Sensitive Immunoassay Based on Biocompatible and Robust Silica-Coated Cd-Free InP-Based Quantum Dots

Abstract

Low-toxic InP quantum dots (QDs) as an ideal candidate for Cd-based QDs have tremendous potential for next-generation commercial display and biological detection applications. However, the progress in biological detection is still far behind that of the Cd-based QDs. This is mainly because the InP-based QDs are of inferior stability and photoluminescence quantum yield (PL QY) in aqueous solution. Here, PL QY of 65% and excellent stability of InP/GaP/ZnS QD@SiO2 nanoparticles have been successfully synthesized via a silica coating method. The containing thiol-capped hydrophobic InP/GaP/ZnS QDs were pre-silanized with waterless, ammonia-free hydrolysis tetraethyl orthosilicate, and subsequently, an outer silica shell was generated in the reverse microemulsion. The corresponding QD-based fluorescence-linked immunosorbent assay exhibits a high sensitivity of 0.9 ng mL–1 for C-reactive protein and the broad detection range of 1–1000 ng mL–1, which was close to that of the state-of-the-art Cd-based QD@SiO2 nanoparticles and had the highest sensitivity of Cd-free QDs so far. This work provides a very successful silica coating method for the containing thiol-capped hydrophobic QDs and the QDs highly sensitive to water and oxygen, and the obtained InP/GaP/ZnS QD@SiO2 nanoparticles were considered as the robust, biocompatible, and promising Cd-free fluorescent labels for the further ultra-sensitive detection.

Organic building blocks at inorganic nanomaterial interfaces

“…Other advantages of silica shells include their ability to be easily processed and tailored by controlling their size and porosity over a wide range. [145][146][147][148] The growth of silica shells on NCs has been extensively studied, with two predominant methods emerging: the Sto ¨ber method and the reverse microemulsion method, as shown in Fig. 4.…”

Synthesis and Application of Silica-Coated Quantum Dots in Biomedicine

“…Xu et al [51], for example, fabricated biocompatible and robust InP/GaP/ZnS QD@SiO 2 particles for a sensitive C-reactive protein (CRP) immunoassay. In this study, oleic acid (OA) and 1-octanethiol (OT)-capped hydrophobic InP/GaP/ZnS QDs were pre-silanized with catalytic-free TEOS hydrolysis, and outer SiO 2 shells were generated on the QD surfaces in a reverse microemulsion.…”

Aminophosphate precursors for the synthesis of near‐unity emitting InP quantum dots and their application in liver cancer diagnosis

“…This can be mainly attributed to the surface oxidation which can easily occur as compared to the Cd‐containing counterparts. [ 16–18 ] An effective strategy for improving the stability of InP QDs is to coat a thick large bandgap ZnS shell, which not only isolates the InP core from the environment, but also strongly confines the carriers inside the QDs. [ 19,20 ] Unfortunately, the growth of a thick ZnS shell on the InP cores remains challenging due to the large lattice mismatch (7.7%) between InP (5.87 Å) and ZnS (5.41 Å).…”