One‐Step Synthesis of Superbright Water‐Soluble Silicon Nanoparticles with Photoluminescence Quantum Yield Exceeding 80%

Fluorescent silicon nanoparticles (SiNPs) have shown potential applications in bioimaging/biolabelling, sensing, and nanomedicine/cancer therapy due to their superior properties such as excellent photostability, low cytotoxicity, and versatile surface modification capability. Here, a simple, high‐yield, and one‐pot method is developed to prepare superbright, water‐soluble, and amine‐functionalized SiNPs with photoluminescence quantum yield (PLQY) comparable to fluorescent II–VI semiconductor quantum dots (QDs) but with much lower cytotoxicity. By introducing a commercially available amine‐containing silane molecule, N‐[3‐(trimethoxysilyl)propyl]ethylenediamine (DAMO), water‐soluble SiNPs are prepared with PLQY of 82.4% via a microwave‐assisted method. To the best of our knowledge, this is the highest PLQY value ever reported for water‐soluble fluorescent SiNPs. The silicon element in our SiNPs is mainly four‐valent silicon and thus these SiNPs may also be termed as oxidized silicon nanospheres or silica nanodots. We have also demonstrated the importance of the silane structure (e.g., a suitable amine content) on the photoluminescence property of the prepared SiNPs. As revealed by the time‐resolved photoluminescence technique, the highest PLQY value of DAMO SiNPs is correlated with their monoexponential decay with a relatively long fluorescence lifetime. In addition, the potential use of these SiNPs has also been demonstrated for fluorescent patterning/printing and ion sensing (including Cu²⁺ and Hg²⁺).     

Generating Silicon Nanoparticles Using Spark Erosion by Flushing High-Pressure Deionized Water

Nanoparticles (NPs) are typically materials with dimensions less than 100 nm. In this work, silicon nanoparticles (SiNPs) were produced by electrical discharge machining of boron doped Si ingot (resistivity 0.01 Ω cm^?1). The “top-down” process used in this work involved vaporizing bulk Si material with spark erosion and rapidly cooling the vapors in the presence of deionized water at high-pressure of up to 0.8 MPa, to produce nanosized spheres. The microtopology and element composition analysis of the SiNPs were done by using scanning electron microscopy/energy-dispersive spectroscopy. It was observed that processing under high-pressure flushing conditions ensured production of SiNPs with average diameter of 30 ～ 50 nm and productivity of 1.5 g h^?1. SiNPs generated were spherical in shape due to the rapid solidification and surface tension. The structure of SiNPs was found to remain crystalline, according to the X-ray diffraction profiles. Transmission electron microscopy verified identical morphology and size for the SiNPs. The results demonstrate great potential for this process to be an industrialized SiNPs preparation method in terms of both particle size and productivity.     

Synthesis and structure evolution of phenolic resin/silicone hybrid composites with improved thermal stability

Phenolic resin/silicone hybrid composites (MPR) were prepared by a facile and low-cost method. FTIR results show that polycondensation of siloxane occurs in the presence of catalyst and water in the system, and siloxane oligomer was formed. During the curing process, the transesterification reaction between siloxane oligomer and phenolic resin (PR) makes silicon incorporated into PR. The TGA results indicate that introducing Si–O structure into PR can effectively improve the thermal stability of the resin. Compared with cured neat PR, temperatures at 5 and 10% mass loss of cured MPR can be improved by 43 and 36 °C. Its char yield at 800 °C was increased by about 9.1%. Cured MPR has been characterized by FTIR, XPS, XRD and Raman spectra to discuss the chemical state changes of silicon during pyrolysis process, as well as the effect of silicon on the char yield. On the one hand, the formation of Si–O–C structure can reduce the number of phenyl hydroxyl groups, which contributes to the reduced weight loss. On the other hand, the results indicate that Si–O_x structure was formed from the oxidation of Si–CH₃ and hydrolysis of Si–O–C structures. According to Raman analyses, introducing silicone into the system cannot help to promote the formation of a more ordered structure. Additionally, the mechanical properties of cured MPR have also been improved.     

