Increase In Emission Intensity Research Articles

Tin sulfides and cadmium sulfide mixture in montmorillonite with enhanced visible-light photocatalytic activity

In situ formation of tin sulfide (SnS) and cadmium sulfide (CdS) mixture in montmorillonite was carried out by the reaction between an aqueous dispersion of Sn2+- and Cd2+-montmorillonite and an aqueous solution of S2− (from Na2S). The effects of Sn2+ / Cd2+ molar ratios were examined. The appearance of two diffraction peaks (d001 = 1.3 and 1.4 nm) and/or the large mismatch (8%) of SnS and CdS lattices were attributed to the possible formation of SnS and CdS in two different interlayer spaces (segregation) of montmorillonite. The blue shifts of the absorption onset relating to the expansion of band gap energy, and the emission band as well as the increase of emission intensity of the intercalated SnS and CdS mixture were observed with increasing SnS / CdS molar ratio. The photodegradation of rhodamine 6G solution was achieved within 360 min by using the product, which has the molar ratio of Sn / Cd = 3:1. The photocatalytic process followed pseudo-first-order kinetic with a rate constant of 0.011 min−1. The scavenger test indicated that superoxide radical (O2•-) was the predominant species involved in the photocatalytic process. This result represented an important role of montmorillonite and the heterostructures of SnS and CdS in tailoring the photocatalytic properties.

Hybrid of Conjugated Polymers with Incorporation of Metal Oxide Nanocomposites for Improving Optoelectronic Properties

Herein, the incorporation of TiO2 nanoparticles (NPs), SiO2 NPs, and their nanocomposite (STNC) to enhance the optoelectronic properties of the hybrid of poly[9,9′‐di‐n‐octylfluorenyl‐2,7‐diyl] (F8), poly[2‐methoxy‐5(2‐ethylhexyl)‐1,4‐phenylenevinylene)] (MEH‐PPV), and poly[2‐methoxy‐5‐(3,7‐dimethyl‐octyloxy)‐1,4‐phenylenevinylene]‐end capped with dimethylphenyl (MDMO–PPV–DMP) are revealed. The tune of the donor (F8) conjugated length can be detected from the red shift in absorption spectra when TiO2 NPs and SiO2 NPs are added, as well as an increase in emission intensity of the donor. The addition of acceptors (MEH–PPV or MDMO–PPV–DMP) to the donor results in a new absorption peak at 510 nm, which increases when TiO2 NPs and SiO2 NPs or STNC are incorporated into the ternary hybrid. The incorporation of STNC into F8 is anticipated to reduce the donor energy bandgap and improve the energy transfer from F8 to both acceptors. Moreover, Förster resonance energy transfer (FRET) is improved in the ternary hybrid, as evidenced by enhanced emission spectra of the donor and both acceptors, increased broadness of photoluminescence excitation spectra, and shifting blue color toward white region. The ternary hybrid with STNC‐based organic light‐emitting diode shows superior current and turn‐on voltage compared to other devices, which is likely due to its superior FRET.

Do technical differences lead to a widening gap in China's regional carbon emissions efficiency? Evidence from a combination of LMDI and PDA approach

The growing disparity in China's regional carbon emission efficiency is an easily overlooked but crucial issue in China's transition to carbon neutrality. To better understand drivers of widening gap of regional carbon emission efficiency in China from technological progress, industrial inequality, regional inequality, and management inequality, a novel approach is developed by combining a logarithmic mean divisia index and production theoretical decomposition analysis based on multi-layer frontier. The results indicate (i) Except for Ningxia and Xinjiang, the energy utilization efficiency of the remaining provinces continued to improve during the study period. The fossil energy consumption structure in most provinces gets gradually improved, favoring fossil energy with less carbon emissions. The industrial structure of most provinces has not improved significantly. (ii) Improving overall energy efficiency and technological progress is extremely important for carbon emission reduction. Potential energy intensity effect and energy technology efficiency gap effect are the key factors to restrain the increase of carbon emission intensity. (iii) For economically developed regions (such as Beijing and Guangdong), technological factors, potential energy efficiency and scale have a greater impact, while industries, regions, and management efficiency have a smaller impact, indicating that developed regions are at the frontier of efficiency and are improving production and energy structure. Moreover, there is an efficiency gap between underdeveloped regions (such as Xinjiang and Qinghai) and economic regions. Hence, while improving the production structure and energy consumption structure, the efficiency gap with developed regions should be narrowed.

