Concentration-dependent Studies Research Articles

Photophysics of TADF Guest-Host Systems: Introducing the Idea of Hosting Potential.

The thermally activated delayed fluorescence (TADF) donor–acceptor (D–A) molecule, DMAC–TRZ, is used as a TADF emitter “probe” to distinguish the environmental effects of a range of solid-state host materials in guest–host systems. Using the guest’s photophysical behavior in solution as a benchmark, a comprehensive study using a variety of typical TADF organic light-emitting diode hosts with different characteristics provides a clearer understanding of guest–host interactions and what affects emitter performance in solid state. We investigate which are the key host characteristics that directly affect charge-transfer (CT) state energy and singlet triplet energy gaps. Using time-resolved photoluminescence measurements, we use the CT state energy distribution obtained from the full width at half-maximum (fwhm) of the emission band and correlate this with other photophysical properties such as the apparent dynamic red shift of CT emission on-set to estimate the disorder-induced heterogeneity of D–A dihedral angles and singlet triplet gaps. Further, the delayed emission stabilization energy value and time-dependent CT band fwhm are shown to be related to a combination of host’s rigidity, emitter molecule packing, and the energy difference between guest and host lowest energy triplet states. Concentration dependence studies show that emitter dimerization/aggregation can improve as well as reduce emission efficiency depending on the characteristics of the host. Two similar host materials, mCPCN and mCBPCN, with optimum host characteristics show completely different behaviors, and their hosting potential is extensively explored. We demonstrate that type I and type III TADF emitters behave differently in the same host and that the materials with intrinsic small ΔEST have the smallest disorder-induced CT energy and reverse intersystem crossing rate dispersion. We also present an optimized method to define the actual triplet energy of a guest–host system, a crucial parameter in understanding the overall mechanism of the TADF efficiency of the system.

RNA-targeted Cu(II)-based potential antitumor drug entity: comprehensive structural, biological {DNA/RNA binding, cleavage, cytotoxicity} and computational studies

Copper-based bis(hydroxy naphthaldehyde) complex with axial mono aqua-coordination was synthesized and thoroughly characterized by various spectroscopic{IR, UV-vis, EPR}, ESI-Mass and single X-ray crystallographic studies. The single X-ray crystallography of the complex revealed the square pyramidal coordination geometry with P21 space group with axial water molecule ligated to copper centre. The geometry of the complex was further validated by DFT calculations, which was in accordance with other spectroscopic studies. The binding profile of the complex with ct-DNA and tRNA was carried out by employing various biophysical (absorption, fluorescence, circular dichroism, morphological studies) and computational studies (DFT, molecular docking). The experimental results revealed efficient binding of the complex with both ct-DNA and tRNA primarily, via non-covalent interactions. The binding studies Kb and K values revealed 10-fold greater binding affinity of the complex for tRNA as compared to ct-DNA. The in silico molecular docking further validated the interaction of complex within the hydrophobic pocket of ct-DNA and tRNA. The concentration and time dependent cleavage studies of DNA and tRNA were performed by employing gel electrophoresis assay. The cytotoxic activity of the complex was performed on a panel of human cell lines viz., leukemia (K-562), pancreatic (MIA-PA-CA-2), hepatoma (Hep-G2), cervical (HeLa), and breast (MDA-MB-231) by SRB assay. The complex exhibited selectively remarkably good cytotoxic potential on leukemia (K-562), cervical (HeLa) and hepatoma (Hep-G2) cancer cell lines. Communicated by Ramaswamy H. Sarma

Transport studies of ionic solutes through chitosan/chondroitin sulfate A (CHI/CS) polyelectrolyte multilayer membranes

