Cu-deficient graded-zinc Cu-In-Zn-S (CIZS) quantum dots (QDs) were synthesized by a two-step solvothermal method. These CIZS QDs exhibited size and composition tunable photoluminescence characteristics with emission color tunable from greenish-yellow to orange to red with a relatively high quantum yield between 45 and 60%. Novel white-light-emitting (WLE) hybrid composite is fabricated by integrating the blue-emissive 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore and quaternary CIZS inorganic QDs. Integrating CIZS QDs with POPOP fluorophore resulted in series of tunable emission colors with CIE coordinates lying in a straight line between the coordinates of the end member. WLE was shown for hybrid mixture comprising 0.5 nM of POPOP and 3 mg/mL of CIZS QDs with color coordinates (0.3312, 0.3324). Thin films of this hybrid mixture in PMMA matrix coated on UV-LED or on glass substrates with UV backlit light also showed broadband WLE with ideal CIE color coordinates of (0.34, 0.33), high color-rendering index value of 92, and correlated color temperature value of 5143 K. The hybrid composite exhibit Forster resonance energy transfer cascading from POPOP to CIZS which results in emission covering the entire visible spectral range. POPOP and CIZS QDs hybrid composite is a versatile material for WLED applications.

No abstract

A: Methods for the determination of efficiency of an aged high purity germanium (HPGe) detector for gaseous sources have been presented in the paper. X-ray radiography of the detector has been performed to get detector dimensions for computational purposes. The dead layer thickness of HPGe detector has been ascertained from experiments and Monte Carlo computations. Experimental work with standard point and liquid sources in several cylindrical geometries has been undertaken for obtaining energy dependant efficiency. Monte Carlo simulations have been performed for computing efficiencies for point, liquid and gaseous sources. Self absorption correction factors have been obtained using mathematical equations for volume sources and MCNP simulations. Self-absorption correction and point source methods have been used to estimate the efficiency for gaseous sources. The efficiencies determined from the present work have been used to estimate activity of cover gas sample of a fast reactor. K: Efficiency for gaseous sources, HPGe detector, dead layer thickness, cover gas activity, Monte Carlo 1Corresponding author.

No abstract

Oleic acid coated LaF 3 :Ce nanoparticles were synthesized and embedded in polyacrylamide through a two-step procedure. In the first step nanoparticles were synthesized by adopting co-precipitation technique and in the second step, nanoparticles were embedded in polyacrylamide (PAM) hydro-gel through the solution route. Nanoparticels were characterized for their crystal structure, particle size, organic coating and photoluminescence behavior using X-ray diffraction, SEM, TEM, FTIR and photoluminescence spectroscopy. Size of nanoparticles was estimated using the Scherer formula. Polymer nano composite (PNC) material was synthesized with two different weight percent of the nano powder viz 1.634% (termed as NG1) and 0.1664% (termed as NG2). The nanoparticle-polymer composite exhibits emissions at 308 and 370 nm. A comparison of the emission spectrum of LaF 3 :Ce nano-powder pellet with that of the composite suggests a suppression of emission from the PAM host in the composite.