DNA manipulation with elastomeric nanostructures fabricated by soft-moulding of a FIB-patterned stamp

A Focused Ion Beam (FIB)-patterned silicon mould is used to fabricate elastomeric nanostructures, whose cross-section can be dynamically and reversibly tuned by applying a controlled mechanical stress. Direct-write, based on FIB milling, allows the fabrication of nanostructures with a variety of different geometries, aspect ratio, spacing and distribution offering a higher flexibility compared to other nanopatterning approaches. Moreover, a simple double replication process based on poly(dimethylsiloxane) permits a strong reduction of the fabrication costs that makes this approach well-suited for the production of low cost nanofluidic devices. DNA stretching and single molecule manipulation capabilities of these platforms have been successfully demonstrated.     

Complete plastic nanofluidic devices for DNA analysis via direct imprinting with polymer stamps

Development of all polymer-based nanofluidic devices using replication technologies, which is a prerequisite for providing devices for a larger user base, is hampered by undesired substrate deformation associated with the replication of multi-scale structures. Therefore, most nanofluidic devices have been fabricated in glass-like substrates or in a polymer resist layer coated on a substrate. This letter presents a rapid, high fidelity direct imprinting process to build polymer nanofluidic devices in a single step. Undesired substrate deformation during imprinting was significantly reduced through the use of a polymer stamp made from a UV-curable resin. The integrity of the enclosed all polymer-based nanofluidic system was verified by a fluorescein filling experiment and translocation/stretching of λ-DNA molecules through the nanochannels. It was also found that the funnel-like design of the nanochannel inlet significantly improved the entrance of DNA molecules into nanochannels compared to an abrupt nanochannel/microfluidic network interface.     

Synthesis of porphyrin-introduced silica gels by sol-gel process

Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed.     

Imprinted functionalized silica sol-gel for solid-phase extraction of triazolamin

A triazolam-imprinted silica microsphere was prepared by combining a surface molecular-imprinting technique with the sol-gel process. The results illustrate that the triazolam-imprinted silica microspheres provided using γ-aminopropyltriethoxysilane and phenyltrimethoxysilane as monomers exhibited higher selectivity than those provided from γ-aminopropyltriethoxysilane and methyltriethoxysilane. In addition, the optimum affinity occurred when the molar ratio of γ-aminopropyltriethoxysilane, phenyltrimethoxysilane, and the template molecule was 4.2:4.7:0.6. Retention factor (k) and imprinting factor (IF) of triazolam on the imprinted and non-imprinted silica microsphere columns were characterized using high performance liquid chromatography (HPLC) with different mobile phases including methanol, acetonitrile, and water solutions. The molecular selectivity of the imprinted silica microspheres was also evaluated for triazolam and its analogue compounds in various mobile phases. The better results indicated that k and IF of triazolam on the imprinted silica microsphere column were 2.1 and 35, respectively, when using methanol/water (1/1, v/v) as the mobile phase. Finally, the imprinted silica was applied as a sorbent in solid-phase extraction (SPE), to selectively extract triazolam and its metabolite, α-hydroxytriazolam, from human urine samples. The limits of detection (LOD) for triazolam and α-hydroxytriazolam in urine samples were 30 ± 0.21 ng mL⁻¹ and 33 ± 0.26 ng mL⁻¹, respectively.     

溶胶凝胶法制备片状氧化硅/氧化锆纳米复合材料(英文)

以氧氯化锆和二甲基二乙氧基硅烷为前驱体,在无任何表面活性剂的条件下,利用溶胶-凝胶法制备了片状SiO_2/ZrO_2复合材料.采用X射线衍射仪、扫描电镜、能谱仪、傅立叶变换红外光谱仪、透射电镜等分析了产物的结构和形貌,并探讨了SiO_2/ZrIO_2纳米复合材料的取向生长机理.结果表明,在正丁醇和水的混合溶液中制备的SiO_2/ZrO_2纳米复合材料的粒径为18nm,将干凝胶的500℃空气气氛中焙烧2h可以得到四方相片状氧化锆晶体.化合物中的硅原子通过Si—O—Zr化学键与锆原子相连;硅的引入仅影响氧化锆晶体的形貌,而不导致四方相氧化锆结构和尺寸的改变.本文所述方法可望拓展用于制备其他具有类似分级结构的无机功能纳米材料.     