Nano scale assembling has led to the capability to directly control and enhance the capabilities and properties of a material through change of its structural makeup at the nano scale. A novel class of functional layers in which various properties can be tunable via in situ modifications of nanostructure through stimuli such as pH, capping, and salt addition provides a promising strategy to develop polyion responsive polyelectrolyte multilayer membranes (PEM’s). The concentration (diffusion dialysis) and pressure dependent (ultrafiltration) studies of solution containing polyvalent ions through the chitosan/chondroitin sulfate A (CHI/CS) multilayers fabricated on ultipore membrane have been studied. The characterization of the bilayer pair was done with analytical instruments like ATR-FTIR, spectroscopic ellipsometry, SEM, AFM and finally TGA for water holding capacity. The characterization of bilayer pairs demonstrated the stability and integrity of bilayer pair. An important bilayer property such as water holding capacity and ion permeability across it was examined and a positive correlation was found with increase in number of bilayers. The possibility of capping a fabricated bilayer with another polyelectrolyte, polyethylene glycol (PEG) was used to examine the extend of efficiency. The permeation rate of ions across bilayers increased with makeup salt concentration was observed with capping. An increase in selectivity was observed with increase in the number of bilayers for Na+/Cu2+, Na+/Ag+ and Na+/Mn3+. 12.5 hybrid CHI/CS-PEG membranes shows a selectivity of 38.52 for Cl−/PO43− with a permeation rate of 37.54 × 10–5 cms−1 and 4.23 × 10–5 cms−1 respectively for Cl− and PO43−. The transport profile of a model vitamin, ascorbic acid (AA) through CHI/CS multilayers showed the capability of bilayer membrane for selective solute transport.

Easily Accessible Schiff Base ESIPT Molecules with Tunable Solid State Fluorescence: Mechanofluorochromism and Highly Selective Co2+ Fluorescence Sensing

AbstractSchiff base molecules of 1–4 ((E)‐N′‐benzylidene‐2‐hydroxybenzohydrazide derivatives) showed structure controlled solid state fluorescence tuning, reversible stimuli induced fluorescence switching and highly selective Co2+ sensing. The strong intramolecular H‐bonding between imine and amine facilitates excited state intramolecular proton transfer (ESIPT) and large red shifted solid state fluorescence. Positional isomers and substitutional change tuned the solid state fluorescence (460 to 605 nm). The substituents and positions control stimuli‐induced fluorescence switching. ESIPT fluorophores showed strong fluorescence in DMF (Φf=0.057 to 0.35 compared to quinine sulphate). ESIPT fluorophores (2–4) exhibited highly selective fluorescence sensing of Co2+ ions without significant interference from other metal ions. Concentration dependent studies of fluorophores show the detection limit (LOD) of 54 nM that is much lower than the Environmental Protection Agency (EPA) guideline value (1.7 μM) in drinking water. Solid state fluorescence of ESIPT fluorophores have been made use to fabricate solid fluorescence assay (PVA polymer composite thin films) and demonstrated highly selective fluorescence sensing of Co2+ upon dipping into aqueous metal ions solution. Thus, the present studies demonstrate the versatility of Schiff base molecules for developing ESIPT fluorophores for stimuli responsive materials and highly selective fluorescence sensing both in solution and solid state.

English

This study aimed at analysing the phytochemical content and antimicrobial activity of Bridelia ferrugine against selected bacteria. Total saponin, alkaloids, tannins, flavonoids and total anthraquinone contents were evaluated using spectrophotometric equivalents of the standards. The antibacterial activity of the plant extracts were determined using Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays against selected bacteria. The root and stem revealed the presence of the phytochemicals tested except the stem that lacked anthraquinones. In vitro antimicrobial activity of the plant extracts against the gram-positive bacteria tested showed that Bacillus cereus was most susceptible to the plant extract having MIC and MBC of 25 and 50 mg/ml, respectively for the stem-bark and root-bark ethanolic extract, while gram-negative bacteria the plant extracts were most active against Proteus mirabilis with MIC and MBC of 50 and 100 mg/ml, respectively. The aqueous extract was most active against Staphylococcus epidermidis with MIC and MBC of 50 and 100 mg/ml for stem-bark and 25 and 50 mg/ml for root-bark extract. Concentration dependent study showed the plant extracts were either bacteriostatic or bactericidal. Only the stem-bark aqueous extract showed no primary effect on the control strains. The study confirmed the presence of some phytochemicals which revealed that the plant is of pharmacological importance going by the ability of these phytochemicals to elicit antibacterial activity. Key words: Antibacterial, phytochemical screening, Bridelia ferruginea, plant extracts.