Cooperative Supramolecular Polymerization of Triphenylamine bis-Urea Macrocycles.

Herein, we probe the hydrogen bond-driven self-assembly of a triphenylamine (TPA) bis-urea macrocycle in the presence and absence of guests. Comprised of methylene urea-bridged TPAs with exterior tridodecyloxy benzene solubilizing groups, the macrocycle exhibits concentration-dependent aggregate formation in THF and H2 O/THF mixtures as characterized by 1 H NMR and DOSY experiments. Its assembly processes were further probed by temperature-dependent UV/Vis and fluorescence spectroscopy. Upon heating, UV/Vis spectra exhibit a hypsochromic shift in the λmax , while fluorescence spectra show an increase in emission intensity. Conversely, the protected macrocycle that lacks hydrogen bond donors demonstrates no significant change. Thermodynamic analysis indicates a cooperative self-assembly pathway with distinct nucleation and elongation regimes. The morphology and structure of the aggregate were elucidated by dynamic light scattering, atomic force microscopy, scanning and transmission electron microscopy. Variable temperature emission spectra were utilized to monitor the impact of guests, such as diphenylacetylene, that can be bound in the columnar channels. The findings suggest that the elongation of assemblies is influenced by the presence of these guests. In comparison, diphenyl sulfoxide, likely functioning as a chain stopper, limited the assembly size. These studies suggest that judicious selection of (co)monomers may modulate the function and utility of these supramolecular systems.

134 Effect of Rumen Degradable Protein Intake on Performance, Carcass Quality, and Methane Emissions of Yearling Finishing Steers

Abstract The performance, economic, and environmental consequences of feeding rumen degradable protein (RDP) levels above and below calculated maximum energy-dependent microbial crude protein (MCP) synthesis potential are poorly understood. Yearling steers (n = 54; initial BW = 484.1 ± 26.03 kg) were assigned to one of two pens that each contained an automated head chamber system (GreenFeed; C-Lock Inc., Rapid City, SD) for individual measurement of enteric methane (CH4) emissions. Each steer was assigned to an individual feed bunk (Calan Gate; American Calan, Northwood, NH) and randomly assigned to one of three dietary treatments: low RDP intake (LRDPI; n = 8), neutral RDP intake (NRDPI; n = 8), or high RDP intake (HRDPI; n = 8) in a completely randomized design. Steers were transitioned to treatment diets utilizing a two-ration blend system for 20-day followed by an 80-day finishing period. Diets were formulated to provide cattle with similar metabolizable protein (MP) and net energy for gain (NEg) but different RDP supply. Diets were formulated to provide approximately 87% (LRDPI), 100% (NRDPI), or 113% (HRDPI) of calculated RDP requirements to maximize energy-allowable MCP-yield. Paired-day, unshrunk BW was collected on d 0, 50, and 80, and cattle were transported to a commercial abattoir for carcass data collection. Statistical analyses were conducted using Analysis of Variance in JMP Pro6.0 using the Fit Model procedure. Least-squares means differences were considered statistically significant if P < 0.05 and considered a tendency toward significant if 0.05 ≤ P < 0.15. Treatment rations provided approximately 94% (LRDPI), 106% (NRDPI), and 118% (HRDPI) of the RDP required to maximize energy-allowable MCP yield, respectively. Daily DMI was similar (P > 0.15) for HRDPI and NRDPI cattle, but LRDPI cattle tended (P = 0.06) to have less DMI than NRDPI cattle. Dietary treatment did not affect (P ≥ 0.32) ADG, feed conversion efficiency, ribeye area, marbling score or carcass yield grade. Yet, LRDPI cattle had lighter hot carcass weight (P < 0.05) and less subcutaneous fat thickness (P < 0.05) than NRDPI cattle, whereas HRDPI cattle were not different (P ≥ 0.15) from the other treatments. On average, LRDPI cattle tended to emit 7.0% more daily CH4 (g×d-1; P = 0.05) than both NRDPI and HRDPI. Moreover, the LRDPI treatment elicited a 14.7% and 18.1% increase in CH4-yield (g CH4×kg DMI-1; P < 0.01) and emission intensity (g CH4×kg ADG-1; P < 0.05) compared with the other treatments, respectively. These data indicate that limiting MCP-yield by restricting RDP intake may reduce subcutaneous fat thickness and carcass weight while increasing enteric CH4 emissions. These results reiterate the importance of meeting RDP requirements and suggest no performance or methane emission benefits of overfeeding RDP.

