Groups Of PAA Research Articles

In-vitro subsurface remineralisation of artificial enamel white spot lesions pre-treated with chitosan

ObjectiveTo test the null hypothesis that chitosan application has no impact on the remineralisation of artificial incipient enamel white spot lesions (WSLs). Methods66 artificial enamel WSLs were assigned to 6 experimental groups (n=11): (1) bioactive glass slurry, (2) bioactive glass containing polyacrylic acid (BG+PAA) slurry, (3) chitosan pre-treated WSLs with BG slurry (CS-BG), (4) chitosan pre-treated WSLs with BG+PAA slurry (CS-BG+PAA), (5) remineralisation solution (RS) and (6) de-ionised water (negative control, NC). Surface and cross-sectional Raman intensity mapping (960cm−1) were performed on 5 samples/group to assess mineral content. Raman spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were used to identify the type of newly formed minerals. Surface and cross-sectional Knoop microhardness were implemented to evaluate the mechanical properties after remineralisation. Surface morphologies and Ca/P ratio were observed using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Data were statistically analysed using one-way ANOVA with Tukey’s test. ResultsBG+PAA, CS-BG, RS presented significantly higher mineral regain compared to NC on lesion surfaces, while CS-BG+PAA had higher subsurface mineral content. Newly mineralised crystals consist of type-B hydroxycarbonate apatite. CS-BG+PAA showed the greatest hardness recovery, followed by CS-BG, both significantly higher than other groups. SEM observations showed altered surface morphologies in all experimental groups except NC post-treatment. EDX suggested a higher content of carbon, oxygen and silicon in the precipitations in CS-BG+PAA group. There was no significant difference between each group in terms of Ca/P ratio. SignificanceThe null hypothesis was rejected. Chitosan pre-treatment enhanced WSL remineralisation with either BG only or with BG-PAA complexes. A further investigation using dynamic remineralisation/demineralisation system is required with regards to clinical application.

Facile fabrication of polyacrylic acid-polyvinyl chloride composite adsorbents for the treatment of cadmium-contaminated wastewater

Facile fabrication of polyacrylic acid-polyvinyl chloride (PAA-PVC) composite adsorbents and their evaluation for Cd(II) adsorption is reported in this study. The sorbents were prepared via a simple phase inversion process by spinning PAA-PVC polymer blends into mixed solution of water and methanol. The prepared fibers were characterized by scanning electron microscopy, energy disperse X-ray microscopy and Fourier transform infra-red microscopy, and their sorption performances were evaluated by batch sorption experiments. Through sorption isotherm, the maximum sorption capacity was estimated as 331.59 mg/g using the Langmuir isotherm model. Intra-particle diffusion played a major role in reaching the adsorption equilibrium. Ion-exchange between the charged carboxyl groups of PAA and the Cd(II) solution was observed to be the main mechanism of Cd(II) sorption. This study is believed to pave way for preparing cost-effective polymeric composite sorbents for the removal of heavy metals from polluted waters.

Liquid-crystal droplets functionalized with a non-enzymatic moiety for glucose sensing

3-Aminophenyl boronic acid (APBA)-decorated 4-cyano-4′-pentylbiphenyl (5CB) microdroplets were utilized for glucose detection with high specificity and sensitivity. APBA decoration was performed by firstly coating poly(acrylic acid) (PAA) on the 5CB droplet with amphiphilic poly(4-cyanobiphenyl-4′-undecylacrylate-b-acrylicacid) (LCP-b-PAA) and performing covalent bonding of APBA to the PAA chains by EDC coupling between the acrylic groups of PAA and the amine groups of APBA. The binding events between APBA and glucose were translated by configurational change (from radial to bipolar) of the 5CB droplets, observed under a polarized optical microscope with crossed polarizers. The liquid crystal (LC) droplet-based non-enzymatic (NE) biosensor for glucose detection exhibited high sensitivity (detection limit of 0.05mM) even in complex serum sample, high selectivity against cholesterol, uric acid, and acetaminophen, and good stability for 30 d. This NE-based glucose LC biosensor is cost-effective and highly stable compared to enzyme-based LC glucose biosensors and thus, could replace such enzyme-based biosensors.

Characterisation of alpha-chitin/poly(acrylic acid) blend films

Chitin whiskers reinforced Poly(acrylicacid) films were prepared by casting. Films were characterised for mechanical and thermal properties. Raman and XRD spectrum and SEM morphology were examined. The tensile strength increased as chitin increases up to 11.39% and gradually decreases. The % strain gradually reduces as whiskers increases. Thermal stability of films improved from those of the pure PAA as the Tg increases at higher whiskers content. The strongest interaction between the carboxylic (CO) group of PAA and the amide (NH3+) of chitin at the amorphous phase occurs at 3.23% whiskers. The particle size of chitin was reduced as revealed by XRD.

