3-氨丙基三乙氧基硅烷表面修饰的磁性Fe3O4纳米粒子合成与表征

以FeCl3、FeSO4为铁源,利用改进共沉淀法合成磁性纳米Fe3O4,在其制备的过程中加入水合肼充当还原剂和沉淀剂,采用3-氨丙基三乙氧基硅烷(APTES),通过硅烷化反应以化学键的方式结合Fe3O4纳米颗粒,获得表面氨基化的磁性Fe3O4纳米复合颗粒。并用XRD、IR、TEM、VSM等分析手段深入研究了APTES修饰前后磁性纳米颗粒结构和性能影响。结果表明APTES成功包覆到磁性纳米粒子表面,其包覆率为21%;磁性颗粒粒径为20nm,晶型为反立方尖晶石型;磁性颗粒具有很好的分散性,其磁化率为2.36×10-6,饱和磁化强度达60.8mT。     

Sonochemical synthesis of (3-aminopropyl)triethoxysilane-modified monodispersed silica nanoparticles for protein immobilization

3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by a rapid sonochemical co-condensation synthesis procedure. The chemical nature of surface organic modifier on the obtained modified silica nanoparticle was characterized by ¹³C and ²⁹Si MAS Nuclear Magnetic Resonance (NMR) spectroscopies, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)- differential scanning calorimetry (DSC). Due to the strengthened positive surface charge of the silica nanoparticles by the modification with aminopropyl groups, the capability for bovine serum albumin (BSA) adsorption was significantly increased as compared with bare silica nanoparticles. 80 mg/g BSA was adsorbed on modified silica nanoparticles, whereas only 20 mg/g BSA could be loaded on pure silica nanoparticles. The enhanced positive surface charge repelled proteins with net positive charge and the modified silica nanoparticles exhibited negligible adsorption of lysozyme, thus a selective adsorption of proteins could be achieved.     

Probing in situ the nucleation and growth of gold nanoparticles by small-angle X-ray scattering

We probe in situ by synchrotron SAXS/WAXS and UV-visible spectroscopy the nucleation and growth of gold nanoparticles. The use of a fast-mixing stopped-flow device enables the assessment of the whole particle formation process with a 200 ms time resolution. The number of particles, their size distribution, and the yield of the reaction is determined in real time through the quantitative analysis of the SAXS data on an absolute scale. Two ligands exhibit drastically different behaviors: when an alkanoic acid is used, a nucleation phase of 1 s is followed by a growth step whose rate is limited by the reaction of the monomers at the interface; on the other hand, when an alkylamine is used, the nucleation rate is increased by an order of magnitude, thus annealing growth by a lack of monomer and yielding R=1 nm particles in 2 s, as compared with R=3.7 nm in 12 s for the acid case.     

Detection of phosphopeptides by localized surface plasma resonance of titania-coated gold nanoparticles immobilized on glass substrates

We herein demonstrate a new sensing method for phosphopeptides by localized surface plasmon resonance (LSPR) using titania-coated gold nanoparticles immobilized on the surface of a glass slide as the sensing substrate and using UV-visible spectrophotometry as the detection tool. Titania has been known to be an effective substrate for binding with phosphorylated species. The detection principle is the shift of wavelength of optical absorption due to SPR of the gold nanoparticles induced by binding of phosphorylated species with titania on the surface of the gold nanoparticles. The feasibility of the approach is demonstrated by detection of tryptic digest products of beta-casein and milk. Gold nanoparticles coated with thin films of titania, immobilized on a glass slide, can selectively bind traces of phosphopeptides from complex samples, resulting in a wavelength shift of the absorption band in the SPR spectrum with good reproducibility. The LSPR results are confirmed by matrix-assisted laser desorption/ionization mass spectrometry. The detection limit for the tryptic digest product of beta-casein is 50 nM.     

