(Invited) Highly Emissive CdTe Quantum Dots Passivated with Novel Branched Ligands as Fluorescent Sensors

Abstract

Fluorescent-based sensors attract enormous attention due to their facile nature, simplicity, superior selectivity and sensitivity, and better reproducibility and reliability. The sensing parameters, such as detection limit, dynamic range, and the possibility for multiplexed detection, rely hugely on the physicochemical properties of the fluorophore used. Therefore, the choice and rational design of fluorescent probes demand considerable attention. The growing interest in highly fluorescent semiconductor quantum dots as sensors or imaging probes is evident from the numerous reports available in the literature. Unlike conventional organic dyes, novel fluorescent quantum dots-inorganic nanocrystals have manifold advantages. QDs have symmetric and narrow emission profiles, high absorption efficiency in the UV region, high quantum yields, especially in the NIR region, exorbitant photo and temporal stability, and shallow photo-bleaching effect. The optical properties of QDs are primarily defined by the nature of constituent materials, size and shape, surface chemistry, and the nature of dangling bonds. The applicability of CdTe QDs was limited in the biological realm mainly due to the highly toxic nature of its constituent materials. The use of benign ligands is one procedure to be adopted to overcome this impediment. Also, the stability of the QDs warrants the limited bleaching of the material. The aqueous solubility of the material is another requirement to be satisfied. The functional groups in ligands also play a significant role in determining the stability of QDs and the utility of the QDs synthesized, as it can advocate the possibility of reactions and recognition of suitable analytes in sensing schemes. This talk will discuss the choice of organic ligands with side methyl chains that can supplement or be used in alternatives to the existing ligands for synthesizing QDs. We have employed easy and facile colloidal synthetic procedures for an extended period for manipulating the size of QDs formed, which can be further implemented for the sensing of various analytes. The side methyl chain added several benefits for the QDs synthesis, such as providing better stability of the QDs and in the sensing scenario.