Zero-dimensional cesium lead halide (Cs4PbBr6) perovskites are distinguished by their structural robustness and defect-mediated optical properties, yet the origin of their emissive behavior remains elusive. Here, we reveal a hierarchical defect architecture in Cs4PbBr6 microcrystals, wherein embedded CsPbBr3 inclusions hosting bromine vacancies (VBr), form multilevel CsPbBr3-VBr coupling states that govern charge-carrier dynamics. A micro-solvent-assisted mechanochemical strategy employing trace DMSO solvent enabled precise defect modulation while achieving low process mass intensity (PMI similar to 5, far below conventional solution routes, similar to 180) and structural fidelity. Comparative analyses of dry-synthesized (D-Cs4PbBr6), DMSO-assisted (B-Cs4PbBr6), and ligand-mediated (L-Cs4PbBr6) microcrystals reveals the presence of hierarchical defect states are confirmed by low-temperature photoluminescence, cathodoluminescence, and transient absorption spectroscopy, with DFT calculations identifying mid-gap states (similar to 1.93 eV) responsible for NIR-range emission. While shallow states drive this emission, detrimental deep traps are effectively neutralized by sulfate-ion passivation, extending carrier lifetimes from 35.48 to 41.43 ns and enabling suppression in photoluminescence quenching. The optimized bromine-vacancy densities facilitate enhanced CO2 photoreduction (70.21 & micro;mol g-1 h-1, apparent quantum yield 1.42%), nearly 1.6 & times; higher than defect-free analogues, consistent with DFT-predicted shallow VBr states enhancing charge availability. These findings establish a scalable, defect-engineered mechanochemical route for multifunctional perovskites, uniting robust luminescence and efficient photocatalytic energy conversion.

The current research work describes the preparation and characterizations of a new metal halide hybrid: (C12H14N2O2S)2(FeCl4)1.5(FeCl6)0.5Cl.3H2O Single crystals of the studied sample were grown by the solvent evaporation method. X ray diffraction results reveal that the new hybrid compound crystallizes in the orthorhombic system with Pnma space group. Raman and infrared spectroscopies confirm the presence of the functional groups of organic cations and the anionic entities. The thermal behavior was examined by TGA, DTA and DSC techniques. The UV-visible study of this new compound was also reported and discussed. The molecular arrangement can be described as alternating of organic cations and layers of anions linked together by hydrogen interactions. Hirshfeld surface analysis was carried out also to gain a quantitative overview of the non-covalent interactions. The results show that interactions dominating the structure are the H...Cl/Cl...H and O center dot center dot center dot H/H center dot center dot center dot O (about 67 %). The semiconductor character of this material was confirmed by AC conductivity measurements the values of which are of the order of 10-5 Omega- 1 cm- 1 . The low activation energy at low temperatures (0.32 eV) indicates the electronic conduction of this material.

Tri-doped phosphor YNbO4:Er3+/Tm3+/Yb3+ was prepared by solid-state reaction method. The XRD and SEM results reveal that the product is a monoclinic phase of YNbO4 with high crystallinity and the particles presenting grains with well-defined boundaries with average size is about 1–5 μm. The temperature-dependent luminescence is investigated with 980 nm laser excitation, whereas temperature sensing behaviour was studied in the range of 300–500 K based on Stark sublevels 1G4(a)/1G4(b) (Tm3+), thermal coupling levels 2H11/2/4S3/2 (Er3+) and non-thermal coupling levels 4F9/2 → 4I15/2 (Er3+) /3F2 → 3H6 (Tm3+), 2H11/2 → 4I15/2 (Er3+) / 4F9/2 → 4I15/2 (Tm3+) and 4S3/2 → 4I15/2 (Er3+) /3F2 → 3H6 (Tm3+), utilizing fluorescence intensity ratio (FIR) technique. It is worth highlighting that 1G4(a)/1G4(b) ratio as is not much employed in thermometry. Regarding, NTCL 3F2/1G4(b) pair exhibited the highest absolute sensitivity (SA) is about 110.2 × 10− 3 K− 1 at 500 K, whereas NTCL 3F2/4F9/2 pair presented the highest relative sensitivity (SR) is 2.1

