Photoluminescence Experiments Research Articles

Improving visible light-driven CO2 conversion to high calorific fuels over sustainable highly crystalline and holey sulphur doped graphitic carbon nitrides

The effectiveness of CO2 reduction through g-C3N4 (CN) is considerably hindered by poor visible light absorption and the high rate of recombination of electron-hole (e−/h+) pairs. An effective method for increasing CO2 photoreduction efficiency is to incorporate non-metal components into the CN to modify its electronic properties and enhance its performance. This research presents the findings of our inquiry into sulfur-doped graphitic carbon nitrides (S–CN) for CO2 reduction through visible light. The XPS study reveals that the substitution of nitrogen atoms in the heptazine ring by sulfur (S) doping significantly influences the electronic configuration of CN, while the UV–visible absorbance spectra reveals that the CN band gap value 2.64 eV has reduced to 2.50 eV after S doping. Therefore, S–CN exhibits exceptional visible-light absorption, separation and migration of photoexcited e−/h+, corroborated by photoluminescence and transient photocurrent response experiments. Besides, S–CN demonstrated remarkable CO2 reduction capabilities without any cocatalyst or sacrificial agent, achieving CO/CH4 formation rates of 25/3 μmolg−1h−1, outperforming traditional CN. Our research highlights the relevance of impeding the e−/h+ recombination process to boost solar energy conversion output, suggesting potential for productive solar fuel generation using g-C3N4.

Optical response of WSe2-based vertical tunneling junction

Layered materials have attracted significant interest because of their unique properties. Van der Waals heterostructures based on transition-metal dichalcogenides have been extensively studied because of potential optoelectronic applications. We investigate the optical response of a light-emitting tunneling structure based on a WSe2 monolayer as an active emission material using the photoluminescence (PL) and electroluminescence (EL) experiments performed at low temperature of 5 K. We found that the application of the bias voltage allows us to change both a sign and a value of free carriers concentrations. Consequently, we address the several excitonic complexes emerging in PL spectra under applied bias voltage. The EL signal was also detected and ascribed to the emission in a high-carrier-concentration regime. The results show that the excitation mechanisms in the PL and EL are different, resulting in various emissions in both types of experimental techniques.

Investigation of inter-dot tunnelling effect in hybrid coupled QDs heterostructures for short-wave infrared detection (SWIR) application

This paper explores the coupling between two different types of dots for enhancing the performance of p type/hole based (p-i-p) quantum dot infrared photodetectors (QDIPs). There are two possible con: Stranski-Krastanov (SK) QDs can be deposited on submonolayer (SML) QDs, or the SML QDs can be deposited first, followed by SK QDs. Here, both configurations are tried, and the fact that the tunnelling improves with a decrease in the barrier is exploited. The tunnelling of carriers from one QD to another QD is facilitated by the overlap of their wavefunctions, which depends on their spatial separations between the dots. A smaller barrier will lead to enhanced tunnelling probability. Utilising this idea, samples with 20 nm and 7.5 nm barriers between the QDs are grown with both types of configurations. An enhancement is anticipated in the absorption and carrier lifetime of the p-i-p QDIP structures, making them well-suited for detection in short-wavelength infra-red regions. The p-i-p configuration with the active layers of coupled QDs sandwiched between p-type dopped layers, can effectively absorb SWIR photons and generate long-lived carriers for improved photodetection performance. With the help of Photoluminescence (PL), Photoluminescence Excitation (PLE), and X-ray Diffraction (XRD) experiments, we expect large dispersion in SK on SML configuration, significantly improved carrier transfer via tunnelling and thermalisation and, changes in dot density for both of the configurations. Development of a more efficient SWIR device is expected by the insightful understanding of carrier transfer by tunnelling and thermalization with respect to the barrier thickness in the coupled QD based heterostructures.