Phosphorescent O2-Probes Based on Ir(III) Complexes for Bioimaging Applications

The design, synthesis, and investigation of new molecular oxygen probes for bioimaging, based on phosphorescent transition metal complexes are among the topical problems of modern chemistry and advanced bioimaging. Three new iridium [Ir(N^C)2(N^N)]+ complexes with cyclometallating 4-(pyridin-2-yl)-benzoic acid derivatives and different di-imine chelate ligands have been synthesized and characterized by mass spectrometry and NMR spectroscopy. The periphery of these complexes is decorated with three relatively small “double-tail” oligo(ethylene glycol) fragments. All these complexes exhibit phosphorescence; their photophysical properties have been thoroughly studied, and quantum chemical calculations of their photophysical properties were also performed. It turned out that the changes in the nature of the di-imine ligand greatly affected the character of the electronic transitions responsible for their emission. Two complexes in this series show the desired photophysical characteristics; they demonstrate appreciable quantum yield (14–15% in degassed aqueous solutions) and a strong response to the changes in oxygen concentration, ca. three-fold increase in emission intensity, and an excited state lifetime upon deaeration of the aqueous solution. The study of their photophysical properties in model biological systems (buffer solutions containing fetal bovine serum—FBS) and cytotoxicity assays (MTT) showed that these complexes satisfy the requirements for application in bioimaging experiments. It was found that these molecular probes are internalized into cultured cancer cells and localized mainly in mitochondria and lysosomes. Phosphorescent lifetime imaging (PLIM) experiments showed that under hypoxic conditions in cells, a 1.5-fold increase in the excitation state lifetime was observed compared to aerated cells, suggesting the applicability of these complexes for the analysis of hypoxia in biological objects.

Construction of Mechanically Interlocked Fluorescence Photoswitchable [2]Rotaxane with Aggregation-Induced Emission and Molecular Shuttling Behaviors

Here, we report the design, synthesis, and optical behaviors of a multistimuli responsive [2]rotaxane system constructed from noncovalent interactions between diarylethene (DAE)-based axle and a tetraphenylethene (TPE)-based macrocycle using a snapping supramolecular assembly approach. The shuttling behavior of the macrocycle (Ring-TPE) between dialkylammonium and urea stations could be realized by the influence of acid-base stimuli using 1H NMR spectroscopy. Switching between the open-form (OF) [2]rotaxanes (DAE-R1-OF and DAE-R2-OF) is highly reversible using external chemical stimuli. These rotaxane systems exhibit enhanced blue fluorescence in their aggregation states despite being weak or nonemissive in solution. A significant increase in fluorescence emission intensity of typical TPE in DAE-R1-OF and DAE-R2-OF at ca. 467 nm was observed as the water content was increased to ≥70% in CH3CN/H2O solvent mixtures. However, the fluorescence emission of TPE at its maximum aggregation state (95% fw) could be rapidly quenched upon UV light irradiation due to a very efficient energy transfer from the excited TPE (donor) to the closed form of DAE (acceptor). In contrast, OF DAE does not affect the fluorescence of the TPE unit, which remains at high level. Furthermore, the [2]rotaxanes showed excellent photochromic and fluorescent properties in solution, making them suitable for information storage and reversible photo-patterning applications.

Rational Molecular Designing of Aggregation-Enhanced Emission (AEE) Active Red-Emitting Iridium(III) Complexes: Effect of Lipophilicity and Nanoparticle Encapsulation on Photodynamic Therapy Efficacy.