Ag3PO4 nanoparticles were successfully synthesized using a simple and rapid hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) as surfactants; the corresponding photocatalysts were denoted as AP-CTAB and AP-SDS, respectively. The photocatalyst prepared without the surfactant was referred to as AP-0. The as-prepared materials were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-Vis diffused reflectance, BET-surface area analysis, and transmission electron microscopy. The photocatalytic activities of the AP-0, AP-CTAB, and AP-SDS catalysts were evaluated by the photodegradation of methylene blue and rhodamine B dyes under simulated visible light. The results revealed that the AP-CTAB catalyst's photocatalytic activity was higher than that of AP-0 and AP-SDS.

The development of highly efficient, stable, and cost-effective electrocatalysts for overall water splitting (OWS) is necessary for future renewable and clean energy systems. In this study, MnCo nanostructures were directly grown on Ni foam by a one-step hydrothermal synthesis method for various reaction times, such as 3, 6, 12, and 24 h, and the synthesized samples are denoted as MnCo-3,(1) MnCo-6,(2) MnCo-12,(3) and MnCo-24,(4) respectively. The scanning electron microscopy (SEM) images confirm the influence of the reaction time on the morphology of the MnCo nanostructures. The synthesized electrocatalysts reveal good catalytic activity for hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER) in 1.0 M KOH. The MnCo-24 electrocatalyst outperformed the other prepared electrocatalysts, with Tafel slopes of 140 and 148 mV dec(-1) and low overpotentials of 200 and 178 mV for the OER and HER, respectively, at a current density of 10 mA cm(-2). The MnCo-24 electrocatalyst exhibited excellent stability for up to 24 h for OWS. This work provides a facile strategy for preparing low-priced electrocatalysts with high catalytic activity.

In this study, bismuth oxyfluoride (BiOF) nanostructures were synthesized using a microwave synthesis method at 150 degrees C, 175 degrees C, and 200 degrees C, which were denoted as BiOF-150, BiOF-175, and BiOF-200, respectively. Their morphological, structural, and electrochemical properties were studied using various techniques. Compared to BiOF-150 and BiOF-200, BiOF-175 exhibited a high specific capacity of 623.4 Fg-1 at a current density of 0.5 A g- 1. Further, the material exhibited a capacitance retention of 77.4 % after 10000 cycles (at 5 A g- 1), highlighting its high cycling stability. The BiOF-175 nanosheets exhibited good electrochemical performance, making them a viable choice for supercapacitor (SCs) applications.

The intention of the Special Issue “Advances in Spectroscopy for Materials: Bridging Science and Engineering” is to include various enthusiastic works that focus on the use of various analytical spectroscopic techniques while characterizing materials [...]

The development of efficient and earth-abundant electrocatalysts for water splitting is necessary and crucial. In this study, NiMn2O4 nanosheets and nanosphericals were grown on Ni foam by microwave synthesis at 150 degrees C and 175 degrees C and the corresponding synthesized materials were referred to as NIM-150 and NIM-175, respectively. These materials were subsequently used as bifunctional electrocatalysts for the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting. The NIM-175 electrocatalyst showed a lower overpotential of 250 mV for the OER and 248 mV for the HER at 10 mA cm-2, and a smaller Tafel slope of 218 mV dec-1 for the OER and 198 mV dec-1 for the HER, compared to NIM-150. The NIM-150 and NIM-175 electrocatalysts exhibited excellent stability for overall water splitting. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The Er3+-doped transparent glasses were the significant materials to design solid state visible lasers, near infrared lasers, upconverters, sensors and fiber amplifiers. The effect of Yb3+ sensitization on 1.53 mu m broadband and 548 nm upconversion green emissions in TeO2-WO3-GeO2-ErF3-YbF3 (TWGErYb) glasses were studied. They were characterized through structural, optical absorption, near infrared and upconversion studies. The Judd-Ofelt theory was adopted to estimate several spectroscopic and radiative parameters. The laser characteristic parameters such as stimulated emission cross sections, gain band widths, figure of merit and quantum efficiencies were evaluated. Conveying the energy from Yb3+ to Er3+ ions and the reasons for non-radiative losses were highlighted. The quenching in luminescence of 1.53 mu m broadband, the 548 nm upconversion green emissions and the enhanced decay time values due to self-absorption were studied. The fitting of decay curves of Er3+: 4I13/ 2 and Er3+: 4S3/2 emission states at higher Yb3+concentrations (>= 1.5 mol%) to Inokuti-Hirayama model were discussed. The TWGErYbx glasses containing 0.5Er3+/2.5Yb3+ show proficiency to design 548 nm green solid state lasers and 1.53 mu m broadband fiber lasers.

