Decrease In Photoluminescence Intensity Research Articles

Impact of composition of AlGaInAs confining barriers on emission of InAs quantum dots embedded in AlGaAs/GaAs dot-in-a-well heterostructures

The emission of InAs quantum dots (QDs) grown on Al0.30 Ga0.70As/GaAs heterostructures and integrated into additional capping/buffer quantum wells (QW), known as dot-in-a-well (DWELL) structures, has been investigated. Two different AlGaInAs confining barriers (CBs) and buffer layers (BLs) are compared. The first QD structure includes the Al0.30 Ga0.70As CB (#1) and the In0.15Ga0.85As BL. The second QD structure consists of the Al0.40Ga0.45In0.15As CB (#2) and the In0.25Ga0.75As BL. Comparison of photoluminescence (PL) spectra has revealed that the ground state (GS) emission band in the structure #2 with Al0.40Ga0.45In0.15As CB is characterized by the lower peak energy, smaller PL linewidth (more homogeneous QD sizes) and higher GS emission intensity compared to that parameters in the structure #1 with Al0.30 Ga0.70As CB. The smaller potential barriers at the Al0.40Ga0.45In0.15As CB/QD interfaces in #2 lead to faster thermal decrease in the GS PL intensity at high temperatures compared with that in #1. High-resolution X-ray diffraction (HR-XRD) method was used for the study of the QD structures with the aim of monitoring the sizes and compositions of QDs and QWs. Numerical simulation of HR-XRD scans has shown that the material compositions of QDs and QW in #2 with Al0.40Ga0.45In0.15As CB has not changed in the process of QD structure growth at high temperatures compared to those in #1. The obtained results are interesting for further improvement of InAs/GaAs QD structures for telecommunication technology and optoelectronic applications.

PH selective fluorometric detection of E. coli using water soluble polyphenothiazine

This work has investigated the use of a novel cationic conjugated polymer, Poly 10-(6-(3-methylimidazolidin-l-yl)hexyl)−9-Phenothiazine (PMP), as a sensing platform for a polymer-based fluorescence sensor for the detection of E. Coli O157:H7. Fourier Transform Infrared Spectroscopy (FTIR), ultraviolet radiation (UV), proton nuclear magnetic resonance (1HNMR), and photoluminescence (PL) analysis were used to characterise the synthesised polymer. The electrostatic interaction between single strand genomic DNA of E.coli (tDNA) and cationic polymer resulted in photoinduced charge transfer (PET) mediated quenching of the fluorescence intensity of PMP, which has been utilized as a tool for the detection DNA of E. coli (tDNA), since the decrease in photoluminescence intensity of cationic polymer was found to be proportional to the concentration of tDNA. The biosensor developed using PMP exhibits sensitive detection of tDNAin the range of 10−18 to 10−21 M concentration with a lowest detection limit of tDNA is 1 × 10−21 M.

The Thermal Stability and Photoluminescence of ZnSeO3 Nanocrystals Chemically Synthesized into SiO2/Si Track Templates

We report the effect of high-temperature treatment on the structure and photoluminescence of zinc selenite nanocrystals (ZnSeO3) deposited into SiO2/Si track templates. The templates were formed via irradiation with Xe ions (200 MeV, 108 ions/cm2) followed by etching in HF solution. ZnSeO3 nanocrystals were obtained via chemical deposition from the aqueous solution of ZnCl2 and SeO2 as Zn-, Se- and O-precursors. To estimate the thermal stability of the deposited precipitates, heat treatment was carried out at 800 and 1000 °C for 60 min in a vacuum environment. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, and electrical measurements were used for the characterization of ZnSeO3/SiO2nanoporous/Si nanocomposites. Thermal treatment of the synthesized nanocomposites resulted in structural transformations with the formation of ZnSe and ZnO phases while the content of the ZnSeO3 phase decreased. For the as-deposited and annealed precipitates, an emission in the range of (400 to 600) nm was observed. PL spectra were approximated by four Gaussian curves with maxima at ~550 nm (2.2 eV), 488 nm (2.54 eV), ~440 nm (2.82 eV), and 410 nm (3.03 eV). Annealing resulted in a decrease in PL intensity that was possibly due to the weight loss of the deposited substance during high-temperature treatment. The redistribution of maxima intensities after annealing was also observed with an increase in blue and violet emissions. The origin of the observed PL is discussed. The I–V curve analysis revealed an electronic type of conductivity for the ZnSeO3(NCs)/SiO2nanoporous/Si structure. The values of the specific conductivity were calculated within the percolation model. The sample annealed at 800 °C showed the highest specific conductivity of 8.5 × 10−6 Ohm−1·cm−1.