Two "aggregation-enhanced emission" (AEE) active cyclometalated phosphorescent iridium(III) complexes, SM2 and SM4, were synthesized to evaluate the influence of lipophilicity on photodynamic therapy efficacy. Compared to SM2, SM4 had a higher logP due to the presence of naphthyl groups. As observed by confocal microscopy, this increased lipophilicity of SM4 significantly enhanced its cellular uptake in breast cancer cells. Both the molecules were found to be noncytotoxic under nonirradiating conditions. However, with light irradiation, SM4 exhibited significant cytotoxicity at a 500 nM dose, whereas SM2 remained noncytotoxic, signifying the influence of lipophilicity on cellular internalization and cytotoxicity. Mechanistically, light-irradiated SM4-treated cancer cells exhibited a significant increase in the intracellular reactive oxygen species (ROS) level. Neutralizing ROS with N-acetylcysteine (NAC) pretreatment partly abolished the cytotoxic ability, indicating ROS as one of the major effectors of cell cytotoxicity. Two nanoparticle (NP) formulations of SM4 were developed to improve the intracellular delivery: a PLGA-based NP and a Soluplus-based micelle. Interestingly, PLGA and Soluplus NP formulations exhibited a 10- and 22-fold increased emission intensity, respectively, compared to SM4. There was also an increase in the excited-state lifetime. Additionally, the Soluplus-based micelles encapsulating SM4 exhibited enhanced cellular uptake and increased cytotoxicity compared to the PLGA NPs encapsulating SM4. Altogether, the current study indicates the importance of rational molecular designing and the significance of a proper delivery vector for improving photodynamic therapy efficacy.

Probing free and bound excitons in Eu-doped CsPbBr3 by temperature-dependent photoluminescence and time-resolved photoluminescence

This report presents the recombination mechanisms of free and bound excitons in Eu-doped CsPbBr3. Through temperature-dependent photoluminescence (PL), the emission intensity of free excitons decreased as the temperature decreased from 300 to 10 K. The emission intensity of bound excitons appeared at T = 100 K and increased rapidly as the temperature decreased to 10 K. These observations are attributable to the dynamic migration of thermal energy between free and bound excitons, which is caused by the richer Eu3+ ion. The exciton-like emission can be demonstrated through power-dependent PL. Furthermore, the radiative and nonradiative recombinations of the bound exciton were determined through temperature-dependent time resolved photoluminescence (TR-PL). As a function of emission energies, the PL lifetimes of the bound exciton were investigated to corroborate that the bound exciton has a larger localization depth with decreasing temperature, which is another reason for the increased emission intensity of the bound exciton.

Tantalum oxide and nitride spectral features from a laser-produced plasma

We report measurements of time-resolved Ta, TaO and TaN emission spectroscopic signatures from a laser-produced plasma. Plasmas were generated using 1064 nm, 6 ns pulses from an Nd:YAG laser focused onto a pure Ta metal target in a gaseous environment with varying percentages of O2/N2 for controlling gas-phase oxidation/plasma chemistry. Time-resolved analysis showed that Ta oxide emission is prominent at later times in plasma evolution, whereas strong atomic emission is present at early times in air. Emission spectral features as a function of O2 partial pressure showed that TaO emission intensity increases, while the peak intensity of TaO appears earlier with increasing O2 availability. We also report emission spectra of TaN, and show that plasma chemistry favors TaO formation instead of TaN when O2 is present in the environment.

Seasonal Variations, Size Distributions, and Sources of Chemical Components of Submicron Particulate Matter in Nanjing

Size-segregated particulate matter (PM) samples were collected in different seasons from 2016 to 2017 at the Xianlin Campus of Nanjing University. Mass concentrations of water-soluble inorganic ions, carbonaceous components, and elements were analyzed for PM with an aerodynamic diameter ≤ 1.1 μm (PM1.1; <0.4 μm, 0.4-0.7 μm, and 0.7-1.1 μm). The results showed that PM1.1, OC, NO3-, SO42-, and NH4+ exhibited higher ambient levels in fall-winter than those in spring-summer, which was attributed to the changes in local diffusion conditions, evaporation, and decomposition of non-refractory components. Elemental carbon (EC) reached its maximum concentration[(1.87±0.98) μg·m-3]in spring due to the increase in industrial and road dust resuspension. According to the characteristic ratio between bulk components, the anions in PM1.1 were dominated by NO3-, SO42-, and Cl- in Nanjing, and the carbonaceous components were mainly from fossil fuel combustions and associated aging processes. As the ambient temperature increased, the size distributions of thermo-unstable components including NH4+, NO3-, and OC shifted towards finer particles, whereas EC became more enriched in coarse particles, possibly due to the increase in emission intensity of motor vehicles and fugitive dust contributions. Since high relative humidity (>70%) is often accompanied by high temperature (>20℃) and improved diffusion conditions, a relative humidity of 60%-70% was more conducive to the formation of secondary inorganic ions in PM1.1. Source apportionment results based on the speciation data of PM1.1 showed that secondary formation processes[(66.6±18.3)%]and dust resuspension[(16.8±14.8)%]were the main contributors to PM1.1 in Nanjing, and further control of the emissions of gaseous precursors and dust is necessary.