Tuned interactions of silver nanoparticles with ZSM-5 zeolite by adhesion-promoting poly(acrylic acid) deposited by electrospray ionization (ESI)

The electrospray ionization (ESI) method was used for deposition of thin films of poly(acrylic acid) (PAA) on Cu/ZSM-5 (5 wt.% Cu) and Ag–Cu/ZSM-5 (1 wt.% Ag and 4 wt.% Cu) composites. For comparative purposes, the ZSM-5 zeolite was synthesized under hydrothermal conditions and loaded with PAA under the same treating conditions as the composites. This method allowed the formation of uniform polymer films of controlled thickness on conductive substrates. The structural characteristics were characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, atomic force microscopy and X-ray diffraction (XRD). The deposited PAA layer over ZSM-5 acts as a common dispersing and stabilizing agent through coordination-driven guest-templated polymer via interaction of Ag+ and Cu2+ with carboxylic acid groups, thus increasing and controlling the adhesion and the release of metallic species. A short exposure to light and temperature has reduced the metal ions to Cu0 and Ag0 metallic nanoparticles. The results of XRD analysis let suggest that the interaction of Cu and Ag with carboxylic groups of PAA inhibits the formation of large metallic silver particles. These samples were being studied for their potential as antibacterial agents toward the bacterial strains such as Staphylococcus pneumonia, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa as Gram positive and Gram negative bacteria, respectively. Aspergillus fumigatus and Candida albicans as Fungi were also evaluated. The Cu/ZSM-5 and Ag–Cu/ZSM-5 nanocomposites coated with a 10 nm thick PAA layer exhibit significant antibacterial activity.

PH-responsive drug release and real-time fluorescence detection of porous silica nanoparticles

In this work, pH-sensitive “dual-switch” porous silica (pSiO2) nanoparticles (NPs) were constructed for drug delivery. Poly(acrylic acid) (PAA) was grafting onto the internal and external surfaces of amino groups functionalized porous silica (pSiO2-NH2) NPs by the amidation between the amino groups and the carboxyl groups of PAA for pH triggered drug release. The resultant pSiO2/PAA NPs have an average diameter of 50–60nm and high specific surface area (914m2·g−1). To improve the loading capacity, ZnO quantum dots (QDs) were used to block the partial pores of pSiO2/PAA and the loading capacity reached to 28% for methotrexate (MTX) model drug. The in vitro cellular cytotoxicity test and a hemolysis assay demonstrated that the pSiO2/PAA/ZnO NPs were highly biocompatible and suitable to utilize as drug carriers. The MTX-loaded pSiO2/PAA/ZnO NPs displayed more efficient cytotoxic to HepG2 cells than free MTX. The pSiO2/PAA/ZnO NPs displayed low premature, pH-responsive release and pH-dependent fluorescence. Moreover, pH-dependent fluorescence enables to trace MTX release behavior.

Morphology and properties of polyimide/multi-walled carbon nanotubes composite aerogels

Polyimide (PI) aerogels are open-celled materials with high porosity, low density, excellent mechanical property and high thermal stability. Linear PI aerogels exhibit drastic shrinkage during the fabrication process. Cross-linked PI aerogels were usually fabricated by utilizing the costly cross-linking agents such as 1,3,5-triaminophenoxybenzene or octa-(aminophenyl)silsesquioxane. Herein, amino functionalized multi-walled carbon nanotubes (MWCNTs-NH2) were prepared by amidation reaction; PI/MWCNTs-NH2 composite aerogels were fabricated by adding MWCNTs-NH2 to anhydride end-capped poly(amic acid) (PAA), chemical imidization of PAA and supercritical carbon dioxide drying. The microstructures, pore size, elastic modulus, thermal properties and other physical properties of the obtained PI/MWCNTs-NH2 composite aerogels were investigated. The results showed that MWCNTs-NH2 could act as a cross-linker of PI because the amino groups of MWCNTs-NH2 could react with the terminal anhydride groups of PAA. With the addition of MWCNTs-NH2, the shrinkage of PI/MWCNTs-NH2 composite aerogels decreased. The densities and Young’s moduli of PI/MWCNTs-NH2 composite aerogels also decreased. The PI/MWCNTs-NH2 composite aerogels had coralline-like structure with mesopores (average pore size: 11–20 nm). The PI/MWCNTs-NH2 composite aerogels also exhibited decent thermal stability and thermal insulating property.

