Enhancement Of Emission Intensity Research Articles

Energy transfer in Bi3+-Sm3+ co-doped phosphors for temperature sensing and imaging

Optical thermometry has the distinct superiority of non-invasive, non-contact, and high spatial resolution. However, the simultaneous improvement of temperature sensitivity and resolution remains challenging. Herein, the tunable emission colors can be realized via energy transfer in Bi3+-Sm3+ co-doped La3Ta0.8Sb0.2O7, which further applied for fluorescence temperature sensing and imaging. With the partial substitution of Sb5+ with Ta5+, the emission peak of La3SbO7:0.04Bi3+ shiftes from 530 nm to 460 nm, together with a 2.1-fold enhancement of emission intensity. The emission shifted from bright blue to purple under 365 nm excitation based on the energy transfer. The energy transfer efficiency from Bi3+ to Sm3+ can reach 41.6 % via dipole–dipole interaction. The La3Ta0.8Sb0.2O7:(0.04Bi3+,0.005Sm3+) phosphors exhibit maximum relative sensitivity (Sr) of 1.32 %K−1 (@498 K) and absolute sensitivity (Sa) of 0.059 K−1 (@417 K), which have excellent temperature resolution and repeatability. Thus, the energy transfer in co-coped phosphors can simultaneously improve the temperature sensitivity and resolution for fluorescence temperature sensing. Besides, the phosphor/PDMS films can exhibit obvious thermochromic imaging.

Microscopic and luminescence characteristics of Dy3+ doped KSrVO4 nanophosphors as energy efficient photoluminescent material with potential application in white light-emitting diodes.

Nanotechnology has drawn an enormous amount of attention by providing various measures to reduce energy consumption. Phosphor-converted white-light emitting diodes (pc-w-LEDs), which are used in lighting applications, are gaining popularity. These materials are affordable, effective, and safe for the environment. Therefore, the main objective of the current study is to synthesize an economical phosphor which consumes low energy and is less harmful to the environment. In this study, Dysprosium (Dy3+) doped Potassium Strontium Vanadate (KSrVO4) nanopowders synthesized via the combustion process and using X-ray diffraction, FESEM, EDAX, HRTEM, UV-Vis spectroscopy, and photoluminescence spectroscopy techniques, we have examined its various structural, spectroscopic, optical, and morphological characteristics. The crystallite size was estimated using the XRD patterns and was found to be 25.724 nm. The functional groups contained in synthesized phosphor were identified using FTIR spectrum measurements. Using HRTEM, a particle size of 36.33 nm was predicted, which is consistent with the XRD results. The Kubelka-Munk approximation is used to determine the band gap energy of the produced nanophosphors. Three major peaks that correspond to the transitions of 4F9/2 → 6HJ (J = 15/2, 13/2, and 11/2) were discovered at 476 nm, 578 nm, and 669 nm, respectively, under the excitation of 390 nm near UV light. We investigated the impact of Dy3+ doping, the enhancement of emission intensity and the mechanism of concentration quenching on the photoluminescence spectra of the KSrVO4 host. KSrVO4:Dy3+ also demonstrated a suitable CCT (3745 K), enhanced color purity and high quantum yield in this work, indicating that this phosphor has potential applications in w-LED devices.

Near-infrared optical nanothermometry via upconversion of Ho3+-sensitized nanoparticles

