The charge of glass and silica surfaces

Behrens, Sven H.; Grier, David G.

doi:10.1063/1.1404988

Cited by 826 publications

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“…where, with respect to amino-modified glass slides, Γ Amin = 90 pmole/ cm 2 to 300 pmole/ cm 2 is the range of densities of amine groups on amino-modified glass surface [11]; Γ Si = 1.3 nmole/cm 2 is the Si density on a glass surface [12]; and Γ DNA is the density of nucleotide phosphate groups inside the particle footprint (see Figure 1). For the 20 nm colloidal particle in low ionic strength solutions, the particle's footprint area is equal to the particle cross-section: π(20 nm/2) 2 = 314 nm 2 .…”

Section: Models and Analysismentioning

confidence: 99%

Section: Models and Analysismentioning

confidence: 99%

“…For a silicon-oxide particle modified by attaching positively charged polymer: (11) where Γ' NH3 + is the density of ionized amino groups on the surface of colloidal particle. For gold colloidal particles encapsulated by a layer of positively charged polymer: (12) where Γ' NH3 + is the density of ionized amino groups and σ Au is the density of the negative charge carried by non-modified gold particle in aqueous solution [15]. For the 20 nm gold particle in aqueous solution having Zeta-potential of 30 mV, the surface charge density estimated from the Graham equation is σ Au = 89.6 mC/m 2 [12,15].…”

Section: Models and Analysismentioning

confidence: 99%

“…For gold colloidal particles encapsulated by a layer of positively charged polymer: (12) where Γ' NH3 + is the density of ionized amino groups and σ Au is the density of the negative charge carried by non-modified gold particle in aqueous solution [15]. For the 20 nm gold particle in aqueous solution having Zeta-potential of 30 mV, the surface charge density estimated from the Graham equation is σ Au = 89.6 mC/m 2 [12,15]. The energy, E, of interaction of the colloidal particle and the substrate surface is proportional to the multiplication of the electric charge densities of the substrate and the net charge of colloidal particle (13) The Eqs.…”

Section: Models and Analysismentioning

confidence: 99%

“…In general, the density of electric charge on solid surface, either the particle or substrate, is given by the sum of electric charges of all ionized chemical groups within the surface unit area. With respect to microarrays manufactured on aminated glass substrates [11], in aqueous solutions the charge-determining ions are the negatively-charged ions of silicon oxide of the glass substrate SiO − , the positivelycharged amino-silane ions R-NH 3 +, and the negatively-charged phosphate groups PO 4 − of the DNA backbone [12,13]:The density of the electric charge on the array surface, σ Surf , is given by the sum of the charges of positive and negative ions on the surface: where Γ NH3 + Γ SiO −, and Γ PO4 − are the surface density of the respective ions, and e is the protonic charge. From the mass action law for protonation and deprotonation reactions:…”

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Label-free detection of biomolecules on microarrays using surface–colloid interaction

Sun

Jacobson

Golovlev

2007

Analytical Biochemistry

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IntroductionMicroarrays are rapidly advancing the technology for analysis of expression of tens of thousands of genes in a single experiment by employing hybridization of target genes to probe molecules immobilized on solid surface [1][2][3]. DNA microarrays usually are small glass, plastic, silicon substrate, or nylon membrane onto which the probe molecules are tethered in the arrays of spots. Each array's spot carries probe molecules specific to one particular gene. The target molecules contained in a sample solution are captured on the array by hybridization to corresponding homologous probe molecules on the array surface. To quantify the number of captured targets on each array spot, the target molecules are usually modified (labeled) by chemical attachment of a fluorescent group [4,5]. The intensity of fluorescence detected from the array spot is the measure of gene expression, i.e., the measure of the abundance of the corresponding mRNA specie in sample solution [6]. Currently, the need for chemical modification of target molecules is a significant limitation of the microarray technology: (1) t chemical modification of targets introduces inaccuracy of quantification due to labeling biases, (2) the chemical labeling requires expensive labeling reagents, and finally (3) the labeling process is time consuming and is often accompanied by a significant loss of sample materials during the post-labeling purification steps.Recently we have reported development of the microarray system for gene expression analysis using cationic gold nanoparticles [7,8]. This approach is significantly different from the previous methods of using gold nanoparticles with oligonucleotides attached to the gold particles for sequence-specific recognition of targets [9,10]. In our approach there is no need to attach a sequence-specific target-recognition agent to the particle surface. The nanoparticles precipitate, under selected conditions, on the hybridized array spots due to electrostatic (e.g., ionic) attraction of the cationic particles and the anionic phosphate groups in the target DNA backbone. The most important aspect of this detection approach is that no covalent chemical modification of target molecules is required for detection. Furthermore, the number of hybridized molecules can be quantified by detecting absorption or light scattering by nanoparticles using a flatbed scanner instead of expensive confocal laser scanners required by conventional fluorescent microarray technologies. The ionic labeling by nanoparticles greatly simplifies procedures and reduces the cost of microarray analysis. In this report we follow up our previous demonstration of the method for label-free detection of DNA hybridization [8], and further investigate the physical chemistry of interaction of colloidal particles and the * Corresponding author. Fax: +1 865 671 2167 E-mail address: golovlev@scien-tec.com (V. Golovlev).Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our cus...