White light (WL) generation in nanoparticles (NPs) using upconversion (UC) is a rapidly growing field in the field of nanophotonics. In UC, multiple low-energy photons are absorbed and combined into one high-energy photon through a nonlinear optical process. NPs exhibit high efficiency in UC due to their small size and large surface area relative to volume. UC nanoparticles (UCNPs) potential uses in WL generation, bioimaging and sensing due to their versatility. In this chapter, we provide an overview of the latest developments in WL generation using UCNPs. We begin by discussing the basic principles WL generation and then focus on the different methods that are used to generate WL using UCNPs, including energy transfer, sum frequency generation and cascaded nonlinear processes. We also address the challenges in achieving efficient WL generation using UCNPs. Additionally, we highlight recent advancements in WL generation using UCNPs, such as the development of new UCNP materials and optimization of the UC process. We also explore the potential applications of WL generated using UCNPs, including in lighting, displays and biomedical imaging. Finally, we discuss future directions for research in this field and the potential impact of UCNPs on the broader field of nanophotonics.

In this study, a CeO2 catalyst was derived from a Ce-based metal-organic framework (Ce-MOF) via an annealing process. Various analytical techniques, including XPS, XRD, SEM/EDX, and HR-TEM, were used to characterize the Ce-MOF-derived CeO2 nanoparticles. The as-synthesized Ce-MOF and Ce-MOF-derived CeO2 catalysts were used for the reduction of methylene blue (MB) and rhodamine B (Rh B) in the presence of NaBH4. Compared with Ce-MOF, the CeO2 catalyst exhibited a 90 % reduction of MB/RhB within 6 and 8 min, respectively.

The oxygen evolution reaction (OER) is a crucial half-reaction in water splitting. However, this reaction is kinetically sluggish owing to the four-electron (4 e−) transfer process. Therefore, the development of low-cost, stable, highly efficient, and earth-abundant electrocatalysts for the OER is highly desirable. Metal oxides derived from metal–organic frameworks (MOFs) are among the most efficient electrocatalysts for the OER. Herein, Ce–MOF-derived CeO2/graphene oxide (GO) composites were successfully prepared using a facile method. The composites with 0, 25, 50, and 100 mg GO were named CeO2, CeO2–GO-1, CeO2–GO-2, and CeO2–GO-3, respectively. The physicochemical characteristics of the electrocatalysts were assessed using several analytical techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis. The TEM results revealed that the CeO2 had a sheet-like morphology and that a GO layer was noticeable in the synthesized CeO2–GO-3 composite. The characterization results confirmed the formation of impurity-free CeO2–GO composites. The OER activity and stability were measured using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The CeO2–GO-3 electrocatalyst has a smaller Tafel slope (176 mV·dec−1) and lower overpotential (240 mV) than the other electrocatalysts. In addition, it exhibited high cyclic stability for up to 10 h. Therefore, the inexpensive CeO2–GO-3 electrocatalyst is a promising OER candidate.