(Invited) Towards Non-Blinking Strongly Confined Perovskite Quantum Dots

Quantum information science has shown its capabilities to enable secure quantum communications. Single photon emitters (SPEs) that emit photons one at a time are fundamental elements of such transformative technologies. Colloidal cesium lead halide (CsPbX3, X=Br, I) perovskite QDs are ideal for next-generation SPEs because of their high room-temperature luminescence efficiency and low-cost, scalable syntheses. Unfortunately, individual perovskite QDs show insufficient photostability and severe photoluminescence (PL) intensity fluctuations (also called blinking). This has greatly limited the spectroscopic studies of perovskite QDs for SPE developments. One major roadblock toward non-blinking, photostable perovskite QDs is their highly ionic crystal structure. When preparing single perovskite QD samples, QD colloids often need to be diluted. During this process ligands can detach from the QD, introducing defects. This is particularly detrimental to strongly confined perovskite QDs since exciton-surface lattice interaction is greatly enhanced. As a result, strongly size confined perovskite QDs are experiencing severe PL blinking with large PL “OFF” occurrences.To suppress perovskite QD blinking and photodegradation, we embedded QDs in an organic crystal matrix consists of Phenethylammonium bromide (PEABr) salts. The bromide rich surface of a QD can be epitaxially anchored onto the PEABr crystals and therefore be stabilized. Individual strongly confined CsPbBr3 QDs in our matrix show nearly non-blinking behavior under non-resonant laser excitations at room temperature. These QDs remain photostable without PL intensity decrease and spectral shift after more than 12 hours of continues excitations. We anticipate that these QDs will lead to more accurate and detailed study of exciton dynamics and structural-optical property relationships in strongly confined perovskite QDs.

Copper doped hybrid 2D ZnO-stearic acid nanocomposite for boosting photocatalytic degradation of organic pollutants under simulated solar light

This study explores the enhancement of photocatalytic performance in 2D ZnO-stearic acid (SA) composites through copper (II) doping. Materials containing 1–10 mol% Cu (II) were synthesized by coprecipitation and characterized using X-ray photoelectron spectroscopy, electron paramagnetic resonance, UV–visible and vibrational spectroscopies, as well as X-ray diffraction. These analyses confirmed the formation of single-phase composites with structures resembling the ZnO-SA precursor, but exhibiting discrete Zn/Cu doping, forming Zn1-xCuOx-SA materials. Scanning electron microscopy and Energy dispersive X-ray spectroscopy analysis revealed layered structure and the elemental compositions of the samples. High-resolution transmission electron microscopy (HR-TEM) images confirm the layered morphology of the Zn0.95Cu0.05O-SA sample, underscoring its two-dimensional material characteristics. Absorption band edge of the undoped hybrid ZnO is centered in the UVA zone, while copper-doped samples expanded into the visible range. Photoluminescence (PL) spectra exhibit multiple emission peaks related to defects within ZnO host. An intensity slight decrease in PL intensity is observed with increasing copper concentration, indicated a low recombination rate. Photoelectrochemical testing showed that Cu doping reduces charge recombination and increases current density, thereby improving photocatalytic degradation of pollutants such as indigo carmine and 4-chlorophenol under simulated sunlight. The optimally doped Zn0.95Cu0.05O-SA displayed significant efficiency improvements, degrading contaminants up to four times faster than the undoped composite and maintaining consistent performance over multiple cycles. Additional testing linked these photocatalytic improvements to enhanced charge separation and electron/hole transfer facilitated by Cu2+ ions, thereby boosting photocatalytic activity.