Trace level toxic ammonia gas sensing of single-walled carbon nanotubes wrapped polyaniline nanofibers

This paper presents a two-step enhancement and a comprehensive analysis of single-walled carbon nanotubes (SWCNTs) wrapped polyaniline nanofiber (NPANI) ammonia (NH3) gas sensor at room temperature. SWCNT-PANI composites are successfully synthesized using an efficient and cost-effective rapid in situ chemical polymerization method. The structural morphology and modification of the samples are characterized using field-emission scanning electron microscopy and HRTEM. FTIR and Raman spectroscopic studies are also performed to gain a better insight into the chemical environmental interaction in the as-prepared nanocomposite. The analysis confirms the successful formation of the nanocomposite. The observed NH3 gas-sensing response at 10 ppm of SWCNT, f-SWCNT (functionalised SWCNT), and SWCNT-PANI composite sensors are 5%–6%, 18%–20%, and 24%–25%, respectively. The SWCNT-PANI composite sensors have shown higher repeatability, selectivity, long-term stability, and fast response-recovery characteristics as compared to f-SWCNTs and pristine SWCNT sensors. Concentration and temperature dependent gas-sensing studies are also analyzed. The sensor response also shows a linear relationship with NH3 gas concentration and an inverse relationship with increasing temperature.

Consecutive Supramolecular Polymerization of a Rylene-Based Twistacene.

The synthesis and self-assembling features of twistacene 1 are reported. The supramolecular polymerization of 1 displays a consecutive pathway to afford slipped (AggI) and rotationally displaced (AggII) aggregates conditioned by the formation of intramolecularly H-bonded pseudocycles. In methylcyclohexane, both AggI and AggII are highly stable and the interconversion of the kinetically controlled AggI into the thermodynamically controlled AggII takes several weeks to occur. The utilization of toluene as solvent changes the energetic level for both aggregates and favors a faster conversion of AggI into AggII within a period of minutes. This conversion can be accelerated by the addition of seeds. Furthermore, concentration dependent kinetic studies demonstrate the consecutive character of the supramolecular polymerization of 1.

Effects of hexamethylenetetramine (HMTA) on the aqueous solution structure, dynamics and ion solvation scenario: A concentration and temperature dependent study with potential HMTA models

The local hydrogen bonding structure of water and its dynamics in hexamethylenetetramine (HMTA) solution is investigated by using classical molecular dynamics simulations. In this study, we have compared two potential HMTA models with different Lennard-Jones (L-J) combination rules. We have considered five different concentrations of HMTA, ranging from pure water to 6.181 m HMTA at 298 K, whereas to calculate the temperature dependence from 298 K to 353 K, we have used 4.187 m concentration of HMTA. From the radial distribution function, it is observed that the addition of HMTA facilitates structural making of water, whereas our calculated values of the tetrahedral order parameter and asphericity of water suggests disordered structure with increasing HMTA concentration. Also there is a significant development of self-aggregation among water and HMTA molecules at higher concentration of HMTA. The self-diffusion coefficient values of water and HMTA is found to be decreased with increasing HMTA concentration in the solution, whereas at concentrations below 1.0 m, it matches well with the experimental observations. Our calculated activation energy of diffusion for HMTA (4.10 ± 0.2 kcal/g mol for Model-II), is very close to the experimental observation (4.34–4.44 kcal/g mol). The structure of the hydration shell of ions of different charges and sizes is also investigated in the presence of HMTA. For all the models, it is observed that the structural and dynamical properties of water and the hydration shell of ion shows negligible difference with varying concentration and temperature. In contrast, the ion−HMTA correlations are model dependent. It is suggested that the HMTA model-I (AM) is the suitable model for representing ion-solvation structure and dynamics particularly at lower concentrations of aqueous-HMTA solution.

Swollen liquid crystalline mesophase assisted synthesis of GO-PANI nanocomposite as a fluorescent probe for purines

This article focuses on the use of graphene oxide-polyaniline (GO-PANI) nanocomposite as fluorescent probe for sensing of adenine (A) and guanine (G). Swollen liquid crystalline mesophase were used for the synthesis of graphene oxide-polyaniline nanocomposite. GO-PANI nanocomposite showed enhanced fluorescent at 441 nm (ƛexcitation = 361 nm) on interaction of purines viz A and G solutions in dimethyl sulfoxide, GO exhibited quenching at 540 nm (ƛexcitation = 261 nm). The fluorescence emission spectra of GO-PANI nanocomposite and GO were recorded in the the pressence of A and G concentrations upto 1.2 × 10−4 M. The limits of detection (LOD) calculated from the concentration dependence study for GO-PANI nanocomposite and GO are 7.5 × 10−6 M and 13.4 × 10−6 M respectively. The LOD in the case of GO is identical for both A (13.0 × 10−6) and G (13.6 × 10−6 M). The binding constant (Kb) determined for GO-PANI with purines are in the range of 0.05-0.08 × 103 M−1 which is higher in the case of GO (2.42–7.52 × 103 M−1). The lifetime measurement demonstrates, an excited state interaction of GO-PANI nanocomposite and GO with purines. This is evident from the increasing lifetime from 4.3 ns to 29.2 ns for GO-PANI nanocomposite, while 17.5 ns to 37.2 ns for GO respectively. The relatively short lifetime of the GO-PANI nanocomposite in comparison with GO suggest an electronic charge dissipation of the excited state between polyaniline and graphene oxide possibly due to the alignment of polyaniline on the graphene oxide sheet. The photopysical properties of GO-PANI nanocomposite and GO observed in this study is new and has potential for application as fluorescent probe for the detection of purines.

