Chirantan Dey

White light emitting Ho3+-doped CdS nanocrystal ingrained glass nanocomposites

We report the generation of white light from Ho3+ ion doped CdS nanocrystal ingrained borosilicate glass nanocomposites prepared by the conventional melt-quench method. Near visible 405 nm diode laser excited white light emission is produced by tuning the blue emission from the Ho3+ ions, green band edge, and orange-red surface-state emissions of the nanocrystalline CdS, which are further controlled by the size of the nanocrystals. The absorption and emission spectra evidenced the excitation of Ho3+ ions by absorption of photons emitted by the CdS nanocrystals. The high color rendering index (CRI = 84–89) and befitting chromaticity coordinates (x = 0.308–0.309, y = 0.326–0.338) of white light emission, near visible harmless excitation wavelength (405 nm), and high absorbance values at excitation wavelength point out that these glass nanocomposites may serve as a prominent candidate for resin free high power white light emitting diodes.

Single-step in-situ synthesis and optical properties of ZnSe nanostructured dielectric nanocomposites

This work provides the evidence of visible red photoluminescent light emission from ZnSe nanocrystals (NCs) grown within a dielectric (borosilicate glass) matrix synthesized by a single step in-situ technique for the first time and the NC sizes were controlled by varying only the concentration of ZnSe in glass matrix. The ZnSe NCs were investigated by UV-Vis optical absorption spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM). The sizes of the ZnSe NCs estimated from the TEM images are found to alter in the range of 2–53 nm. Their smaller sizes of the NCs were also calculated by using the optical absorption spectra and the effective mass approximation model. The band gap enlargements both for carrier and exciton confinements were evaluated and found to be changed in the range of 0–1.0 eV. The Raman spectroscopic studies showed blue shifted Raman peaks of ZnSe at 295 and 315 cm−1 indicating phonon confinement effect as well as compressive stress effect on the surface atoms of the...

Synthesis and properties of ZnTe and Eu3+ ion co-doped glass nanocomposites

In this study, ZnTe (II-VI) semiconductor and Eu+3-ion co-doped borosilicate glass has been prepared in the SiO2-K2O-CaO-BaO-B2O3 glass system followed by controlled heat-treatment to produce glass nanocomposites. Glass transition temperature and crystallization peak temperature have been evaluated using DSC analysis. Dilatometric studies were carried out to evaluate thermal expansion co-efficient, glass transition temperature, and dilatometric softening temperature and found to be 10.7 × 10−6/K, 580° C and 628° C, respectively. TEM micrographs demonstrate formation of nano sized crystallites of less than 50 nm. The ZnTe crystal formation also established through selected area electron diffraction (SAED) analysis and high resolution images obtained through TEM studies. With increasing heat treatment time, optical transmission cut-off wavelength (λcut-off) shifted towards higher wavelength. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the 5D0 → 7F2 transition. An inten...

CdSe nanocrystals ingrained dielectric nanocomposites: synthesis and photoluminescence properties

Cadmium selenide (CdSe) nanocrystals ingrained dielectric nanocomposites in a B2O3–SiO2–Al2O3–Na2O–K2O borosilicate glass system were synthesized by a single step in situ melt quenching technique. The sizes of the nanocrystals as well as the band gap of the nanocomposites were controlled by both concentration of CdSe and post thermal treatment duration. The nanocomposites were characterized by different instrumental techniques including detailed photoluminescence studies. The sizes of the CdSe nanocrystals were found to alter in the range 4–16 nm as estimated from the effective mass approximation model and optical absorption spectroscopy. However, the TEM analysis revealed the generation of two different size ranges, 3–4 and 23–45 nm, of the particles within the dielectric matrix. Selected area diffraction (SAED) and x-ray diffraction (XRD) patterns authenticate the formation of hexagonal nanostructures of CdSe. These nanocomposites were found to be capable of exhibiting strong visible red luminescence around 715 nm on excitation at 446 nm. This has originated from the electron–hole recombination of CdSe nanocrystal and defects or traps related transitions. The properties of these nanocomposites advocate their significant applications as semiconductor based luminescent materials.

Enhanced green and orange photoluminescence of nanostructured CdS in glass nanocomposites by energy transfer From Ho3+ and Eu3+ ions

We report enhanced photoluminescence (PL) of both band edge and trap state emissions in Ho3+ or Eu3+ ion doped CdS (II-VI semiconductor) nanoparticles (NPs) containing glass nanocomposites. These glass nanocomposites were synthesized by the conventional melt-quench technique. The sizes of CdS NPs are found to increase from 5-15 nm to 40-80 nm with the increase in thermal treatment. Band edge emission (green emission, peak around 495 nm) of CdS NPs is controlled by their size and enhanced about three to nine-fold by Ho3+ ions on excitation at 446 nm by a diode laser. Under the same excitation, twelve to fifty-fold enhanced trap state emission (orange and red emissions about 550-900 nm) of CdS NPs is obtained by Eu3+-doping compared to undoped CdS NPs containing glass nanocomposites. The predominant mechanism of PL enhancement is the energy transfer from rare earth ions to CdS NPs. Enhanced PL of these nanocomposites enables their applications in efficient solar concentrators, green and red light emitting component for white light emission devices.

Semiconductor Glass Nanocomposites: Preparation, Properties, and Applications

Abstract In this chapter, the synthesis of semiconductor nanocrystal or quantum dot containing glass nanocomposites, their structural analyses, photoluminescence, and other optical properties are reviewed along with recent findings. The effects of rare earth ions on the luminescence properties of semiconductor glass nanocomposites have also been described. In addition, the theory of quantum confinement effect of semiconductor quantum dots within glass matrix has been discussed. The effect of dielectric medium surrounding the nanocrystals on confinement effect is enlightened. The nonlinear optical properties of different semiconductor containing glass nanocomposites are also assessed. Their applications in the area of solid-state laser, photonic, white light emitting, optoelectronic, and nonlinear devices are discussed.