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.

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.

scholarly journals Near-Infrared pH Sensor Based on a SPEEK–Polyaniline Polyelectrolyte Complex Membrane

Proceedings ◽  
2018 ◽  
Vol 3 (1) ◽  
pp. 11 ◽  
Author(s):  
Nedal Y. Abu-Thabit
Keyword(s):  
Polyelectrolyte Complex ◽  
Near Infrared ◽  
Response Times ◽  
Oxidative Polymerization ◽  
Ph Sensor ◽  
Ph Sensing ◽  
Ph Values ◽  
Sensing Applications ◽  
Ph Range ◽  
Speek Membrane

A polyelectrolyte complex (PEC) membrane based on sulfonated poly (ether ether ketone) and polyaniline (SPEEK-PANI) was developed for pH sensing applications. Aniline was polymerized in the presence of the SPEEK membrane by using in situ chemical oxidative polymerization to yield an ionically crosslinked SPEEK-PANI membrane. The fabricated membrane exhibited sensitivity in the physiological pH range of 2–8. The PEC membrane pH sensor showed good absorption properties in the near-infrared region (NIR). The membrane showed fast response during a de-doping process (≈90 s), while longer response times are essential for doping processes from the alkaline/neutral pH region to the acidic pH region, which is attributed to the presence of highly acidic sulfonic acid groups with a high buffering capacity in the PEC membrane. The SPEEK-PANI membrane exhibited slightly higher water uptake compared to the neat SPEEK membrane. The membrane exhibited good stability, as it was stored in 1M HCl solution for more than 2 years without physical or visual deterioration. A preconditioning step in 1M HCl ensured that the results were reproducible and allows the pH sensor to be used repeatedly. The PEC sensor membranes are suitable for applications that start at low pH values and move upwards to higher pH values in the 2–8 pH range.

scholarly journals Fabrication and Characterization of Antibacterial-active Multilayer Films Based on Keggin Polyoxometalates and Methylene Blue

2010 ◽  
Vol 65 (2) ◽  
pp. 140-146 ◽  
Author(s):  
Dan Chen ◽  
Jun Peng ◽  
Haijun Pang ◽  
Pengpeng Zhang ◽  
Yuan Chen ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Self Assembly ◽  
Multilayer Films ◽  
Photoelectron Spectra ◽  
Layer By Layer ◽  
Force Microscopy ◽  
Atomic Force ◽  
Assembly Technique ◽  
Lbl Films ◽  
Cv Measurements

Two kinds of multilayer films based on Keggin polyoxometalates α-[SiW12O40]4−/α- [PMo12O40]3− and methylene blue have been prepared via the layer-by-layer (LBL) self-assembly technique. The multilayer films were characterized by UV/Vis spectra, atomic force microscopy (AFM) and X-ray photoelectron spectra (XPS). The cyclic voltammetry (CV) measurements have demonstrated that the electrochemical properties of POMs are maintained in the LBL films. The antibacterial activity of the LBL films has also been investigated, which shows a distinct antibacterial effect against Escherichia coli.

Nanografting of Polymer Brushes on Gold Substrate by RAFT-RIGP

2021 ◽  
Vol 7 (1) ◽  
pp. 5
Author(s):  
Bin Jeremiah D. Barba ◽  
Patricia Nyn L. Heruela ◽  
Patrick Jay E. Cabalar ◽  
John Andrew A. Luna ◽  
Allan Christopher C. Yago ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
Optical Sensors ◽  
Self Assembly ◽  
Polymer Brushes ◽  
Incident Light ◽  
Organosulfur Compounds ◽  
Layer By Layer ◽  
Label Free ◽  
Sensing Applications ◽  
Wide Range

Optical sensors based on surface plasmon resonance (SPR) have made great strides in the detection of various chemical and biological analytes. A surface plasmon is a bound, non-radiative evanescent wave generated as resonant electrons on a metal–dielectric surface to absorb energy from an incident light. As analytes bind to a functionalized metal substrate, the refractometric response generated can be used for quantitation with great selectivity, sensitivity, and capacity for label-free real-time analysis. Polymer nanobrushes are ideal recognition elements because of their greater surface area and their wide range of functional versatility. Here, we introduce a simple “grafting-from” method to covalently attach nanometer-thick polymer chains on a gold surface. Nanografting on gold-coated BK-7 glass was performed in two steps: (1) self-assembly of organosulfur compounds; and (2) RAFT-mediated radiation-induced graft polymerization (RAFT-RIGP) of polyglycidyl methacrylate (PGMA). Surface modification was monitored and verified using FTIR and SPR. Layer-by-layer thickness calculated based on Winspall 3.02 simulation fitted with experimental SPR curves showed successful self-assembly of 1-dodecanethiol (DDT) monolayer with thickness measuring 1.4 nm. These alkane chains of DDT served as the graft initiation sites for RAFT-RIGP. Nanografting was controlled by adjusting the absorbed dose in the presence of chain transfer agent, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid. The molecular weight of grafted polymers measuring 2.8 and 4.3 kDa corresponded to a thickness increase of 3.6 and 7.9 nm, respectively. These stable nanografted gold substrates may be further functionalized for sensing applications.

scholarly journals Polymer Fibers Covered by Soft Multilayered Films for Sensing Applications in Composite Materials

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 4052 ◽  
Author(s):  
Dorian Nikoniuk ◽  
Karolina Bednarska ◽  
Maksymilian Sienkiewicz ◽  
Grzegorz Krzesiński ◽  
Mateusz Olszyna ◽  
...  
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Optical Fibers ◽  
Temperature Sensitivity ◽  
Polymer Coating ◽  
Layer By Layer ◽  
Sensor Applications ◽  
Sensing Applications ◽  
Polymer Optical Fibers ◽  
Soft Polymer

