Low‐Cost Water Soluble Silicon Quantum Dots and Biocompatible Fluorescent Composite Films

Abstract

Si-QDs are ultrasmall crystals with the size of only a few nanometers. [10] Based on the original properties of silicon materials, they also possess the unique fluorescence properties of QDs. Compared with traditional organic fluorescent materials, these quantum dots have good electronic properties, large surface-to-volume ratio, [11][12][13] size-dependent and tunable fluorescence emission, increased interband transition probability and high stability for photobleaching, [14][15][16] which make them potential options for the next generation optoelectronic devices, solar cells, and fluorescent biological imaging/sensing reagents. [17,18] In addition, luminescent silicon nanoparticles are chemically engineered to become specific probes to accumulation at sites of interest for labeling and imaging. [19] Generally speaking from the synthesis principle, [20][21][22] there are three classes of methods for manufacturing Si-QDs, such as the top-down methods, the bottom-up methods, and a combination of both. As the name suggests, the top-down method is the decomposition of large pieces of silicon into small nanocrystals. [23] The most common method is based on acid-based etching or electrochemical potential, the advantage of which is that these methods provide good color adjustability by controlling the particle size. In contrast, the bottom-up method uses the principle of self-assembly to construct nanocrystals from smaller chemical components. The construction process of this method is similar to that of traditional quantum dot manufacturing technology and the process is relatively mature. It is worth mentioning that since Raj and his colleagues first reported the synthesis of thiol-terminated cadmium telluride quantum dots in aqueous solution in 1993, most of the work on the synthesis of quantum dots has focused on environmentally friendly, and low-cost methods, which can be directly applied to the hydrothermal method for biological research. [24] Recently, research work on fluorescent polymers such as quantum dots has focused on encapsulating fluorescent materials and realizing their fictionalization and device application. [25,26] Quantum dots can be compounded with other polymers with special functions to form a new type of material. This way of combining the two through physical or chemical means endows the composite material with excellent performance, attracting worldwide attention. So far, there has been much research on semiconductor quantum dots and functional polymer composite materials. These reports also demonstrate great application potential in the fields of photoelectric Silicon quantum dots (Si-QDs) with the advantages of excellent biocompatibility, rich sources of raw materials, and low synthesis cost, are attracting enormous attention as ideal candidates for replacing existing semiconductor quantum dot products. The water-soluble fluorescent Si-QDs and the Si-QDs/Chitosan composite material are successfully prepared here by combined microwave-assisted and traditional one-step hydrothermal synthesis u...

Poly(vinyl alcohol)-Modified Colloidal Silicon Nanoparticles for Flexible Screen Printing Inks and Anticounterfeiting Applications

“…Figure S2 illustrates that the absorption peak at about 265 nm gradually decreases with the increase in the reaction time, attributed to the n → π* transition on the surface of the nanoparticle. Notably, there was no distinct absorption peak in the 300–500 nm range, and the absorption intensity decreases with the increase of wavelength, characteristic of a semiconductor’s indirect band gap transition . In subsequent experiments, we found that the PL spectrum of Si NPs solution showed a blue shift after 5 days of storage (Figure S3).…”

“…Notably, there was no distinct absorption peak in the 300−500 nm range, and the absorption intensity decreases with the increase of wavelength, characteristic of a semiconductor's indirect band gap transition. 52 In subsequent experiments, we found that the PL spectrum of Si NPs solution showed a blue shift after 5 days of storage (Figure S3). The literature suggests that the reduction in Si NPs size due to oxidation leads to a blue shift in the luminescence peak position.…”

“…50,51 However, some reports propose that characteristic luminescence behavior is related to the nitrogen doping effect. 38,52,53 To explore this, TEM tests were conducted on Si NPs prepared at different reaction times. It is evident that the crystal size of Si NPs remains relatively unchanged but noticeable aggregation occurs (Figure S4).…”

“…In subsequent experiments, we found that the PL spectrum of Si NPs solution showed a blue shift after 5 days of storage (Figure S3). The literature suggests that the reduction in Si NPs size due to oxidation leads to a blue shift in the luminescence peak position. , However, some reports propose that characteristic luminescence behavior is related to the nitrogen doping effect. ,, To explore this, TEM tests were conducted on Si NPs prepared at different reaction times. It is evident that the crystal size of Si NPs remains relatively unchanged but noticeable aggregation occurs (Figure S4).…”

A Review of Selenium (Se) Nanoparticles: From Synthesis to Applications

“…on carbon, [50][51][52] silicon, [53,54] and sulfur nanoparticles. [55][56][57] Recently, small-sized SeNPs have emerged as a new class of fluorescent nanomaterial and have gained researchers' attention.…”