The effects of a glow discharge on the nucleation characteristics of gold on polymer substrates

Small amounts of gold were deposited onto organic substrates of stearic acid and polyethylene. Some nucleation characteristics of the gold were studied using transmission electron microscopy and were compared with the nucleation characteristics observed on the more conventional carbon substrates. It was shown that, by exposing the organic substrates to a glow discharge in air, their surface structure was changed by the removal of hydrogen by plasma etching. This produced a surface layer composed mainly of carbon or of carbon and oxygen and it was demonstrated that the subsequent nucleation behaviour of gold on these exposed surfaces was very similar to that of gold on pure carbon films.     

A new and clean method on synthesis of gold nanoparticles from bulk gold substrates

In this work, we report a new pathway to prepare clean gold nanoparticles in neutral solutions with aid of natural chitosan. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1N NaCl and 1 g L^?1 chitosan from ?0.28 to +1.22 V vs. Ag/AgCl at 500 mV s^?1 for 200 scans. The durations at the cathodic and anodic vertices are 10 and 5 s, respectively. After this process, positively charged Au- and chitosan-containing complexes were produced in the solution. Then the solution was heated from room temperature to boiling at a heating rate of 6 °C min^?1 to prepare Au nanoparticles. The particle sizes of prepared Au (1 1 1) nanoparticles are ca. 10 nm. Moreover, the prepared Au nanoparticles in solutions are capable for anti-oxidation and stable in an ambient atmosphere for at least three months.     

Modeling of nucleation and growth during vapor condensation on liquid substrates

The study investigates the effect of inherent structural properties of liquid substrates on physical vapor-deposited metallic condensates. Due to the limitations in characterizing the atomic structure of different kinds of liquids, quantitative analysis of all the influencing parameters of the liquid substrate is difficult. Real time considered computing simulation is called for to realize the effects of such properties, which gives direct analyzable results. As representatives of physical and chemical properties of substrates, the molecular frequency and adsorption probability (~binding energy) are utilized as the key simulation parameters. Nucleation kinetics represented by conventional equations and an adapted time algorithm are employed to guarantee a correct, comparable and efficient simulation technique. The results show the substrates’ influence on the ‘morphology’ and ‘formation time’ of the film. In particular, the non-uniform morphology and low coverage observed under ‘liquid-substrate conditions’ are in agreement with experimental observations. The method can also be applied for predicting the condensate morphology for various vapor/substrate systems with known conditions.     

Synthesis of mercaptothiadiazole-functionalized gold nanoparticles and their self-assembly on Au substrates

Gold nanoparticles (AuNPs) stabilized with mercaptothiadiazole ligands, 2,5-dimercapto-1,3,4-thiadiazole (DMT), 5-amino-2-mercapto-1,3,4-thiadiazole (AMT) and 5-methyl-2-mercapto-1,3,4-thiadiazole (MMT), were prepared by the reaction of the respective ligands with HAuCl(4) and NaBH(4) in an aqueous medium. TEM images show that the average size of AuNPs was 6.5 ± 0.5?nm, irrespective of the capping ligands. The colloidal solution of both DMT-capped AuNPs (DMT-AuNPs) and AMT-capped AuNPs (AMT-AuNPs) were highly stable for several months. However, several changes were noticed for MMT-capped AuNPs (MMT-AuNPs) after 2?h from its formation. The SPR band intensity at 518?nm decreases and the narrow SPR absorption band slowly changes into a flat absorption pattern with a broad peak from 518 to 1000?nm which was accompanied by a colour change of the solution from red to purple and then blue and thereafter unchanged. The TEM image of MMT-AuNPs after 96?h shows that most of the spherical shape of the AuNPs assembled to form a nanowire-like structure. The observed changes may be due to the absence of a strong stabilizing force on the surface of the MMT-AuNPs. The amino and thiolate groups on the surface of the AMT-AuNPs and DMT-AuNPs, respectively, were directly self-assembled on Au electrodes. They exhibit excellent electrocatalytic activity towards the oxidation of AA by enhancing its oxidation current twice in addition to more than 200?mV negative shift in the oxidation potential in contrast to bare Au electrode.     