A band gap and photoluminescence properties engineering in BaO semiconductor for ultraviolet (UV) photodetector applications: A comprehensive role of co-doping

We report on ultra-violet (UV) photodetectors based on BaO nanoparticles by the detailed investigation of band gap and photoluminescence properties. The BaO nanomaterials were fabricated by the modified sol–gel technique. The innovation of co-doping can modulate the photoluminescence or sensing properties by narrowing the band gap related to enhancing the high carrier concentration, higher electronic lifetime, and low carriers recombination. It is investigated that the BaO nanoparticles with co-doping reveals a highly reduced band gap and exceptional photoluminescence properties as compared to the pristine BaO nanoparticles due to hindering carrier,s recombination for Ultra-violet (UV) photodetectors. The optical studies revealed that the addition of co-dopants in BaO host material creates new energy sites, so the band gap declines up to 1.31 eV as compared to that of pristine BaO (1.36 eV). The photoluminescence properties recorded with photoluminescence (PL) spectroscopy were recorded which revealed the decrease in PL intensity due to the hindering of carriers recombination with the addition of co-dopant metal ions. Furthermore, the inclusion of co-dopant metals results in an improvement in electrical conductivity because of a decline in carrier recombination, according to an I-V characteristic study. This factor contributes to enhance the photoluminescence properties of BaO which, in turn, contributes to enhance the sensing capability of the photodetector device. These obtained features modify optoelectronic properties are far superior as compared to that of previously reported literature on BaO nanomaterials, and the synthesized BaO semiconductor material becomes a potential candidate for efficient use in the ultraviolet (UV) photodetectors device applications.

Abatement of microbes and organic pollutants using heterostructural nanocomposites of rice straw CQDs with substituted strontium ferrite

Sustainable use of agricultural waste still remains a challenging task. Herein, we used rice straw as a carbon precursor to prepare carbon quantum dots (CQDs) for photocatalytic applications. Nanocomposites of CQDs with Ti4+ and Mg2+ substituted strontium ferrite (Sr0·4Ti0·4Mg0·2Fe2O4.4) nanoparticles (NPs) in varying w:w ratio was synthesized by ultrasonication method. The successful formation of nanocomposites was confirmed by various microscopic and spectroscopic techniques. The photocatalytic and antibacterial activity of NPs, CQDs and nanocomposites was comparatively evaluated using tetracycline hydrochloride, azure B, Staphylococcus aureus and Escherichia coli as model pollutants. The CQDs-Sr0.4Ti0·4Mg0·2Fe2O4.4 nanocomposite with a w:w ratio of 2:1 showed excellent photocatalytic and antibacterial activity, with the degradation and inactivation efficiency ranging from 97.1% to 99.0% in presence of visible light. The increased specific surface area (117.2 m2/g), and reduction in band gap (2.48 eV–2.09 eV) and decreased photoluminescence intensity of nanocomposites all corroborated these results. The impacting experimental parameters such as catalyst dose, pH and contact time were also examined. Quenching experiments confirmed that hydroxyl radicals (HO∙) radicals and holes (h+) played a vital role in the degradation of pollutants. The kinetics of photodegradation was explained by using the Langmuir-Hinshelwood model. Box-Behnken statistical modelling was used to optimize photocatalytic parameters. Results indicated that the nanocomposite of CQDs with Sr0·4Ti0·4Mg0·2Fe2O4.4 can serve as a promising photocatalyst for the removal of pollutants and microbes.

Highly sensitive optical approach towards Cu (II) ions detection in water sample using thioglycolic acid capped vanadium disulfide-based dichalcogenide quantum dots