Efficient Energy Transfer from Quantum Dots to Closely‐Bound Dye Molecules without Spectral Overlap

Quantum dots (QDs) are semiconductor nanocrystals whose optical properties can be tuned by altering their size. By combining QDs with dyes we can make hybrid QD‐dye systems exhibiting energy transfer (ET) between QDs and dyes, which is important in sensing and lighting applications. In conventional QDs that need a shell to passivate surface defects, ET usually proceeds through Förster resonance energy transfer (FRET) that requires significant spectral overlap between QD emission and dye absorbance, as well as large oscillator strengths of those transitions. This considerably limits the choice of dyes. In contrast, perovskite QDs do not require passivating shells for bright emission, which makes ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr3 QD‐dye system to achieve efficient ET from CsPbBr3 QDs to dyes with dimethyl iminium binding groups where the close binding of dyes surface facilitates spatial wavefunction overlap. Using steady‐state and time‐resolved photoluminescence experiments, we demonstrate that efficient ET from CsPbBr3 to dyes with minimal spectral overlap proceeds via the Dexter exchange‐type mechanism, which overcomes the conventional restriction of spectral overlap that severely limits the tunability of these systems. This approach opens new avenues for QD‐molecule hybrids for a wide range of applications.

Efficient Energy Transfer from Quantum Dots to Closely-Bound Dye Molecules without Spectral Overlap.

Quantum dots (QDs) are semiconductor nanocrystals whose optical properties can be tuned by altering their size. By combining QDs with dyes we can make hybrid QD-dye systems exhibiting energy transfer (ET) between QDs and dyes, which is important in sensing and lighting applications. In conventional QDs that need a shell to passivate surface defects, ET usually proceeds through Förster resonance energy transfer (FRET) that requires significant spectral overlap between QD emission and dye absorbance, as well as large oscillator strengths of those transitions. This considerably limits the choice of dyes. In contrast, perovskite QDs do not require passivating shells for bright emission, which makes ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr3 QD-dye system to achieve efficient ET from CsPbBr3 QDs to dyes with dimethyl iminium binding groups where the close binding of dyes surface facilitates spatial wavefunction overlap. Using steady-state and time-resolved photoluminescence experiments, we demonstrate that efficient ET from CsPbBr3 to dyes with minimal spectral overlap proceeds via the Dexter exchange-type mechanism, which overcomes the conventional restriction of spectral overlap that severely limits the tunability of these systems. This approach opens new avenues for QD-molecule hybrids for a wide range of applications.

Two mercury(II) halide coordination polymers with efficient photoluminescence

Two coordination polymers (CPs), [Hg(Bpbp)X2]n (X = Br (1), I (2), Bpbp = 4,4′-bis(4-pyridyl)-biphenyl), were synthesized via solvothermal synthesis methods, and were further fully characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, FT-IR spectroscopy, and thermogravimetric analyses. The two CPs exhibit similar one-dimensional zigzag chain structures constructed by Bpbp ligand connecting Hg(II) cations with halide ions as terminal ligands, while the zigzag chains show different configurations, symmetries and packing modes. The results of photoluminescence experiments and DFT calculations indicate that both the halide anions and conjugated Bpbp ligands show important roles in the emission process of CPs, and halide anions may tune the luminescence properties of CPs.

Designing Zero-Dimensional Cadmium-Based Organic-Inorganic Hybrids: The Role of Halogen Doping in Modulating Multifunctional Properties.