Recently, materials revealing the upconversion (UC) phenomenon, which is a conversion of low-energy photons to higher-energy ones, have attracted considerable attention in luminescence thermometry due to the possibility of precise and remote optical thermal sensing. The most widely studied type of luminescent thermometry uses a ratiometric approach based on changes in the UC luminescence intensity, mainly of lanthanide ions’ thermally coupled energy levels. In this work, NaYF4:Ho3+@NaYF4, and NaYF4:Ho3+, Er3+@NaYF4 nanoparticles (NPs) were synthesized by the controlled reaction in oleic acid and octadecene at 573 K. The obtained nanoparticles had hexagonal structures, oval shapes, and average sizes of 22.5 ± 2.2 nm and 22.2 ± 2.0 nm, respectively. The spectroscopic properties of the products were investigated by measurements of the UC emission under 1151 nm laser excitation in the temperature range between 295 to 378 K. The sample doped with Ho3+ and Er3+ ions showed unique behavior of enhancing emission intensity with the temperature. The relative sensitivity determined for the NPs containing Ho3+ and Er3+ ions, reached the maximum value of 1.80%/K at 378 K. Here, we prove that the NaYF4:Ho3+, Er3+@NaYF4 system presents unique and excellent optical temperature sensing properties based on the luminescence intensity ratios of the near-infrared bands of both Ho3+ and Er3+ ions.

Influence of Thermionic Emission on He Ionization and Plasma Enhancement in Thermionic Energy Conversion

In this paper, the influence of thermionic emission on He ionization and plasma enhancement in thermionic energy conversion (TEC) are studied by experiment and numerical simulation. A 1D unsteady plasma TEC model, which includes a He ionization model, plasma conservation equations, and a thermionic emission formula for the wall, is developed. A He plasma thermionic energy conversion device composed of a barium–tungsten cathode and a tungsten anode is established. The volt–ampere curves of the He plasma TEC device are measured at 1050 K, 1150 K, 1250 K, 1300 K, and 1350 K temperatures. Both important cathode parameters, work function and emission area, are estimated. Based on the modelling simulation and the experiment, the He ionization mechanism in plasma TEC is discovered. The effects of cathode temperature on several distributions of plasma reaction rates, particle number density, and potential in He plasma TEC are described. Some important parameters, including electron mobility, resistivity, and plasma equilibrium are analyzed. The relationship of thermionic emission on plasma enhancement to the output power of plasma TEC is presented. The output powers of plasma TEC and vacuum TEC are compared at various cathode temperatures. A dimensionless analyzing method concerning thermionic emission intensity and plasma enhancement power is proposed. A brief dimensionless relationship is deduced regarding thermionic emission intensity and the plasma enhancement contribution of TEC. The principles and methods for quantitative calculations concerning the output power of plasma TEC under the action of thermionic emission are established. It is possible to do quantitative research on the effects of thermionic emission on plasma-enhanced TEC.

The emission intensity enhancement and improved limit of detection of Cu, Ag, and Au using electric field assisted LIBS

Conventional LIBS suffers from several challenges including high detection limit and low sensitivity. The current approaches include electric field-assisted laser-induced breakdown spectroscopy (EF-LIBS) to study the laser ablation process and characterize the effectiveness of this method on several parameters such as plasma temperature, electron number density, intensity enhancement, and limits of detection. The purpose of the present study is to analyze the improvement in the signal intensity and limits of detection of Copper (Cu), Silver (Ag), and Gold (Au) using EF-LIBS. The laser plasma is generated by focusing a high-power laser beam on gold alloy samples. The intensities of Cu and Ag lines were normalized using the Au line to reduce the statistical errors. Calibration curves were drawn for each element to determine the limit of detection (LOD). The detection sensitivity was enhanced using an external electric field to the axial direction of plasma. The effect of the electric field on plasma parameters, limits of detection, and signal intensities has been studied. It was observed that LODs of Cu and Ag were improved from 14.3 ppm to 4.6 ppm–1.7 ppm and 2.06 ppm respectively with significant enhancement in the emission intensity. The present study demonstrates that EF-LIBS can be utilized for the better detection of precious elements in geological mineralogical and alloy samples. In addition, results showed that the single-shot EF-LIBS is a better choice for precious samples because of a smaller mass ablation against standard LIBS and it is a low-cost setup as compared to other analytical techniques.