Copper-dependent enzymes play an important role in the biological functions of the human body, plants, various micro/macro-organisms and animals. However, extensive and excessive consumption of Cu leads to damage of DNA strands, irregulating antioxidant enzyme function, brain damage, and other acute diseases like fever, nausea, headache, vomiting, diarrhea, etc. Herein, we synthesized water-soluble thioglycolic acid (TGA) capped vanadium disulfide-based dichalcogenide quantum dots (TGA@VS2 QDs) via a facile hydrothermal method. TGA acts as the sulfur source and capping group to making QDs water-soluble. Apart from this, TGA also provides high stability to QDs by preventing agglomeration as well as improving biocompatibility properties. The present study has proposed the interaction of TGA@VS2 QDs with environmental pollutant metal ions Zn (II), Pd (II), Fe (III), Cu (II), K (I), Cr (VI), Cd (II), and Ca (II) in the aqueous solution through photoluminescence (PL) spectroscopy. PL study showed specific interaction towards Cu (II) using TGA@VS2 QDs. The response study was carried out in two concentrations range from 10−8 M – 10−3 M in two parts from 10−8 M – 10−5 M & 10−5 M – 10−3 M and observed the linear decrease of PL intensity. While other metal ions Zn (II), Pb (II), Fe (III), K (I), Cr (VI), Cd (II), and Ca (II) did not show a quenching process with TGA@VS2 QDs. The quenching process involved is the static in nature for Cu (II) and it was confirmed by UV–visible, PL studies and Time-correlated single-photon counting (TCSPC) with a limit of detection 50 nM.

Photoluminescence of bulk α -In2Se3 crystals irradiated by high-energy electrons

The photoluminescence (PL) spectra of bulk α-In2Se3 crystals before and after 10 MeV electrons irradiation with the 1015 and 1017 cm−2 fluences were studied in the temperature range from 7 to 340 K. Three main types of radiative recombinations corresponding to band-to-tail (BT), deep defects, and band-to-band (BB) recombination were manifested in the non-irradiated α-In2Se3 crystals. Also recombinations that can be associated with exciton recombinations at temperatures below 45 K are observed. After electron irradiation, noticeable changes in the PL spectra are observed. We detected a slight increase in activation energy of the BT recombination. An increase in the concentration of deep defects is also noted. The significant decrease in PL intensity of the BB recombinations indicates the formation of non-radiative recombination centers after electron irradiation with the 1017 cm−2 fluence. Our study may be useful for understanding the effects of high-energy electrons irradiation on the performance of electronic and photovoltaic devices based on α-In2Se3.

Energy transfer-based color tunability, thermal quenching, and quantum yield of Sm3+/Eu3+ codoped lithium zinc borophosphate glasses

Lithium zinc borophosphate (LZBP) glasses, imbedded with Sm3+, Eu3+, & Sm3+/Eu3+ ions in solely and combinedly were synthesized using melt-quenching technique, and their energy-transfer-dependent photoluminescence (PL)-related characteristics were explored. LZBP: 0.5 % Sm3+ and LZBP: 0.5 % Eu3+ glasses exhibited intense orange and red emissions under 404 and 394 nm excitation wavelengths, respectively. When the Sm3+/Eu3+ codoped glass systems were excited with Sm3+ excitation (404 nm), has lead to a noticeable drop in the emission intensity of Sm3+ peaks at 562 nm (4G5/2 → 6H5/2; yellow), 602 nm (4G5/2 → 6H7/2, orange), and 645 nm (4G5/2 → 6H9/2, red) whereas the emission intensity of Eu3+ peaks at 591 nm (5D0→7F1; orange) and 617 nm (5D0→7F2; red) has enhanced. At the same time, the decay lifetime of singly doped Sm3+ decreased from 1.54 to 0.91 ms, with codoping different concentrations of Eu3+ ions. The decrease in both PL intensity and lifetimes of Sm3+ in the presence of Eu3+ suggests an efficient energy transfer (ET) from Sm3+→Eu3+, which is facilitated by dipole-dipole interaction. The ET from Sm3+→Eu3+ achieved through the channels, Sm3+:4G5/2 + Eu3+:7F1 → Sm3+:6H7/2 + Eu3+:5D0 and Sm3+:4G5/2 + Eu3+:7F2 → Sm3+:6H5/2 + Eu3+:5D1. Furthermore, ET from Sm3+ to Eu3+ is supported by the spectral overlay between Sm3+ emission and Eu3+ absorption, ET parameters (η(Sm3+⟶Eu3+) = 40.91 % and P(Sm3+⟶Eu3+) = 1098.9 S-1). The shift in color coordinated from orange to red, with an increase in Eu3+ doping content in the codoped glasses at 404 nm excitation demonstrates the promising application of the Sm3+/Eu3+ codoped glass system in orange-red light-emitting diodes. LZBP: 0.5 Sm3+/1.0 Eu3+ codoped glass exhibited good thermal stability (Ea = 0.19 eV), depending on temperature-dependent PL properties. The quantum yield (η) for the LZBP glass containing 0.5 Sm3+/1.0 Eu3+ codoped ions is evaluated to be 44.6 %.