Influence of pressure on bonding of alumina with molten aluminium as insert

Abstract

Alumina cylinders of 91% purity were bonded at 1073 K with aluminium foil of different thicknesses (5 and 50 μm) under different pressures (0–2 MPa) to examine the effect of pressure on the reaction of molten aluminium with silica contained in alumina as a binding agent. The reaction process at the bonding interface was also examined. The thicknesses of the interlayer and the reaction zone decreased with decreasing foil thickness. The interlayer was composed of silicon crystals and hypereutectic Al–Si alloy melt. Cavities were also observed. The constitution of the interlayer changed with time following the migration of silicon from the alumina: the amount of Al–Si alloy decreased with time, and the amounts of crystallised silicon and the total cavity volume increased with time. The bonding pressure reduced the thicknesses of the interlayer and the reaction zone. The amount of silicon contained in the interlayer was also reduced by pressure.

MST/3035     

Silicon Migration from High‐barrier Coated Multilayer Polymeric Films to Selected Food Simulants after Microwave Processing Treatments

The use of microwave (MW) technology for in‐package food sterilization and pasteurization has the potential for widespread use in the food industry. Because the use of MW technology requires that food be processed inside its packaging, the interaction between food and its packaging during processing must be studied to ensure package integrity as well as consumer safety. In this study, two commercially available multilayer films developed for retort sterilization were evaluated for their suitability to MW processing. Film A was composed of oriented nylon//coated polyethylene terephthalate//cast polypropylene (CPP); film B consisted of oriented nylon//coated nylon//CPP with overall oxygen transmission rates <0.2 cc/m². day. Silicon (Si) was a major component in the coated polyethylene terephthalate layer and food‐contact CPP layer. This study evaluated the influence of MW processing on Si migration from films into selected food‐simulating liquids (FSLs; water and 3% acetic acid) using inductively coupled plasma‐mass spectroscopy, as compared with conventional thermal processing. This study also assessed migration of Si into FSL in terms of process temperature (70–123 °C) and time (18–34 min). A Fourier transform infrared spectrometer was used to evaluate the stability of the silicon–oxygen (Si–O) bonds in the metal‐oxide coated and food‐contact layer of the packaging film. Overall, there were no significant differences (p > 0.05) between the level of Si migration from films to FSL and the stability of Si–O–Si bonds during MW processing as compared with the conventional thermal processing. However, we found that the final processing temperature and time had a significant (p < 0.05) impact on Si migration into the FSL. Copyright © 2013 John Wiley & Sons, Ltd.     

Silicon-substituted hydroxyapatite: The next generation of bioactive coatings

Silicon-substituted hydroxyapatite (Si–HA) coatings with three different Si compositions (0.8, 2.2 and 4.9 wt.%) were produced as thin films on titanium substrates by magnetron co-sputtering. Following heat-treatment, a crystalline, single-phase apatite structure was obtained for all coatings, as evidenced by the presence of characteristic peaks for HA in X-ray diffraction traces, and infrared absorption P–O and O–H bands. A human osteoblast-like (HOB) cell model was employed to assess the biocompatibility of these Si–HA coatings. Unsubstituted HA thin coatings were used as a control. The results demonstrated that Si–HA elicited a significantly more rapid growth response by the HOBs as compared to HA, although cells spread well on both coatings, with the formation of extracellular matrix. The cytoskeletons on Si–HA showed clear and distinct actin filaments that were parallel to the long axis of the cells. In contrast, a more diffuse actin cytoskeleton organisation was observed on HA. Biomineralisation was seen on both coatings after 42 days of culturing, with a higher level observed on the Si–HA samples. In conclusion, Si–HA offers great potential as a coating material for future medical applications in hard and soft tissue replacements.     

A silicon nanoparticle/reduced graphene oxide composite anode with excellent nanoparticle dispersion to improve lithium ion battery performance

Composite anodes of Si nanoparticles (SiNPs) and reduced graphene oxide (RGO) sheets with highly dispersed SiNPs were synthesized to investigate the performance-related improvements that particle dispersion can impart. Three composites with varying degrees of particle dispersions were prepared using different ultrasonication, and a combination of ultrasonication and surfactant. With more dispersed SiNPs, the capacity retention and rate performance as evaluated by galvanostatic cycling using increasing current density rates (500–2500 mA/g) also improved compared with anodes that have poor particle dispersion. These results demonstrate that better nanoparticle dispersion (small clusters to mono-dispersed particles) between the stable and the highly conducting RGO layers, allows the carbonaceous matrix material to complement the SiNP-Li⁺ electrochemistry by becoming highly involved in the charge–discharge reaction mechanisms as indicated by chronopotentiometry and cyclic voltammetry (CV). Particle dispersion improvement was confirmed to be a key component in a composite anode design to maximize Si for high-performance lithium ion battery (LIB) application.     

