Hybrid Micro-Optical Sensors via Sol-Gel Soft Lithography

2000 ◽  
Vol 628 ◽  
Author(s):  
Mark A. Clarner ◽  
Michael J. Lochhead
Keyword(s):  
Optical Sensors ◽  
Soft Lithography ◽  
Sol Gel ◽  
Silica Gels ◽  
Ph Sensing ◽  
Ambient Conditions ◽  
Sensor Applications ◽  
Patterned Structures ◽  
Biological Functionality ◽  
Indicator Dyes

ABSTRACTOrganically modified silica gels and dye-doped silica gels have been patterned into micrometer-scale structures on a substrate using micro molding in capillaries (MIMIC). This approach is from a class of elastomeric stamping and molding techniques collectively known as soft lithography. Soft lithography and sol-gel processing share attractive features in that they are relatively benign processes performed at ambient conditions, which makes both techniques compatible with a wide variety of organic molecules, molecular assemblies, and biomolecules. The combination of sol-gel and soft lithography, therefore, holds enormous promise as a tool for microfabrication of materials with optical, chemical, or biological functionality that are not readily patterned with conventional methods. This paper describes our investigation of micro-patterned organic-inorganic hybrid materials containing indicator dyes for microfluidic sensor applications. Reversible colorimetric pH sensing via entrapped reagents is demonstrated in a prototype microfluidic sensor element. Patterned structures range from one to tens of micrometers in cross-section and are up to centimeters in length. Fundamental chemical processing issues associated with mold filling, cracking and sensor stability are discussed.

Influence of Formation Parameters on the Mechanical Properties of Wet Gels

1986 ◽  
Vol 88 ◽  
Author(s):  
S. A. Pardenek ◽  
J. W. Fleming ◽  
L. C. Klein
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Sol Gel ◽  
Silica Gels ◽  
Ambient Conditions ◽  
Relaxation Measurements ◽  
Beam Bending ◽  
Gel Composition ◽  
Processing Steps ◽  
Made In

ABSTRACTThe mechanical behavior of wet silica gels formed by various sol-gel processes has been studied. Samples were analyzed with a beam-bending apparatus specifically designed for accurate measurements of very low strength solids. Breaking strength, viscosity and relaxation measurements were made on gelled bodies. Specimens were studied in an undried gel state, molded in shapes suitable for the particular experiments. Tests were made in several ambient conditions including immersion in a liquid bath. The mechanical properties of gels are dependent upon the gel composition, gel age and other formation parameters such as pH, temperature and pressure. An understanding of these properties is particularly important in determining the nature of subsequent processing steps. Models for the structures of the various gels are proposed which explain variation in mechanical behavior.

scholarly journals Study and Optimization of Self-Assembled Polymeric Multilayer Structures with Neutral Red for pH Sensing Applications

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Javier Goicoechea ◽  
Francisco J. Arregui ◽  
Jesus M. Corres ◽  
Ignacio R. Matias
Keyword(s):  
Optical Sensors ◽  
Response Times ◽  
Neutral Red ◽  
Layer By Layer ◽  
Ph Sensing ◽  
Force Microscopy ◽  
Sensor Applications ◽  
Sensing Applications ◽  
Lbl Films ◽  
Self Assembled

The characterization of nanostructured thin films is critical in the design and fabrication of optical sensors. Particularly, this work is a detailed study of the properties of layer-by-layer electrostatic self-assembled multilayer (LbL) structures fabricated using poly(allylamine hydrochloride) (PAH) and Neutral Red (NR) as cations, and poly(acrylic acid) (PAA) as polyanion. These LbL films, due to the colorimetric properties of the NR, are suitable for sensor applications such as pH sensing in the physiological range. In the (PAH+NR/PAA) LbL structure, it has been observed a very important influence of the pH of the solutions in the properties of the resultant films. Different techniques such as spectroscopy and atomic force microscopy (AFM) are combined to characterize the films, and the results are analyzed showing coherence with previous works. The LbL structure is finally optimized and dramatically improved nanostructured films were fabricated, showing good sensing properties, short response times, and good stability.

