Enhanced photoluminescence stability of CdS nanocrystals through a zinc acetate reagent

Full-Spectrum InP-Based Quantum Dots with Near-Unity Photoluminescence Quantum Efficiency

Photoluminescent color conversion by quantum dots (QDs) makes possible the formation of spectrum-on-demand light sources by combining blue LEDs with the light generated by a specific blend of QDs. Such applications, however, require a near-unity photoluminescence quantum efficiency since self-absorption magnifies disproportionally the impact of photon losses on the overall conversion efficiency. Here, we present a synthesis protocol for forming InP-based QDs with +90% quantum efficiency across the full visible spectrum from blue/cyan to red. The central features of our approach are as follows: (1) the formation of InP core QDs through one-batch-one-size reactions based on aminophosphine as the phosphorus precursor, (2) the introduction of a core/shell/shell InP/Zn(Se,S)/ZnS structure, and (3) the use of specific interfacial treatments, most notably the saturation of the ZnSe surface with zinc acetate prior to ZnS shell growth. Moreover, we adapted the composition of the Zn(Se,S) inner shell to attain the intended emission color while minimizing line broadening induced by the InP/ZnS lattice mismatch. The protocol is established by analysis of the QD composition and structure using multiple techniques, including solid-state nuclear magnetic resonance spectroscopy and Raman spectroscopy, and verified for reproducibility by having different researchers execute the same protocol. The realization of full-spectrum, +90% quantum efficiency will strongly facilitate research into light-matter interaction in general and luminescent color conversion in particular through InP-based QDs.

Quantitative comparison of luminescence probes for biomedical applications

Optical imaging holds great promise for the early-stage detection of diseases. It plays an important role in the process of protecting the patient's health. Most of the organic dyes suffer due to photobleaching, light scattering, short light penetration depth, and autofluorescence of specimen, thus, need to be replaced with alternative nanoprobes emitting light in the optical biological window (700-1350 nm). The group of candidates which can challenged described problems are colloidal quantum dots (e.g. CdSe and PbS) and upconverting nanocrystals (e.g. NaGdF₄:Er, Yb). This paper presents comprehensive and systematic studies of the aforementioned probes, using specially designed tissue phantom, and custom-built wide-field fluorescence microscope. We investigated how the absorption and scattering of light at the water, hemoglobin, and intralipid may affect the intensity of luminescence probes and the quality of optical images. We propose a protocol, that could be easily implemented for investigating other nanoprobes that allow for comparison of their optical performance.

CdS Dots, Rods and Platelets-How to Obtain Predefined Shapes in a One-Pot Synthesis of Nanoparticles

In recent years, numerous protocols for nanoplatelet synthesis have been developed. Here, we present a facile, one-pot method for controlling cadmium sulfide (CdS) nanoparticles' shape that allows for obtaining zero-dimensional, one-dimensional, or two-dimensional structures. The proposed synthesis protocol is a simple heating-up approach and does not involve any inconvenient steps such as injection and/or pouring the precursors at elevated temperatures. Because of this, the synthesis protocol is highly repeatable. A gradual increase in the zinc acetate concentration causes the particles' shape to undergo a transition from isotropic quantum dots through rods to highly anisotropic nanoplatelets. We identified conditions at which synthesized platelets were purely five monolayers thick. All samples acquired during different stages of the reaction were characterized via optical spectroscopy, which allowed for the identification of the presence of high-temperature, magic-size clusters prior to the platelets' formation.

A two-target responsive reversible ratiometric pH nanoprobe: a white light emitting quantum dot complex

Ratiometric pH sensing in the physiological range of pH 6.5–10.3 by a white light emitting quantum dot complex – following the changes in luminescence intensity ratio, color and chromaticity – is described herein.