Surface Polarity and Self-Structured Nanogrooves Collaboratively Oriented Molecular Packing for High Crystallinity toward Efficient Charge Transport.

Efficient charge transport in organic semiconductors is essential for construction of high performance optoelectronic devices. Herein, for the first time, we demonstrate that poly(amic acid) (PAA), a facilely deposited and annealing-free dielectric layer, can tailor the growth of organic semiconductor films with large area and high crystallinity toward efficient charge transport and high mobility in their thin film transistors. Pentacene is used as a model system to demonstrate the concept with mobility up to 30.6 cm2 V-1 s-1, comparable to its high quality single crystal devices. The structure of PAA has corrugations with OH groups pointing out of the surface, and the presence of an amide bond further allows adjacent polymer strands to interact via hydrogen bonding, leading to a self-rippled surface perpendicular to the corrugation. On the other hand, the strong polar groups (-COOH/-CONH) of PAA could provide repulsive forces between PAA and pentacene, which results in the vertical orientation of pentacene on the dielectric surface. Indeed, in comparison with its imidized counterpart polyimide (PI), PAA dielectric significantly enhances the film crystallinity, drastically increases the domain size, and decreases the interface trap density, giving rise to superior device performance with high mobility. This concept can be extended to more organic semiconducting systems, e.g., 2,6-diphenylanthracene (DPA), tetracene, copper phthalocyanine (CuPc), and copper hexadecafluorophthalocyanine (F16CuPc), demonstrating the general applicability. The results show the importance of combining surface nanogrooves with the strong polarity in orienting the molecular arrangement for high crystallinity toward efficient charge transport in organic semiconductors.

有機・無機複合薄膜を修飾した水晶振動子センサによるアンモニアおよびホルムアルデヒドの二成分ガス検知

Quartz crystal microbalance (QCM) gas sensors based on the alternate deposition of TiO2 and polymers were developed for the detection of ammonia and formaldehyde odors. For sensitive detection of both analytes, poly(acrylic acid), PAA, and poly(allyamine hydrochloride), PAH, were employed in the film along with TiO2 thin layers that were prepared by the gas-phase surface sol-gel (GSSG) process. The alternate (TiO2/PAA/TiO2/PAH) film-deposited QCM sensor showed linear responses to ammonia in the concentration range 0.5-40 ppm and to formaldehyde in the concentration range 0.3-20 ppm. The sensor response was very fast, stable, and repeatable. The ammonia or formaldehyde binding is based on the acid-base interaction to the free carboxyl or amino groups of PAA or PAH. TiO2 thin layers deposited by the GSSG process played significant roles in preventing the electrostatic interaction of polymer layers and in improving the diffusion of gaseous analytes inside the film.

Temperature-, pH- and CO₂-Sensitive Poly(N-isopropylacryl amide-co-acrylic acid) Copolymers with High Glass Transition Temperatures.

A series of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAAm-co-PAA) random copolymers were synthesized through free radical copolymerization in MeOH. The incorporation of the acrylic acid units into PNIPAAm tended to enhance the glass transition temperature (Tg), due to strong intermolecular hydrogen bonding between the amide groups of PNIPAAm and the carboxyl groups of PAA, as observed using 1H nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopic analyses. The lower critical solution temperature (LCST) increased upon increasing the pH of the aqueous solution containing PNIPAAm-co-PAA because the COOH groups of the PAA segment dissociated into COO− groups, enhancing the solubility of the copolymer. In addition, high-pressure differential scanning calorimetry revealed that the LCSTs of all the aqueous solutions of the copolymers decreased upon increasing the pressure of CO2, suggesting that CO2 molecules had displaced H2O molecules around the polar CONH and COOH groups in PNIPAAm-co-PAA, thereby promoting the hydrophobicity of the copolymers in the aqueous solution. In addition, the values of Tg of a film sample increased upon treatment with supercritical CO2, implying that intermolecular interactions in the copolymer had been enhanced after such treatment.