Efficient Near-Infrared Luminescence of Self-Assembled Platinum(II) Complexes: From Fundamentals to Applications.

ConspectusDesigning bright and efficient near-infrared (NIR) emitters has drawn much attention due to numerous applications ranging from biological imaging, medical therapy, optical communication, and night-vision devices. However, polyatomic organic and organometallic molecules with energy gaps close to the deep red and NIR regime are subject to dominant nonradiative internal conversion (IC) processes, which drastically reduces the emission intensity and exciton diffusion length of organic materials and hence hampers the optoelectronic performances. To suppress nonradiative IC rates, we suggested two complementary approaches to solve the issues: exciton delocalization and molecular deuteration. First, exciton delocalization efficiently suppresses the molecular reorganization energy through partitioning to all aggregated molecules. According to the IC theory together with the effect of exciton delocalization, the simulated nonradiative rates with the energy gap ΔE = 104 cm-1 decrease by around 104 fold when the exciton delocalization length equals 5 (promoting vibronic frequency ωl = 1500 cm-1). Second, molecular deuterations reduce Franck-Condon vibrational overlaps and vibrational frequencies of promoting modes, which decreases IC rates by 1 order of magnitude in comparison to the rates of nondeuterated molecules under ΔE of 104 cm-1. Although deuteration of molecules has long been attempted to increase emission intensity, the results have been mixed. Here, we provide a robust derivation of the IC theory to demonstrate its validity, especially to emission in the NIR region.The concepts are experimentally verified by the strategic design and synthesis of a class of square-planar Pt(II) complexes, which form crystalline aggregates in vapor deposited thin films. The packing geometries are well characterized by the grazing angle X-ray diffraction (GIXD), showing domino-like packing arrangements with the short ππ separation of 3.4-3.7 Å. Upon photoexcitation, such closely packed assemblies exhibit intense NIR emission maximized in the 740-970 nm region through metal-metal-to-ligand charge transfer (MMLCT) transition with unprecedented photoluminescent quantum yield (PLQY) of 8-82%. To validate the existence of exciton delocalization, we applied time-resolved step-scan Fourier transform UV-vis spectroscopy to probe the exciton delocalization length of Pt(II) aggregates, which is 5-9 molecules (2.1-4.5 nm) assuming that excitons mainly delocalized along the direction of ππ stacking. According to the dependence of delocalization length vs simulated IC rates, we verify that the observed delocalization lengths contribute to the high NIR PLQY of the aggregated Pt(II) complexes. To probe the isotope effect, both partially and completely deuterated Pt(II) complexes were synthesized. For the case of the 970 nm Pt(II) emitter, the vapor deposited films of per-deuterated Pt(II) complexes exhibit the same emission peak as that of the nondeuterated one, whereas PLQY increases ∼50%. To put the fundamental studies into practice, organic light-emitting diodes (OLEDs) were fabricated with a variety of NIR Pt(II) complexes as the emitting layer, showing the outstanding external quantum efficiencies (EQEs) of 2-25% and the remarkable radiances 10-40 W sr-1 m-2 at 740-1002 nm. The prominent device performances not only successfully prove our designed concept but also reach a new milestone for highly efficient NIR OLED devices.This Account thus summarizes our approaches about how to boost the efficiency of the NIR emission of organic molecules from an in-depth fundamental basis, i.e., molecular design, photophysical characterization, and device fabrication. The concept of the exciton delocalization and molecular deuteration may also be applicable to a single molecular system to achieve efficient NIR radiance, which is worth further investigation in the future.

Ortho-Vanillin based multifunctional scaffold for selective detection of Al3+ and Zn2+ employing molecular logic with DFT study and cell imaging with live Grass pea

