A New Solution Route to Hydrogen Terminated Silicon Nanoparticles: Synthesis, Functionalization, and Water Stability.
Ontology highlight
ABSTRACT:
SUBMITTER: Zhang X
PROVIDER: S-EPMC4144428 | biostudies-literature | 2007 Jan
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Silicon nanoparticles (Si NPs) are highly attractive materials for typical quantum dots functions, such as in light-emitting and bioimaging applications, owing to silicon's intrinsic merits of minimal toxicity, low cost, high abundance, and easy and highly stable functionalization. Especially nonoxidized Si NPs with a covalently bound coating serve well in these respects, given the minimization of surface defects upon hydrosilylation of H-terminated Si NPs. However, to date, methods to obtain such H-terminated Si NPs are still not easy. Herein, we report a new synthetic method to produce size-tunable robust, highly crystalline H-terminated Si NPs (4-9 nm) using microwave irradiation within 5 min at temperatures between 25 and 200 °C and their further covalent functionalization. The key step to obtain highly fluorescent (quantum yield of 7-16%) green-red Si NPs in one simple step is the reduction of triethoxysilane and (+)-sodium l-ascorbate, yielding routinely ∼1 g of H-Si NPs via a highly scalable route in 5-15 min. Subsequent functionalization via hydrosilylation yielded Si NPs with an emission quantum yield of 12-14%. This approach can be used to easily produce high-quality H-Si NPs in gram-scale quantities, which brings the application of functionalized Si NPs significantly closer.
| S-EPMC6160286 | biostudies-literature
Project description:Surface functionalization of inorganic semiconductor substrates, particularly silicon, has focused attention toward many technologically important applications, involving photovoltaic energy, biosensing and catalysis. For such modification processes, oxide-free (H-terminated) silicon surfaces are highly required, and different chemical approaches have been described in the past decades. However, their reactivity is often poor, requiring long reaction times (2-18 h) or the use of UV light (10-30 min). Here, we report a simple and rapid surface functionalization for H-terminated Si(111) surfaces using alkyl silanols. This catalyst-free surface reaction is fast (15 min at room temperature) and can be accelerated with UV light irradiation, reducing the reaction time to 1-2 min. This grafting procedure leads to densely packed organic monolayers that are hydrolytically stable (even up to 30 days at pH 3 or 11) and can display excellent antifouling behavior against a range of organic polymers.
| S-EPMC5419668 | biostudies-literature
Project description:With the advent of gene therapy, the development of an effective in vivo nucleotide-payload delivery system has become of parallel import. Fusogenic porous silicon nanoparticles (F-pSiNPs) have recently demonstrated high in vivo gene silencing efficacy due to its high oligonucleotide loading capacity and unique cellular uptake pathway that avoids endocytosis. The synthesis of F-pSiNPs is a multi-step process that includes: (1) loading and sealing of oligonucleotide payloads in the silicon pores; (2) simultaneous coating and sizing of fusogenic lipids around the porous silicon cores; and (3) conjugation of targeting peptides and washing to remove excess oligonucleotide, silicon debris, and peptide. The particle's size uniformity is characterized by dynamic light scattering, and its core-shell structure may be verified by transmission electron microscopy. The fusogenic uptake is validated by loading a lipophilic dye, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), into the fusogenic lipid bilayer and treating it to cells in vitro to observe for plasma membrane staining versus endocytic localizations. The targeting and in vivo gene silencing efficacies were previously quantified in a mouse model of Staphylococcus aureus pneumonia, in which the targeting peptide is expected to help the F-pSiNPs to home to the site of infection. Beyond its application in S. aureus infection, the F-pSiNP system may be used to deliver any oligonucleotide for gene therapy of a wide range of diseases, including viral infections, cancer, and autoimmune diseases.
| S-EPMC7261218 | biostudies-literature
Project description:The origin of bond-resolved atomic force microscope images remains controversial. Moreover, most work to date has involved planar, conjugated hydrocarbon molecules on a metal substrate thereby limiting knowledge of the generality of findings made about the imaging mechanism. Here we report the study of a very different sample; a hydrogen-terminated silicon surface. A procedure to obtain a passivated hydrogen-functionalized tip is defined and evolution of atomic force microscopy images at different tip elevations are shown. At relatively large tip-sample distances, the topmost atoms appear as distinct protrusions. However, on decreasing the tip-sample distance, features consistent with the silicon covalent bonds of the surface emerge. Using a density functional tight-binding-based method to simulate atomic force microscopy images, we reproduce the experimental results. The role of the tip flexibility and the nature of bonds and false bond-like features are discussed.
| S-EPMC5316802 | biostudies-literature
Project description:We present an enhanced method to form stable dispersions of medium-sized silicon nanoparticles for solar cell applications by thermally induced grafting of acrylic acid to the nanoparticle surface. In order to confirm their covalent attachment on the silicon nanoparticles and to assess the quality of the functionalization, X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier spectroscopy measurements were carried out. The stability of the dispersion was elucidated by dynamic light scattering and Zeta-potential measurements, showing no sign of degradation for months.
| S-EPMC3312836 | biostudies-other
Project description:Bimetallic Pd1-x Pt x solid-solution nanoparticles (NPs) display charging/discharging of hydrogen gas, which has relevance for fuel cell technologies; however, the constituent elements are immiscible in the bulk phase. We examined these material systems using high-energy synchrotron X-ray diffraction, X-ray absorption fine structure and hard X-ray photoelectron spectroscopy techniques. Recent studies have demonstrated the hydrogen storage properties and catalytic activities of Pd-Pt alloys; however, comprehensive details of their structural and electronic functionality at the atomic scale have yet to be reported. Three-dimensional atomic-scale structure results obtained from the pair distribution function (PDF) and reverse Monte Carlo (RMC) methods suggest the formation of a highly disordered structure with a high cavity-volume-fraction for low-Pt content NPs. The NP conduction band features, as extracted from X-ray absorption near-edge spectra at the Pd and Pt L III -edge, suggest that the Pd conduction band is filled by Pt valence electrons. This behaviour is consistent with observations of the hydrogen storage capacity of these NPs. The broadening of the valence band width and the down-shift of the d-band centre away from the Fermi level upon Pt substitution also provided evidence for enhanced stability of the hydride (ΔH) features of the Pd1-x Pt x solid-solution NPs with a Pt content of 8-21 atomic percent.