Control Synthesis of Metallic Gold Decorated ZnO Nanoparticles for Photocatalytic Degradation of Rhodamine B, Methylene Blue and Eriochrome Black T Dyes

AbstractPure ZnO and metallic gold (Au) decorated ZnO (Au‐ZnO) nanoparticles were prepared by a modified sol‐gel method employing (CTAB, C19H42BrN) as a cationic surfactant. XRD analysis shows the wurtzite hexagonal structure of pure ZnO and confirms the modification in the structure with the decoration of Au metal in ZnO. TEM characterization illustrates the dispersion of metallic gold on the hexagonal surface of ZnO which confirms the result obtained by XRD. The ZnO and Au‐ZnO nanoparticles had negative charge surface values (−16.7 eV) and (−36.6 eV) which enhance an excellent degradation for cationic dyes. Optical studies show that gap energy decreases from 3.19 eV to 3.11 eV upon the decoration of Au on ZnO surface. The decrease in photoluminescence intensity reflects the positive effects of the role of metallic Au on the photodegradation capacity of Au‐ZnO. Photocatalytic results show that Au‐ZnO exhibits a higher efficiencies degradation of 93 % (k=0.016 min−1) in the case of Rhodamine B and 73 % (k=0.001 min−1) of Methylene blue compared to pure ZnO. In the case of Eriochrome Black T, Au‐ZnO presents low degradation efficiency.

Novel mesoporous Pt@n-AgI/n-α-MoO3 ternary nanocomposite for enhanced hydrogen production from glycerol under visible illumination

A novel mesoporous n-AgI/n-α-MoO3 nanocomposites with large surface area were constructed by hydrothermal approach utilizing hexamethylenetetramine (HMT) as an organic building block (cage-like). Pt nanoparticles (NPs) were highly distributed over AgI/α-MoO3 nanocomposites in situ during the photocatalysis reaction for photocatalytic H2 evolution under visible exposure. The H2 evolution results indicated that 9%AgI/α-MoO3 nanocomposite exhibited the best H2 evolution ability, and the total H2 amount was determined at about 24100 μmolg−1 within 9 h illumination using 1 g/L the photocatalyst dosage, which increased to 28920 μmolg−1 at 2.5 g/L. The H2 amount of AgI/α-MoO3 photocatalyst was fostered ∼40 and 10 times larger than that of α-MoO3 and AgI NPs. The optimal 9%AgI/α-MoO3 (2521.8 μmolg−1h−1) presented 34.4 and 8.61 times higher H2 evolution rate compared to α-MoO3 (73.23 μmolg−1h−1) AgI (292.91μmolg−1h−1). The resultant S-scheme AgI/α-MoO3 heterojunctions enhanced the separation efficiency of photocarriers with a remarkable enhancement of H2 evolution. The n-n heterojunction AgI/α-MoO3 nanocomposite inhibited the recombination of electrons and holes, decreased photoluminescence intensity, enhanced the current density, and promoted photocatalytic ability. The obtained AgI/α-MoO3 nanocomposite can maintain stability for 45 h of illumination continuously in the photocatalysis reactions for five consecutive cycles. These results provide a simple approach to designing S-scheme photocatalysts with a high separation rate of carriers to promote solar energy conversion efficiency.