Advances in materials science are increasingly dependent on the development of multifunctional materials capable of improving system efficiency and reducing the environmental impact. In this study, two zero-dimensional (0D) cadmium-based organic-inorganic hybrid materials (BEMPD)2CdBr4 (BEMPD-Br, 1) and (BEMPD)2CdBr2Cl2 (BEMPD-ClBr, 2) (BEMPD = 1-(2-bromoethyl)-1-methylpiperidine) were prepared by halogen doping. Compound 2 is a mixed halide in which there are two halogen sites, Cl and Br, and in a disordered state, which has a regulatory effect on the structural distortion and properties of the compound. The Curie temperatures of compounds 1 and 2 are 348 and 390 K, respectively, and the UV-vis absorption spectra showed that the direct band gaps of compounds 1 and 2 were 4.68 and 4.8 eV, respectively. In addition, room-temperature photoluminescence experiments show broadband emission peaks at 717 and 683 nm for compounds 1 and 2, respectively, with fluorescence lifetimes of 2.414 and 3.915 μs. These 0D hybrids provide an avenue for the development of smart materials and optoelectronic devices, and also provide positive clues for manipulating the properties of organic-inorganic hybrid compounds.

Texture-Induced Strain in a WS2 Single Layer to Monitor Spin-Valley Polarization.

Nanoscale-engineered surfaces induce regulated strain in atomic layers of 2D materials that could be useful for unprecedented photonics applications and for storing and processing quantum information. Nevertheless, these strained structures need to be investigated extensively. Here, we present texture-induced strain distribution in single-layer WS2 (1L-WS2) transferred over Si/SiO2 (285 nm) substrate. The detailed nanoscale landscapes and their optical detection are carried out through Atomic Force Microscopy, Scanning Electron Microscopy, and optical spectroscopy. Remarkable differences have been observed in the WS2 sheet localized in the confined well and at the periphery of the cylindrical geometry of the capped engineered surface. Raman spectroscopy independently maps the whole landscape of the samples, and temperature-dependent helicity-resolved photoluminescence (PL) experiments (off-resonance excitation) show that suspended areas sustain circular polarization from 150 K up to 300 K, in contrast to supported (on un-patterned area of Si/SiO2) and strained 1L-WS2. Our study highlights the impact of the dielectric environment on the optical properties of two-dimensional (2D) materials, providing valuable insights into the selection of appropriate substrates for implementing atomically thin materials in advanced optoelectronic devices.

Tetrazole and Oxadiazole Derivatives as Thermally Activated Delayed Fluorescence Emitters.

Organic light-emitting diodes (OLEDs) are promising lighting solutions for sustainability and energy efficiency. Incorporating thermally activated delayed fluorescence (TADF) molecules enables OLEDs to achieve internal quantum efficiency (IQE), in principle, up to 100 %; therefore, new classes of promising TADF emitters and modifications of existing ones are sought after. This study explores the TADF emission properties of six designed TADF emitters, examining their photophysical responses using experimental and theoretical methods. The design strategy involves creating six distinct types of a donor-acceptor (D-A) system, where tert-butylcarbazoles are used as donors, while the acceptor component incorporates three different functional groups: nitrile, tetrazole and oxadiazole, with varying electron-withdrawing character. Additionally, the donor-acceptor distance is adjusted using a phenylene spacer, and its influence on TADF functionality is examined. The clear dependency of an additional spacer, inhibiting TADF, could be revealed. Emitters with a direct donor-acceptor connection are demonstrated to exhibit TADF moderate emissive behavior. The analysis emphasizes the impact of charge transfer, singlet-triplet energy gaps (ΔEST), and other microscopic parameters on photophysical rates, permitting TADF. Among the emitters, TCz-CN shows optimal performance as a blue-green emitter with an 88 % photoluminescence quantum yield (PLQY) and fast rate of reversible intersystem crossing of 2×106 s-1 and 1×107 s-1, obtained from time-resolved photoluminescence (TRPL) experiment in PMMA matrix and quantum mechanical calculations, respectively. This comprehensive exploration identifies molecular bases of superior TADF emitters and provides insights for future designs, advancing the optimization of TADF properties in OLEDs.

