Red Shift In Band Gap Research Articles

Examining the electronic, structural, optical, and photovoltaic capabilities of Sr3AsBr3 perovskite under tensile and compressive strains with DFT and SCAPS-1D

A significant amount of interest in the field of solar energy has recently been generated by the remarkable optical, structural, and electronic attributes of inorganic perovskite-based substances. A thorough investigation was conducted on how tensile along with compressive strains influence the electronic and optical properties of halide perovskite Sr3AsBr3, utilizing FP-DFT. The PBE functional is used to determine the direct bandgap of 1.512 eV for unstrained Sr3AsBr3 at the Γ position. The bandgap redshifts (1.216 eV at -4 % strain) under compressive strain and slightly increases (1.728 eV at +4 % strain) under tensile tension, causing the absorption coefficient to blueshift. The optical properties, including the functions of dielectric, electron energy loss function, and absorption coefficient, all indicate a considerable capacity for absorption in the area of the visible spectrum, and the band characteristics of this component agree with these qualities. We used Sr3AsBr3 absorbers and CdS electron transport layers (ETL) with different thicknesses, defect densities, and doping concentrations to study solar power capabilities using the SCAPS-1D simulator. The most effective arrangement (at -4 % strain) had a fill factor (FF) of 86.76 %, a short-circuit current density (JSC) of 37.5593 mAcm−2, an open-circuit voltage (VOC) of 0.8712 V, and a power conversion efficiency (PCE) of 28.39 %. Our findings support additional research into Sr3AsBr3, a promising perovskite for optoelectronic uses.

Superior photocatalytic degradation of pharmaceuticals and antimicrobial Features of iron-doped zinc oxide sub-microparticles synthesized via laser-assisted chemical bath technique

Addressing the dual challenges of antimicrobial resistance and pharmaceutical contamination in wastewater is crucial for global health and environmental preservation. Predictions estimate up to 10 million annual deaths by 2050 due to antimicrobial resistance, underscoring the urgent need for innovative solutions. This study explores the potential of zinc oxide Sub-Microparticles (ZnO SMPs) doped with iron (Fe) to enhance the photocatalytic degradation of pharmaceutical compounds in water and improve antimicrobial efficacy. A green laser-assisted chemical bath synthesis method created ZnO SMPs with varying Fe dopant concentrations (1 %, 1.5 %, and 3 %). The synthesized Sub-Microparticles underwent rigorous structural analysis using X-ray diffractometry, SEM, EDX, FTIR, and UV–visible spectrophotometry techniques. Their photocatalytic performance was evaluated in the degradation of paracetamol under blue laser light, and their antimicrobial properties were assessed following CLSI guidelines. Structural analyses confirmed the hexagonal wurtzite structure of ZnO SMPs, with noticeable changes due to Fe doping, including a transition from sub-microrods to sub-microsheets and a redshift in the optical band gap. Photocatalytic tests revealed a significant enhancement in paracetamol degradation efficiency, increasing from 53.41 % with pure ZnO to 98.99 % with 3 % Fe-doped ZnO in 50 min. Antimicrobial assays demonstrated an increased inhibitory effect against pathogens, with Fe-doped ZnO outperforming control discs. This study substantiates the potential of Fe-doped ZnO SMPs in wastewater treatment and antimicrobial applications, showcasing significant improvements in photocatalytic degradation of pharmaceutical compounds and antimicrobial efficacy. The findings underscore the importance of continuing research in this domain for environmental and public health benefits.

Femtosecond nonlinear optical properties of Ti-doped In2Te3 thin films grown by magnetron co-sputtering