Synthesis of Self-Assembled Molecules Based on Tetraphenylethene-Core Inducing Emission

Aggregation-induced emission (AIE) organic materials have been extensively explored for a future sensible and interactive display to provide high luminescence in ordered states. However, it is challenging for reducing exciton quenching of aggregated materials to achieve high emission and increasing ordered structure to yield high crystallinity as well. To this end, the new structures based on tetraphenylene (TP) core were synthesized by attaching TP with clipping groups (C) consisting of a self-assembling group (SAG) to enhance emission intensity and spectra shift.As the emissive materials for self-assembly, TPCns with different clip numbers (n=1,2,4) were synthesized through the Wittig-Hörner reaction, where clips consist of extended π-conjugated moiety and the alkyl chain as a segment. The clips could introduce van der Waals interaction to facilitate self-assembly among clips and clip-connected aromatic units. These structures were confirmed and analyzed by different tools including 1HNMR, 13CNMR, FTIR-ATR, element analysis, MALDI-TOF/TOF. The optical properties of TPCns were discussed in solution state and solid state. In terms of photoluminescent emission, the TPC4 showed a more yellowish-green emission (λem = 525nm in THF) and large aggregation-induced emission enhancement (EAIE) in aqueous (fw > 50%) THF solution. The greenish blue emission was realized for TPC1 at the maxima wavelength 481 nm and reached 100% quantum yield in the solid state. Furthermore, due to strong twisted intramolecular charge transfer, TPCn molecules had large Stokes shifts in ranges of 5800–6800 cm−1 for TPC1, TPC2, and 10700–12500 cm−1 for TPC4.

Synthesis and luminescent properties of Na5(La,Y) (MoO4)4: Sm3+ phosphors for solid-state lighting application

The Sm3+ and La3+ co-doped Na5Y(MoO4)4 orange-red phosphors were synthesized by solid phase method at 600 °C. The crystal structure, phase purity, thermal stability, and luminescence performance were comprehensively analyzed. Under 405 nm excitation, the phosphors emit the orange-red light because of the 4G5/2-6H5/2, 4G5/2-6H7/2, 4G5/2-6H9/2, and 4G5/2-6H11/2 transitions of Sm3+ ions. The enhancement of emission intensity with La3+ ions doping in phosphors is due to the environmental effect of the crystal field around the luminous center. When it is combined with commercial LED chips, the device emits orange-red light, and the luminescence spectrum coincides with the PR pigment absorption spectrum of the plant, indicating that the potential of Sm3+ and La3+ co-doped Na5Y(MoO4)4 phosphors in solid-state lighting application.

Enhancement of Fluorescence Emission Intensity in a Sulfonyl Hydrazide Derivative of tri(biphenyl‐4‐yl)amine via Solid‐state Grinding with Various Metal Salts: Combined Experimental and Computational Studies

AbstractSolid‐state fluorescent materials are in huge demand owing to their potential applications in sensors, imaging, and LEDs. The molecular aggregations in the solid state limit their usage in practical applications. Typically, J‐aggregates show enhanced emission, while H‐aggregates show quenching in the solid state. Few supramolecular approaches (like creating hydrogen bonds) were developed to disturb the π–π and other supramolecular interactions in solid‐state H‐aggregates. Herein, we are reporting a p‐toulenesulfonyl hydrazide derivative of tri(biphenyl‐4‐yl)amine (TBA‐THZ) in the solid state showed negligible emission while grinding with M+X− (M+=alkali and alkali earth metal) salts showed enhanced emission. Existing supramolecular interactions were disturbed by dipole‐ion interactions between S=O⋅⋅⋅M+. The micro/nanometer‐sized salt crystal particles serve as templates for the TBA‐THZ molecules, and in the broad sense, the salt crystal surfaces act as a “solid‐state solvent.” The TBA‐THZ ground with various metal salts showed varied emission intensities; the BaCl2 ⋅ 2H2O salt ground sample exhibited the maximum emission intensity. The KPF6+18‐Crown‐6 sample showed 84 times enhanced emission than the pristine TBA‐THZ. The role of 18‐crown‐6 ether was observed as a donor type for K+ ions. The expected S=O⋅⋅⋅K+ dipole‐ion interactions were elucidated through FT‐IR and computational modelling. The slight change in emission wavelength to the higher side after grinding with metal salt indicates that dipole‐ion interactions might slightly modify the chromophore's electronic structure, encouraging radiative decay and higher emission intensity. In contrast, a similar molecule, TBA‐PH, with no sulfonyl functional group, was silent in emission intensity. The TBA‐PH solid has no significant emission even after grinding with metal salts. The emission capacity of the TBA‐THZ salt‐ground powder remained unchanged at higher temperatures and in a highly humid environment. The fluorescent active salt ground matrix of the TBA‐THZ responded admirably to HCl acid fumes and was regenerated upon exposure to ammonia vapours.