Study of carbide-forming element interlayers for diamond nucleation and growth on silicon and WC-Co substrates

Diamond nucleation and growth on several typical carbide-forming elements (CFE) (Ti, Cr and W) coated Si and WC-Co substrates were studied. The ion beam sputtered CFE interlayers show an amorphous/nanocrystalline microstructure. The diamond formed on the CFE coated substrates shows higher nucleation density and rate and finer grain structure than on uncoated substrates. Consequently, nanocrystalline diamond thin films can be formed on the CFE coated substrates under conventional microcrystalline diamond growth conditions. Among the three tested CFE interlayers, diamond has the highest nucleation density and rate on W layer and the lowest on Ti layer. The diamond nucleation density and rate on CFE coated WC-Co are much higher than those on widely used metal nitride coated WC-Co.     

A simple and cost-effective sensing strategy of mercury (II) based on analyte-inhibited aggregation of gold nanoparticles

A simple, cheap and ultrasensitive colorimetric Hg2+ sensing strategy has been developed in this paper. It was based on a special 'Hg2+-inhibited aggregation' mechanism, in which the pyridine-induced aggregation of unmodified gold nanoparticles (AuNPs) could be inhibited upon addition of Hg2+. Compared with the previous Hg2+-induced aggregation mechanism, the new design just employed a cheap and facile chemical reagent, pyridine, as an inducer of aggregation of AuNPs and elimination of the modifying or labeling step. The effects of pyridine concentration and size of AuNPs were investigated. The calibration curve showed that the extinction ratio value at 525 and 700 nm increased linearly over the Hg2+ concentration range of 0.15-3.00 μM with a detection limit of 55 nM. The specificity of this sensor is remarkably high over that of the other metal ions without adding any masking agent.     

Assembly-disassembly of DNAs and gold nanoparticles: a strategy of intervention based on oligonucleotides and restriction enzymes

The ability to manipulate and intervene in the processes of assembly and disassembly of DNAs and nanoparticles is important for the exploitation of nanoparticles in medical diagnostics and drug delivery. This report describes the results of an investigation of a strategy to intervene in the assembly and disassembly processes of DNAs and gold nanoparticles based on two approaches. The first approach explores the viability of molecular intervention to the assembly-disassembly-reassembly process. The temperature-induced assembly and disassembly processes of DNAs and gold nanoparticles were studied as a model system to illustrate this approach. The introduction of a molecular recognition probe leads to intervention in the assembly-disassembly process depending on its specific biorecognition. This process was detected by monitoring the change in the optical properties of gold nanoparticles and their DNA assemblies. The second approach involves the disassembly of the DNA-linked assembly of nanoparticles using restriction enzymes (e.g., MspI). The presence of the double stranded DNAs in the nanoparticle assembly was also substantiated by a Southern blot. Implications of the results to exploration of the molecular intervention for fine-tuning interfacial reactivities in DNA-based bioassays are also discussed.     

Geometry dependent nucleation mechanism for SiGe islands grown on pit-patterned Si(001) substrates

SiGe islands grown on pit-patterned Si(001) substrates show significant dependence on the surface geometry of the substrate, especially when the period of the patterning is reduced to below 300 nm. With different geometry of pit-patterned substrates, SiGe islands are observed to preferentially nucleate at the bottom of shallow pits after a ripple formation of the SiGe wetting layer, or at the top terrace when the pits are deep and steep.     

Fabrication of 3-D gelatin-patterned glass substrates with layer-by-layer and lift-off (LbL-LO) technology

The assembly of multilayer films of gelatin onto glass substrates using layer-by-layer and lift-off (LbL-LO) technology to modify the surface topography and chemistry properties of in vitro cell culture scaffolds is described. The ability to generate such nanoscale systems containing cell-adhesive materials on optically transparent substrates with microscale lateral dimensions, nanoscale vertical dimensions, molecular vertical precision, and flexibility in material selection has important implications for tissue engineering, drug discovery, and basic research in cell biology. Toward this goal, a systematic study on the electrostatic adsorption properties of fluorescein 5-isothiocyanate-gelatin B (FITC-gelatin) was completed. In addition, the integration of protein nanoassembly with microlithographic feature definition was used to pattern three-dimensional FITC-gelatin nanofilms on planar glass substrates. The experimental results indicate that FITC-gelatin is negatively charged at pH 9 and can be alternately assembled with a positively charged polyion, poly(diallyldimethylammonium chloride) (PDDA), to form multilayer films on solid templates with thickness of 5-10 nm per bilayer. Furthermore, images of protein/polymer nanocomposites indicate that LbL-LO is an efficient way to realize the designed substrates. These findings will benefit future research on cell culture and tissue engineering that require methods of generating protein patterns to fabricate novel in vitro cell culture systems.     