Labelling of human breast cancer cells with PEG/biotin encapsulated B-type Y2O3: Eu nanophosphors for fluorescence detection

The development of non-toxic quantum dots (QDs) for fluorescence labelling of cancer cells can bring significant advancements in the disease detection. Such findings can effectively replace the conventional toxic fluorescent probes by virtue of its tunable optical characteristics. Through this work, we present the development of an efficient fluorescent probe based on B-type Y2O3: Eu QDs for labelling MCF 7 cell lines. The QDs surface was encapsulated by poly ethylene glycol (PEG) along with tumour targeting ligand, biotin. The luminescence capability of the QDs were established through photoluminescence experiments. The QDs were tested to be non-toxic through MTT assay. Fluorescence detection experiments on MCF 7 cells using the nanophosphor established the material’s potential to serve as an efficient probe for cancer cell detection.

Optical Properties of Europium-Doped Silicon-Based Thin Films

The integration of a silicon-based light emitter into existing CMOS technology has long been intriguing due to its optoelectronic compatibility with microelectronics [1]. However, the indirect band gap nature of bulk silicon has hindered its effectiveness as a light emitter. In addressing this limitation, rare earth ions have emerged as significantly interesting candidates owing to their unique optical and electronic properties. Rare earth-doped silicon structures have earned special attention as they exhibit sharp light emission in different spectral regions [2] . This notable feature is attributed to the effective excitation of rare earth ions within the host matrix. Efficiently excited rare earth ions can produce visible emissions ranging from infrared to ultraviolet, presenting possibilities in diverse applications such as solid-state lighting, displays, lasers, photovoltaics, and optical communication. The incorporation of rare earth-doped silicon structures presents a promising solution to overcome the challenges posed by silicon's intrinsic properties, thereby paving the way for improved performance across a diverse range of optoelectronic applications. Europium is a attractive rare earth material with two optically active states, Eu2+ and Eu3+, enabling it to generate a diverse range of color emissions extending from blue to red depending on the surrounding matrix [3].In this study, we investigated the optical properties and compositions of europium (Eu)-doped thin films including silicon oxide, silicon oxynitride, and silicon carbonitride. For this purpose, thin films were fabricated by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) with in-situ magnetron sputtering on p-type 3" Si (100) substrates. In-situ Eu doping was performed by a radio frequency (RF) magnetron sputtering gun, using a 0.25 in. thick, 2 in. (diameter) 99.9% pure Eu sputtering target. Precursor gases, including silane (diluted in 90% argon), oxygen (diluted in 90% argon), nitrogen (diluted in 90% argon), and ethane were utilized. Annealing was performed on the as-deposited films over a broad temperature range, from 600° to 1100°C, in a nitrogen (N2) environment. Rutherford backscattering spectrometry (RBS) was performed to determine the atomic concentration of the film constituents. Variable angle spectroscopic ellipsometry (VASE) analysis was conducted to investigate the optical properties of the films. Room temperature photoluminescence (PL) experiments were performed using a laser diode excitation source operating at a wavelength of 375nm. Notably, bright visible emission was observed in some of the thin films. Finally, we discuss the influence of the atomic concentration of Eu and the annealing temperature on the emission properties observed in the photoluminescence experiments.[1] F. Azmi, Y. Gao, Z. Khatami, and P. Mascher, “ Tunable emission from Eu:SiOxNy thin films prepared by integrated magnetron sputtering and plasma enhanced chemical vapor deposition ,” J. Vac. Sci. Technol. A, vol. 40, no. 4, p. 043402, 2022, doi: 10.1116/6.0001761.[2] A. Brik et al., “Annealing Effects on Structural Characteristics of Europium Doped Silicon-Rich Silicon Nitride,” Silicon, vol. 14, no. 14, pp. 8417–8425, 2022, doi: 10.1007/s12633-021-01636-w.[3] D. Li, X. Zhang, L. Jin, and D. Yang, “Structure and luminescence evolution of annealed Europium-doped silicon oxides films,” Opt. Express, vol. 18, no. 26, p. 27191, 2010, doi: 10.1364/oe.18.027191.