Broadband Dielectric Spectroscopy Study of the Ion Dynamics in Blends of Polymerized and Molecular Ionic Liquids

The primary focus in describing the decoupling of ion dynamics from the structural relaxation and dynamic glass transition (Tg) in polymerized ionic liquids (PILs) has been the effect of polymer molecular weight and chemistry of the ionic repeat unit. A particular aspect that has not been studied in attempt to understand the physicochemical properties of these fascinating materials is the concentration dependence of PILs with their low molecular weight or monomeric derivatives. Here we present studies of mixtures containing the low molecular weight monomer and the corresponding polymer of [(methacryloyloxy)ethyl]dimethylammonium (DMAEMA+), the quaternized ammonium cation of dimethylaminoethyl methacrylate, with the bis[(trifluoromethyl)sulfonyl]imide (NTf2) counter anion. The temperature dependent ion dynamics were measured using broadband dielectric spectroscopy. Our results show that there is an exponential relationship between the dc conductivity and concentration which decreases with temperature. At ~80mol% PIL this this inverse relationship between log σ0 and concentration “saturates” then reverses approaching 100% PIL. Only a single calorimetric glass transition temperature was observed for each of the concentrations measured. The Tg is concentration independent from 0-75% (~-60°C) then rapidly increases to that of the polymer (~55°C). The S-N-S bending modes, as observed in the Raman spectrum of the blends, blueshifts with increasing concentration, but exhibits a slight redshift from 85-100% polymer. This suggests the anion becomes more coordinated to the cation with increasing polymer concentration, but then reverses approaching pure polymer. In concert with results from a recent simulation study, we suggest that the ion hopping mechanism changes drastically from dilute to concentrated PIL/IL blends at a characteristic concentration (~85% for DMAEMA+ NTf2), but then this mechanism reverses as the ion dynamics and structural relaxation become decoupled in the pure polymer. A continuation of these concentration dependent studies of PIL and low molecular weight ionic liquid blends is a promising direction toward fully understanding the dynamics in these systems for rational design of PILs. Figure 1

Low cost, highly sensitive and selective electrochemical detection of arsenic (III) using silane grafted based nanocomposite

Novel silane grafted bentonite was obtained using the natural bentonite as precursor material. The material which is termed as nanocomposite was characterized by the Fourier Transform Infra-red (FT-IR) and X-ray diffraction (XRD) methods. The surface imaging and elemental mapping was performed using Scanning Electron Microscopic (SEM/EDX) technique. The electroanalytical studies were performed using the nanocomposite electrode. The electroactive surface area of nanocomposite electrode was significantly increased than the pristine bentonite or bare carbon paste based working electrode. The impedance spectroscopic studies were conducted to simulate the equivalent circuit and Nyquist plots were drawn for the carbon paste electrode and nanocomposite electrodes. A single step oxidation/reduction process occurred for As(III) having ΔE value 0.36 V at pH 2.0. The anodic stripping voltammetry was performed for concentration dependence studies of As(III) (0.5 to 20.0 μg/L) and reasonably a good linear relationship was obtained. The detection limit of the As(III) detection was calculated as 0.00360±0.00002 μg/L having with observed relative standard deviations (RSD) less than 4%. The presence of several cations and anions has not affected the detection of As(III) however, the presence of Cu(II) and Mn(II) affected the detection of As(III). The selectivity of As(III) was achieved using the Tlawng river water sample spiked with As(III).