Monitoring disease-implicated hydrogen sulfide in blood using a facile deproteinization-based electrochemiluminescence chemosensor system

Hydrogen sulfide (H2S), an antioxidant and cell signaling molecule, plays a critical role in redox reactions in the biological system, and its imbalances in blood levels have been implicated in various diseases. Here, we demonstrate a novel chemosensor-based “turn-on” electrochemiluminescence (ECL) system for the selective and sensitive detection of H2S in a type 1 diabetes rat model. Our luminogenic chemosensor (Probe) is a redox-stable cyclometalating iridium (III) complex with emission-quenching 2,4-dinitrophenyl ether (DNP) that shows a significant enhancement in emission intensity upon cleavage of DNP by selective reaction towards H2S. To achieve robust and reliable ECL emission of Probe for biological analysis, we developed a facile deproteinization protocol based on organic solvent-induced protein precipitation/syringe filtration that eliminates uncontrolled protein adsorption on the electrode surface from protein-rich biological samples. Our deproteinization-assisted ECL chemosensor system showed effectiveness in detecting disease-associated H2S levels in biological media with a linear response in the range of 0–250 µM (R2: 0.992). It enables reliable in vitro monitoring of H2S level changes in blood samples of a type 1 diabetes rat model (P = 0.0296). This strategy to integrate chemosensor-based ECL and facile deproteinization protocol provides a sensitive and rapid disease-monitoring platform for detecting small-molecule biomarkers.

Enhancement of stimulated emission in Eu3+ activated oxyfluoroborotellurite glasses for reddish orange laser material

Eu3+ activated oxyfluoroborotellurite glasses are enhancement stimulated emission by substitution of B2O3 with NaF whereas concentration of Eu3+ are fixed at 1.00 mol%. The present glasses have been prepared by melt quenching method. Seven absorption bands of present glasses have been observed in UV–VIS and NIR regions which originated from ground 7F0 and thermally populated 7F1 states to excited states. The absorption transitions of 7F0→5L6 and 7F0→7F6 were more intense compared to all transitions. The substitution of B2O3 with NaF has led to minor change absorption intensities. By stimulating with 395 nm, the emission spectra of present glasses exhibited four peaks which corresponding to 5D0→7F1,2,3,4 transitions. The transition of 5D0→7F2 showed the highest emission intensity. The substitution of B2O3 with NaF can enhance emission intensity due to the reduction of hydroxyl group. While the highest emission intensity has been found to be 35 mol% of NaF concentration. The absorption and emission results have been calculated stimulated emission by using Judd-Ofelt (JO) theory. The stimulated emission is found to be 109.1 × 10–21 cm2. Including the branching ratio is higher than 0.50. In the frame of chromaticity color coordinate which the present glasses are fallen in the reddish orange region. The results indicate that Eu3+ activated oxyfluoroborotellurite glasses could be used potentially for reddish orange laser material.