| S-EPMC5668347 | biostudies-literature
Project description:Silicon-containing compounds have been largely ignored in drug design and development, despite their potential to improve not only the potency but also the physicochemical and ADMET ( absorption, distribution, metabolism, excretion, toxicity) properties of drug-like candidates because of the unique characteristics of silicon. This deficiency is in large part attributable to a lack of general methods for synthesizing diverse organosilicon structures. Accordingly, a new building block strategy has been developed that diverges from traditional approaches to incorporation of silicon into drug candidates. Flexible, multi-gram-scale syntheses of silicon-containing tetrahydroquinoline and tetrahydroisoquinoline building blocks are described, along with methods by which diversely functionalized silicon-containing nitrogen heterocycles can be rapidly built using common reactions optimized to accommodate the properties of silicon. Furthermore, to better clarify the liabilities and advantages of silicon incorporation, select compounds and their carbon analogues were challenged in ADMET-focused biological studies.
| S-EPMC6011798 | biostudies-literature
Project description:We have developed a versatile, one-step melt synthesis of water-soluble, highly emissive silicon nanoparticles using bi-functional, low-melting solids (such as glutaric acid) as reaction media. Characterization through transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy shows that the one-step melt synthesis produces nanoscale Si cores surrounded by a silicon oxide shell. Analysis of the nanoparticle surface using FT-IR, zeta potential, and gel electrophoresis indicates that the bi-functional ligand used in the one-step synthesis is grafted onto the nanoparticle, which allows for tuning of the particle surface charge, solubility, and functionality. Photoluminescence spectra of the as-prepared glutaric acid-synthesized silicon nanoparticles show an intense blue-green emission with a short (ns) lifetime suitable for biological imaging. These nanoparticles are found to be stable in biological media and have been used to examine cellular uptake and distribution in live N2a cells.
| S-EPMC3490632 | biostudies-literature
Project description:Porous silicon (PSi) nanoparticles have been applied in various fields, such as catalysis, imaging, and biomedical applications, because of their large specific surface area, easily modifiable surface chemistry, biocompatibility, and biodegradability. For biomedical applications, it is important to precisely control the surface modification of PSi-based materials and quantify the functionalization density, which determines the nanoparticle's behavior in the biological system. Therefore, we propose here an optimized solution to quantify the functionalization groups on PSi, based on the nuclear magnetic resonance (NMR) method by combining the hydrolysis with standard 1H NMR experiments. We optimized the hydrolysis conditions to degrade the PSi, providing mobility to the molecules for NMR detection. The NMR parameters were also optimized by relaxation delay and the number of scans to provide reliable NMR spectra. With an internal standard, we quantitatively analyzed the surficial amine groups and their sequential modification of polyethylene glycol. Our investigation provides a reliable, fast, and straightforward method in quantitative analysis of the surficial modification characterization of PSi requiring a small amount of sample.
| S-EPMC9554871 | biostudies-literature
Project description:A series of azopyridine-terminated poly(N-isopropylacrylamide)s (PNIPAM) (C12-PN-AzPy) (∼5000 < M w < 20 000 g mol-1, polydispersity index 1.25 or less) were prepared by reversible addition-fragmentation chain-transfer polymerization of NIPAM in the presence of a chain-transfer agent that contains an AzPy group and an n-dodecyl chain. In cold water, the polymers form nanoparticles (5.9 nm < R h < 10.9 nm) that were characterized by light scattering (LS), 1H NMR diffusion experiments, and high-resolution transmission electron microscopy. We monitored the pH-dependent photoisomerization of C12-PN-AzPy nanoparticles by steady-state and time-resolved UV-vis absorption spectroscopy. Azopyridine is known to undergo a very fast cis-to-trans thermal relaxation when the azopyridine nitrogen is quaternized or bound to a hydrogen bond donor. The cis-to-trans thermal relaxation of the AzPy chromophore in an acidic nanoparticle suspension is very fast with a half-life τ = 2.3 ms at pH 3.0. It slows down slightly for nanoparticles in neutral water (τ = 0.96 s, pH 7.0), and it is very slow for AzPy-PNIPAM particles in alkaline medium (τ > 3600 s, pH 10). The pH-dependent dynamics of the cis-to-trans dark relaxation, supported by Fourier transform infrared spectroscopy, 1H NMR spectroscopy, and LS analysis, suggest that in acidic medium, the nanoparticles consist of a core of assembled C12 chains surrounded by a shell of hydrated PNIPAM chains with the AzPy+ end groups preferentially located near the particle/water interface. In neutral medium, the shell surrounding the core contains AzPy groups H-bonded to the amide hydrogen of the PNIPAM chain repeat units. At pH 10.0, the amide hydrogen binds preferentially to the hydroxide anions. The AzPy groups reside preferentially in the vicinity of the C12 core of the nanoparticles. The morphology of the nanoparticles results from the competition between the segregation of the hydrophobic and hydrophilic components and weak attractive interactions, such as H-bonds between the AzPy groups and the amide hydrogen of the PNIPAM repeat units.
| S-EPMC6727601 | biostudies-literature