Ligand (E)-N’-(2-hydroxy-3-methoxybenzylidene) acetohydrazide (HL) has been designed and synthesized from o-vanillin and acetohydrazide for selective sensing of Al3+ and Zn2+ ions. In the photoluminescence studies, the receptor HL itself shows very poor fluorescence but on incremental addition of Al3+ and Zn2+ ions in solution of the probe HL individually leads to a sharp increase in emission intensities at wavelengths 468 nm (∼15 fold) and 504 nm (∼8 fold) respectively. Due to excited state intramolecular proton transfer (ESIPT), HL exhibits weak emission in absence of any analytes but in presence of Al3+ and Zn2+, chelation-enhanced fluorescence (CHEF) with coordination of Al3+ and Zn2+ inhibits ESIPT, which results large increase of fluorescence enhancement. The ligand HL shows high selectivity and sensitivity to detect Al3+ and Zn2+ among various metal ions with LOD (Limit of Detection) 0.836 × 10−6 M and 1.01 × 10−6 M respectively. DFT calculation has been performed to study the binding phenomenon of ligand HL with metal ions. A molecular logic gate has been build-up with Al3+ and Zn2+ and EDTA as three chemical input. Simultaneously, cytotoxicity and cell biology for the probe and corresponding Al3+ sensing were observed.

Effect of Gd3+, La3+, Lu3+ Co-Doping on the Morphology and Luminescent Properties of NaYF4:Sm3+ Phosphors

The series of luminescent NaYF4:Sm3+ nano- and microcrystalline materials co-doped by La3+, Gd3+, and Lu3+ ions were synthesized by hydrothermal method using rare earth chlorides as the precursors and citric acid as a stabilizing agent. The phase composition of synthesized compounds was studied by PXRD. All synthesized materials except ones with high La3+ content (where LaF3 is formed) have a β-NaYF4 crystalline phase. SEM images demonstrate that all particles have shape of hexagonal prisms. The type and content of doping REE significantly effect on the particle size. Upon 400 nm excitation, phosphors exhibit distinct emission peaks in visible part of the spectrum attributed to 4G5/2→6HJ transitions (J = 5/2-11/2) of Sm3+ ion. Increasing the samarium (III) content results in concentration quenching by dipole-dipole interactions, the optimum Sm3+concentration is found to be of 2%. Co-doping by non-luminescent La3+, Gd3+ and Lu3+ ions leads to an increase in emission intensity. This effect was explained from the Sm3+ local symmetry point of view.

Novel Aggregation-Induced Emission Fluorescent Molecule for Platinum(IV) Ion-Selective Recognition and Imaging of Controlled Release in Cells.

The loading, delivery, and release of Pt(IV) precursors in living organisms are important aspects of exploring the development of platinum drugs. In recent years, the biological application of the fluorescent sensors to platinum drugs has been insufficient to meet the study of Pt(IV) precursors. It is urgent to design and develop a biocompatible, multifunctional fluorescent sensor for the study of loading, transport, and release of Pt(IV) ions. Herein, we report a fluorescent molecule (E)-6-(diethylamino)-N'-(4-(diphenylamino) benzylidene)-2-oxo-2H-chromene-3 carbohydrazide (CHTPA). CHTPA has good sensitivity and selectivity to Pt(IV) when the water content is 5%, and significant increase of the fluorescence emission intensity of CHTPA is observed with Pt(IV) concentration. The sensing mechanism is attributed to photo-induced electron transfer, which is verified by X-ray absorption near edge spectroscopy spectra, UV-vis absorption spectroscopy, 1H NMR spectra, and Fourier transform infrared spectra. Furthermore, the CHTPA-Pt(IV) complex is able to release Pt(IV) in aqueous solution, and the green fluorescence of CHTPA based on the aggregation-induced emission effect can be observed. Inspired by these, the amphiphilic block copolymer poly(ethyloxide)-block-polystyrene (PEO-b-PS) is used to prepare the nonconjugated polymer dots (Pdots). The experimental results show that Pdots can effectively slow down the release speed of Pt(IV) in aqueous solution and it has a great monodispersity in aqueous solution. Meanwhile, Pdots show low cytotoxicity, and this is favorable for intracellular applications. The investigation of cellular imaging indicates that these Pdots can act as a carrier to deliver Pt(IV) into MCF-7 cells for visualized delivery and sustained release of platinum(IV) ions. Therefore, this study provides a new avenue to design and develop a biocompatible multifunctional fluorescent sensor for studying the loading, delivery, and release of Pt(IV) in cells.