Analysis of Radial Dependences of the Electron Concentration and Plasma Velocity in the Region of Accelerated Solar Wind

Results of experimental studies of the electron concentration and near-solar plasma velocity dependences on the heliocentric distance obtained in 1970–2012 by the method of radio transillumination by signals of spacecraft for the region of 3–50 solar radii are presented. A comparative analysis of different approximations of these dependences is given and it is shown that joint analysis of the data on the plasma velocity and concentration with allowance for independence of the plasma integral flux on the heliocentric distance makes it possible to find analytical expressions corresponding well to experimental data. Analytical approximations and graphs of dependences of the velocity, concentration, acceleration, force, and kinetic energy on the distance in the regions of solar wind acceleration for low and moderate solar activity are presented.

Rewritable fluorescent platform and reusable hydrazine sensing thin film using aldehyde functionalized fluorophore integrated PMMA polymer matrix

Triphenylamine (TPA) based di-aldehyde fluorophores have been synthesised and utilized for fabricating solid thin film fluorescence assay for hydrazine sensing and rewritable fluorescence platform. Addition of hydrazine reacts with aldehyde and strongly quenched the fluorescence intensity in solutions. Interestingly, fluorophores integrated into PMMA thin films showed strong blue fluorescence and exhibited turn-off fluorescence upon immersing in hydrazine solution (5%) and turn-on fluorescence by immersing in acetic acid (5%). Concentration dependent studies revealed the limit of detection (LOD) of 9.3–14.0 μM in solution and 0.021% by solid matrix. Reversible off-on fluorescence switching both in solution and PMMA matrix has been achieved by acid and base exposure that has been successfully used for demonstrating rewritable fluorescent platforms.

A carnegieite type red emitting NaAlSiO4:Eu3+ phosphor: Concentration dependent time resolved photoluminescence and Judd-Ofelt analysis

This work discusses about synthesis of relatively unexplored carnegieite type NaAlSiO4 and designing it as efficient europium ion doped red phosphor. The synthesized powder has been systematically characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetry - Differential Thermal Analysis (TG-DTA) and photoluminescence (PL) techniques. The effects of Eu3+ concentration on the photoluminescence properties were investigated. Concentration dependent emission spectroscopic studies suggested quenching at 0.5% doping level due to multipolar interaction. Stark splitting analyses revealed that the point group around Na+ ions decreases with Eu3+ doping and it is found to be C4v in Eu3+ doped NaAlSiO4. The asymmetry ratio was found to increase monotonically with europium concentration due to increasing density of sodium ion vacancies (VNa) which further distort the structure of NaAlSiO4. Lifetime spectroscopic studies suggested stabilization of europium ion at sodium site in two different environment; one nearer to charge compensating defect and one at far off distance. Judd-Ofelt analysis suggested asymmetric and highly polarizable environment around europium ion lead to enhanced red emission. The structure-property correlations indicate the potential of such structures for enhanced luminescence, scintillation and other optoelectronic properties.

Dispersible hydrolytically sensitive nanoparticles for nasal delivery of thyrotropin releasing hormone (TRH)

Nose-to-brain delivery of drugs is affected by nanoparticles (NPs) deposited on the olfactory surface and absorbed directly into the brain. Thyrotropin releasing hormone (TRH), a water soluble drug used for treating suicidal patients, was incorporated into a fast degrading poly(sebacic anhydride) (PSA) NPs. NPs were prepared by a solvent-antisolvent process under strict anhydrous environment to obtain high TRH loading and to avoid premature PSA degradation and TRH release. PSA and TRH were dissolved in a mixture of dichloromethane and ethanol and added dropwise to a dispersion of mannitol particles in heptane as an antisolvent. Mannitol powder was included in the antisolvent, so that formed NPs adhered to the mannitol microparticles for easy isolation and immediate dispersion in water prior to use. The size, surface charge, and morphology of the TRH-PSA NPs were determined using dynamic light scattering (DLS), zeta-potential, and Scanning Electron Microscopy (SEM), respectively. The NPs prepared were uniform and spherical of ~250 nm. Further, the in vitro release profile of TRH from NPs lasted for 12 h with most TRH released within the first hour in water. Concentration dependent cell toxicity studies revealed low toxicity level at low concentrations of the NPs. Surface adsorption of the NPs was also uniform on the cell surface as examined through the odyssey near infrared fluorescence (NIR) images using Indocyanine green (ICG). The NPs are designed to enable direct delivery to the olfactory epithelium using a refillable nasal atomizer that deposits mist onto the olfactory neuro-epithelium.

Paper-Based System for Ion Transfer Across the Liquid-Liquid Interface.