Herein, we successfully prepared Ti-doped In2Te3 and pure In2Te3 films by magnetron co-sputtering at room temperature. The film structure was measured using x-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS), while the linear optical constant of the films was measured using a spectroscopic ellipsometer (SE). The nonlinear optical properties of the films were examined using the Z-scan technique, wherein the samples were irradiated with 140 fs laser pulses at a wavelength of 800 nm and a repetition rate of 80 MHz, with an input intensity of 1.2GW/cm2. Ti incorporation led to decreased crystallinity and a reduction (redshift) in the optical bandgap (E g ). All films exhibit reverse saturation absorption (RSA) and self-focusing effect. A ninefold increase in the nonlinear refractive index (n2) and a fourfold increase in the nonlinear absorption coefficient (β) were observed for the Ti-doped S40 sample in comparison to the pure S0 sample. Adjusting the phase transition between amorphous and crystalline states in Ti-doped In2Te3 films further modulated their nonlinear optical properties. The optical limiting (OL) behavior of pure In2Te3 and Ti-doped In2Te3 thin films was investigated, and the results demonstrated that Ti-doped In2Te3 films show great promise as optical limiter devices in nonlinear photonics.

Influence of cobalt doping on structural, optical, and electrical properties of zinc oxide nanoparticles prepared by polymeric precursor method

Cobalt-doped ZnO nanoparticles at different compositions have been obtained by the polymeric precursor method. The nanoparticles were obtained at the working pH from 8.3 to 8.5 and synthesized at 550 °C. The properties were studied using X-ray diffraction (XRD), vibrational spectroscopy (FTIR/Raman), diffuse reflectance absorbance spectroscopy (DR UV–Vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM/EDS), and impedance spectroscopy. The lattice parameters were determined at room temperature by Rietveld refinement, confirming single-phase composition with a hexagonal wurtzite structure. FTIR and Raman analyzes identified the characteristic vibrations of the synthesized system and the typical deformations of the wurtzite-type hexagonal structure, corroborating the results obtained from XRD. A redshift in the optical energy band gap (Egopt) was observed with increasing cobalt content compared to the ZnO sample. Considering the doping percentage, Egopt value varied between 3.13 eV and 3.04 eV for pure ZnO and Co-doped ZnO with 5 at. %., indicating that the optical properties of the nanoparticles were affected by dopant concentration. PL and SEM/EDS characterization were used to determine the associated defects for each sample and the morphology and composition of the nanoparticles. PL results showed a strong blue emission at around 439 nm (2.83 eV), which is redshift with cobalt content (ΔE between 0.05 eV and 0.01 eV), attributed to the surface defects present in the doped samples. Conductivity analysis to temperature revealed a semiconductor behavior for all samples, and their respective activation energies determined. The results provide an easy method to obtain Co-doped ZnO nanoparticles with interesting properties for optoelectronics devices.

Synthesis of silica inverse opal and evaluation of its potential as an optical chemical sensor for detection of metal salts

In this paper, SiO2 inverse opal photonic crystals, made by the co-assembly of SiO2 and polymethylmethacrylate (PMMA) microspheres, were used to detect 20 different metal salts with a concentration of 0.002 mol/L. Surprisingly, two different behaviors were observed. Some metal salts caused a redshift in photonic bandgap (PBG) while the others led to a PBG’s blueshift. The observed different behaviors of salts are due to their distinct influence on the lattice constant of the inverse structures which was precisely investigated by analyzing the field emission scanning electron microscopy (FESEM) images and ultraviolet–visible (UV–Vis) spectroscopy. It has been revealed that the competition between the hydrophilicity of SiO2 and the hygroscopicity of metal salts led to a shift of PBG toward blue or red. The maximum shift in the PBG range was observed for mercury (II) nitrate salt (19 nm), which indicates a sensitivity of 9.5 nm per concentration unit (mM). Furthermore, the lowest displacement of the PBG was observed for the sodium nitrate salt (5 nm), which represents a sensitivity of 2.5 nm/mM. The lowest and highest values of the detection limit (LOD) for mercury (II) nitrate salt and sodium nitrate salt equal 0.193 mmol/L and 0.887 mmol/L, respectively. In addition, according to the calibration curve, with a regression coefficient of R2 > 0.95, there is a linear relationship between the salt concentration and the displacement of the PBG of the structure. Based on the results illustrating the sensitivity of the synthesized inverse opal to the type and concentration of the salts, inverse opal can be regarded as a promising structure to create a new perspective in the field of chemical sensing.