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Section: Models and Analysismentioning

confidence: 99%

Section: Models and Analysismentioning

confidence: 99%

Section: Models and Analysismentioning

confidence: 99%

Section: Models and Analysismentioning

confidence: 99%

mentioning

confidence: 99%

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Label-free detection of biomolecules on microarrays using surface–colloid interaction

Sun

Jacobson

Golovlev

2007

Analytical Biochemistry

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Optical Response of Porous Titania-Silica Waveguides to Surface Charging in Electrolyte Filled Pores

Šefčı́k

Kroslak

Morbidelli

2002

HCA

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Dedicated to Professor Dieter Seebach on the occasion of his 65th birthdayIn this work, we present a novel method for in situ investigation of surface charging and ion transport inside nanopores of titania-silica waveguide by means of the optical-waveguide-lightmode spectroscopy. Porous oxide waveguides show a strong optical response when exposed to electrolyte solutions, and this response is consistent with oxide surface charging due to changes in ionic strength and pH of the solution in contact with the waveguide. The optical response to pH or electrolyte concentration change is stabilized within several minutes when the solution ionic strength is sufficiently high (0.1m), while it takes two orders of magnitude longer to reach stable optical response at very low ionic strengths (< 0.1mm). The relaxation times at the high ionic strength are still by several orders of magnitude slower than expected from bulk diffusion coefficients of electrolytes in water. Our results indicate that diffusion of electrolytes is severely hindered (and more so with decreasing ionic strength) in charged pores inside waveguides.1. Introduction. ± Sol-gel-based silica-titania mixed oxides are important materials in catalysis [1] [2] and optical applications [3 ± 5]. Sol-gel synthesis typically involves one or more metal alkoxides undergoing hydrolysis in aqueous solutions and subsequent condensation eventually forming particles or gels [6]. Resulting materials are usually nanoporous with substantial internal surface areas on the order of 100 m 2 / cm 3 and even higher, when pore filling surfactants or molecular templates are used. Water can be removed from wet gels by supercritical drying to produce low-density aerogels or at ambient pressure with various heating protocols. Ambient-pressure drying causes further condensation and collapse of nanopores due to capillary pressure, resulting in densification and internal surface loss. Heat treatment promotes phase changes such as nucleation and growth of crystalline phases, and phase separation, also leading to densification and decreased porosity. Microstructure of mixed oxides is thus influenced in early stages, when small metal-oxide oligomers have a chance for heterocondensation to achieve molecular-scale homogeneity in the wet gel, as well as in later stages, when porosity and homogeneity can be severely modified during drying.Planar optical waveguides can be prepared by coating silica-titania sols on appropriate substrates to obtain wet gel films, into which diffraction gratings are embossed, followed by further heat treatment in order to achieve required film hardness and stability [7] [8]. The final waveguide thickness is on the order of few hundred nanometers. Depending on temperature and duration of drying, the film porosity can be as high as 20%. For standard drying procedures (few hours at 5008) typical porosity was found to be around 15% [9]. With temperatures as high as 9008, the porosity of silica-titania films can be reduced below 1% [10].

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Fining

2016

Understanding Wine Chemistry

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The charge of glass and silica surfaces

Cited by 826 publications

References 37 publications

Label-free detection of biomolecules on microarrays using surface–colloid interaction

Label-free detection of biomolecules on microarrays using surface–colloid interaction

Optical Response of Porous Titania-Silica Waveguides to Surface Charging in Electrolyte Filled Pores

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