A5057451986- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Perovskite Materials and Applications
- Electrochemical Analysis and Applications
- TiO2 Photocatalysis and Solar Cells
- Semiconductor Quantum Structures and Devices
- Photochemistry and Electron Transfer Studies
- Spectroscopy and Quantum Chemical Studies
- Advanced Photocatalysis Techniques
- Electrochemical sensors and biosensors
- Optical properties and cooling technologies in crystalline materials
- Solid-state spectroscopy and crystallography
- Non-Destructive Testing Techniques
- Nanocluster Synthesis and Applications
- Integrated Circuits and Semiconductor Failure Analysis
- Copper-based nanomaterials and applications
- Molecular Junctions and Nanostructures
- Gold and Silver Nanoparticles Synthesis and Applications
- Electronic and Structural Properties of Oxides
- Advanced Surface Polishing Techniques
- Graphene research and applications
Bhabha Atomic Research Centre
2009-2021
Bhabha Atomic Research Center Hospital
2009-2010
We are reporting ultrafast charge carrier and transfer dynamics of the CdTe quantum dot (QD) type II CdTe/CdS core−shell QD materials with different shell (CdS) thicknesses. Herein, we have synthesized dots by using 3-mercaptopropionic acid as a capping agent. Steady state absorption emission studies confirmed successful synthesis materials. Time-resolved indicate longer lifetime compared to materials, where in both cases only gets excited. carried out femtosecond transient these exciting...
We have employed ultrafast optical pump–probe spectroscopy to study excited dynamics of graphene oxide (GO) and reduced (RGO) dispersed in water by exciting the samples at 400 nm laser light. observed multiexponential relaxation nonequilibrium photogenerated carriers for both GO RGO with time constants varying from 0.8 >400 ps. Our analysis on charge revealed involvement phonon trap states dynamics. Transient absorption visible region longer scale is attributed mainly due electron which been...
Nanodendrites of silver were synthesized by electrodeposition using AgNO3 as the source in ammoniacal solution. The method was remarkably fast, simple and scalable. X-ray diffraction (XRD) studies confirmed formation a cubic phase silver. Scanning electron microscopy (SEM) revealed well-shaped dendrites. nanodendrites hyperbranched with lengths order few micrometres. concentration NH3 electrolyte solution found to have remarkable influence on morphology, crystallite size branched...
Femtosecond time-resolved absorption and picosecond emission studies have been carried out to study the indirect type exciton of CdS/ZnSe core/shell quantum dots (QDs). The QD samples are synthesized with increasing thickness ZnSe shell on CdS core QDs. In these samples, a new energy band lower than gap both has observed attributed bandgap transitions from valence conduction core. transient PL revealed that exciton, e(CdS)/h(ZnSe) due photoexcitation this low-energy band, endures less...
We report the ultrafast charge carrier relaxation dynamics of mercaptopropionic acid capped CdTe quantum dot (QD) using femtosecond transient absorption spectroscopy by exciting particles with 400 nm laser light and monitoring transients in visible to near IR region. Cooling population different quantized states carriers were monitored following growth kinetics bleach at excitonic positions. The cooling time second first found be 150 fs 500 fs, respectively, which increases non-linearly its...
We report synthesis and ultrafast charge transfer dynamics of photoexcited CdTe quantum dots (QDs) decorated on graphene. have synthesized QD particles 2.2 nm sizes with first exciton (1S3/2-1Se) band ∼450 then the graphene which has been confirmed by HRTEM studies. The named as G-CdTe. Steady state emission studies revealed that surface gets quenched drastically indicates from to To unravel in time scale we carried out femtosecond transient absorption exciting monitoring transients visible...
We have synthesized thiol-capped CdSe/ZnTe quantum dot core−shell nanostructures by colloidal methods, characterized them steady-state absorption and photoluminescence (PL) spectroscopy further confirmed high resolution transmission electron microscopy X-ray diffraction measurements. Clear red shift on shell formation was observed in optical studies. Time-resolved emission studies indicate longer lifetime of as compared to CdSe QD material where both cases only gets excited, which indicates...
We have investigated the interfacial electron-transfer dynamics in ultrasmall TiO2 nanoparticles sensitized by alizarin using a femtosecond transient absorption technique. Electron injection has been confirmed direct detection of electron conduction band and cation radical adsorbed dye as monitored spectroscopy visible near-IR region. The event was followed monitoring formation at 550 nm also 900 nm, which revealed multiexponential with time constants 100 fs 17 50 ps. This observation...
We have synthesized CdTe/ZnTe type II core–shell quantum dots at lower temperature by using 3-mercaptopropionic acid (SHCH2CH2COOH, thiol) as a capping agent, and they are characterized steady-state absorption, emission studies, high-resolution transmission electron microscopy. observed red shift in optical absorption spectra with the increase ZnTe shell thickness. Time-resolved studies indicate longer average lifetime for QDs compared that CdTe QDs. Femtosecond transient spectroscopy was...