Controlled AFM detachments and movement of nanoparticles: gold clusters on HOPG at different temperatures

The effect of temperature on the onset of movement of gold nanoclusters (diameter 27 nm) deposited on highly oriented pyrolytic graphite (HOPG) has been studied by atomic force microscopy (AFM) techniques. Using the AFM with amplitude modulation (tapping mode AFM) we have stimulated and controlled the movement of individual clusters. We show how, at room temperature, controlled detachments and smooth movements can be obtained for clusters having dimensions comparable to or smaller than the tip radius. Displacement is practically visible in real time and it can be started and stopped easily by adjusting only one parameter, the tip amplitude oscillation. Analysing the energy dissipation signal at the onset of nanocluster sliding we evaluated a detachment threshold energy as a function of temperature in the range 300-413 K. We also analysed single cluster thermal induced displacement and combining this delicate procedure with AFM forced movement behaviour we conclude that detachment threshold energy is directly related to the activation energy of nanocluster diffusion and it scales linearly with temperature as expected for a single-particle thermally activated process.     

Crystallization kinetics of Ni-P glass — activation energies for nucleation and growth of nuclei

A pre-anneal treatment was introduced to a melt-spun Ni-P alloy. By crystallizing the asquenched and pre-annealed samples in a differential scanning calorimeter at different heating rates and isothermal process, the apparent activation energies for the total crystallization of the Ni-P samples were obtained by using the Kissinger technique and the Arrhenius relation. It was found that the apparent activation energy, E _c, decreased and tended to a certain value of 180 kJ mol^–1, with increase of pre-anneal time. According to the classical phase transformation theory, the activation energies for nucleation and growth of nuclei in the Ni-P glasses were deduced to be 324 and 180 kJ mol^–1, respectively, which are very close to the values previously reported by our laboratory. The weight parameters of nucleation, a, and growth, b, decrease monotonically and increase and tend to certain values with an increase of pre-anneal time, respectively.     

Gelatin stabilized iron oxide nanoparticles as a three dimensional template for the hydroxyapatite crystal nucleation and growth

Inspired by the structural similarity of gelatin (and collagen) linked to a mineral phase based on Ca-phosphates compounds with natural bone and increasing application of magnetic iron oxides in hyperthermia, gelatin coated iron oxide (GIO) was synthesized and hydroxyapatite (HAp) crystal nucleation and growth in the nanoparticles was explored. A series of GIO/HAp nanocomposites with various amount of GIO were synthesized by co-precipitation technique using calcium hydroxide and phosphoric acid as precursor. Various physico-chemical analysis showed that the HAp crystal nucleation and growth occurred at acidic group of gelatin, while magnetic iron oxide nanoparticles (< 8nm) were bound to the amide groups of the gelatin chain. Moreover, the growth of HAp nanocrystals in aq. GIO solution was highly influenced by the GIO contents in the solution. The mineralized composite with magnetic properties could have great scope in biomedical field as a thermoseed to kill the cancerous cell in bone side by side for the bone reinforcement.     

The nucleation and growth of borophene on the Ag (111) surface

B sheets have been intently studied, and various candidates with vacancies have been reported in theoretical investigations, including their possible growth on metal surfaces. However, a recent experiment reported that the borophene formed on a Ag (111) surface consisted of a buckled triangular lattice without vacancies. Our calculations propose a novel nucleation mechanism of B clusters and emphasize the B–Ag interaction in the growth process of borophene, demonstrating the structural evolution of triangular fragments with various profiles and vacancy distributions. Compared with the triangular lattice without vacancies, we have confirmed that the sheet energetically favored during the nucleation and growth is that containing 1/6 vacancies in a stripe pattern, whose scanning tunneling microscopy image is in better agreement with the experimental observation.

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