of the films revealed the decrement of the conductivity in the doped film. The decrement in the conductivity upon Sn doping is explained considering the grain-boundary conduction model and piezoelectric scattering mechanism. The Figure of Merit was calculated to assess the efficiency of the prepared film and was found that the film Sn: ZnO (3 at.%) shows the highest value. The obtained results confirm that Sn dopant has considerable effects on the properties of ZnO thin films and can be used as promising transparent conducting oxide films for optoelectronic applications.

Characterization of chemically deposited nanocrystalline CdSe thin films from transmittance spectra

Optical properties of nanocrystalline films of CdSe prepared by chemical bath deposition technique are studied as a function of molar concentration. Analyses of the transmittance spectra over 350–900 nm photon wavelengths of CdSe films indicates the existence of direct optical transition. A blue shift of absorption edge was observed which indicates a decrease in crystallite size. The optical band gap (Eg) was found to be in the range of 1.93–2.10 eV for as-prepared films. After annealing the band gap was found to decrease. The crystallite size was found in the range of 3.34–4.99 nm using the effective mass approximation model. Different optical parameters such as absorption coefficient, refractive index, extinction coefficient, optical conductivity, dielectric constants were determined from the transmittance spectra.

Tunable Optical Properties of Amorphous-Like Ga2O3 Thin Films Deposited by Electron-Beam Evaporation with Varying Oxygen Partial Pressures.

Ga2O3 thin films were fabricated by the electron-beam evaporation technique at a varying oxygen partial pressure from 0 to 2.0 × 10−2 Pa. The effect of oxygen partial pressure on the crystalline structure and optical properties of the Ga2O3 films was analyzed using sophisticated techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, spectroscopic ellipsometry, ultraviolet-visible spectroscopy and a laser-induced damage test system. The correlation between the oxygen partial pressure and the film’s properties in optics and materials were investigated. XRD and Raman revealed that all films were amorphous in spite of applying a varying oxygen partial pressure. With the change of oxygen partial pressure, XPS data indicated that the content of oxygen in the Ga2O3 films could be broadly modulable. As a result, a changeable refractive index of the Ga2O3 film is realizable and a variable blue-shift of absorption edges in transmittance spectra of the films is achievable. Moreover, the damage threshold value varied from 0.41 to 7.51 J/cm2 according to the rise of oxygen partial pressure. These results demonstrated that the optical properties of Ga2O3 film can be broadly tunable by controlling the oxygen content in the film.

Exploring the effect of Ga3+ doping on structural, electronic and optical properties of CH3NH3PbCl3 perovskites: an experimental study

Pure and gallium (Ga)-doped CH3NH3PbCl3 perovskites are systematically prepared via a simple solution-processed technique. The as-synthesized perovskites are then analysed for their structural, optical, morphological, elemental and electronic properties using X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis-DRS), field emission gun-scanning electron microscopy (FEG-SEM), energy-dispersive spectroscopy (EDS) and photoluminescence spectroscopy (PL), respectively. The detailed structural study reveals the formation of the cubic structure with space group pm3m for pristine and Ga-doped CH3NH3PbCl3 perovskites. Microstrain and lattice dislocation density of doped perovskites increase with increasing Ga composition, compared to the undoped CH3NH3PbCl3. Optical properties show the bandgap narrowing up to 10% Ga doping, and any further increase in doping concentrations again increases the bandgap. This blue shift in absorption edge, i.e. bandgap widening behaviour, of highly doped CH3NH3PbCl3 (20% and 30%) perovskites justifies the Burstein–Moss effect in doped semiconductors. The highest Urbach tail energy is observed for 10% Ga-doped compound, which in turn results in the highest electron–phonon interaction. Morphological imaging shows that optimum Ga doping (10%) can improve the characteristic in terms of homogeneity and defect-free surface, compared to pristine perovskite. However, doping beyond the optimal value can further deteriorate the surface morphology by enhancing the surface inhomogeneity and defects. XRD and EDS both confirm the purity of the synthesized materials. Here, doping increases non-radiative recombination which suppresses the radiative recombination of pure CH3NH3PbCl3. These observations unfold the prospect for a new insight of post-transition metals, to fabricate lead-free perovskite materials with advanced optoelectronic properties.