Molecular assembly and photoluminescence of novel rare earth/inorganic/polymeric hybrid materials with functional covalent linkages

In the context, organic polymeric precursor, polyethylene glycol (PEG) was firstly modified by inorganic component of 3-(triethoxysilyl)-propyl isocyanate (TEPIC) to form the inorganic/organic polymeric functional bridge precursor. Subsequently, the corresponding organic/inorganic molecular-based hybrids were assembled to behave the structural polymeric ligands with the two components equipped with covalent bonds. The coupling reagent part is a functional ureasils –NHC(=O)–O–group which is applied to coordinate to RE³⁺ and further formed Si–O backbones after hydrolysis and polycondensation processes. Furthermore, aromatic carboxylic acids (picolinic acid (HPIC), 2-chlorobenzoic acid (HCBA) and salicylic acid (HSAL)) were used as functional sensitized ligands to coordinate with RE³⁺(Eu³⁺, Tb³⁺ and Dy³⁺) and resulting in the quaternary rare earth/inorganic/organic polymeric hybrid materials with chemical bond (covalent bonds of –CO–NH– and Si–O, coordination bond of RE–O–C). Luminescence spectra were utilized to characterize the photophysical properties of the obtained hybrid material and the intramolecular energy transfer process took place within these molecular-based hybrids and characteristic emissions of RE³⁺ have been achieved.     

Microstructure and wear behaviour of silicon doped Cr–N nanocomposite coatings

Hard Cr–N and silicon doped Cr–Si–N nanocomposite coatings were deposited using closed unbalanced magnetron sputtering ion plating system. Coatings doped with various Si contents were synthesized by changing the power applied on Si targets. Composition of the films was analyzed using glow discharge optical emission spectrometry (GDOES). Microstructure and properties of the coatings were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and nano-indentation. The harnesses and the elastic modulus of Cr–Si–N coatings gradually increased with rising of silicon content and exhibited a maximum at silicon content of 4.1 at.% and 5.5 at.%. The maximum hardness and elastic modulus of the Cr–Si–N nanocomposite coatings were approximately 30 GPa and 352 GPa, respectively. Further increase in the silicon content resulted in a decrease in the hardness and the elastic modulus of the coatings. Results from XRD analyses of CrN coatings indicated that strongly preferred orientations of (111) were detected. The diffraction patterns of Cr–Si–N coatings showed a clear (220) with weak (200) and (311) preferred orientations, but the peak of CrN (111) was decreased with the increase of Si concentration. The XRD data of single-phase Si₃N₄ was free of peak. The peaks of CrN (111) and (220) were shifted slightly and broadened with the increase of silicon content. SEM observations of the sections of Cr–Si–N coatings with different silicon concentrations showed a typical columnar structure. It was evident from TEM observation that nanocomposite Cr–Si–N coatings exhibited nano-scale grain size. Friction coefficient and specific wear rate (SWR) of silicon doped Cr–N coatings from pin-on-disk test were significantly lower in comparison to that of CrN coatings.     

Microstructural,mechanical and tribological properties of Al–7Si–(0–5)Zn alloys

A series of Al–7Si–(0–5)Zn alloys were produced by permanent mould casting and their microstructure, mechanical and tribological properties were investigated in as-cast state. The microstructure of Al–7Si alloy consisted of α-Al dendrites surrounded by eutectic Al–Si mixture and a small amount of primary silicon particles. Addition of zinc into Al–7Si alloy resulted in the formation of α-solid solution and an increase in size and volume fraction of primary silicon particles. Moreover, these particles gathered inside interdendritic regions of the ternary Al–7Si–Zn alloys. The density, strength and hardness of Al–7Si–Zn alloys increased continuously with increasing zinc content, but their elongation to fracture and impact energy showed a reverse trend. It was also observed that zinc had no significant effect on the friction coefficient of the alloys, but their wear volume decreased with increasing zinc content up to 4%, above which the trend reversed. The wear surfaces of the alloys were characterized mainly by smearing layer with some degree of oxidation. In addition, delamination and fine scratches were observed on the worn surface. It was concluded that the addition of zinc up to 4% improves both mechanical and wear behaviour of Al–7Si alloy.     

