High Quantum Yield Water‐Dispersed Near‐Infrared In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots with Robust Stability for Bioimaging

Abstract

noninvasive biomedical images are created through optical and tomographic imaging such as X-ray, positron emission tomography (PET), magnetic resonance imaging (MRI), and computed tomography (CT). [1] These modalities however, depend on the use of heavy doses of ionizing radiation and/or hazardous optical contrast agents such as radioactive 18 F in the form of flurodeoxyglucose for PET, paramagnetic 64 Gd for MRI, and iodine or barium for X-ray and CT scans. [1,2] Even with the use of such harmful radiocontrast agents or ionizing radiation, these present imaging tools are still predominantly limited by their low millimeter spatial and temporal resolution for reconstructing 3D images of biological systems. [1] On the other hand, fluorescence labeling and imaging are not subject to the adverse use of ionizing radiation or radioactive tracing agents that hinder conventional tomographic imaging tools. Furthermore, fluorescent probes afford real-time image acquisition with a vastly improved spatial resolution, all while employing medically-safe visible light, near-infrared (NIR), or infrared (IR) radiation. [3,4] Amongst the different classes of fluorescent probes such as organic molecular dyes, carbon dots, and metallic clusters, colloidal semiconductor quantum dots (QDs) have emerged as promising candidates for clinical applications beyond the laboratory setting. This is due, in part, to their superior optical qualities such as a broad-based absorption spectrum with a large absorption cross-section and high photoluminescence quantum yield (PLQY). [2,5,6] Flexible tuning of QD photoluminescence (PL) to emit from ultraviolet to IR radiation through size and compositional control also realizes the possibility of multiplex detection (through dual PL emissions) and multimodal imaging to combine more than one imaging tool such as MRI and fluorescence optical imaging. [7,8] In particular, tuning the QDs' PL emission to either of the two biological spectral windows (in the NIR from 650-900 nm, or IR from 1000-1350 nm) have facilitated bioimaging with minimal tissue scattering and autofluorescence, accompanied by a significant improvement in imaging depth and spatial resolution as compared to imaging using visible light. [9-11]

Ti3C2Tx MXene Nanosheet-Based Probe for Ion Fluorescence and Visual Detection of Ag+ in Aqueous Solution and Living Cells

“…A series of detection methods have been developed to detect silver ions, such as atomic absorption spectroscopy, inductively coupled plasma–mass spectroscopy, and ion-selective electrodes. , However, these methods mentioned above all require expensive equipment or complex technology. − On this basis, fluorescent probes have become a popular method due to their high sensitivity, rapidity, simple operation, common instruments, and suitability for biological systems. − In the past years, some fluorescent probes for detecting silver ions have been developed, but the following defects are still not solved. − First, some currently reported methods utilize the “silent ion” of silver ions to quench their fluorescence, which is not conducive to high signal output. , Second, the proposed probes only show moderate fluorescence changes, small response range to silver ion concentration, so the sensitivity of these probes is usually not enough to detect low concentrations of silver ions in water samples. , Finally, the probes reported in the literature are difficult to distinguish Ag + from other metal ions (such as Au 3+ ). , Therefore, it is an urgent need to develop a novel fluorescent probe with high sensitivity and selectivity in real samples. − …”

Ultra-Confined Visible-Light-Emitting Colloidal Indium Arsenide Quantum Dots

“…InAs QDs, which have a bulk semiconductor bandgap of 0.35 eV, have played a unique role in near-infrared (NIR) emission and are thus useful for covert illumination, security, motion-sensing, depth-sensing, and bioimaging applications. − We have previously reported the synthesis of giant shell InAs/InP QDs that emit in the NIR window and demonstrated its application in NIR LEDs, in vitro cell imaging, and deep tissue imaging. − It is, in theory, possible to tune the spectral emission of InAs into the visible region through stronger quantum confinement effects to enable broader optical applications, but the realization of few-atom-thick InAs is synthetically challenging, and visible-emitting InAs has not been demonstrated in previous works.…”