Surface analysis by X-ray photoelectron spectroscopy of sol-gel silica modified with covalently bound peptides

Chemical surface characterization of biologically modified sol-gel derived silica is critical but somewhat limited. This work demonstrates the ability of x-ray photoelectron spectroscopy (XPS) to characterize the surface chemistry of peptide modified sol-gel thin films based on the example of four different free peptide-silanes, denoted RGD, NID, KDI ,and YIG. The N 1s and C 1s peaks were found to be good fingerprints of the peptides, whereas O 1s overlapped with the signal of substrate oxygen and, therefore, the O 1s peak was not informative in the case of the thin films. The C 1s peak was fitted and the contribution of the residual hydrocarbons was sorted out. The curve-fitting procedure of the C 1s peak accounted for the different chemical states of carbon atoms in the peptide structure. The curve-fitting procedure was validated by analyzing free peptides in the powder form and was then applied to the characterization of the peptide-modified thin films. The XPS measured ratio between nitrogen and carbon for the peptide thin film was similar to the corresponding value calculated from the peptide structures. Angle resolved XPS confirmed the surface nature of peptides in modified thin films. The coverage and thickness of the peptides on the thin film surface depended on the peptide sequence. The coverage was in the range of 10% of a monolayer, and the layer thickness varied from 10 to 30 A. We believe that the different thicknesses and surface coverage are due to the local structure of the peptides, with the RGD and NID peptides taking a globule conformation and the YIG and KDI peptides adopting a more linear structure.     

sol-gel 法在有机-无机杂化体系中制备二氧化硅微粒

利用sol-gel法,通过正硅酸乙酯（tetraethyl orthosilicate（TEOS））在聚氧化乙烯／二甲基甲酰胺溶液中水解、缩聚,制备了粒径分布均匀的微米级二氧化硅粒子;利用扫描电子显微镜观测了制备条件对二氧化硅粒子的粒度和形貌的影响;研究了这一方法在制备无机粒子过程中的原理．     

Immobilization of urease on the silica gel surface by sol-gel method

The possibility of “double immobilization” of urease on silica gel, involving enzyme incorporation into the polysiloxane polymer prepared by sol-gel procedure on the surface of an inorganic support was studied. The optimal composition and thickness of the polysiloxane film, providing relatively high activity of urease, were determined.     

A silica monolithic column prepared by the sol-gel process for enantiomeric separation by capillary electrochromatography

A method for the preparation of a silica monolithic capillary electrochromatography (CEC) column for the separation of enantiomers has been developed. The porous silica monolith was fabricated inside a fused-silica capillary column by using the sol-gel process. After gelation for 24 h, hydrothermal treatment at 100 degrees C for 24 h was performed to prevent the sol-gel matrix from cracking. The prepared monolith was then coated with Chirasil-beta-Dex which represents a chiral polymer prepared by grafting permethyl-beta-cyclodextrin to polymethylsiloxane with an octamethylene spacer. Immobilization of Chirasil-beta-Dex was performed by heat treatment at 120 degrees C for 48 h to give a nonextractable coating. The column performance was evaluated by using racemic hexobarbital as a model compound. The efficiency of 9.2 x 10(4) theoretical plates/m for the first eluted enantiomer of hexobarbital was obtained at an optimal flow rate of the mobile phase. The effect of mobile phase composition on enantiomeric separation of hexobarbital was also investigated. The column proved to be stable for more than one hundreds of runs during a two-months period. The enantiomers of several neutral and negatively charged chiral compounds were baseline separated on this column.     

