Water-soluble Silicon Quantum Dots Research Articles

Fabrication of silicon quantum dots-methyl viologen nanohybrids: Turn-On-Off-On fluorescence nanoprobe for the detection of d-penicillamine

This study provides a straightforward, one-step hydrothermal approach for synthesizing water-soluble silicon quantum dots (SiQDs). The surface of the synthesized SiQDs is modified by the carboxylic acid functional group (A:SiQDs) after succinic anhydride treatment. The modified A:SiQDs, which emitted blue light fluorescence, showed high stability against photobleaching, thermal stability, and good water solubility. The A:SiQDs are conjugated with methyl viologen (MV2+) to develop a nanohybrid for specific D-Penicillamine (D-PA) detection with an LOD of 8 nM. The suggested sensor was effectively used to analyze D-PA in commercial pharmaceutical formulations using the conventional addition method, and it produced results with good accuracy and precision that were nearly equal to those measured.

Preparation of water-soluble silicon quantum dots and their optical property

Preparation of water-soluble silicon quantum dots and their optical property

Luminescent, protein-binding and imaging properties of hyper-stable water-soluble silicon quantum dots

Silicon quantum dots (SiQDs) bear the advantages of photostability and biocompatibility, but their synthesis and purification are relatively complex, and explorations on their protein-binding behaviors are very limited. Herein, water-soluble amino-terminated SiQDs were firstly synthesized in the absence of any extra reductants or catalysts. The absorption of synthesized SiQDs covered the entire UV band with the maximum absorption wavelength around 290 nm. Both their powder and solution emitted strong blue fluorescence when excited by UV light of 365 nm. The luminescent property of SiQDS aqueous solution was stable under broad regions of acidity (pH 1–12) and temperature (0–80 °C), which was also not affected by proteins. The SiQDs could bind with human serum albumin (HSA) through hydrogen bonds, which made fluorescence resonance energy transfer and quenching occur. The interaction mechanisms were analyzed through fluorescence lifetime decay curves, UV spectra, thermodynamics, and molecular surface modeling. The structural alterations were systematically deciphered by 3D fluorescence and circular dichroism spectra. Meanwhile, the cytotoxicity and cell fluorescence imaging performance were investigated using human cervical carcinoma cell lines (HeLa). The results suggested an exciting prospect of as-synthesized SiQDs in fluorescence imaging and related biomedical applications.

Nano-Bio Interaction between Blood Plasma Proteins and Water-Soluble Silicon Quantum Dots with Enabled Cellular Uptake and Minimal Cytotoxicity.

A better understanding of the compatibility of water-soluble semiconductor quantum dots (QDs) upon contact with the bloodstream is important for biological applications, including biomarkers working in the first therapeutic spectral window for deep tissue imaging. Herein, we investigated the conformational changes of blood plasma proteins during the interaction with near-infrared light-emitting nanoparticles, consisting of Pluronic F127 shells and cores comprised of assembled silicon QDs terminated with decane monolayers. Albumin and transferrin have high quenching constants and form a hard protein corona on the nanoparticle. In contrast, fibrinogen has low quenching constants and forms a soft protein corona. A circular dichroism (CD) spectrometric study investigates changes in the protein’s secondary and tertiary structures with incremental changes in the nanoparticle concentrations. As expected, the addition of nanoparticles causes the denaturation of the plasma proteins. However, it is noteworthy that the conformational recovery phenomena are observed for fibrinogen and transferrin, suggesting that the nanoparticle does not influence the ordered structure of proteins in the bloodstream. In addition, we observed enabled cellular uptake (NIH3T3 Fibroblasts) and minimal cytotoxicity using different cell lines (HeLa, A549, and NIH3T3). This study offers a basis to design QDs without altering the biomacromolecule’s original conformation with enabled cellular uptake with minimal cytotoxicity.

Water Soluble Silicon Quantum Dots Grafted with Amoxicillin as a Drug Delivery System.