Nanoparticle‐Reinforced Silica Gels with Enhanced Mechanical Properties and Excellent pH‐Sensing Performance

2020 ◽  
Vol 37 (2) ◽  
pp. 1900404
Author(s):  
Xinyuan Xie ◽  
Yingshi Deng ◽  
Jiehui Peng ◽  
Shiqi Zheng ◽  
Chezheng Cao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Silica Gels ◽  
Ph Sensing ◽  
Sensing Performance

Sol-Gel Optical Sensors for Glutamate

2000 ◽  
Vol 662 ◽  
Author(s):  
Jenna L. Rickus ◽  
Esther Lan ◽  
Allan J. Tobin ◽  
Jeffery I. Zink ◽  
Bruce Dunn
Keyword(s):  
Optical Sensors ◽  
Sol Gel ◽  
Kinetic Studies ◽  
Excitatory Neurotransmitter ◽  
Nadh Fluorescence ◽  
Millisecond Time Scale ◽  
Temporal And Spatial ◽  
Sensor Detection ◽  
The Brain ◽  
Amino Acid Glutamate

AbstractThe amino acid glutamate is the major excitatory neurotransmitter used in the nervous system for interneuronal communication. It is used throughout the brain by various neuronal pathways including those involved in learning and memory, locomotion, and sensory perception. Because glutamate is released from neurons on a millisecond time scale into sub-micrometer spaces, the development of a glutamate biosensor with high temporal and spatial resolution is of great interest for the study of neurological function and disease. Here, we demonstrate the feasibility of an optical glutamate sensor based on the sol-gel encapsulation of the enzyme glutamate dehydrogenase (GDH). GDH catalyses the oxidative deamination of glutamate and the reduction of NAD+ to NADH. NADH fluorescence is the basis of the sensor detection. Thermodynamic and kinetic studies show that GDH remains active in the sol-gel matrix and that the reaction rate is correlated to the glutamate concentration.

scholarly journals SiO2-SnO2:Er3+ Glass-Ceramic Monoliths

2018 ◽  
Author(s):  
Lam Thi Ngoc Tran ◽  
Damiano Massella ◽  
Lidia Zur ◽  
Alessandro Chiasera ◽  
Stefano Varas ◽  
...  
Keyword(s):  
Rare Earth ◽  
Optical Sensors ◽  
Tin Dioxide ◽  
Sol Gel ◽  
Glass Ceramics ◽  
Building Blocks ◽  
Spectroscopic Properties ◽  
Silica Matrix ◽  
Rare Earth Ions ◽  
Planar Waveguides

The development of efficient luminescent systems, such as microcavities, solid state lasers, integrated optical amplifiers, optical sensors is the main topic in glass photonics. The building blocks of these systems are glass-ceramics activated by rare earth ions because they exhibit specific morphologic, structural and spectroscopic properties. Among various materials that could be used as nanocrystals to be imbedded in silica matrix, tin dioxide presents some interesting peculiarities, e.g. the presence of tin dioxide nanocrystals allows increase in both solubility and emission of rare earth ions. Here, we focus our attention on Er3+ - doped silica – tin dioxide photonic glass-ceramics fabricated by sol-gel route. Although the SiO2-SnO2:Er3+ could be fabricated in different geometrical systems: thin films, monoliths and planar waveguides we herein limit ourselves to the monoliths. The effective role of tin dioxide as luminescence sensitizer for Er3+ ions is confirmed by spectroscopic measurements and detailed fabrication protocols are discussed.

Characterization of Selenium Doped Silica Gels Synthesized by Sol-Gel Method

2014 ◽  
Vol 805 ◽  
pp. 564-569
Author(s):  
Renata Andrade Kobayashi ◽  
Samuel Marcio Toffoli
Keyword(s):  
Sol Gel ◽  
Silica Gels ◽  
Glassy Matrix ◽  
Industrial Glass ◽  
Rare Element ◽  
Gel Method ◽  
Sol Gel Method ◽  
Red Color ◽  
Synthesized Materials

Selenium is a rare element in nature. It is used in the food, pharmaceutical, and glass industries. In commercial glasses, selenium is the element responsible for most of the pink or light red color, but its effect is primarily dependent on the oxidation state of the element in the glassy matrix. Besides, selenium is highly volatile, and as high as 80 wt% may be lost in the furnace during the industrial glass elaboration. The sol–gel method yields synthesized materials of high purity and homogeneity, and uses low processing temperatures. Samples of silica gels were obtained by sol-gel method, incorporating precursors of selenium, with the main objective of reducing selenium losses during its heating. The results of optical absorption, XRD and thermal analysis (TGA, DSC) of the gels are presented and discussed.