Catalytic effect of aluminum on the structural, optical, and electrical properties of LaSrCrO3-δ anode

Solid oxide fuel cell is promising conversion technology due to fuel flexibility, higher efficiency, and environment friendly compared to traditional technology. To enhance the efficiency of the device, selection of anode material is important because it affects the electrochemical performance and operating temperature of the cell. In this work, La0.5Sr0.5AlxCr1-xO3-δ (x = 0, 0.1, 0.2, 0.3, 0.4) anode has been developed using sol-gel method. XRD analysis exhibited a two-phase structure of the prepared anode, one orthorhombic and second rhombohedral phase with crystalline size in the range 15–18 nm. The surface morphology of the prepared anode material shows nano-spheres, dumbbells, and platelets. The elemental analysis confirms the presence of Sr, Cr, La, Al, and O in the prepared material. The metal-oxide formation has been confirmed with Fourier Transform Infrared Spectroscopy. The absorption spectra revealed red shift in bandgap 3.65–2.85 eV by increasing the Al concentration. The maximum dc electrical conductivity of the composition anode La0.5Sr0.5Al0.4Cr0.6O3-δ is found to be 8.01 Scm−1 at 600 °C. The achieved power density of the anode La0.5Sr0.5Al0.4Cr0.6O3-δ is 69 mWcm−2 using hydrogen fuel at 600 °C.

Thermal colour map of 4D smart microtags made by Two-Photon Lithography in cholesteric reactive mesogens

ABSTRACT The helicoidal architecture of cholesteric reactive mesogens allows for smart 4D responsive microdevices that reflect selectively the wavelength and polarisation of the incident light. Two-photon lithography is an effective 4D microprinting technology which also enables fine tuning of the Bragg reflection, as a function of the energy delivered during the manufacturing and the polymerisation degree. When CRMs objects undergo temperature variation, thermal expansion causes the elongation of the effective helix pitch and the consequent red-shift of the photonic band gap. A thermal characterisation of the optical response of CRMs microcylinders is presented, showing a tunable red-shift from 2 to 37 nm in the 30–150°C range. The red-shift is enhanced for tall structures, with high polymerisation degree. This characterisation is exploited to add a security label to a 4D cholesteric QR code.

Fabrication of highly sensitive memristive device using NiO nanoparticles synthesized by single step wet chemical method

Single step wet chemical method is used to prepare molar concentration varied NiO nanoparticle using PVP as the capping agent. Structural, optical and electrical properties are investigated on the prepared samples and are correlated with growth. TEM shows particle size distribution ∼ 3–4 nm synthesized in the range 0.001–1 M which agrees with XRD and optical measurements. Red shift in absorption is observed in optical measurement with enhancing molarity. Because of lesser size distribution of NiO nanoparticles, larger native defect in the form of oxygen vacancies is expected which may beutilized in fabrication of memristive devices. The sensitivity of the devices is estimated through Roff/Ron and area of pinched hysteresis loopwhich shows promising result. Higher sensitivity is explained due to incorporation of more oxygen vacancies during the growth of NiO nanoparticles synthesized at higher concentration. The experimental memristive characteristics are validated through theoretical model fitting using different window functions.

Impact of Zn alloying on structural, mechanical anisotropy, acoustic speeds, electronic, optical, and photocatalytic response of KMgF3 perovskite material

This study explores the optoelectronic potential of advanced perovskite materials, with a primary focus on alloying KMgF3 with 3d transition metals. Through this alloying process, the study employs density functional theory (DFT) with the GGA-PBE functional to tailor the atomic structure and various properties, including optoelectronic, mechanical, acoustic, anisotropic, and photocatalytic attributes. The introduction of Zn to KMgF3 triggers a noticeable bandgap redshift and significant improvements in mechanical stability and photocatalytic performance. Increasing Zn content induces a transition in KMgF3's crystal structure to a pseudo-cubic tetragonal form, which remains mechanically stable for both pristine KMgF3 and KMg(1-x)ZnxF3. Zn inclusion introduces versatile nonlinearity in terms of brittleness, stiffness, mechanical strength, and thermal behavior. This comprehensive analysis underscores anisotropy, mixed bonding, Debye fluctuations, and melting temperature variations. Notably, among the systems examined, KMg0.25Zn0.75F3 stands out as an outstanding candidate for applications in photovoltaics and water splitting, thanks to its exceptional optical performance.