This paper presents the possibility of applying a soft polymer coating by means of a layer-by-layer (LbL) technique to highly birefringent polymer optical fibers designed for laminating in composite materials. In contrast to optical fibers made of pure silica glass, polymer optical fibers are manufactured without a soft polymer coating. In typical sensor applications, the absence of a buffer coating is an advantage. However, highly birefringent polymer optical fibers laminated in a composite material are much more sensitive to temperature changes than polymer optical fibers in a free space as a result of the thermal expansion of the composite material. To prevent this, we have covered highly birefringent polymer optical fibers with a soft polymer coating of different thickness and measured the temperature sensitivity of each solution. The results obtained show that the undesired temperature sensitivity of the laminated optical fiber decreases as the thickness of the coating layer increases.

LAYER-BY-LAYER SELF-ASSEMBLED FILMS OF ROSE BENGAL

2011 ◽  
Vol 25 (29) ◽  
pp. 4039-4046 ◽  
Author(s):  
S. A. HUSSAIN ◽  
D. DEY ◽  
D. BHATTACHARJEE
Keyword(s):  
Rose Bengal ◽  
Quartz Substrate ◽  
Film Deposition ◽  
Amine Hydrochloride ◽  
Layer By Layer ◽  
Material Loss ◽  
Absorption Studies ◽  
Lbl Films ◽  
Self Assembled ◽  
To Come

Layer-by-Layer (LBL) self-assembled films of rose bengal (RB) have been fabricated onto quartz substrate by the alternative adsorption of polycation poly (amine hydrochloride) (PAH) and RB. UV–Vis absorption studies reveal the formation of RB dimmer in PAH-RB LbL films. Scanning Electron Micrograph (SEM) picture confirms the aggregation of RB molecules in LbL films. Almost 15 min is required to complete the interaction between RB and PAH molecules in the 1 bilayer LbL film. The dye (RB) was found to come off the film during the subsequent poly cation (PAH) deposition. As an alternative approach RB was anchored to the polycation PAH via physiadsorption and controlling the concentration of the combination of RB and PAH was used as polycation and poly (acrylic acid) (PAA) as polyanion for film deposition. The absorption spectra after each deposition showed that there was no material loss during layer depositions via second method.

Optical fiber pH sensors based on layer-by-layer electrostatic self-assembled Neutral Red

2008 ◽  
Vol 132 (1) ◽  
pp. 305-311 ◽  
Author(s):  
J. Goicoechea ◽  
C.R. Zamarreño ◽  
I.R. Matías ◽  
F.J. Arregui
Keyword(s):  
Optical Fiber ◽  
Neutral Red ◽  
Layer By Layer ◽  
Ph Sensors ◽  
Self Assembled

The Role of Hydrophobicity in the Stability and pH-Switchability of (RXDX)4 and Coumarin-RXDX Conjugate β-Sheets

2020 ◽  
Author(s):  
Ryan Weber ◽  
Martin McCullagh
Keyword(s):  
Biological Imaging ◽  
Ph Sensing ◽  
Hydrophobic Residue ◽  
Ideal Candidate ◽  
Self Assembling ◽  
Sensing Applications ◽  
Β Sheets ◽  
The Stability ◽  
Dynamics Simulations

<p>pH-switchable, self-assembling materials are of interest in biological imaging and sensing applications. Here we propose that combining the pH-switchability of RXDX (X=Ala, Val, Leu, Ile, Phe) peptides and the optical properties of coumarin creates an ideal candidate for these materials. This suggestion is tested with a thorough set of all-atom molecular dynamics simulations. We first investigate the dependence of pH-switchabiliy on the identity of the hydrophobic residue, X, in the bare (RXDX)<sub>4</sub> systems. Increasing the hydrophobicity stabilizes the fiber which, in turn, reduces the pH-switchabilty of the system. This behavior is found to be somewhat transferable to systems in which a single hydrophobic residue is replaced with a coumarin containing amino acid. In this case, conjugates with X=Ala are found to be unstable and both pHs while conjugates with X=Val, Leu, Ile and Phe are found to form stable β-sheets at least at neutral pH. The (RFDF)<sub>4</sub>-coumarin conjugate is found to have the largest relative entropy value of 0.884 +/- 0.001 between neutral and acidic coumarin ordering distributions. Thus, we posit that coumarin-(RFDF)<sub>4</sub> containing peptide sequences are ideal candidates for pH-sensing bioelectronic materials.</p>

Low Molecular Weight Microfibers with Light Sensing Properties

2017 ◽  
Vol 54 (4) ◽  
pp. 655-658
Author(s):  
Andrei Bejan ◽  
Dragos Peptanariu ◽  
Bogdan Chiricuta ◽  
Elena Bicu ◽  
Dalila Belei
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
Aromatic Rings ◽  
X Ray ◽  
Force Microscopy ◽  
Light Sensing ◽  
Sensing Applications ◽  
Atomic Force ◽  
Low Molecular Weight Compounds

Microfibers were obtained from organic low molecular weight compounds based on heteroaromatic and aromatic rings connected by aliphatic spacers. The obtaining of microfibers was proved by scanning electron microscopy. The deciphering of the mechanism of microfiber formation has been elucidated by X-ray diffraction, infrared spectroscopy, and atomic force microscopy measurements. By exciting with light of different wavelength, florescence microscopy revealed a specific optical response, recommending these materials for light sensing applications.

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