PH-responsive cholesteric liquid crystal double emulsion droplets prepared by microfluidics

Functionalized cholesteric liquid crystal (CLC) double emulsion droplets (DEDs) were prepared from nematic LCs of MLC-2132 doped with (S)-4-cyano-4′-(2-methylbutyl)biphenyl (CB15) by using a microfluidic method, employing glass capillaries with a combined co-flow and flow-focusing geometry. Both planar (P) and homeotropic (H) anchoring on the surfaces of the CLC DEDs could be achieved using poly(vinyl alcohol) (PVA) and a mixture of sodium dodecyl sulfate (SDS)/polysorbate 80 (TWEEN 80), respectively. The H configuration was unstable when used with SDS alone, and hence required the use of a mixture of SDS and TWEEN 80. The P/P, P/H, H/P, and H/H configurations on the inner/outer surfaces exhibited different surface morphologies, which were observed in reflection-mode bright-field image patterns. The P/P configuration displayed a distinct, circular central spot with a reflection color that represented the helical pitch of the CLC, since the planar orientation of the mesogenic groups caused a parallel orientation of helical layers relative to the droplet surface, (which meets the Bragg reflection condition). The P/H, H/P, and P/P images observed from the same mode exhibited small, black circular spots assembled in a pseudo-hexagonal fashion, with reflected colored light coming from the boundary regions between the circular spots. This result indicated that the small, circular spots were due to the perpendicular orientation of the helical layers that resulted from the homeotropic orientation of the mesogenic groups (which does not meet the Bragg reflection condition). The CLC DEDs coated with poly(acrylic acid)-b-poly(4-cyanobiphenyl-4′-oxyundecylacrylate) (PAA-b-LCP) on the outer surface (CLC DEDPAA) were pH-responsive. When the inner surface was controlled to have a P configuration with water, the central, circular reflection color pattern changed to a small, black circular spot pattern with increasing pH. This indicated that protonation and deprotonation of the carboxylic group of PAA occurred, which in turn led to planar (tangential) and perpendicular (homeotropic) orientations, respectively. These pH-sensitive, mono-dispersed CLC DEDs have potential use as biosensors, where immobilization of the ligands causes local changes in pH in response to analytes.

Cholesteric Liquid Crystal Droplets for Biosensors

By utilizing a microfluidics approach, we prepared uniformly sized cholesteric liquid crystal (CLC) droplets from MLC-2132 doped with a chiral dopant (S)-4-cyano-4'-(2-methylbutyl)biphenyl (CB15). We studied the helical structures and reflecting color patterns of high- and low-dopant CLC droplets coated with poly(vinyl alcohol) (PVA) and sodium dodecyl sulfate (SDS). One central large spot with reflecting color in the CLC droplets (initially coated with PVA for planar anchoring) changed to many small spots with the same reflecting color (chicken-skin pattern) when an SDS aqueous solution was introduced to increase the homeotropic anchoring power. These small spots subsequently merged into several spots (flashlight pattern) with time. The CLC droplets coated with poly(acrylic acid)-b-poly(4-cyanobiphenyl-4'-oxyundecyl acrylate) (PAA-b-LCP) (CLCPAA droplets) were pH-responsive. Their helical structure and the reflecting color pattern changed because of protonation (at low pH) and deprotonation (at high pH) of the carboxylic group of PAA, which causes the planar (tangential) and perpendicular (homeotropic) orientations, respectively. The CLCPAA droplets immobilized with glucose oxidase (GOx) and cholesterol oxidase (ChO) (CLCPAA-GOx and CLCPAA-ChO droplets, respectively), for glucose and cholesterol detection, exhibited high sensitivity (0.5 and 2.5 μM for the CLCPAA-GOx and CLCPAA-ChO droplets, respectively), good selectivity, and fast response (≤4 s). Further optimization will enhance their performance as biosensors. With this novel approach, detection is possible by observing the coloring pattern of CLC droplets, without the crossed polarizers that are necessary for nematic LC biosensor systems.

Nanoporous polyimide film from poly(ethylene glycol-co-imide) using a one-step heat calcination process

ABSTRACTPolyamic acid (PAA) made from 3,3, 4,4-biphenyltetracarboxylic dianhydride and 4,4-diaminodiphenyl ether was synthesized and used as the backbone of nanoporous polyimide. Thermally labile polyethylene glycol (PEG) at 10, 20 or 30 wt% was introduced to the end group of PAA. Self-assembled PAA-b-PEG micelle-like nanoparticles could be formed as a result of amphiphilic characteristics of hydrophobic PAA and hydrophilic PEG. Thermal imidization and degradation of spin-coated amphiphilic PAA-b-PEG film were performed sequentially through one-step heat treatment to obtain polyimide film with nanopores. Pore sizes decreased with increasing amount of PEG block and their dielectric constants decreased from 2.71 ± 0.13 to 2.38 ± 0.11.