Comparative study of thermochromic properties on fresh and aged vanadium dioxide films

Vanadium dioxide (VO2) thin films were fabricated by means of DC reactive magnetron sputtering at low temperature, and then were aged in air for 5 years. The thermochromic properties of the fresh VO2 film and aged one were investigated by UV–visible spectrophotometer. The experimental results show that the fresh VO2 film shows excellent thermochromic properties with a high visible transmittance of 40.8% and a large switching efficiency of 73% at 2500 nm. For the film aged in ambient air for 5 years, the visible transmittance is increased to 54.0% due to a blue-shift of absorption edge and a decrease in luminous absorbance. More interestingly, the aged VO2 film still keeps a relatively large switching efficiency of 51% at 2500 nm, suggesting the deposited VO2 film has a good thermochromic stability in ambient air. These characteristics indicate the practical applications of VO2 film to smart optical devices.

Synthesis of submicron-sized CdS particles using reverse micelles

We synthesized cadmium sulfide (CdS) submicron particles in reverse micelles. We chose the surfactants and the water-to-surfactant molar ratio to influence the formation of reverse micelles such that their average size was 100 nm. The actual size of the particles that we synthesized was consistent with the expected reverse micelle size. The synthesized CdS particles exhibited a strong photoluminescence that comprised an interband emission with a quantum confinement effect and a broad emission that originated from the surface trap states. When combined with the blueshifted absorption edge seen in the submicron particle solution, our prepared submicron particles were an aggregation of semiconductor quantum dots. The submicron-size semiconductor particle is appropriate as an optical trapping target in a variety environments and is beneficial for sophisticated resonant optical manipulation, including enhanced optical trapping force and recoil force manipulation.

Impact of Hydrogen flow rate on physical properties of ZnS thin films: As potential buffer layer in solar cells

The exceptional need of potential Cd-free buffer layer in thin film solar cell devices motivated us to study the role of post-deposition Hydrogen annealing for the optimization of physical properties of ZnS thin films. The deposited films of thickness 200 nm were hydrogenated within the flow rate range of 50.0–150.0 sccm at 200 °C. XRD analysis revealed transformation of amorphous into cubic phase with maximum crystallinity at 150.0 sccm for films deposited on glass substrate while into wurtzite structure for films on ITO substrate with enhanced crystallinity. A mixed phase (cubic and hexagonal) at 150.0 sccm also appeared. Electrical behaviour (I–V) exhibits ohmic nature with maximum carrier concentration at 100.0 sccm. The blue shift in absorption edge and maximum of 95% transmittance were recorded in the visible region with optical energy band gap of 3.41 eV at 150.0 sccm. The reduction in surface roughness is observed in surface topographical analysis while the photoluminescence (PL) study indicated a sharp peak at 2.95 eV with strongest emission for 150.0 sccm attributed to reduction of defects at interstitial sites and passivation of grain boundaries. These results are useful to understand the Hydrogen related impurities in ZnS films and the improvement caused by hydrogenation to physical properties suited for buffer layer in solar cells.

Structural, optical and antibacterial investigation of La, Cu dual doped ZnO nanoparticles prepared by co-precipitation method

La, Cu dual doped ZnO with Cu = 0%-4% were prepared by co-precipitation route. The XRD pattern optimized the Cu content as 2% which restrict the secondary phase formation. The new phase at 38.7° corresponding to CuO (111) and the another phase at 42.3° related to Zn (101) came from un-reacted Zn2+ ions appeared in Cu = 4% doped sample. Zeta potential measurements confirms the stability of the particles. The blue shift of absorption edge and the energy gap from 3.66 eV to 3.99 eV by Cu doping was discussed by the shape of the particles, the distortion of the host lattice and generation of defect concentrations. The characteristic IR peaks around 470-489 cm-1 was related to the octahedral sites of Zn-O for Cu = 0 and 2% which is shifted to 616 cm-1 corresponding to the tetrahedral site at Cu = 4%. The shift in frequency was originated from the dissimilarity in the volume and bond lengths by the substitution of La and Cu in Zn-O. Based on the antibacterial report, it can be concluded that the Cu-doped Zn-La-O solid solution compose an effectual antimicrobial agent against pathogenic microorganisms. Cu = 4% doped sample possessed highest bacterial killing capacity because of the enhanced crystallite size and high density of oxygen vacancies which led the higher ROS values. Tuning of crystallite size and energy gap and the enhanced bactericial killing capacity by Cu addition is useful for opto-electronic device and medical applications.