HIGH-ACIDITY OPTICAL SENSORS BASED ON SOL-GEL-DERIVED THIN FILMS

2001 ◽  
Vol 34 (10) ◽  
pp. 1603-1616 ◽  
Author(s):  
Mojtaba Shamsipur ◽  
Gholamhassan Azimi
Keyword(s):  
Thin Films ◽  
Optical Sensors ◽  
Sol Gel ◽  
High Acidity

Preparation and Characterization of Carbon Xerogel Based Composites for Electrochemical Sensing and Photocatalytic Degradation

2021 ◽  
Vol 21 (4) ◽  
pp. 2323-2333
Author(s):  
Carmen I. Fort ◽  
Mihai M. Rusu ◽  
Lucian C. Pop ◽  
Liviu C. Cotet ◽  
Adriana Vulpoi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Degradation ◽  
Electrochemical Sensors ◽  
Sol Gel ◽  
Nanocomposite Material ◽  
Electrochemical Sensing ◽  
Ambient Conditions ◽  
Carbon Xerogel ◽  
Voltammetric Detection

In order to obtain a multifunctional nanocomposite material-for electrochemical sensors and photocatalytic applications, structures based on Bi, Fe and TiO2 were grown inside carbon xerogel supports (BiFeCX and BiFeCX-TiO2). First, a wet polymer containing Bi and Fe salts was obtained by following a modified resorcinol-formaldehyde based sol–gel route, followed by drying in ambient conditions, and pyrolysis under inert atmosphere. Then, through TiCl4 hydrolysis, TiO2 nanoparticles were deposited on the BiFeCX xerogel leading to BiFeCX-TiO2. The morphological and structural characterization of the investigated nanocomposites consisted in X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and N2 adsorption measurements, revealing porous carbon structures with embedded nanoparticles and the particularities driven by the pyrolysis and TiCl4 treatment. The new modified electrodes based on BiFeCX or BiFeCX-TiO2 nanocomposite materials, kept in a chitosan matrix (Chi) and deposited on a glassy carbon (GC) electrode surface (GC/Chi-BiFeCX or GC/Chi-BiFeCX-TiO2), were obtained and investigated for Pb(II) voltammetric detection and H2O2 amperometric detection. Moreover, the BiFeCX-TiO2 nanocomposite was tested for the photocatalytic degradation of methyl orange. The great potential of BiFeCX nanocomposite material for developing electrochemical sensors, or BiFeCX-TiO2 for sensors application and photocatalytic application was demonstrated.

Sol-Gel Polymerization of Tetraalkoxygermanium and Organotrialkoxygermanium Monomers

1996 ◽  
Vol 431 ◽  
Author(s):  
Brigitta M. Baugher ◽  
Douglas A. Loy
Keyword(s):  
Chemical Modification ◽  
Sol Gel ◽  
Silica Gels ◽  
Germanium Oxide ◽  
Oxide Materials ◽  
Siloxane Bond ◽  
Mild Conditions ◽  
Condensation Reactions ◽  
Hydrolysis And Condensation ◽  
Opening Up

AbstractWhile the sol-gel polymerizations of tetraalkoxy- and organotrialkoxysilanes have been extensively studied, there have been few reports of similar investigations with the analogous tetraalkoxygermanium and organotrialkoxygermanium compounds. Germanium alkoxides have received less attention due, in part to their higher cost, but also their greater reactivity towards hydrolysis and condensation reactions. Germanium oxide materials are potentially interesting because the Ge-O-Ge linkage is labile (compared with the siloxane bond in silica gels and polysilsesquioxanes) opening up the possibility of further chemical modification of the polymeric architecture. This may permit hydrolytic reorganization of germanium oxide networks under relatively mild conditions. In this paper, we will present the results of our investigations of the solgel polymerizations of tetraethoxygermanium 1, tetraisopropoxygermanium 2, and methyltriethoxy-germanium 3 to afford network materials as both xerogels and aerogels.

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