Aggregated CdS Quantum Dots:  Host of Biomolecular Ligands

Abstract

In this contribution, we have studied structural and photophysical properties of aggregated CdS quantum dots (QDs) capped with 2-mercaptoethanol in aqueous medium. The hydrodynamic diameter of the nanostructures in aqueous solution was found to be ∼160 nm with the dynamic light scattering (DLS) technique, which is in close agreement with atomic force microscopy (AFM) studies (diameter ∼150 nm). However, the UVvis absorption spectroscopy, powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) studies confirm the average particle size (QD) in the nanoaggregate to be 4.0 ( 0.5 nm. The steady-state and time-resolved photoluminescence studies on the QDs further confirm preservation of electronic band structure of the QDs in the nanoaggregate. To study the nature of the nanoaggregate we have used small fluorescent probes, which are widely used as biomolecular ligands (2,6-p-toluidinonaphthalene sulfonate (TNS) and Oxazine 1), and found the pores of the aggregate to be hydrophobic in nature. The significantly large spectral overlap of the host quantum dots (donor) with that of the guest fluorescent probe Oxazine 1 (acceptor) allows us to carry out Förster resonance energy transfer (FRET) studies to estimate average donor-acceptor distance in the nanostructure, found to be ∼25 Å. The quantum dot aggregate and the characterization techniques reported here could have implications in the future application of the QD-nanoaggregate as host of small ligand molecules of biological interest.

Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films

“…The mean lateral sizes deduced from AFM experiment are in the range between 15 and 40 nm and they seem to be larger than the values calculated from the optical absorption and XRD study. This should be attributed to the intrinsic enlarging effect of the microscopic pinpoint to the measured nanoparticles, leading to overestimated dimensions (Shankara Narayanan and Kumar 2006; Nayan et al 2013). It is also expected that XRD measurements offer the size of the crystalline domain which may be encapsulated by a layer of the amorphous material.…”

Investigation of multielemental catalysts based on decreasing the band gap of titania for enhanced visible light photocatalysis

“…There is no shift in the peak position caused by the C-, N-, B-, and F-codoping, suggesting that the dopant ions are uniformly distributed on the TiO 2 surface with keeping the anatase phase under 800°C. [25][26][27]. This suggests that it is difficult for C atoms to penetrate into the TiO 2 lattice and that they most likely exist on the surface of TiO 2 nanoparticles and form a layer composed of carbonate species, resulting in the suppression of crystal growth.…”

A sensitive chemiluminescence method for the determination of cysteine based on silver nanoclusters

“…The study of functional nanomaterials has attracted tremendous attention because of their potential applications in microelectronics, catalysis, molecular recognition, and chemical and biological labels [12][13][14][15]. Traditionally, the investigation of CL phenomenon is limited to certain molecular systems with considerably strong CL emission [16].…”