8-aminoquinoline functionalized silica nanoparticles: a fluorescent nanosensor for detection of divalent zinc in aqueous and in yeast cell suspension

Zinc is one of the most important transition metal of physiological importance, existing primarily as a divalent cation. A number of sensors have been developed for Zn(II) detection. Here, we present a novel fluorescent nanosensor for Zn(II) detection using a derivative of 8-aminoquinoline (N-(quinolin-8-yl)-2-(3 (triethoxysilyl)propylamino)acetamide (QTEPA) grafted on silica nanoparticles (SiNPs). These functionalized SiNPs were used to demonstrate specific detection of Zn(II) in tris-HCl buffer (pH 7.22), in yeast cell (Saccharomyces cerevisiae) suspension, and in tap water. The silane QTEPA, SiNPs and final product were characterized using solution and solid state nuclear magnetic resonance, Fourier transform infrared, ultraviolet-visible absorption spectroscopy, transmission electron microscopy, elemental analysis, thermogravimetric techniques, and fluorescence spectroscopy. The nanosensor shows almost 2.8-fold fluorescence emission enhancement and about 55 nm red-shift upon excitation with 330 ± 5 nm wavelength in presence of 1 μM Zn(II) ions in tris-HCl (pH 7.22). The presence of other metal ions has no observable effect on the sensitivity and selectivity of nanosensor. This sensor selectively detects Zn(II) ions with submicromolar detection to a limit of 0.1 μM. The sensor shows good applicability in the determination of Zn(II) in tris-HCl buffer and yeast cell environment. Further, it shows enhancement in fluorescence intensity in tap water samples.     

Ultrasonically carbon coated Si nanoparticles for lithium ion batteries

A new and simple method for making nano-sized silicon/carbon composite materials was developed. The composite powders were prepared by dispersing HF-etched SiNPs in CHCl3, followed by bath sonication. Transmission Electron Microscopy (TEM) was used to identify the carbon layer outside the silicon particle. Impedance spectroscopy and cyclic voltammetry confirmed the improved electrode conductivity due to the carbon layer and the subsequent increased involvement of the silicon in the lithiation/delithiation process. The optimal composition of the composite, 20 wt.% SiNP/C, and 20 wt.% graphite, exhibited excellent cyclability after ten cycles with a reversible discharging capacity near 465 mAhg(-1) which is 1.5 times larger than that of the graphite and SiNPs electrode without ultrasonic process.     

Electron probe microanalysis of Nicalon fibres

Electron probe microanalysis of a sample of Nicalon fibre showed it to consist of 54.9 wt% Si, 32.1 wt% C and 11.6 wt% O. Studies of the fine structure of the X-ray emission bands suggested these elements were combined as 46 vol% silicon carbide, 34 vol% silicon oxycarbide and 20 vol% free carbon, with the oxycarbide in the outermost regions of the fibre being significantly richer in oxygen. The silicon carbide was composed of microcrystallites several micrometres in diameter and the remaining material formed an amorphous network of material surrounding the microcrystallites.     

Enhanced photoluminescence from porous silicon passivated with an ultrathin aluminum film

The photoluminescence (PL) of the porous silicon (PS) can be enhanced by coating it with an ultrathin aluminum (Al) film. The PL intensity of PS was found to increase up to ~ 67% by radio frequency (RF) sputter deposition of 5.2 nm Al film on PS. Fourier transform infrared (FTIR) spectroscopy analysis results suggest that the PL enhancement is related to change of Si–H and Si–O–Si bonds into Si–Al bonds as well as the increase in the carrier concentration participating in the radiative recombination under photoexcitation. On the other hand, the PL of the Al-passivated PS was found to be significantly deteriorated by postannealing owing to the thermal oxidation of the Al layer during annealing.     