Water soluble silicon quantum dots (Si QDs) are prepared and used for the measurement of the efficiency for the controlled release drug delivery. Amoxicillin, antibiotics, is covalently grafted with Si QDs through a surface derivatization reaction. Si QDs are embedded in hydrogel polymer. The release of amoxicillin has been measured by using Ultra violet-visible (UV-vis) absorption spectrometer. Amoxicillin-embedded hydrogels exhibit a burst release for 1 h, however covalently loaded Amoxi-Si QDs hydrogel composite exhibited very slow release. Absorption analysis reveals that the Si QDs exhibits a great potential candidate for controlled release of drug. The controlled drugrelease profiles depend on the hydrolysis of amoxicillin from the surface of Si QDs.

Amplified light harvesting for enhancing Italian lettuce photosynthesis using water soluble silicon quantum dots as artificial antennas.

Maximizing the utilization of the ultraviolet portion in the solar radiation spectrum has always been a goal for plant growth in order to minimize the harm and harvest the benefits. For this reason, fluorescent, amine-functionalized, and water-soluble silicon quantum dots (SiQDs) were fabricated with a mono-dispersed size of 2.4 nm. The SiQDs were used as artificial antennas to amplify the light harvesting ability and consequently enhance the photosynthesis in Italian lettuce. Upon ultraviolet excitation, the intense blue emission from the quantum dots matched very well to the absorption of the chloroplasts, allowing for the ultraviolet portion in solar radiation to be effectively utilized. The consumed optical energy enhanced the photosystem II activity, which made the amplification of photosynthesis possible. More importantly, in vivo, the quantum dots significantly promoted Italian lettuce seedling growth at concentrations below 30 mg L-1 on the root length, seedling height, and biomass by increasing the soluble sugar and water content by 49.8% and 40.9%, respectively. Interestingly, the chlorophyll a and b content increased to 41.0 and 114.8%, respectively, with no inhibition, even at the highest dose of 200 mg L-1. This study provides a new perspective on the use of quantum dots to amplify the utilization of ultraviolet light in agriculture.

Water-dispersed silicon quantum dots for on-off-on fluorometric determination of chromium(VI) and ascorbic acid.

Water-dispersed silicon quantum dots (SiQDs) with the quantum yield of 25% was prepared using aminopropyltrimethoxysilane as the silicon source and ascorbic acid (AA) as the reduction reagent. The SiQDs display blue fluorescence with excitation/emission peaks at 350nm/440nm. The synthesized SiQDs are shown to be a viable "on-off-on" fluorescent probe for the detection of Cr(VI) and AA. Cr(VI) ions exert an inner filter effect on the fluorescence of the SiQDs which results in a reduction of fluorescence (off-state). On addition of AA, Cr(VI) is chemically reduced to Cr(III) which weakens the inner filter effect and restores fluorescence (on-state). The method has low detection limits for both Cr(VI) and AA (0.16μM and 0.57μM, respectively). It was applied to the analysis of spiked lotus seeds and human serum samples. Graphical abstract A simple and facile "on-off-on" fluorometric method for Cr(VI) and ascorbic acid (AA) was developed using water-soluble silicon quantum dots (SiQDs) as the fluorescent probe. The approach was also used to assay Cr(VI) and AA in the lotus seeds and human serum, respectively.

Nonlinear Doping, Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis**Supported by the National Natural Science Foundation of China under Grant No 61575216.

A series of boron- and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals (nc-Si) by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be <5 nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence (PL) intensity evolution. The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.

Silicon quantum dots delivered phthalocyanine for fluorescence guided photodynamic therapy of tumor**Project supported by the National Natural Science Foundation of China (Grant Nos. 21374074, 21422404, and U1532108) and the Undergraduate Training Program for Innovation and Entrepreneurship of Soochow University, China (Grant No. 2016xj010).

Imaging-guided cancer therapy provides a simultaneous tumor imaging and treatment, which helps to eliminate the excessive toxicity to the healthy tissues. For this purpose, multifunctional probes capable of both imaging and curing are needed. In this work, we synthesize water-soluble silicon quantum dots (Si QDs) smaller than 5 nm. Such Si QDs are used for delivering the hydrophobic drug phthalocyanine (Pc). The as-prepared Si/Pc nanocomposite particles show efficient transmembrane delivery into cells and feasible biocompatibility. Moreover, these composite particles emit dual-channel fluorescence signals even after cellular internalization and demonstrate robust photostability in the Si channel. More interestingly, the Si/Pc composite particles show efficient photodynamic therapy effects against tumors both in vitro and in vivo.