Design of AIEgen‐based porphyrin for efficient heterogeneous photocatalytic hydrogen evolution

AbstractTetraphenylethylene (TPE)‐conjugated porphyrin TPE‐ZnPF is synthesized in high yield and characterized by single‐crystal X‐ray diffraction. The propeller‐shaped TPE groups not only enable exceptional aggregation‐induced emission (AIE) in the solid state but also abolish the strong π‐π stacking of porphyrin moieties and thus prohibit aggregation‐caused quenching (ACQ). TPE‐ZnPF aggregates feature long‐lived photoexcited states, which subsequently suppress non‐radiative decay channels and enhance emission intensity. Moreover, its aggregates show more efficient light‐harvesting ability due to the Förster resonance energy transfer from the TPE energy donor to the porphyrin core energy acceptor, well‐defined nanosphere morphology, and more efficient photoinduced charge separation than the porphyrin Ph‐ZnPF, which possesses ACQ and agglomerated morphology. As a result, an excellent photocatalytic hydrogen evolution rate (ηH2) of 56.20 mmol g‒1 h‒1 is recorded for TPE‐ZnPF aggregates, which is 94‐fold higher than that of the aggregates of Ph‐ZnPF (0.60 mmol g‒1 h‒1) without the TPE groups.

Triazine based fluorescent sensor for sequential detection of Hg2+ and L-Cysteine in real samples and application in logic Gate: A combination of Extensive experimental and theoretical analysis

Triazine based fluorescent sensor TBT was rationally designed and synthesized to achieve sequential detection of Hg2+ and L-cysteine based on the presence of sulfur moiety and suitable cavity in the molecule. Sensor TBT exhibited excellent sensing potential for the selective detection of Hg2+ ions and L-cysteine (Cys) in real samples. Upon addition of Hg2+ to sensor TBT, enhancement in emission intensity of sensor TBT was observed which was accredited to the presence of sulfur moiety and size of cavity in the sensor. Upon interaction with Hg2+ blockage of intramolecular charge transfer (ICT) along with chelation-enhanced fluorescence (CHEF) resulted in the increase in fluorescence emission intensity of sensor TBT. Further, TBT-Hg2+ complex was employed for the selective detection of Cys through fluorescence quenching mechanism. This was attributed to the significantly stronger interaction of Cys with Hg2+, which resulted in the formation of Cys-Hg2+ complex and subsequently sensor TBT was released from TBT-Hg2+ complex. The nature of interaction between TBT-Hg2+ and Cys-Hg2+ complex was evaluated through 1H NMR titration experimentations. Extensive DFT studies were also carried out which include thermodynamic stability, frontier molecular orbitals (FMO), density of states (DOS), non-covalent interaction (NCI), quantum theory of atom in molecule (QTAIM), electron density differences (EDD) and natural bond orbital (NBO) analyses. All the studies supported the non-covalent type of interaction between analytes and sensor TBT. The limit of detection for Hg2+ ions was found to be as low as 61.9 nM. Sensor TBT was also employed for the quantitative detection of Hg2+ and Cys in real samples. Additionally, logic gate was fabricated by using sequential detection strategy.

Plasmonic Nanopyramid Array Enhancing Luminescence of MoS2 Investigated by Cathodoluminescence

AbstractTransition metal dichalcogenides (TMDs) like molybdenum disulfide (MoS2) have unique optical properties such as strong luminescence and a tunable bandgap. However, the small interaction distance due to the atomically thin nature of these materials is a limitation for applications. In this study, a significant enhancement of the A‐ and B‐exciton emission in MoS2 flakes through coupling with plasmonic Au nano‐pyramid arrays fabricated by a colloidal lithography technique is reported. This study experimentally maps local emission enhancement from the structure with a nanometer spatial resolution by cathodoluminescence (CL) technique. Strongly enhanced emission intensity within the MoS2‐Au pyramids is achieved due to the localized surface plasmon resonance confined in nano‐pyramids and its interaction with the periodicity‐based resonance of the array structure. The results provide an approach to significantly improve the luminescence intensity of MoS2 through optical interaction with the local plasmonic field, which is promising for applications in optoelectronic devices and nanophotonics.