Influence of vanadium in sensitized luminescence mechanism and Judd-Ofelt analysis in Er3+/Ho3+ doped mixed ionic-electronic glass system

Er3+/Ho3+ Doped Al₂O₃-Na₂O–TeO2 mixed ionic-electronic glasses containing different concentrations of V₂O5 ranging from 0 to 2.0 mol% were prepared using melt-quenching method. The structural, optical and photoluminescence properties of the glass were studied using FTIR, UV–Vis, and photoluminescence spectroscopy measurements. XRD analysis confirms the amorphous nature of the glass system. The relative areas of TeO4 and TeO3 were measured to demonstrate the correlation of bridging/non-bridging oxygen that exist in the glass network. It was observed that the relatively high TeO3 indicates that the environment of the glass system is NBO-rich despite the increase in BO attributed to V2O5. Analysis on optical absorption edge by Tauc's plot revealed that EOpti decreases due to the prevalence of NBO in the glass system. The Judd-Ofelt oscillator strength, fexp increases accompanied with an anomalous drop at x = 1.0 mol% due to the competition between BO and NBO that has altered the covalency and asymmetry of the Er3+ with the local environment ligand. Meanwhile, the Judd-Ofelt parameter Ω2 decreases generally suggesting that the glass system has underwent some structural modification due to the increase in BO in the host matrix contributed by the VO5. Photoluminescence spectra revealed three dominant emissions in the green region (525 nm;2H11/2 ➝ 4I15/2, 532 nm; 5F4 + 5S2➝ 5I8, 547 nm;4S3/2 ➝ 4I15/2) and 2 emissions in the red region (659 nm; 5F5 ➝ 5I8, 662 nm; 4F9/2 ➝ 4I15/2). As vanadium increased, a decrease in photoluminescence intensity is observed as a result of concentration quenching between V4+ and Ho3+.

Analysis and characterization of opto-electronic properties of iron oxide (Fe2O3) with transition metals (Co, Ni) for the use in the photodetector application

There are several uses for ultraviolet photodetectors, including in the scientific, military, and industrial sectors. In this sense, UV photodetectors must have high responsiveness, be insensitive to visible light, and be inexpensive to produce. For this purpose, we report the development of Co and Ni based iron oxide nanoparticles via the cost effective low temperature sol–gel auto-combustion process. XRD study approves the cubic crystal structure of iron oxide (Fe2O3) with predominant orientation along (311) direction. A sharp and strong peak is obtained at 583 cm−1 and 594 cm−1 for both samples in FT-IR spectra assigned to metal oxide Fe–O network system which approves the formation of iron oxide. Raman spectroscopy analysis reveals the presence of two A1g and five Eg phonon modes in the case of both samples. Absorption study exhibits the strong absorption peaks for the iron oxide sample doped with cobalt and nickel, while poor absorption was noticed from the pure iron oxide nanoparticles. The large and low energy band gap values are found to be 2.77 eV and 1.68 eV for pure Fe2O3 and cobalt and nickel doped Fe2O3 nanoparticles, respectively. Stone and cloud-like shape morphology was observed from SEM analysis. The EDX spectra reveal the presence of essential elements, like Fe and O in the case of pure iron oxide while Fe, O, Co and Ni in the case of transition metals doped iron oxide nanoparticles. The photoluminescence (PL) spectroscopy technique was recorded the luminescent properties which reveals the decrease in PL intensity that confirms the decline in electron–hole recombination. Therefore, I–V characterization analysis reveals that electrical conductivity increases with the addition of metals due to decrease in electron–hole recombination with the co-doping of metals. These modified opto-electronic properties of the developed Fe2O3 by metals co-doping make it suitable candidate for the use in photodetector application.