Tailoring the linear and nonlinear optical properties of PVC/PE blend polymer by insertion the spindle copper nanoparticles

PVC/PE polymer nanocomposites were synthesized with 0–3 wt% copper (Cu) nanoparticles via melt extrusion. XRD analysis showed characteristic peaks corresponding to crystalline PVC, PE, and Cu phases. FTIR confirmed the presence of signature vibrational modes of PVC and PE. Optical studies revealed tunable light absorption, refractive index, dielectric response, and bandgap by tailoring copper content. The composites displayed enhanced linear and nonlinear optical susceptibilities, with potential applications in photonics. Optical absorption studies revealed a redshift in bandgap from 3.38 eV to 2.19 eV as Cu concentration increased from 0 to 3%, indicating enhanced visible light absorption. The real dielectric constant rose from 1.3527 to 1.4578 at 190 nm wavelength when Cu content was raised from 0 to 3%. Imaginary dielectric constant exhibited a stepwise enhancement from 2.43 × 10−3 to 3.97 × 10−3 at 190 nm with increasing Cu loading up to 3 %. The nonlinear refractive index varied from 1.2 × 10−8 cm2/W to 2.1 × 10−8 cm2/W across 500–900 nm wavelengths for 0–3% Cu. Meanwhile, the dispersion parameters including, the single oscillator energy (Eo) and the dispersion energy (Ed) were extracted. The relaxation time of the studied samples were extracted, which decreased after the insertion the nanofillers. The outcomes revealed that Cu nanoparticles' doped films favor a high-speed optoelectronic device more than the pristine film.The results demonstrate tunable optical and dielectric characteristics, underscoring the potential of Cu-based PVC/PE nanocomposites.

Structural and magnetic properties of Fe and Ni co-doped SnO2 nanoparticles prepared by co-precipitation method

In this research work Fe and Ni co-doped Tin oxide (SnO2) nanoparticles have been prepared by co-precipitation method. The samples were prepared at various combination of Fe and Ni from 0% up to 10%. The produced nanoparticles were studied by x-ray diffraction (XRD), Scanning Electron Microscopy (SEM), UV–vis Spectrophotometer, Fourier Transformation Infrared Spectroscopy (FTIR) and Vibrating Sample Magnetometer (VSM). The XRD study reveals the formation of rutile structure of the undoped and doped SnO2 nanoparticles with the average crystallite size of 1.5–10.8 nm. Metal oxide bonding is confirmed through FTIR measurement. Optical band gap redshift (3.9 to 3.64 eV) with doping of Fe and Ni atom is observed. SEM image confirms the formation of spheroidal nanoparticles and size of the nanoparticle varies from 36 to 15 nm. The VSM study shows the ferromagnetic phase transition at 7% Ni, Fe doped SnO2 nanoparticles. This ferromagnetism arises for the oxygen vacancies and defect states. Further, increase of doping concentration of 10%, nanoparticles show the phase transition from ferromagnetic to paramagnetic. Such transition can be applicable in hyperthermia treatment and memory devices.

Structural, Optical, and Magnetic Properties of Pure and Ni-Fe-Codoped Zinc Oxide Nanoparticles Synthesized by a Sol-Gel Autocombustion Method.

Pure and Ni-Fe-codoped Zn1-2xNixFexO (x = 0.01, 0.02, 0.03, and 0.04) nanoparticles were effectively synthesized using a sol-gel autocombustion procedure. The structural, optical, morphological, and magnetic properties were determined by using X-ray diffraction (XRD), ultraviolet-visible (UV-vis), scanning electron microscopy, and vibrating sample magnetometer techniques. The XRD confirmed the purity of the hexagonal wurtzite crystal structure. XRD analysis further indicated that Fe and Ni successfully substituted the lattice site of Zn and generated a single-phase Zn1-2xNixFexO magnetic oxide. In addition, a significant morphological change was observed with an increase in the dopant concentration by using high-resolution scanning electron microscopy. The UV-vis spectroscopy analysis indicated the redshift in the optical band gap with increasing dopant concentration signifying a progressive decrease in the optical band gap. The vibrating sample magnetometer analysis revealed that the doped samples exhibited ferromagnetic properties at room temperature with an increase in the dopant concentration. Dopant concentration was confirmed by using energy-dispersive X-ray spectroscopy. The current results provide a vital method to improve the magnetic properties of ZnO nanoparticles, which may get significant attention from researchers in the field of magnetic semiconductors.