The Bi 2 O 3 -B 2 O 3 -CaF 2 -EuF 3 (BiBCEu) glass and glass–ceramics were prepared by controlled heat treatment method for orange-red laser sources and characterized through X-ray diffraction, Fourier transform infrared, Raman, transmission electron microscopy, photoluminescence excitation, emission and luminescence decay studies. Up on 396 nm excitation, the BiBCEu glass–ceramics containing Bi 3 B 5 O 12 and CaF 2 nanocrystallites exhibit an enhanced orange-red luminescence through Eu 3+ : 5 D 0 → 7 F 2 (616 nm) transition. The radiative parameters such as radiative emission probability rate (A R ), luminescence branching ratio (β R ) and radiative decay time (τ R ) were determined using the intensities of Eu 3+ : 5 D 0 → 7 F J (J = 1, 2, 4) emission transitions following the Judd–Ofelt theory. The chromaticity coordinates of BiBCEu glass–ceramic heat treated at 575 °C for 10 h are situated in the orange-red region of the CIE diagram. The BiBCEu glass–ceramic synthesized at 575 °C for 10 h has an excellent proficiency for solid state orange-red laser sources.

The Bi2O3-B2O3-CaF2-EuF3 (BiBCEu) glass and glass–ceramics were prepared by controlled heat treatment method for orange-red laser sources and characterized through X-ray diffraction, Fourier transform infrared, Raman, transmission electron microscopy, photoluminescence excitation, emission and luminescence decay studies. Up on 396 nm excitation, the BiBCEu glass–ceramics containing Bi3B5O12 and CaF2 nanocrystallites exhibit an enhanced orange-red luminescence through Eu3+:5D0 → 7F2 (616 nm) transition. The radiative parameters such as radiative emission probability rate (AR), luminescence branching ratio (βR) and radiative decay time (τR) were determined using the intensities of Eu3+: 5D0 → 7FJ (J = 1, 2, 4) emission transitions following the Judd–Ofelt theory. The chromaticity coordinates of BiBCEu glass–ceramic heat treated at 575 °C for 10 h are situated in the orange-red region of the CIE diagram. The BiBCEu glass–ceramic synthesized at 575 °C for 10 h has an excellent proficiency for solid state orange-red laser sources.

A series of Sr1−xZr4(PO4)6:xPr (x = 0, 0.01, 0.03, 0.05, 0.07, and 0.09) nanophosphors were prepared by simple sol–gel technique. The crystal structure, vibrational properties, surface morphology, elemental composition, and particle size were investigated using X-ray diffraction-Rietveld refinements, FTIR, SEM-EDAX, and TEM techniques. The effect of dopant concentration of Pr3+ ions in SrZr4(PO4)6 nanophosphors was analysed, and their photoluminescence properties were investigated along with lifetime measurements. Under 448 nm excitation, due to 3P0–3F2 transition of Pr3+ ions, it shows intense reddish emission at 650 nm. Energy-level diagram explains energy transfer mechanisms and concentration quenching mechanisms in detail. The appropriate incorporation of dopant ions (x = 0.03 mol

The development of efficient red and far-red emitters, for efficient plant absorption in the Photosynthetically Active Radiation (PAR) region, holds significance in contemporary plant growth control. This study focuses on the synthesis and characterization of LaAlO3 as a host material, doped with Eu3+ and Mn4+ ions, using a solid-state reaction method. The investigation encompasses the creation and analysis of both single-doped and co-doped samples, employing techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. XRD analysis consistently confirmed the perovskite-like structure of all samples, devoid of detectable impurities or major structural changes due to doping. SEM images revealed a uniform distribution of regularly shaped particles for the co-doped sample. The PL spectroscopy showed that the doping led to strong photoluminescence, with the co-doped sample exhibiting the intensity of each of the ions independently neither exhibiting quenching nor energy transfer mechanisms. The excitation spectrum of Eu3+ exhibited a broad charge transfer band at approximately 328 nm, coupled with characteristic f-f excitation bands. On the other hand, the Mn4+ ion's excitation spectrum featured transitions from ground state (4A(2g)) electrons excited to higher excited states (4T(1g), 2T(2g), and 4T(2g)) centered at 350 nm and within the region 250-550 nm. The co-doped sample was excited at a common excitation wavelength of 460 nm and underwent an in-depth examination of its photoluminescent properties, including decay curves analysis and time dependence also. The results from this study suggest that the synthesized phosphor materials exhibit substantial potential for diverse applications, including but not limited to solid-state lighting for efficient plant growth.