Synthesis and spectroscopy of tpps-doped silica gels by the sol-gel process

Tetraphenylporphinetetrasulfonic acid (TPPS), which is well known as a photochemical hole-burning (PHB) dye, was incorporated in silica gels obtained by the sol-gel process from tetramethoxysilane (TMOS). The form of TPPS must be free base (H₂P), which exists in basic condition, to be active in PHB. To obtain transparent and higher density silica gels doped with free-base TPPS, two-step hydrolysis processes using solutions containing NaOH were developed, and the gels having bulk density of about 1.5 g/cm³ were synthesized. The form of TPPS in the gels was investigated by measuring the absorption and luminescence spectra, and it was found that in the silica gels almost all the TPPS retained free-base form at the molar ratio of NaOH/TMOS above 10^–3.     

Nano fabricated silicon nanorod array with titanium nitride coating for on-chip supercapacitors

We demonstrate high aspect ratio silicon nanorod arrays by cyclic deep reactive ion etching (DRIE) process as a scaffold to enhance the energy density of a Si-based supercapacitor. By unique atomic layer deposition (ALD) technology, a conformal nanolayer of TiN was deposited on the silicon nanorod arrays as the active material. The TiN coated silicon nanorods as a supercapacitor electrode lead to a 6 times improvement in capacitance compared to flat TiN film electrode.     

Photo-curable siloxane hybrid material fabricated by a thiol-ene reaction of sol-gel synthesized oligosiloxanes

The thiol-ene reaction of a sol-gel synthesized oligosiloxane thiol-ene mixture was processed through UV irradiation, resulting in transparency, high refractive index, good thermal stability and especially excellent electrical insulation materials. It provides new strong potential of the thiol-ene system for application in dielectric materials.     

Liposomes as protective capsules for active silica sol-gel biocomposite synthesis

Using liposome to shield an enzyme from hostile chemical environments during the sol-gel formation process has resulted in a novel approach to synthesizing silica sol-gel biocomposite materials. By reporting the encapsulation of horseradish peroxidase and firefly luciferase, we demonstrate that this new protocol can produce silica biocomposites that are more active than trapping the enzymes directly into hydrogels.     

Electrochemical and surface characterization of mild steel with corrosion resistant zirconia network fabricated by aqueous sol-gel technique

Zirconia (ZrO₂) coating was developed on mild steel surface through an aqueous sol-gel route followed by heat treatment. The coating quality was optimized by varying dipping time, curing time, and drying temperature. ZrO₂ coating was competent to prevent a substantial corrosion loss in 0.5 ​M–2 ​M hydrochloric acid with more than 90% efficiency. The morphology of coated surface has revealed the formation of a fine ZrO₂ network on the metal surface at optimum conditions. This network is found to be effective to control steel deterioration in hydrochloric acid and the same appeared to be either cracked or irregular for less efficient formulations.     

The microstructure of titanium-modified silica glass waveguides prepared by the sol-gel method

Waveguides were prepared by the sol-gel method at ambient temperature from titanium alkoxides and an organically modified silane using the chemically controlled condensation procedure. The structure was studied using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A biphasic structure containing (a) modified silica that may form micellar clusters and (b) titania clusters containing chelating acetate with dimensions in the nanometer range is proposed. The composite glass was doped by the pH indicator methyl red and the existence of two separate dye populations was demonstrated. This finding is attributed to dye molecules in separate phases. The optical and spectral properties of the glass are explained by its proposed structure.     

Characterization of microchip electrophoresis devices fabricated by direct‐printing process with colored toner

This paper reports for the first time the use of colored toner to produce polyester toner (PT) ME devices. Colored PT devices were designed in drawing software and printed on a polyester film using a color laser printer with 3600 dpi resolution. The colored toner is composed of a copolymer mixture (styrene and acrylate), wax, silicon dioxide, and pigments. The presence of silica in the toner composition has enhanced the EOF magnitude and improved the analytical performance. For a pH range between 2 and 12, the EOF measured on a magenta PT chip, for example, ranged from 3.8 to 5.8 (× 10^?4 cm² V^?1 s^?1). Typical separations of inorganic cations (K⁺, Na⁺, and Li⁺) were used as model system to investigate the analytical feasibility of the proposed devices. The repeatability for the migration times of all analytes exhibited RSD values lower than 1% (n = 10). The separation efficiencies found on colored PT devices ranged from 10 000 to 49 000 plates/m, which means between 7 and 23% of the maximum theoretical efficiency on this microfluidic platform (1.85 × 10⁵ plates/m). The improvements achieved on the proposed devices are associated with the small additional amount of silica on the toner composition as well as the printing of channels with smoother surfaces and better uniformity when compared to the conventional PT chips printed with monochromatic laser printers.     