Enhancement of NIR-triggered photocatalytic activity of Ln3+-doped NaYF4@SiO2/Ag@TiO2 nanospheres through synergistic upconversion and plasmonic effect

The multishell-structured NaYF4:Yb,Tm,Nd@NaYF4:Yb,Nd@SiO2/Ag@TiO2 (UC@SiO2/Ag@TiO2) nanospheres were prepared for the first time, which possessed the enhanced NIR-triggered photocatalytic activity under the synergistic effect of upconversion and plasmons. The design of active-core@active-shell structure for NaYF4:Yb,Tm,Nd@NaYF4:Yb,Nd upconversion nanophosphors (Yb/Tm/Nd@Yb/Nd UCNPs) significantly improved their upconversion luminescence (UCL) efficiency, which was increased by 12 times after coating a Yb/Nd shell on Yb/Tm/Nd seed crystals via epitaxial growth. After introduction of Ag nanoparticles, the UCL intensity of the obtained UC@SiO2/Ag was further enhanced by 3.3 times compared with the bare UCNPs because the plasmon resonance frequency of Ag overlapped with the visible emission peaks of UCNPs, which permitted an effective surface plasmon-coupled emission, resulting in the increase of emission intensity for UCNPs. Therefore, the final UC@SiO2/Ag@TiO2 could absorb the plasmon-enhanced NIR-to-UV/Vis lights from UCNPs to obtain its photocatalytic activity. Significantly, the photodegradation of Rhodamine B under the action of UC@SiO2/Ag@TiO2 was 26.9 % higher than that under the action of UC@SiO2@TiO2. UC@SiO2/Ag@TiO2 also exhibited a better photocatalytic antibacterial activity against B. subtilis than UC@SiO2@TiO2. In the presence of UC@SiO2/Ag@TiO2, bacteria were completely killed after 15 min of 808 nm NIR illumination. Finally, the possible photocatalytic mechanism of UC@SiO2/Ag@TiO2 was discussed based on the results of scavenger test.

Enhanced Magnetic, Dielectric, Optical and Ferro-Photovoltaic Properties of Barium Ferrite (BaFe2O4) Nanoparticles with Zn doping for Photovoltaic Applications

Aim: Enhanced Magnetic, Dielectric, Optical and Ferro-Photovoltaic Properties of Barium Ferrite (BaFe2O4) Nanoparticles with Zn doping for Photovoltaic Applications Background: A complete examination of structural, magnetic, di-electric, photovoltaic, and optical properties of Zn doped barium ferrite particles has been performed, using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Vibrating sample magnetometer (VSM), Impedance Analyzer, UV Visible spectroscopy, and Fluorescence spectrophotometer. Objective: The valuable results of magnetic, optical, and photovoltaic properties of Zn doped barium ferrites presented a novel idea for utilizing magnetic ferrites in photovoltaic applications. Method: Magnetic Ba1-xZnxFe2O4 (x = 0.0, 0.2, 0.3, 0.5) nanoparticles have been prepared by sol-gel auto combustion method. Result: The ferroelectricity and photovoltaic response were explored by Multiferroics system and Electrochemical impedance spectroscopy, respectively. The structure was detected orthorhombic with space group Pnma 3 for pure and Zn doped samples. The magnetization value for pure BaFe2O4 was increased from 1.4 emu/g to 15.3 emu/g for Ba0.7Zn0.3Fe2O4 sample. The ferroelectric behavior was reflected equally in pure BaF and Zn-doped samples. The photovoltaic results revealed an increase in photocurrent upon illumination in Zn = 0.3 sample. The dielectric properties showed direct relation with each other and supported ferroelectricity. The energy band gap value for pure barium ferrite (BaF) was reduced from 1.54 eV to 1.33 eV for Zn = 0.3 sample. The photoluminescence resulted in increasing emission intensity spectra for Zn = 0.3 and Zn = 0.5 at wavelength of 607 nm and 430 nm. Conclusion: The nanoparticles revealed an orthorhombic crystal structure with degraded particle size from 43-26.5 nm with increasing concentration of Zn doping. The same movement was followed by grain size from 245 to 33 nm. The lattice constant ‘a’, micro-strain, and dislocation density were increased. The growth of spherical nanoparticles and the desired composition of chemical bonds were verified by SEM and FTIR individually. The magnetization was upgraded from 1.4 emu/g to 15.32 emu/g, while coercivity was lessened with doping.