Upconversion nanoparticles have gained significant attention for their potential in modern technology due to their ability to exhibit wide and continuous tuning of excitation and emission wavelengths. However, challenges such as low-energy photon absorption, dependence on bias for color variation, high manufacturing costs, and lack of long-term stability of emitters limit the potential of these materials. To overcome these obstacles and improve tuneability for technological applications, researchers have explored various methods of tuning the frequency upconversion process by altering the physical, chemical, and morphological properties of the upconversion material. This chapter delves into the different aspects of color tunability in upconversion nanoparticles, examining the conditions that lead to changes in color output and highlighting research in this field.

Using the melt-quench technique, potassium zinc borophosphate (KZnBP) glasses incorporated with Dy3+, Eu3+, and Dy3+/Eu3+ ions individually and combinedly were prepared, and their photoluminescence (PL)-related features were investigated. The KZnBP glass containing an optimized content of Dy3+ (0.5 mol%) is co-doped with Eu3+ in various contents, and the energy transfer (ET) process between them was studied at lambda(exci) = 349, 364, 387 (Dy3+), and 394 nm (Eu3+). The Dy3+/Eu3+ co-doped system, when excited with Dy3+ excitations has resulted in a significant decrease in the intensity of Dy3+ peaks observed at 480 nm (F-4(9/2)-> H-6(15/2), blue) and 574 nm (F-4(9/2)-> H-6(13/2), yellow), with simultaneous enhancement of the intensity of Eu3+ peaks at 591 nm (D-5(0)-> F-7(1), orange) and 617 nm (D-5(0)-> F-7(2), red). This trend is due to the efficient energy transfer from Dy3+ to Eu3+, indicating that Eu3+ ions were sensitized by Dy3+ ions. Dexter's theory and the Inokuti-Hirayama (I-H) model revealed that the dipole-dipole interaction is accountable for the energy transfer from Dy3+ to Eu3+ through energy-transfer channels [F-4(9/2)(Dy3+)+F-7(1,2)(Eu3+)-> H-6(15/2)(Dy3+)+D-5(2)(Eu3+)] and [F-4(9/2)(Dy3+)+F-7(0)(Eu3+)-> H-6(13/2)(Dy3+)+D-5(0)(Eu3+)]. The color coordinates of the Dy3+/Eu3+ co-doped glasses under various excitations fall within the white light emission spectrum, indicating their potential application in warm white LEDs.

The photoluminescence properties of different concentrations of Sm3+ activated Sr3Gd(PO4)(3) phosphors synthesized by modified citrate gel-combustion method were investigated for white light emitting diode (w-LED) applications. The studied phosphors were characterized through powder x-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), photoluminescence excitation, emission and lifetime studies. The PXRD profiles confirmed the body centred cubic structure of undoped and Sm3+ -doped phosphors. The SEM studies showed the distribution and agglomeration of particles. The characteristic emission transitions such as (4)G(5/2) -> H-6(5/)2 (similar to 561 nm), (4)G(5/2) -> H-6(7/2) (similar to 598 nm), (4)G(5/)(2) -> H-6(9/)2 (similar to 645 nm) and (4)G(5/2) -> H-6(11/2) (similar to 705 nm) were noticed at their respective po- sitions when excited at 403 nm wavelength. The highest luminescence intensity was found for 1.0 mol% of Sm3+ doped phosphors at 403 nm excitation showing luminescence quenching and it was ascribed to dipole-dipole interaction type of energy transfer among the excited Sm3+ ions at higher concentrations. The reddish-orange color of emitted luminescence was examined by evaluating the chromaticity coordinates. The experimental results confirm the potentiality of studied phosphors for w-LED applications. (C) 2022 Elsevier B.V. All rights reserved.