Crystal Structure, Thermal Expansion and Luminescence of Ca10.5−xNix(VO4)7

The structural and luminescence properties of a new material, Ca10.5−xNix(VO4)7, formed by substitution of a fraction of calcium by nickel, are studied as a function of the Ni content (x). The powder X-ray diffraction results for the polycrystals, synthesized using a solid-state reaction method, show that in the studied temperature range (300–1150 K), the structure of the unsubstituted material (space group R3c, whitlockite-β-Ca3(PO4)2 structure type) is conserved up to the solubility limit, x = 0.72(2), determined on the basis of variation of unit cell size with x. The samples of nominal composition exceeding this limit contain a significant amount of the impurity phase.The structural refinements demonstrate that Ni atoms preferentially occupy the M5 site (one of the five independent Ca sites, M1–M5). The unit cell size was equally studied in the range of 300–1150 K, leading to the determination of the thermal expansion coefficients. It was found that with rising Ni content, the room temperature volumetric thermal expansion decreases from 41.80 MK−1 (x = 0.16) to 39.24 MK−1 (x = 0.66) and to 38.92 MK−1 at the solubility limit, this reduction being in line with earlier reported data for x=0. In the unit cell variation, around 800–900 K, a weak anomaly is observed, detectable most clearly for the axial ratio; it is also visible at thermal expansion coefficient temperature dependence. Substitution of Ca by Ni ions reduces the optical band gap of Ca10.5−xNix(VO4)7 from 3.56 (x = 0) to 3.29 and 3.16 eV observed for Ni-containing samples (x = 0.33 and 0.66, respectively). Observed bands in the absorption and photoluminescence spectra are assigned to electronic transitions in both VO43− groups and Ni2+ ions, confirming that Ni mainly occupies the M5 site. The band gap narrowing and decrease in photoluminescence intensity when the Ni concentration increases makes Ni-substituted compounds attractive for application, e.g., as photocatalysts.

Cu/CuO-Doped ZnO Nanocomposites via Solution Combustion Synthesis for Catalytic 4-Nitrophenol Reduction.

The synthesis of optoelectrically enhanced nanomaterials should be continuously improved by employing time- and energy-saving techniques. The porous zinc oxide (ZnO) and copper-doped ZnO nanocomposites (NCs) were synthesized by the time- and energy-efficient solution combustion synthesis (SCS) approach. In this SCS approach, once the precursor-surfactant complex ignition point is reached, the reaction starts and ends within a short time without the need for any external energy. The TGA-DTA analysis confirmed that 500 °C was the point at which stable metal oxide was obtained. The doping and heterojunction strategy improved the optoelectric properties of the NCs more than the individual constituents, which then enhanced the materials' charge transfer and optical absorption capabilities. The porosity, nanoscale crystallite size (15-50 nm), and formation of Cu/CuO-ZnO NCs materials were confirmed from the XRD, SEM, and TEM/HRTEM analyses. The obtained d-spacing values of 0.275 and 0.234 nm confirm the formation of ZnO and CuO crystals, respectively. The decrease in photoluminescence intensity for the doped NCs corroborates a reduction in electron-hole recombination. On the Mott-Schottky analysis, the positive slope for ZnO confirms the n-type character, while the negative and positive slopes of the NCs confirm the p- and n-type characters, respectively. A diffusion-controlled type of charge transfer process on the electrode surface was confirmed from the cyclic voltammetric analysis. Thus, the overall analysis shows the applicability of the less expensive and more efficient SCS for several applications, such as catalysis and sensors. To confirm this, an organic catalytic reduction reaction of 4-nitrophenol to 4-aminophenol was tested. Within three and a half minutes, the catalytic reduction result showed the great potential of NCs over ZnO NPs. Thus, the energy- and time-saving SCS approach has a great future outlook as an industrial pollutant catalytic reduction application.

Effects of concertation and size of aqueous QDs on the detection of ionizing radiation based on changes in optical properties

Colloidal quantum dots (QDs) have recently been used in many applications. In particular, semiconductor and luminescent QDs are suitable candidate for use in optoelectronic devices and optical sensors. The optical properties of aqueous CdTe QDs with high efficiency photoluminescence (PL) make them good candidates for new dosimetry applications. Therefore, comprehensive studies are required of the effects of ionizing radiation on the optical properties of CdTe QDs. In the present study, we investigated the properties of aqueous CdTe QDs by a gamma 60Co source at different doses. For the first time, we determined the effects of the concentration and size of QDs, which are key factors in a gamma dosimeter. The results demonstrated the concentration-dependent photobleaching property of QDs, which grater changes in the optical properties occurred. The initial size of the QDs affected their optical properties, where red-shifting of PL peak position increased with smaller sizes. Analysis of the effect of gamma irradiation on the thin film QDs indicated that the PL intensity decrease as the dose increased. with increasing dose. X-ray diffraction analysis found no changes in the crystal structure. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy indicated decomposition of the capping agent thioglycolic acid on CdTe QDs after gamma irradiation.