Electrically tunable layer-hybridized trions in doped WSe2 bilayers

Doped van der Waals heterostructures host layer-hybridized trions, i.e. charged excitons with layer-delocalized constituents holding promise for highly controllable optoelectronics. Combining a microscopic theory with photoluminescence (PL) experiments, we demonstrate the electrical tunability of the trion energy landscape in naturally stacked WSe2 bilayers. We show that an out-of-plane electric field modifies the energetic ordering of the lowest lying trion states, which consist of layer-hybridized Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda$$\\end{document}-point electrons and layer-localized K-point holes. At small fields, intralayer-like trions yield distinct PL signatures in opposite doping regimes characterized by weak Stark shifts in both cases. Above a doping-asymmetric critical field, interlayer-like species are energetically favored and produce PL peaks with a pronounced Stark red-shift and a counter-intuitively large intensity arising from efficient phonon-assisted recombination. Our work presents an important step forward in the microscopic understanding of layer-hybridized trions in van der Waals heterostructures and paves the way towards optoelectronic applications based on electrically controllable atomically-thin semiconductors.

In2S3-modified ZnIn2S4 enhanced photogenerated carrier separation efficiency and photocatalytic hydrogen evolution under visible light

ZnIn2S4 (ZIS) has limited photocatalytic hydrogen production due to low visible light utilisation and insufficient separation efficiency of photogenerated carriers. This study utilized a simple hydrothermal method to prepare In2S3/ZnIn2S4 (INS/ZIS) heterojunctions. The addition of In2S3 (INS) improves the separation and movement of photogenerated charges, and makes better use of visible light. The material was analysed using SEM, TEM, XRD, XPS and photoelectrochemical tests. Results from the transient photocurrent (TPR) and photoluminescence (PL) experiments show a photocurrent density of approximately 1.8 μA/cm2, which is 3 times greater than the ZIS (0.6 μA/cm2) density, when the INS mass is 5 %. And at this time, INS/ZIS boasts the most effective photogenerated carrier separation. The hydrogen photocatalytic generation test results showed that the photocatalytic hydrogen production rate of 5-INS/ZIS (5690 μmol/g/h) was 8.4 and 66.9 times higher than that of pure ZIS (710 μmol/g/h) and INS (89 μmol/g/h), respectively. The enhanced activity is due to the creation of type II heterojunctions, which improve the separation and transfer of light-generated charges. The research presents an innovative approach to creating composites based on ZIS.

Temperature- and pressure-responsive photoluminescence in a 1D hybrid lead halide

Low-dimensional hybrid lead halides with responsive emissions have attracted considerable attention due to their potential applications in sensing. Herein, a new one-dimensional hybrid lead bromide CyPbBr3 (Cy = cytosine cation) was synthesized to explore its emission evolution in response to temperature and pressure. The compound possesses an edge-sharing 1D double-chain structure and emits warm white light across nearly the entire visible spectrum upon ultraviolet excitation. This emission arises from the self-trapped excitons and its broadband feature is attributed to the strong electron-phonon coupling as revealed by the variable-temperature photoluminescence experiments. Moreover, a 4.5-fold pressure-induced emission enhancement was observed at 2.7 GPa which is caused by the pressure suppressed non-radiative energy loss. Furthermore, in-situ powder X-ray diffraction and Raman experiments reveal the maxima of the emission enhancement is associated with a phase transition at the same pressure. Our work demonstrates that low-dimensional metal halides are a promising class of stimuli-responsive materials which could have potential applications in temperature and pressure sensing.

Stress-induced fluorescence in diamond at ultrahigh pressures and low temperatures

Diamond is widely used as an anvil material in high pressure experiments, such as diamond anvil cell (DAC). The study of the fluorescence emission behaviour of the diamond at high pressure is of great significance for understanding its band structure and optical properties. Here, by combining low-temperature photoluminescence experiments, and fluorescence spectroscopy at controlled pressure (181 GPa–122 GPa) and temperature (296 K–77 K) reveals the relationship between stress-induced diamond fluorescence as a function of temperature and pressure. We also demonstrate that the electron-phonon interaction has an effect on the diamond energy gap, and the temperature and pressure jointly affect the band structure. The electron band gap decreases rapidly under low temperature and high-pressure conditions.