(Invited) Plasma-Liquid Interactions for Nanoparticle Synthesis, Functionalization and Biomedical Interactions

Non-equilibrium atmospheric pressure plasmas interacting with liquids offer a unique source of highly reactive chemistry beneficial for many applications in biology, medicine and advanced materials manufacturing. Plasma-liquid interactions can involve synthesis of nanoparticles (NPs) and inactivation of pathogens. While the underlying mechanisms of these processes are poorly understood, the application potential is enormous. The presentation will highlight some examples of reaction pathways responsible for the synthesis of AgNPs at the plasma-liquid interface. This will include a detailed analysis of the reduction mechanism of Ag+, the initial step for the formation of NPs in solution, through various mechanisms proposed in literature including solvated electrons, UV photons and hydrogen atoms. Plasmas are typically oxidizing and not reducing environments as they produce an abundant source of reactive oxygen species (ROS). We will present the possibility of using these ROS for the functionalization of NPs and in particular the generation of luminescent and hydrophobic water-soluble silicon quantum dots. In addition, we will discuss the importance of these ROS in the inactivation of pathogens in solutions. We will conclude with an overview of the challenges and opportunities ahead.

The preparation of high-quality water-soluble silicon quantum dots and their application in the detection of formaldehyde

This paper reports the synthesis of water-soluble fluorescence silicon quantum dots (Si QDs) through a hydrothermal route with urea propyl triethoxysilane (UPTES) as the source of silicon and sodium citrate as the deoxidizer.

Water-Soluble Silicon Quantum Dots with Quasi-Blue Emission.

In this study, water-soluble silicon quantum dots have quasi-blue emission at 390 nm by being capped with 1-vinylimidazole in resese micelles. As-obtained silicon quantum dots have a diameter of 2~5 nm and high crystallinity. The quasi-blue emission of the silicon quantum dots is likely attributed to the polarity of the capping ligands. Moreover, the silicon quantum dots are water-soluble and have photoluminescence nanosecond decay time, suggesting their potential application in biological field.

Preparation, cytotoxicity and in vivo bioimaging of highly luminescent water-soluble silicon quantum dots

Designing various inorganic nanomaterials that are cost effective, water soluble, optically photostable, highly fluorescent and biocompatible for bioimaging applications is a challenging task. Similar to semiconducting quantum dots (QDs), silicon QDs are another alternative and are highly fluorescent, but non-water soluble. Several surface modification strategies were adopted to make them water soluble. However, the photoluminescence of Si QDs was seriously quenched in the aqueous environment. In this report, highly luminescent, water-dispersible, blue- and green-emitting Si QDs were prepared with good photostability. In vitro studies in monocytes reveal that Si QDs exhibit good biocompatibility and excellent distribution throughout the cytoplasm region, along with the significant fraction translocated into the nucleus. The in vivo zebrafish studies also reveal that Si QDs can be evenly distributed in the yolk-sac region. Overall, our results demonstrate the applicability of water-soluble and highly fluorescent Si QDs as excellent in vitro and in vivo bioimaging probes.

Versatile “Click Chemistry” Approach to Functionalizing Silicon Quantum Dots: Applications toward Fluorescent Cellular Imaging

In this study, we describe a solution procedure for the preparation and surface modification of photostable colloidal silicon quantum dots (SiQDs) for imaging of cancer cells. Photoluminescent SiQDs were synthesized by reduction of halogenated silane precursors using a microemulsion process. It was shown that 1,8-nonadiyne molecules could be grafted onto the surface of hydrogen-terminated SiQDs via ultraviolet (UV)-promoted hydrosilylation, demonstrated by Fourier transform infrared spectroscopy (FTIR) measurements. In addition, various azide molecules were coupled onto nonadiyne-functionalized particles, rendering particles dispersible in selected polar and nonpolar solvents. The photoluminescence of functionalized SiQDs was stable against photobleaching and did not vary appreciably within biologically applicable pH and temperature ranges. To demonstrate compatibility with biological systems, water-soluble SiQDs were used for fluorescent imaging of HeLa cells. In addition, the SiQDs were shown to be non-cytotoxic at concentrations up to 240 μg/mL. The results presented herein provide good evidence for the versatility of functionalized SiQDs for fluorescent bioimaging application.