Manipulating time-dependent size distribution of sulfur quantum dots and their fluorescence sensing for ascorbic acid

Sulfur quantum dots as sustainable materials for biomedical applications: Current trends and future perspectives

Discovered over a decade ago, sulfur quantum dots (SQDs) have rapidly emerged as a sustainable, safe, and inexpensive quantum material. Sustainably synthesizing SQDs using sublimed sulfur powders, typically produced as waste in industrial petrochemical refining processes, has attracted researchers to use these functional quantum materials in various research fields. SQDs quickly found applications in various research fields, such as electronics, environmental sensing, food packaging, and biomedical engineering. Although low production yields, time-consuming and energy-intensive synthetic methods, and low photoluminescence quantum yield (PLQY) have been some problems, researchers have found ways to improve synthetic methods, develop passivating agents, and systematically modify reaction schemes and energy sources to achieve large-scale synthesis of stable SQDs with high PLQY. Nonetheless, SQDs have succeeded tremendously in biomedical and related applications due to their low toxicity, antibacterial and antioxidant properties, biocompatibility, appropriate cellular uptake, and photoluminescent properties. Although the bioimaging applications of SQDs have been extensively studied, their other reported properties indicate their suitability for use as antimicrobial agents, free radical scavengers, and drug carriers in other biomedical applications, such as tissue regeneration, wound healing, and targeted drug delivery.

Facile synthesis of multicolor emitting sulfur quantum dots and their applications in light blocking field, anti-counterfeiting and sensing

Sulfur quantum dots (SQDs) have aroused widespread interest from researchers in a wide range of fields due to their excellent photoluminescent properties. Ethylenediamine, diaminopropane and butanediamine were used as precursor amine raw materials to interact with sublimated sulfur to synthesize SQDs with blue, cyan and green fluorescence emission, respectively. Multicolour emitting SQDs were first prepared via sulfur-amine interactions. Further characterization and calculations showed that the precursor amine substances could alter growth size and band gap energy of SQDs to allow for a wider absorption and fluorescence transfer to long wavelength emission region, resulting in tunable fluorescence emission. In terms of application, the excellent down-conversion properties of SQDs were utilized to obtain highly transparent and flexible photoblocking films by blending SQDs with polyvinyl alcohol matrixes, achieving a blocking of light in UV region of up to 99.69 %. In addition, we constructed an encoded storage microarray based on standard 8-bit ASCII character binary codes using BSQDs and GSQDs to store and encrypt important information. Finally, GSQDs-based fluorescent sensors were designed to achieve fluorescent trace detection of o-nitrophenols with limits of detection as low as 2.54 μM. The multicolor emitting SQDs prepared in this work have great potential for applications in analytical detection, optical anti-counterfeiting and light blocking.

Shaping Sulfur Precursors to Low Dimensional (0D, 1D and 2D) Sulfur Nanomaterials: Synthesis, Characterization, Mechanism, Functionalization, and Applications

Low-dimensional sulfur nanomaterials featuring with 0D sulfur nanoparticles (SNPs), sulfur nanodots (SNDs) and sulfur quantum dots (SQDs), 1D sulfur nanorods (SNRs), and 2D sulfur nanosheets (SNSs) have emerged as an environmentally friendly, biocompatible class of metal-free nanomaterials, sparking extensive interest in a wide range application. In this review, various synthetic methods, precise characterization, creative formation mechanism, delicate functionalization, and versatile applications of low dimensional sulfur nanomaterials over the last decades are systematically summarized. Initially, it is striven to summarize the progress of low dimensional sulfur nanomaterials from versatile precursors by using different synthetic approaches and various characterization. Then, a multi-faceted proposed formation mechanism with emphasis on how these different precursors produce corresponding SNPs, SNDs, SQDs, SNRs, and SNSs is highlighted. Besides, it is essential to fine-tune the surface functional groups of low dimensional sulfur nanomaterials to form new complex nanomaterials. Finally, these sulfur nanomaterials are being investigated in bio-sensing, bio-imaging, lithium-sulfur batteries, antibacterial activities, plant growth along with future perspective and challenges in emerging fields. The purpose of this review is to tailor low dimensional nanomaterials through accurately selecting precursors or synthetic approach and provide a foundation for the formation of versatile sulfur nanostructure.

One-pot synthesis of robust dendritic sulfur quantum dots for two-photon fluorescence imaging and "off-on" detection of hydroxyl radicals and ascorbic acid

The straightforward preparation of fluorescent sulfur quantum dots (SQDs) with good photostability and biocompatibility and multifunction remains a challenge. Herein, a simple method to improve the performance of SQDs is reported, that is, using hyperbranched polyglycerol (HPG) as a ligand to direct the synthesis of dendritic HPG-SQD nanocomposites from cheap elemental sulfur. Thanks to the protection of HPG, the HPG-SQDs show much better biocompatibility and photostability as compared with the widely reported polyethylene glycol (PEG) ligand-capped SQDs (PEG-SQDs). In addition, the HPG-SQDs also present excellent aqueous solubility, stable fluorescence against environmental variation, good cell uptake capability, and strong single- and two-photon fluorescence. Moreover, the HPG-SQDs display sensitive and selective fluorescence "off-on" behavior to hydroxyl radicals (˙OH) and ascorbic acid (AA), respectively, and thereby hold potential as a fluorescent switch to detect ˙OH and AA. For the first time, the utilization of two-photon fluorescence of HPG-SQDs to monitor ˙OH and AA in cells is demonstrated in this study.