The effect of composition on the structure, optical, and room-temperature ferromagnetic properties of hydrothermally synthesized (ZnSn)1-xCuxO nanocomposites

(ZnSn)1-xCuxO nanocomposites (NCs) with nanorods and nanosheet morphologies were synthesized by a facile hydrothermal technique. (ZnSn)1-xCuxO NCs exhibited a gradual band gap redshift from UV to visible spectral region with increasing Cu-content. The room temperature magnetic hysteresis loop indicated the improvement of room temperature ferromagnetic (RTFM) behavior of (ZnSn)1-xCuxO NCs compared with nanostructured ZnSnO NCs induced by the exchange interaction of Cu-bound polarons with the localized spins and free carriers. The (ZnSn)60Cu40O NCs exhibited the highest saturation magnetization (Ms) of 0.539 emu·g−1. Further increase in Cu-content resulted in the deterioration of crystalline domains and the reduction of Ms to 0.259 emu·g−1. This behavior revealed that the electronic and magnetic properties of (ZnSn)1-xCuxO NCs were so sensitive to the dopant concentration that need to be utilized for improving their performance as good candidate NCs for spintronic applications.

Phase transitions and optical properties of Tb3+ activated NaY(WO4)2 phosphors

Well-defined NaY(WO4)2:Tb3+ nanoflowers were prepared through the controllable structural transition of hydroxyl sodium yttrium tungstate precursor, which exhibit a fascinating luminescent property as activated by Tb3+ dopant. NaY(WO4)2:Tb3+ nanoflowers were systematically characterized with a series of tests including XRD, SEM, FT-IR, TG-DTA, UV–Vis, and PL. XRD analyses indicate that NaY(WO4)2:Tb3+ crystalizes in the scheelite structure with broadened diffraction peaks and expanded cell volume with increasing Tb3+ content as revealed by Rietveld refinement. FT-IR and TG-DTA results show that NaY(WO4)2:Tb3+ is formed via the structural transition of hydroxyl sodium yttrium tungstate at calcination temperature above 600 °C. UV–Vis test discloses the bandgap red-shift of NaY(WO4)2 via doping Tb3+ ions. Noticeably, PL measurement discloses the green luminescence of NaY(WO4)2:Tb3+ attributable to 5D4→7F5 transition with the optimal Tb3+ doping content of 13 mol%, which manifests the effective energy transfer from WO42− groups to Tb3+ ions and reveals relatively good thermal stability. Furthermore, the tunable color emission from blue to green to yellowish green can be achieved in flower-like NaY(WO4)2:Tb3+ phosphors by controlling the doping content of Tb3+ ions, which may provide promising application in the field of multicolor lighting and displays.

Impacts of dielectric screening on the luminescence of monolayer WSe2

Single layers of transition metal dichalcogenides (TMDCs), such as WSe2 have gathered increasing attention due to their intense electron–hole interactions, being considered promising candidates for developing novel optical applications. Within the few-layer regime, these systems become highly sensitive to the surrounding environment, enabling the possibility of using a proper substrate to tune desired aspects of these atomically-thin semiconductors. In this scenario, the dielectric environment provided by the substrates exerts significant influence on electronic and optical properties of these layered materials, affecting the electronic band-gap and the exciton binding energy. However, the corresponding effect on the luminescence of TMDCs is still under discussion. To elucidate these impacts, we used a broad set of materials as substrates for single-layers of WSe2, enabling the observation of these effects over a wide range of electrical permittivities. Our results demonstrate that an increasing permittivity induces a systematic red-shift of the optical band-gap of WSe2, intrinsically related to a considerable reduction of the luminescence intensity. Moreover, we annealed the samples to ensure a tight coupling between WSe2 and its substrates, reducing the effect of undesired adsorbates trapped in the interface. Ultimately, our findings reveal how critical the annealing temperature can be, indicating that above a certain threshold, the heating treatment can induce adverse impacts on the luminescence. Furthermore, our conclusions highlight the influence the dielectric properties of the substrate have on the luminescence of WSe2, showing that a low electrical permittivity favours preserving the native properties of the adjacent monolayer.

