Surfactant-dependent photoluminescence of CdTe/CdS nanocrystals

Abstract

The photoluminescence of aqueously synthesised core/shell CdTe/ CdS quantum dots (QDs) was investigated. Two molar ratios (2.4 and 1.3) of thioglycolic acid (TGA) to Cd 2C were compared to determine the best synthesis conditions for high photoluminescent quantum yield (PLQY) and photostability. A difference in the PLQY of the CdTe/CdS QDs was observed when CdS shells were grown with different TGA/Cd 2C ratios. The difference in the observed PLQY was attributed to the quality of the passivation of the CdTe during the CdS shell growth. At TGA/Cd 2C ratio of 1.3, the CdS shell forms through homogeneous nucleation, which is limited by diffusion of growth material from the solution onto the QDs surface. Due to the lattice mismatch of CdTe and CdS, the core will experience coherence strain resulting in dislocation sites and surface defects between nucleation sites which can result in non-radiative trap states. When the TGA/Cd 2C ratio is 2.0, the CdS shell grows epitaxially, minimising the number of surface trap states. Finally, we observed that the fluorescence intermittency was supressed for CdTe QDs after UV light illumination, attributed to annealing of deep surface trap states by UV light.

A glass matrices-assisted quantum dots-based biosensor for selective capturing and detection ofEscherichia coli

“…The modified QDs, nevertheless, were found to retain substantial fluorescent properties (Supplementary Figure S3(a, b)). Furthermore, the mean quantum yield of conjugated QDs relative to that of non-conjugated ones was about 62%, suggesting substantial retention in the fluorescent characteristics of the QDs, even after bioconjugation (Ferrari & Bergquist 2007;Virzbickas et al 2017).…”

“…The quantum yield of the hydrophilic QDs was computed using Rhodamine 6G, as per a previously reported procedure (Grabolle et al 2009). Rhodamine 6G was dissolved in absolute ethanol as the reference standard (quantum yield 100%, concentration 31 nmol mL À1 ) (Virzbickas et al 2017). The relative quantum yield of the QDs was calculated using Equation (3).…”

Design and Construction of Fluorescent Cellulose Nanocrystals for Biomedical Applications

“…[94,95] Therefore, nonradiative exciton recombination is predominant in the QDs prepared under low temperature. [96] Practically, the weak fluorescence intensity of fluorescent CNCs possibly gives rise to unsatisfying signal-to-noise ratios in fluorescent sensing/labeling/imaging applications. For the second, biocompatibility of the fluorescent CNCs is negatively affected due to the introductions of heavy metal ions, cadmium in particular.…”

Screening and characterisation of CdTe/CdS quantum dot-binding peptides for material surface functionalisation

“…TGA-capped CdTe/CdS core/shell QDs were prepared with a similar method to an earlier work. 25 The CdTe core was grown by reuxing a solution of Cd(ClO 4 ) 2 and TGA (molar ratio of 1 : 1.3), which was introduced with H 2 Te gas and deoxygenated by N 2 gas, at 100 C for 2 h. To grow the CdS core, thiourea (CH 4 N 2 S) was added to the core QD dispersion before the mixture was further reuxed overnight. QDs were cleaned by adding two parts of isopropanol to one part aqueous QD solution and agitating.…”

“…23,24 Since CdTe/CdS core/shell QDs with high quantum yield can be aqueously synthesised, this QD type is one of the widely used QDs for biological uorescence probes. 25 Despite its potent material, no peptide binders to CdTe/CdS QDs have been reported up to date.…”