Laminated biomorphous SiC/Si porous ceramics made from wood veneer

Biomorphous SiC/Si porous ceramics with laminated structure are prepared from beech veneer and phenolic resin. The preparation involves carbonization under vacuum and reaction with melted silicon to obtain the biomorphous carbide template. X-ray diffraction confirms that the biomorphous SiC/Si porous ceramics are mainly composed of β-SiC, free silicon and residual carbon. Scanning election microscopy observations indicate a laminated structure and 1–10 μm microporous structures, which suggest retention of the native characteristics of the wood. This paper examines mechanical properties of the final composite in relation to the lamination, porous structure, and free silicon content. The bending strength of the ceramics decreases as the apparent porosity increases. The fracture toughness increases initially with apparent density and then decreases. The fracture toughness load–displacement curve presents a step-like pattern, which suggests that the laminated SiC/Si porous ceramics have high fracture toughness.     

Doxorubicin-loaded silicon nanoparticles impregnated into red blood cells featuring bright fluorescence,strong photostability,and lengthened blood residency

Nano Research - Based on the unique advantages of fluorescent silicon nanoparticles (SiNPs), long circulation red blood cells (RBCs), and anti-cancer drug molecules (i.e., doxorubicin (DOX)), we...     

若丹明6G在丙烯酸酯－丙烯腈共聚物固溶态中的荧光行为

研究了若丹明６Ｇ（Ｒ６Ｇ）在甲基丙烯酸甲酯（ＭＭＡ）、丙烯醚（ＡＡ）、甲基丙烯醚（ＭＡ）、丙烯腈（ＡＮ）和乙醇中以及在它们的二元和三元混合体系中的荧光行为，发现含ＡＮ的体系的荧光强度（Ｆ）比较接近于含乙醇体系的Ｆ值，并且ＡＮ的存在有利于减少荧光熄灭和内滤作用。找到了比较合适的单体混合比例，即ＭＭＡ：ＭＡ（ＡＡ）：ＡＮ＝１０：２：１时，体系的Ｆ和荧光量子效率接近于含同等量乙醇体系的Ｆ，并且其聚合物的玻璃化温度、硬度和透光率均接近于聚甲基丙烯酸甲酯的相应值。用ＡＮ取代乙醇作为染料增溶剂是可行的。     

Atomic oxygen adsorption on the silicon-doped hafnium carbide (0 0 1) surface from first principles

To improve the oxidation resistance of Hafnium carbide (HfC) surface, we investigated the adsorption of atomic oxygen on the silicon–doped HfC (0 0 1) surface by first principles. The O/HfC (0 0 1) system was also calculated for comparison. The (√2 × √2) R45° supercell was constructed to calculate the adsorption. In calculations, we treated the exchange and correlation potential with the revised version of the Perdew–Burke–Ernzerhof generalized-gradient approximation (GGA-RPBE). Our data demonstrate that the preference adsorption site for oxygen atom is the 4–fold hollow site on the silicon–doped HfC (0 0 1) surface. The oxygen on the silicon–doped surface receives more charges from silicon atoms than that in O/HfC (0 0 1) from carbon atoms. The Si–O bonds exhibit ionic and covalent characteristics, while the C–O bond exhibits primarily covalence. And the covalence of Si–Hf bonds is stronger than that of C–Hf bonds. The strong Si–O and Si–Hf bonds indicate the strong interactions of oxygen with the silicon–doped surface. The strong interactions can explain the possibility of improving the oxidation resistance of HfC surface via doping silicon.     

Optical and photovoltaic properties of silicon wire solar cells with controlled ZnO nanorods antireflection coating

We introduce a new type of silicon micro-wire (SiMW) solar cell with a conformal zinc oxide (ZnO) nanorods anti-reflection coating (ARC) and discuss the optical and photovoltaic properties of the SiMW solar cells with controlled ZnO nanorods. The fabrication processes were composed of metal-assisted electroless etching combined with photolithography, spin-on-dopant diffusion, and hydrothermal synthesized ZnO nanorods growth. We found that the combination of Si wire geometry and ZnO ARC was able to maximize the light absorption and to minimize the light reflectance. Illuminated current–voltage (I–V) results show that the photovoltaic efficiency of SiMW solar cells with optimized ZnO ARC was enhanced more than 50% and the short-circuit current density was improved by over 43% compared to SiMW solar cells without ZnO ARC. This is mainly attributed to the reduced light reflectance and enhanced photon absorption. These hybrid structures are promising for making low-cost Si wire solar cells and making them applicable to photovoltaic devices with large areas.