Thickness and porosity characterization in porous silicon photonic crystals: The etch-stop effect

One-dimensional photonic crystals and microcavities were fabricated using porous silicon via anodization. The study investigated the effect of an etch-stop layer, which is included between two adjacent porous layers to resolve the issue of HF diffusion during pore formation. Although proposed as a solution, no systematic investigation had been conducted on this parameter until now. Our study found that the etch-stop layer induces a redshift in the photonic bandgap, regardless of the electrolyte solution used. The fitting analysis of both single and multilayer structures revealed that the redshift resulted from an increase in the silicon etch rate and a decrease in porosity due to the enhancement of HF diffusion through the porous structure. Furthermore, an analysis of oxidation as a function of temperature demonstrated that the inclusion of the etch-stop layer led to the formation of porous layers with varying microstructures. This effect was particularly pronounced in devices where the first upper layer had high porosity. The thermal treatment caused a photonic bandgap inhibition, which was linked to the contraction-expansion phenomena of the low and high porosity layers, respectively. This resulted in the partial violation of Bragg's law. Overall, our study provides insights into the influence of etch-stop layers on the optical properties of porous silicon-based photonic structures.

Conformal CVD-Grown MoS2 on Three-Dimensional Woodpile Photonic Crystals for Photonic Bandgap Engineering.

To achieve the modification of photonic band structures and realize the dispersion control toward functional photonic devices, composites of photonic crystal templates with high-refractive-index material are fabricated. A two-step process is used: 3D polymeric woodpile templates are fabricated by a direct laser writing method followed by chemical vapor deposition of MoS2. We observed red-shifts of partial bandgaps at the near-infrared region when the thickness of deposited MoS2 films increases. A ∼10 nm red-shift of fundamental and high-order bandgap is measured after each 1 nm MoS2 thin film deposition and confirmed by simulations and optical measurements using an angle-resolved Fourier imaging spectroscopy system.

Hydrogenation Influences on the Structural, Optical, and Insulating Properties of (Bi+Cr) Codoped Anatase TiO2 Nanoparticles

AbstractThis paper presents the investigation results for pure and (Bi/Cr) codoped TiO2 nanoparticles (NPs) synthesized by using a hydrothermal precipitation technique. The synthesized NPs are characterized by using X‐ray diffraction (XRD) and optical spectroscopy. The XRD patterns show a single anatase phase of an average nano‐crystallite size ≈6–9 nm. In addition, it was noticed that the hydrogenation of the NPs of the ceramic samples reduced the crystallite sizes due to the creation of O‐vacancies and microstrain. The optical absorption spectra show redshift of the bandgap. Moreover, an absorption hump in the high‐wavelength range of 630–800 nm is observed and attributed to the d‐d transitions in Cr3+ ions. Then, it is studied hydrogenation's significant effect on the absorption spectrum for λ > 370 nm, which attributes to the creation of a high density of point defects and structural microstrain that enhances the redshift of bandgap. The permittivity at 1 kHz of the prepared (Bi/Cr):TiO2 ceramic is found to be of large value (≈670), which is enhanced up to ≈103 by the hydrogenation. It is concluded that the hydrogenation in the present investigation supports the effects of the Bi3+ ions on the dielectric properties rather than that of Cr3+ ions, which mostly substitute the Ti ions (TiCr) due to the similarity of Ti3+ and Cr3+ ions. Thus, the measured dielectric constant of the hydrogenated sample [(Bi/Cr):TiO2‐H] is almost equal to that value of the host TiO2 doped with only Bi ions (Bi:TiO2). Moreover, it is concluded that the hydrogenation has a negligible effect on the effective polaron hopping energy, but increases the sample maximum barrier height (WM) by ≈55% causing an increase in the measured values of the permittivity.