We have employed femtosecond transient absorption spectroscopy in enediol-TiO2 systems (catechol, resorcinol, and quinol) to understand localized vs delocalized interfacial electron transfer dynamics dye-nanoparticle systems. Optical studies confirmed the formation of a charge (CT) complex between enediols TiO2 nanoparticles. CT interaction was found be decreased from catechol resorcinol quinol. The decrease strength quinol explained on basis reduced overlap HOMO enediol conduction band...
We report the synthesis, structural characterisation and charge separation behaviour in an interface graded Type II CdSe–CdTe core–shell nanostructure. The gradation was accomplished by use of two layers consisting alloyed composition with increasing Te between CdSe core finally a CdTe shell grown successive ionic layer adsorption reaction (SILAR) method. effect analysed steady state UV-Vis absorption, photoluminescence (PL) spectroscopy, time-resolved luminescence femtosecond transient...
Dye-sensitized quantum dots (QDs) are promising candidates for dye-sensitized solar cells (DSSCs). Here, we report steady state (absorption and photoluminescence) optical measurements on several sizes of CdS QDs ligated with Coumarin 343 dye (C-343) two different solvents, viz., chloroform toluene. We further detailed first principles density functional theory time-dependent studies the geometric, electronic emission) properties three sized capped QDs, C-343 dye. The absorption spectrum...
Femtosecond pump–probe spectroscopic studies on a series of newly synthesized resorcinol-based Ru(II) and Re(I) complexes oleic acid capped TiO2 nanoparticles have been carried out in chloroform, the results are compared with those catechol analogues. The ruthenium complex shows biexponential injection; second component arises due to injection from thermally equilibrated 3MLCT states as result weaker strength resorcinolate binding. Also, comparison binding, greater diffusion injected...
We have demonstrated optical and photophysical properties of newly synthesized ultrasmall TiO2nanoparticles. The particles are by arrested precipitation method in trioctylphosphine oxide (TOPO) benzophenone as the capping agent also solvent at high temperature Ar atmosphere. High-resolution TEM XRD measurements revealed that size range 3.3–3.5 nm. Optical absorption spectra these show large blue shift indicating a quantum confinement effect. highly luminescent, which is very unusual for an...
The synthesis of two new ruthenium(II)- and osmium(II)-polypyridyl complexes 3 4, respectively, with resorcinol as the enediol anchoring moiety, is described. Steady-state photochemical electrochemical studies sensitizer dyes confirm strong binding to TiO2 in water. Femtosecond transient absorption have been carried out on dye-TiO2 systems water reveal <120 fs 1.5 ps electron injection times along 30% slower back transfer time for ruthenium complex 3. However, corresponding osmium 4 shows...
Abstract Herein, we report the synthesis of aqueous CdTe/CdSe type‐II core–shell quantum dots (QDs) in which 3‐mercaptopropionic acid is used as capping agent. The CdTe QDs and are characterized by X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR‐TEM), steady‐state absorption, emission spectroscopy. A red shift absorption bands observed with increasing CdSe shell thickness over QDs. XRD pattern indicates that peaks shifted to higher angles after growth on HR‐TEM...
Water soluble cubic ZnS nanoparticles (NPs) have been synthesized at room temperature by using 3-mercaptopropionic acid (MPA) as a modifier molecule and characterized X-ray diffraction (XRD), steady-state absorption, emission spectroscopy. Electron transfer (ET) dynamics carried out in semiconductor quinizarin (Qz) molecules studied picosecond time-resolved fluorescence We proposed that electron injection takes place from photoexcited Qz into the surface states of wide band gap NPs. revealed...
Thiol-capped type I CdSe/ZnS core–shell quantum dot nanostructures have been synthesized at low temperature in water; and then characterized by steady-state absorption photoluminescence (PL) studies high resolution TEM (HRTEM) measurements. On excitation of CdSe predominantly surface state emission was detected, however on ZnS shell formation prominent exciton with much higher overall yield observed. Femtosecond up-conversion measurements reveal that found to decay faster as compared...
The possibility of exciton delocalization in alkyldithiocarbamate (ATC)-capped CdSe has been investigated for several alkyl groups and compared with phenyldithiocarbamates (PTCs). We find a bathochromic shift ATC similar to the one obtained PTC. Our computational studies show reduction HOMO-LUMO gaps both PTC ATC, albeit lower shift. However, TDDFT revealed that ATC-capped is more localized HOMO state as partly delocalized PTC-capped CdSe, hinting at difference electronic interaction between...