Local piezoelectric doping of monolayer WSe2

We report non-contact local doping of a monolayer WSe2 transferred onto a piezoelectric substrate having surface potential wells (SPWs) induced by structural inhomogeneities. We used epitaxial GaN and InP/GaInP2 structures, in which there are SPWs ∼0.2 V deep and 0.1–2 μm in size. Using surface topography and potential scanning probe microscopy, as well as optical reflectance, photoluminescence, and Raman spectroscopy measurements, we observed strong enhancement of charged exciton emission and Raman intensity in the SPW regions of the monolayer WSe2, which indicate on piezoelectric doping at a level n ≥ 1012 cm−2 on a length scale ∼0.2–1 μm. Our results can be used to create electron/hole quantum puddles with anyon states in transition metal dichalcogenides, promising for the development of room temperature and magnetic-field-free fault-tolerant topological quantum computing.

Rhodamine B-Quinoline based schiff base as fluorescent ‘turn on’ sensor of Al3+, Cr3+, HSO4− and its cytotoxicity and cell imaging application on TPC-1 and HtH-7 cell lines

A designed Rhodamine-B-quinoline based Schiff base chemosensor (RhBQ) has been synthesized and characterized using various spectroscopic techniques. It shows ‘turn on’ fluorescence emission and also colorimetric sensitivity and selectivity towards trivalent metal ions (Al3+ and Cr3+) and anion (HSO4−) present in aqueous medium. Stoichiometry of both metal (Al3+ & Cr3+) - RhBQ complexes are found to be 1:1 using Job’s plot. A notable enhancement in emission intensity for RhBQ-Al3+ (∼341 fold), RhBQ-Cr3+ (∼292 fold), and RhBQ-HSO4− (∼136 fold) complexes compare to RhBQ are observed. Sensing mechanism i.e. opening of spirolactam ring of RhBQ has been confirmed through various spectroscopic techniques such as; 1H NMR, 13C NMR, ESI-MS, TRPL, FT-IR, and DFT based computational study. The limit of detection (LOD) for Al3+, Cr3+, and HSO4− are found to be 2.2 × 10−8 M, 2.12 × 10−8 M and 8.63 × 10−7 M respectively. An advanced level 3 input OR–INHIBIT logic gate are constructed using chelating ligand EDTA. For onsite detection, TLC paper strip spot of the probe, RhBQ is prepared and the detection of Al3+ in few antacid drug are presented. In addition, cell-imaging analysis of Al3+, Cr3+, and HSO4− ions in the Human papillary thyroid carcinoma cell line (TPC-1) & Human anaplastic thyroid cancer cell lines (HtH-7) are presented and shows promising concentration and time-dependent detection results.

Red-emitting Styryl-BODIPY dye with donor-π-acceptor architecture: Selective interaction with serum albumin via disaggregation-induced emission