Tunable heptazine/triazine feature of nitrogen deficient graphitic carbon nitride for electronic modulation and boosting photocatalytic hydrogen evolution

Construction of nitrogen deficient graphitic carbon nitride with heptazine/triazine feature to boost photocatalytic hydrogen evolution • Nitrogen deficient graphitic carbon nitride with tunable heptazine/triazine feature was constructed. • The photocatalytic hydrogen production rate of CCN-10% was boosted to 569.5 μmol g -1 h -1 , which was 8.12 times than bulk g-C 3 N 4 . • CCN-10% showed an enhanced surface area, light harvesting and photogenerated charge separation capacity. • CCN-10% showed preferable reusability and durability. Graphitic carbon nitride (g-C 3 N 4 ) as metal-free semiconductor was a fascinating photocatalyst for hydrogen production, suffering from fast charge recombination due to incomplete polymerization. In this regard, nitrogen deficient crystalline with tunable heptazine/triazine feature was obtained. It’s found that incorporation of 2,4-diamino-6-hydroxypyrimidine into g-C 3 N 4 framework and the subsequent molten salt re-polymerization process led to nitride deficient feature and maneuverable tuned heptazine/triazine units, resulting the band gap red shift from 2.53 to 2.08 eV with broadened band tail in the range of about 480-800 nm. Careful characterizations revealed that nitrogen deficient crystalline g-C 3 N 4 exhibited more negative band edge potential and faster charge carrier transfer, which was superior to undoped g-C 3 N 4 . The photocatalytic hydrogen production rate of nitrogen deficient crystalline g-C 3 N 4 was boosted to 569.5 μmol g -1 h -1 , which was 3.44 and 8.12 times higher than undoped g-C 3 N 4 and bulk g-C 3 N 4 . Besides, the apparent quantum efficiency of optimal catalyst was obtained 10.71% at 435 nm. This work may offer a useful route to fabricate tunable heptazine/triazine-based carbon nitride photocatalyst for hydrogen production.

Morphological variations of ZnO nanostructures and its influence on the photovoltaic performance when used as photoanodes in dye sensitized solar cells

Different hierarchical architectures of ZnO were synthesized via optimization of ethylenediamine (EDA) concentration in a simple low-temperature hydrothermal route and their various photoanode characteristics are effectively used in superior DSSC performance. In a sequence of morphological changes from the nanoparticles to nanorods and the nanoflowers structures, gradually and systematically, the zinc-interstitial and oxygen-vacancy related phases reduce, bandgap redshifts relative to its bulk structure, surface area increases and the dye-loading capacity improves. In photoanodes with ZnO nanoflower structures, the incident photon-to-current conversion efficiency gradually increases to ∼46.6% via significant photo-absorption by a larger number of dye-molecules adsorbed on its enhanced specific surface area and via its high dye-loading capacity that facilitate an amplified photogeneration of electrons upon light-exposure on the DSSC. Furthermore, the lowest charge transfer resistance and hence an improved charge transport pathway prevailing in the device consequences superior photovoltaic conversion efficiency (η) of the DSSCs, which gradually advances to ∼4.42%, via increasing the short-circuit current density (J SC ) to ∼10.75 mA cm −2 and the open-circuit voltage (V OC ) to 0.73 V. Morphological changes in the ZnO nanostructures are demonstrated to significantly influence the photovoltaic performance when used as an effective photoanode of the DSSCs, which has never been reported earlier. Highlights • Variety of ZnO nanostructures are synthesized, their striking features are ably used in photoanodes for superior DSSC activity. • Morphological changes from nanoparticle to nanorod to nanoflower sequentially reduce defects, bandgaps, increase surface area. • ZnO nanoflower photoanode with high dye-loading capacity gets good IPCE via better photocarrier generation by adsorbed dye-molecules. • Besides, the lowest charge transfer resistance facilitates superior photovoltaic conversion efficiency (η ∼4.42%). • ZnO in specific morphology significantly influences the PV performance when used as active photoanode in DSSCs.