Direct bandgap quantum wells in hexagonal Silicon Germanium

Silicon is indisputably the most advanced material for scalable electronics, but it is a poor choice as a light source for photonic applications, due to its indirect band gap. The recently developed hexagonal Si1−xGex semiconductor features a direct bandgap at least for x > 0.65, and the realization of quantum heterostructures would unlock new opportunities for advanced optoelectronic devices based on the SiGe system. Here, we demonstrate the synthesis and characterization of direct bandgap quantum wells realized in the hexagonal Si1−xGex system. Photoluminescence experiments on hex-Ge/Si0.2Ge0.8 quantum wells demonstrate quantum confinement in the hex-Ge segment with type-I band alignment, showing light emission up to room temperature. Moreover, the tuning range of the quantum well emission energy can be extended using hexagonal Si1−xGex/Si1−yGey quantum wells with additional Si in the well. These experimental findings are supported with ab initio bandstructure calculations. A direct bandgap with type-I band alignment is pivotal for the development of novel low-dimensional light emitting devices based on hexagonal Si1−xGex alloys, which have been out of reach for this material system until now.

Wireless Powered Microwave-Light Conversion Platform with Dual-Stimulus Nanoresponder Coating for Deep-Seated Photodynamic Therapy.

Traditional external field-assisted therapies, e.g., microwave (MW) therapy and phototherapy, cannot effectively and minimally damage eliminate deep-seated infection, owing to the poor penetrability of light and low reactive oxygen species (ROS) stimulation capability of MW. Herein, an implantable and wireless-powered therapeutic platform (CNT-FeTHQ-TS), in which external MW can be converted into internal light via MW wireless-powered light-emitting chips, is designed to eradicate deep-seated tissue infections by MW-induced deep-seated photodynamic therapy. In application, CNT-FeTHQ-TS is implanted at internal lesions, and the chip emits light under external MW irradiation. Subsequently, CNT-FeTHQ coating in the platform can respond to both MW and light simultaneously to generate ROS and MW-hyperthermia for rapid and precise sterilization at focus. Importantly, MW also improves the photodynamic performance of CNT-FeTHQ by introducing vacancies in FeTHQ to facilitate the photoexcitation process and changing the spin state of electrons to inhibit the complexation of photogenerated electron-hole pairs, which were confirmed by simulation calculations and in situ MW-irradiated photoluminescence experiments. In vivo, CNT-FeTHQ-TS can effectively cure mice with Staphylococcus aureus infection in dorsal subcutaneous tissue. This work overcomes the key clinical limitations of safe energy transmission and conversion for treating deep-seated infections.

Preparation, Structures, Photoluminescence and Semiconductive Properties of Two Novel Lanthanide Mercury Materials with a 3-D Framework Structure.

Two novel lanthanide mercury materials, [Gd(IA)3(H3O)2Hg3Br6]n·2nCl (1) and [La(IA)3(H3O)2Hg3Br6]n·2nCl (2) (IA = isonicotinic anion), have been prepared under solvothermal conditions and characterized by single-crystal X-ray diffraction techniques. They are isomorphic and characterized by a three-dimensional (3-D) framework structure. The lanthanide ions are bound by eight oxygen atoms to exhibit a square antiprismatic geometry. The solid-state photoluminescence experiment discovers that compound 1 shows a strong emission in the red region. Compound 1 possesses CIE (Commission Internationale de I'Éclairage) chromaticity coordinates of 0.7347 and 0.2653. Its CCT (correlated color temperature) is 6514 K. Compound 2 displays yellow photoluminescence and it has CIE chromaticity coordinates of 0.4411 and 0.5151. The CCT of compound 2 is 3633 K. Solid-state UV/Vis diffuse reflectance spectra revealed that their semiconductor band gaps are 2.16 eV and 2.85 eV, respectively.

