Nanotubes with hybrid CdTe nanocrystals: Fabrication, property, and surface functional decoration for bioapplications

Abstract

We have demonstrated a two-step synthesis for preparing morphology- and luminescence-tunable fibers that uses green-emitting CdTe nanocrystals (NCs), Cd²⁺, thioglycolic acid (TGA), and tetraethyl orthosilicate (TEOS). Hybrid CdTe NCs consisted of a CdTe core and CdS-like clusters in the fibers were created during the synthesis. The CdTe NCs were first coated with a very thin SiO₂ shell containing Cd²⁺ and TGA molecules in an alkaline condition. The SiO₂-coated CdTe NCs were assembled together with Cd–TGA clusters for the formation of the fibers. A subsequent reflux process enabled the creation of fibers and caused the formation of CdS-like clusters in the vicinity of CdTe NCs in the fibers. Because of these clusters closed to the CdTe NCs, their effective size increases to reduce the quantum size effect. This special core-shell structure was found to have extraordinary properties: a narrowed photoluminescence (PL) spectrum, a red-shifted PL peak, and a high PL efficiency. The morphology of the fibers (tubal and solid) depends on the concentrations of TGA, Cd²⁺ ions, and TEOS in the precursor solution together with the concentration of CdTe NCs in a subsequent reflux. These fibers, especially for nanotubes, exhibited not only a tunable morphology and emitting color but also a functional surface, making them well suited for a variety of applications, such as bio-probing and drug delivery. The nanotubes were conjugated with immunoglobulin G (IgG) by using a zero-length cross linker because of carboxyl groups on their surface. The SiO₂ component in the nanotubes enables bio-conjugation with IgG through other functional groups, making these nanotubes amenable for bioapplications.