While ion transfer studies were shown to be a promising method for fundamental electrochemistry, pharmacokinetic studies, and sensing, they suffer from inherent instability of the interface formed between the organic and aqueous phases. This limits to some extent the range of solvents which can be used and confines these studies to the laboratory. We propose here the use of paper, which has revolutionized the way we think of miniaturized analytical devices during the past decade, as a perfect substrate for ion transfer studies across the liquid-liquid interface. We describe the design of a simple three-phase electrode paper-based setup for redox-driven transfer of anions from anaqueous to anorganic phase. Electrochemical measurements of seven different anions and concentration dependence studies are in good agreement with the results obtained with traditional setups. Additionally, we show the applicability and limitations of such setups to the analysis of anion mixtures.

Self-assembly of water soluble perylene tetracarboxylic acid with metal cations: Selective fluorescence sensing of Cu2+ and Pb2+ ions in paper strips, zebrafish and yeast

Self-assembly of water soluble highly fluorescent perylene tetracarboxylic (PTCA, Φf = 0.67) dye via metal coordination has been leads to the selective fluorescence sensing of Cu2+ and Pb2+ ions at neutral pH and Ag+ ions sensing via nanoparticles formation at basic medium. High-resolution transmission electron microscopic (HR-TEM) analysis revealed the conversion 1-D nanostructures of PTCA to spherical aggregates with Cu2+ and hexagonal prisms with Pb2+ ions. However, Ag+ ions were reduced to silver nanoparticles (AgNPs) at higher pH. The concentration dependent studies showed detection of both metal ions up to µM concentration level. Interference studies suggested good selectivity for both Cu2+ and Pb2+ ions at neutral pH in presence of other metal cations. Importantly, application potential of PTCA for selective fluorescence sensing of Cu2+ and Pb2+ ions have been demonstrated in filter paper as well as biological environment such as zebrafish and yeast.

Effect of increasing concentration of paracetamol on performance of Vigna radiata: A concentration dependent study

In the recent times, it was shown that panadol (paracetamol) are involved in the processes of growth and development of plants. With this motion the present work was undertaken to explore the effect of panadol treatment on germination and various growth biomarkers of 30-days-old plants of mung bean (Vigna radiata). At 10 days stage of growth, seedlings were sprayed with distilled water (control), 0.0001, 0.0005, 0.001, 0.005, 0.01, 0.1 mg/L of panadol for 10 days. Treated plants were harvested at 30 days of growth to asses various parameters. The plants that developed from the panadol treatment demonstrated improved germination and growth traits in a concentration dependent manner. Out of the various concentrations (0.0001, 0.0005, 0.001, 0.005, 0.01, 0.1 or 1.0 mg/L) of panadol tested, 0.1 mg/L proved to be the best.

Preparation and luminescence properties of Dy3+-doped Na3Gd(PO4)2 nanophosphor for solid state white LEDs

White emitting Na3Gd(PO4)2 nanocrystalline phosphors doped with trivalent dysprosium (Dy3+) ions were synthesized by using citrate gel combustion technique. The structure of the compound is found to be orthorhombic with a particle size is 10 nm. Luminescence properties have been characterized using photoluminescence (PL), excitation, emission spectra and decay time measurements. In emission spectrum sharp emission peaks were observed 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transition of Dy3+ ions. From the concentration dependent PL studies, the optimum concentration of Dy3+ ions in Na3Gd(PO4)2 is found to be 1.0 mol %, where intense near white light for 352 nm pump wavelength. The yellow to blue intensity ratios, CIE chromaticity coordinates and correlated color temperature studies has shown the possibility of using this phosphor for W-LEDs

Synthesis, characterization and electrical properties of PANI-Ni2O3 nanocomposites

White emitting Na3Gd(PO4)2 nanocrystalline phosphors doped with trivalent dysprosium (Dy3+) ions were synthesized by using citrate gel combustion technique. The structure of the compound is found to be orthorhombic with a particle size is 10 nm. Luminescence properties have been characterized using photoluminescence (PL), excitation, emission spectra and decay time measurements. In emission spectrum sharp emission peaks were observed 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transition of Dy3+ ions. From the concentration dependent PL studies, the optimum concentration of Dy3+ ions in Na3Gd(PO4)2 is found to be 1.0 mol %, where intense near white light for 352 nm pump wavelength. The yellow to blue intensity ratios, CIE chromaticity coordinates and correlated color temperature studies has shown the possibility of using this phosphor for W-LEDs.