Microstructures and structural properties of sol-gel silica foams

Silica xerogels were synthesized and annealed at 1000 degrees C for different durations to yield stable silica materials. The samples were prepared through base-catalyzed hydrolysis and condensation of tetramethyl orthosilicate in methanol. After aging and drying steps, clear and solid xerogels exhibiting a narrow pore size distribution were achieved. The annealing treatment of these xerogels was performed at 1000 degrees C and proved in the present study to lead to a monolithic glass when a progressive heat-treatment procedure was employed to attain 1000 degrees C. In addition to the expected glass, silica foams and ordered phases were observed when the samples were instantaneously heat-treated at 1000 degrees C. Raman spectra of the foamed materials exhibit the classical features of amorphous silica, whereas transmission electronic microscopy pictures reveal the presence of crystallized domains within the vitreous matrix. These crystallites are prone to nucleation and growth processes, which jeopardize the believed stability of the silica foam. The assessment of the hydroxyl content by IR spectroscopy reveals the role played by the latter polycondensation of silanols. The occurrence of foaming process was thus found to result from two competitive phenomena occurring at 1000 degrees C: evacuation of water-related species and viscous sintering.     

Novel unbreakable solid-phase microextraction fiber by electrodeposition of silica sol-gel on gold

A new technique for preparation of an unbreakable solid-phase microextraction (SPME) fiber, using sol-gel technology is developed. Primarily, an ultrathin two-dimensional intermediate film was prepared by hydrolysis of 3-(trimethoxysilyl)-1-propanthiol self-assembled monolayer grafted onto gold, then a stationary phase by electrodeposition of 3-(trimethoxysilyl)propylmethacrylate as a precursor, tetramethyl orthosilicate and polyethylene glycol as a coating polymer was produced. The scanning electron microscopy images revealed that the new fiber exhibits a rather porous and homogenous surface. The thermal stability of the fabricated fiber was investigated by thermogravimetric analysis. The applicability of the prepared fiber coating in conjunction with gas chromatography-mass spectrometry was examined by SPME of polycyclic aromatic hydrocarbons, as model analytes, from aquatic media. An extraction time of 20 min at 50 °C gave maximum peak areas when NaCl, 15% was added to the aqueous samples. Limits of detection were in the range of 0.01-0.02 ng/mL and relative standard deviation values were in the range of 4-16% at 1 ng/mL. The developed method was successfully applied for the analysis of real water samples while the relative recovery percentage was in the range of 102-118%.     

Probing local effects in silica sol-gel media by fluorescence spectroscopy of p-DASPMI

Stillbazolium salts present remarkable potential for application in several scientific areas. Their versatile behavior is explained by invoking the "twisted intramolecular charge-transfer" (TICT) mechanism, a model that describes the multiple fluorescence of DASPMI (4-(4-(dimethylamino)styryl)- N-methylpyridiniumiodine). One feature of their behavior is the sensitivity of the fluorescence lifetime to viscosity, thus identifying them as suitable probes for microheterogeneous systems, such as cells and sol-gel derived media. Because of their optical transparency, sol-gel matrices are light addressable and therefore appropriate for performing spectroscopic studies. The sol-gel process has been successfully used to produce hosts to biomolecules like proteins, for biosensor applications; however, these systems have to be optimized. Therefore, in this study modification of the matrices was performed through the incorporation of either silanes or polymers. (Aminopropyl)triethoxysilane, trimethoxypropylsilane, or (glycidyloxypropyl)triethoxysilane were added. The modification was also extended to the incorporation of the polymers poly(ethylene glycol) (molecular weight 300 and 20000) and Gelrite. The effect of these modifiers upon the gelation and aging processes was examined via the study of the photophysics of p-DASPMI by using both steady-state and time-resolved fluorescence. It was possible to discriminate the dominant dye-host interactions in each of the main steps of the preparation of modified sol-gel matrices.