Spatial Control of Substitutional Dopants in Hexagonal Monolayer WS2: The Effect of Edge Termination (Small 6/2023)

The Effect of Edge Termination In article number 2205800, Humberto Terrones, Ana Laura Elías, Mauricio Terrones, and co-workers demonstrate the importance of atomic edge termination in determining the spatial distribution of substitutional dopants in 2D transition metal dichalcogenide (TMD) hexagonal monolayers. Preferential iron and vanadium doping occurs on the sulfur-terminated edges of the hexagonal monolayers, causing a decrease in photoluminescence intensity and forming binary optical/electrical domains.

Fabrication of Reduced Ag Nanoparticle Using Crude Extract of Cinnamon Decorated on ZnO as a Photocatalyst for Hexavalent Chromium Reduction

The crude extract of cinnamon (after abbreviated as KM) was used to produce silver nanoparticles (AgKM). This was subsequently utilized for the hydrothermal production of a composite consisting of AgKM decorated on zinc oxide (AgKM/ZnO) as a photocatalyst for reducing hexavalent chromium (Cr(VI)). Several methods e.g., XRD, SEM, TEM, XPS, PL, and RDB-PAS were used to analyze the optical and physicochemical properties of ZnO/AgKM samples in order to better comprehend the impact of the development of the AgKM-ZnO heterojunction in comparison to pure ZnO. In 60 min, the optimized ZnO/AgKM reduced Cr(VI) by more than 98%, with a rate constant 63 times faster than that of pure ZnO. The enhancement of the separation and transportation of photogenerated electron-hole pairs, as proven by a decrease in photoluminescence intensity when compared with ZnO, was attributed to the composite’s higher Cr(VI) reduction rate. Also, the formation of a new electronic level was created when AgKM are loaded on the surface of ZnO in the composites, as shown by the energy-resolved distribution of the electron trap (ERDT) pattern resulting to enhancement of light absorption ability by narrowing the energy band gap. Thus, ZnO/AgKM composite’s photocatalytic efficacy was enhanced by its narrow energy band gap and reduced charge recombination. Therefore, the newly produced ZnO/AgKM composite can be used as a photocatalyst to purify Cr(VI)-containing wastewater.

Significance of microstrain in impacting band gap and photoluminescence behavior of Ce-doped ZnO thin films deposited via sol-gel process

The purpose of this study is to analyse the importance of micro-strain in affecting the band gap and photoluminescence (PL) intensity of sol-gel-spin-coated Ce-doped ZnO thin films on glass slides. The presence of the (100) plane in the fabricated thin film was discovered using x-ray diffraction thereby indicating the presence of strongly orientated monocrystalline ZnO hexagonal wurtzite phase. On doping with Ce, the micro-strain in the ZnO thin films changed from (2.49–4.84) × 10–3, and the crystallite size ranged from 26.23 to 43.03 nm. UV-visible spectroscopy revealed that the optical transparency of the undoped and Ce-doped ZnO films was between 60 to 85 percent, however the doped films’ absorption dip was slightly shifted from 378 to 380 nm. For Ce-doped ZnO thin films, the increase in band gap values determined using Tauc’s plot was in the range of 3.19 to 3.44 eV. No change in the peak of UV emission was visible in the PL emission spectra after Ce doping. The micro-strain brought on by doping ZnO with Ce controlled the decrease in PL intensity. On doping with Ce up to 3 at.%, PL intensity and micro-strain both reduced, then climbed till Ce 5 at.%, and ultimately declined when the Ce content was 6 at.%. According to studies using scanning electron microscopy, the undoped ZnO film morphology was characterised by spherical particles with rod-like growth structures. For 1, 2, 5, and 6 at.% Ce-doped ZnO thin films, this structure was changed to a nanorod-like structure with small nanorods attached to a long rod. But lengthy chain linkage structures were found in the event of 3 at.% Ce doping. The preceding results are discussed from a doping perspective.