Serum albumin (SA) is an abundant protein in mammalian blood plasma and a biomarker for various diseases, such as cirrhosis or hepatitis in the case of the liver. The research of fluorescent probes for SA based on host-guest interactions provides an opportunity to study the nature of intermolecular interactions and thus reveals the structure information of SA at the molecular level. However, some commercially available fluorescent probes, such as boron dipyrromethenes (BODIPYs) have a general tendency to form aggregates under an aqueous environment, which is a drawback for their use due to the strong quenching of the emission. Additionally, short emission wavelength and small Stokes shift are the other common shortcomings. In this work, we explore this unfavourable property and provide an effective method for developing an “off-on” type probe for SA. A new probe named BOD-Red with red-emitting aggregation/disaggregation characters was then designed, consisting of donor-π-acceptor (D-π-A) architecture where boron-dipyrromethene (BODIPY) core as electron acceptor and N-phenylpiperazine as electron donor. The extended π-conjugation system provides not only the increase of emission wavelength due to the enhancement of intramolecular charge transfer strength, but also forms a higher rigid coplanar backbone, which can modulate the photophysical properties and aggregation process. Furthermore, the incorporated N-(2-hydroxyethyl) piperazine group behaves as a SA-binding receptor. BOD-Red formed aggregates in an aqueous solution and was non-emissive. In the presence of SA, it exhibited a pronounced enhancement of emission intensity centred at 630 nm owing to the disaggregation-induce emission. Notably, this probe in solution was non-responsive to any other tested proteins and small molecules. The mechanism responsible for the binding of BOD-Red with BSA was analyzed by a combined experimental and computational approach. The practical utility of BOD-Red as a fluorescent turn-on sensor was validated by quantifying BSA in real samples with reasonable recovery percentages.

Enhanced emission intensity in (Li+/Ca2+/Bi3+) ions co-doped NaLa(MoO4)2: Dy3+phosphors and their Judd-Ofelt analysis for WLEDs applications

In the present study, we have synthesized a series of Dy3+ ion doped NaLa(MoO4)2phosphors by the conventional solid-state method at 750 °C for 4h. All the compounds were crystallized in the tetragonal scheelite type structure with space group (I41/a, No.88). The morphology and functional group were confirmed by the field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared(FTIR)spectroscopy. Upon near-Ultraviolet (n-UV) excitation, the PL spectra exhibit the two characteristic emissions of Dy3+ ions, blue (4F9/2 → 6H15/2) at 487 nm and yellow (4F9/2 → 6H13/2) at 574nm respectively. The optimum concentration of Dy3+ionis 3 mol% and then quenching occurred due to multipolar interaction. Further, enhanced the emission intensity by co-doping with monovalent (Li+), divalent (Ca2+) and trivalent (Bi3+) ions. Among them, Li+ ion co-doped samples are shown maximum intensity (50 times) more than Dy3+ doped phosphors as relaxation of parity restriction of electric dipole transition because of local distortion of crystal field around the Dy3+ ions. In addition, by incorporation of Eu3+ ions into NaLa(MoO4)2:Dy3+system, tuned the emission color from white to red, owing to energy transfer from Dy3+ to Eu3+ ions. The intensity parameters (Ω2, Ω4) and radiative properties such as transition probabilities (A T), radiative lifetime (τ rad), and branching ratio were calculated using the Judd-Ofelt theory. CIE color coordinates, CCT values indicates that these phosphors exhibit an excellent white emission. The determined radiative properties, CIE and CCT results revealed that the Dy3+-activated NaLa(MoO4)2phosphors are potential materials for developing white LEDs, and optoelectronic device fabrications.

Anthracene scaffold as highly selective chemosensor for Al3+ and its AIEE activity.

Fluorescent chemosensor, 3-(Anthracen-2-yliminomethyl)-benzene-1,2-diol (ANB) has been synthesized by one-step condensation of 2-aminoanthracene and 2,3-dihydroxybenzaldehyde and characterized using 1H-NMR, FT-IR and Mass spectroscopic techniques. The probe ANB was found to be an efficient 'turn-on' fluorescence chemosensor for the selective detection of Al3+ ion over other metal ions in an aqueous solution. The chemosensor exhibits ~ 27-fold enhancement of emission intensity in presence of Al3+ ion. Fluorescence quantum values for ANB and (Al3+-ANB)-complex are 0.004 and 0.097, respectively. In addition, the binding constant and the limit of detection were found to be 1.22 × 104M-1 and 0.391µM, respectively. The chemosensor ANB binds to Al3+ ions in 2:1 stoichiometric ratio which was supported by Job's plot, 1H-NMR titration and florescence titration. Fluorescence reversibility of the sensor complex was well established by adding EDTA in the same condition and a molecular INHIBIT logic gate was fabricated using this reversible nature of the sensor complex. Additionally, the chemosensor ANB shows a novel aggregation-induced enhanced emission phenomenon, where the aggregate hydrosol of ANB shows enhance emission intensity.