Linker Engineering toward Tunable Emission Behavior of Porous Interpenetrated Zr-Organic Frameworks.

Conjugated molecules with donor-acceptor-donor (D-A-D) moieties have garnered significant attention for their ability to form luminescent metal-organic frameworks (LMOFs). D-A-D molecules feature tunable bandgaps, which can be varied systematically to control the fluorescence wavelength of LMOFs. In this study, we prepared and characterized the fluorescence properties of two porous interpenetrated Zr-organic frameworks (PIZOFs) constructed using 4,4'-(benzo[c][1,2,5]selenadiazole-4,7-diylbis(ethyne-2,1-diyl))dibenzoic acid (L-Se) or 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))dibenzoic acid (L-S) as linkers. The corresponding MOFs are denoted as PIZOF-Se and PIZOF-S, respectively. Through our investigation, we explored the correlation between the structure of the frameworks and their respective optical properties. Our findings revealed that there are distinct differences in the fluorescence properties of the two PIZOFs. Specifically, the fluorescence of PIZOF-S is red-shifted from that characteristic of the corresponding linker, L-S. By contrast, the fluorescence of PIZOF-Se is substantially blue-shifted from that of linker L-Se. The emission of mixed-linker MOFs is explored by combining L-S or L-Se with structurally analogous, but nonfluorescent linker, 4,4'-((perfluoro-1,4-phenylene)bis(ethyne-2,1-diyl))dibenzoic acid (L-F). Based on steady-state and time-resolved photoluminescence experiments, as well as confocal fluorescence microscopy combined with fluorescence lifetime imaging (FILM), we demonstrated that linker engineering is an effective method to tune the emission behavior of LMOFs.

Electrochemical and photoluminescence properties of Zinc vanadate nanoparticles synthesized via chemical and green mediated route

Zinc vanadate (Zn2V2O7) nanoparticles (NPs) are successfully synthesized through a solution combustion method, employing Menthaspicata leaves extract as a reducing agent (ZVP) and urea as a chemical fuel (ZVU). Subsequently, the resulting NPs undergo calcination at 600 °C for a duration of 3 h. The pure orthorhombic crystal structure with Cmce space group Bragg reflections are observed in ZVP NPs. However, along with pure orthorhombic phase, few planes corresponding to V2O5 are observed. Green extract helps to retain the single orthorhombic phase. Irregular shaped and bigger sized NPs are observed in ZVU whereas in ZVP, few hexagonal and irregular sized NPs gets decorated on the bigger sized NPs. Better crystalline structure and shape are observed in ZVP compared to ZVU. Transmission electron microscopy analysis matches well with the XRD results. The selected area electron diffraction pattern of ZVP confirms the formation of purity of the sample. The direct energy band gap estimated from the Wood and Tauc’s plot was found to be 3 and 3.04 eV for ZVU and ZVP NPs respectively. The photoluminescence experiment was carried out at 290 and 310 nm excitation wavelengths. As excitation wavelength changes, tuning of emission color is observed from blue to red region. This tuning of color is observed in CIE plot. The CCT value clearly indicates that the samples excited under 290 nm can be utilized for cool LEDs whereas, the sample excited under 310 nm can be utilized for warm LEDs. Thus, the synthesized Zinc vanadate NPs might be the promising candidates for warm/cool display technologies as a nanophosphor based on the excitation wavelength. The electrochemical studies and the capacitance process was evaluated in a 1.0 M Na2SO4 solution utilizing a specific three-electrode setup. The calculated specific capacitance values exhibited variability within the range of 56.8 to 89.7 F/g at scan rates ranging from 10 to 100 mV.