A single‐phase, thermally stable and color-tunable white light emitting Na2Ca1-x-yCexMnyP2O7 phosphors for white light emitting diodes via energy transfer

The solid-state reaction method was used to develop a series of Na2Ca1-x-yCexMnyP2O7 phosphors in an H2–N2 environment. The crystal structure of the pyrophosphate host, valence state of dopants (Ce, Mn), emission behavior of dopants, energy transfer mechanism, and thermal quenching behavior were thoroughly examined. Doping with Ce3+ and Mn2+ ions enhanced the photoluminescence characteristics of Na2Ca1-x-yCexMnyP2O7 while having negligible effect on the host's phase purity. Under 365 nm UV light irradiation, the addition of Ce3+ ion in the Na2CaP2O7 host revealed an asymmetric band with the typical blue emission around 415 nm and a shoulder around 455 nm. To obtain white light, Mn2+ ion was supplementarily substituted to the present system. When the Mn2+ ions concentration was elevated in the Na2CaP2O7 host, the emission intensity of 560 nm peak corresponding to Mn2+ transition enhanced significantly at the cost of Ce3+ emission of 415 nm. The systematic decrease of Ce3+ emission intensity and corresponding increase in the Mn2+ intensity with the increase in Mn2+ concentration indicated the possibility of effective energy transfer from Ce3+ to Mn2+ ions. The obtained results indicated that energy transfer from the Ce3+ to Mn2+ ions governed by dipole-quadrupole interaction. Because of the efficient energy transfer, the blue emission from Ce3+ and the orange red emission of Mn2+ provide white light from a single host along with high value of activation energy and low thermal quenching behaviour make the present phosphors to be suitable for high-power LEDs.

Fluorescence in colloidal solutions: Scattering vs physicochemical effects on line shape

Line shapes of anionic fluorescein fluorescence in suspensions of polystyrene nanoparticles (PSNP), anionic and cationic micelles, lipid vesicles, and of laurdan in lipid vesicles were investigated. Computed second harmonic of measured spectra indicated three lines for fluorescein and two for laurdan. Accordingly, fluorescein spectra were fit to three Gaussians and laurdan spectra to two lognormal distributions. Resolved line parameters were examined against particle concentration. Scattering, although wavelength dependent, affected intensity but not line shape. Inner filter effects of scattering on line shape are insignificant because multiple scattering, redirection of scattered photons into the detector, and inclusion of scattered photons in collection and detection minimize wavelength dependent effects. Dominant effects on line width and peak positions are due to physicochemical effects of dye-particle-solvent interactions rather than scattering. Fluorescein does not interact with anionic micelles and lipid vesicles, but remains in the aqueous phase, and responds to pH increase induced by these additives. Blue shift in peak position, decrease in line width, and increase in emission intensity in these systems are like those in NaOH solutions. Fluorescein does interact with cationic micelles and hydrophobic PSNP, and its emission is red shifted. Laurdan in lipid vesicles senses interface polarity. Blue shift and decrease in line width of its emission line indicate decreasing polarity with lipid concentration. Scattering, as well as interactions affect emission intensity. Physicochemical effects distort line shape and modify intrinsic spectra. Line shape changes are better markers than intensity to investigate interactions and reactions.

Cost-effective screen printing approach for Ce/Nd-doped ZnAl2O4 films: tuning crystallinity induced by the substrate.

Near-infrared (NIR) emitting phosphors are currently receiving considerable attention owing to their high demand in various applications, such as light detection and ranging (LiDAR), short-range communications, security, biosensing and night vision lighting applications. The miniaturization of photonic components demands the integration of thin films into exploitable devices. In this context, NIR emitting ZnAl2O4:Ce/Nd films of hundreds of nanometer thickness are synthesized using a scalable and cost-efficient approach to screen printing. Cerium co-doping is responsible for the Nd emission in the NIR through energy transfer by exciting the films under UV excitation at around 360 nm. Through the proper design of ink, dense Nd/Ce doped ZnAl2O4 ceramic films were produced using polycrystalline alumina. The use of polycrystalline alumina substrates opens up new opportunities because this ceramic is a cheap and well-known substrate for optoelectronic packaging. During manufacturing, as a direct effect of predominant crystal growth over the polycrystalline alumina substrate, an increase in emission intensity is achieved. The results obtained by X-ray photoelectron (XPS) and X-ray absorption near edge spectroscopy (XANES) serve to determine the oxidation state of Ce. The findings of this study indicate that a higher concentration of Ce4+ promotes NIR emission. This study may contribute to a better understanding of film production processes of films based on the ZnAl2O4 matrix and guide future studies on films for NIR emitters.