Aza-phenol Based Macrocyclic Probes Design for "CHEF-on" Multi Analytes Sensor: Crystal Structure Elucidation and Application in Biological Cell Imaging.

Metal bound macrocyclic compounds found in biological systems inspired us to design and synthesize two Robson-type macrocyclic Schiff-base chemosensors, H 2 L1 (H 2 L1=1,11-dimethyl-6,16-dithia-3,9,13,19-tetraaza-1,11(1,3)-dibenzenacycloicosaphane-2,9,12,19-tetraene-1,11-diol) and H 2 L2 (H 2 L2=1,11-dimethyl-6,16-dioxa-3,9,13,19-tetraaza-1,11(1,3)-dibenzenacycloicosaphane-2,9,12,19-tetraene-1,11-diol). Both the chemosensors have been characterized with different spectroscopic techniques. They act as multianalyte sensor and exhibit "turn-on" fluorescence toward different metal ions in 1X PBS (Phosphate Buffered Saline) solution. In presence of Zn2+, Al3+, Cr3+ and Fe3+ ions, H 2 L1 exhibits ∼6-fold enhancement of emission intensity, while H 2 L2 shows ∼6-fold enhancement of emission intensity in the presence of Zn2+, Al3+ and Cr3+ ions. The interaction between the different metal ion and chemosensor have been examined by absorption, emission, and 1H NMR spectroscopy as well as by ESI-MS+ analysis. We have successfully isolated and solved the crystal structure of the complex [Zn(H 2 L1)(NO3)]NO3 (1) by X-ray crystallography. The crystal structure of 1 shows 1:1 metal:ligand stoichiometry and helps to understand the observed PET-Off-CHEF-On sensing mechanism. LOD values of H 2 L1 and H 2 L2 toward metal ions are found to be ∼10-8 and ∼10-7 M, respectively. Large Stokes shifts of the probes against analytes (∼100 nm) make them a suitable candidate for biological cell imaging studies. Robson type phenol based macrocyclic fluorescence sensors are very scarce in the literature. Therefore, the tuning of structural parameters as the number and nature of donor atoms, their relative locations and presence of rigid aromatic groups can lead to the design of new chemosensors, which can accommodate different charged/neutral guest(s) inside its cavity. The study of the spectroscopic properties of this type of macrocyclic ligands and their complexes might open a new avenue of chemosensors.

Suppression of kernel vibrations by layer-by-layer ligand engineering boosts photoluminescence efficiency of gold nanoclusters

The restriction of structural vibration has assumed great importance in attaining bright emission of luminescent metal nanoclusters (NCs), where tremendous efforts are devoted to manipulating the surface landscape yet remain challenges for modulation of the structural vibration of the metal kernel. Here, we report efficient suppression of kernel vibration achieving enhancement in emission intensity, by rigidifying the surface of metal NCs and propagating as-developed strains into the metal core. Specifically, a layer-by-layer triple-ligands surface engineering is deployed to allow the solution-phase Au NCs with strong metal core-dictated fluorescence, up to the high absolute quantum yields of 90.3 ± 3.5%. The as-rigidified surface imposed by synergistic supramolecular interactions greatly influences the low-frequency acoustic vibration of the metal kernel, resulting in a subtle change in vibration frequency but a reduction in amplitude of oscillation. This scenario therewith impedes the non-radiative relaxation of electron dynamics, rendering the Au NCs with strong emission. The presented study exemplifies the linkage between surface chemistry and core-state emission of metal NCs, and proposes a strategy for brighter emitting metal NCs by regulating their interior metal core-involved motion.