Effects of a supplement combining Pycnogenol® and l-arginine aspartate on lower urinary dysfunction compared with saw palmetto extract

ObjectivesLower urinary tract symptoms (LUTS) and sexual dysfunction (SDys) are common problems that affect quality of life (QOL) in elderly men. In addition to prescribed drugs, many over-the-counter medications including supplements are used to treat QOL diseases. Phosphodiesterase inhibitors are reported to be effective for both LUTS and SDys by increasing nitric oxide levels. French maritime pine bark extract Pycnogenol®, which is a potent nitric oxide donor, is reported to be effective for SDys. However, no reports have been published on whether it ameliorates LUTS. DesignOpen-labeled, randomized study. The effects of two supplements, Nokogiriyashi EX® containing 160 mg saw palmetto (SP) extract per tablet and Edicare® containing 10 mg of Pycnogenol®, 115 mg of l-arginine and 92 mg of aspartate (PAA) per tablet on International Prostate Symptom Score (IPSS), IPSS–QOL, Overactive Bladder Symptom Score (OABSS), International Index of Erectile Function 5 (IIEF5), Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF), urinary 8-OHdG and uroflowmetry (UFM) of total 40 men with LUTS and SDys were examined. Results19 subjects were instructed to take two tablets of SP, on the other 20 were on four tablets of PAA for 16 weeks. IPSS and IPSS–QOL showed statistically significant improvements in both groups. OABSS and IIEF5 were significantly improved in the PAA group. Conversely, ICIQ-SF, 8-OHdG and UFM did not change in either group. ConclusionsPAA might be an effective therapeutic alternative for elderly patients with LUTS and SDys.

Polymer-Templated Carbon Hybridized Nanostructured Transition Metal Oxide As Advanced Lithium-Ion Anodes

An enormous spectrum of applications of lithium-ion batteries (LIBs), particularly in electric vehicles (EVs), hybrid EVs and electric grids, invokes essential requirements on their energy storage capabilities. However, the most common commercial graphite anode material still exhibits a relatively low theoretical specific capacity of 372 mAh g-1, which cannot meet the demand of the high-energy applications noted above. To date, a wide variety of anode materials with much higher capacities have been extensively investigated. In this regard, transition metal oxides (MxOy, where M is Fe, Co, Ni, Cu, Sn, Mn, etc.) clearly stand out as the promising alternatives to graphite owing to their attractive higher theoretical capacities (＞ 600 mAh g-1), low cost, environmental friendliness and wide availability containing earth-abundant elements. To further achieve high rate capability, hybrid nanomaterials with more conductive carbonaceous materials have been constructured. The ability to create a synergistic effect of nanostructure engineering and its hybridization with conductive carbonaceous material is highly desirable for attaining high-performance lithium ion batteries (LIBs). However, it remains challenging to achieve this synergy. Here we propose a general method to create a synergistic effect of nanostructure engineering and its hybridization with conductive carbonaceous material. Star-like and bottlebrush-like poly (acrylic acid)-block-polystyrene (PAA-PS) diblock copolymer and polystyrene-block-poly(acrylic acid)-block-polystyrene (PS-PAA-PS) triblock copolymer with controlled dimensions will be synthesized through atom transfer rapid polymerization (ATRP). Through a strong coordination bonding between the metal moiety of inorganic precursors and the functional groups of PAA (-COOH), the inorganic precursors can be selectively incorporated into the space formed by the PAA block. As a result, nanostructured transition metal oxide solid nanocrystals and hollow nanocrystals can be synthesized guided by the PAA-PS and PS-PAA-PS templates, respectively. In addition, by changing the polymeric templates from star-like to bottlebrush-like structure, the transition metal oxide nanocrystals varied from isotropic (i.e. nanoparticles, hollow nanoparticles) to anisotropic (i.e. nanorods, nanotubes). The diameter of the transition metal oxide nanocrystals is determined by the dimension of the PAA part, and it could be easily changed by varying the molecular weight of PAA part in the polymeric templates. Morever, the polymeric template not only serves as an easy control over the size and shape of the inorganic nanocrystals, but also acts as carbon source when calcinated at high temperature at argon atmosphere. We demonstrated that the carbon-hybridized nanocrystals obtained by the polymer templating method would be superior anode materials for LIBs.

Loading of Antibiotics into Polyelectrolyte Multilayers after Self-Assembly and Tunable Release by Catechol Reaction

The colonization of bacteria on biomedical implants and subsequent forming of biofilm often leads to serious infections. In this work, poly(acrylic acid) modified by dopamine (PAA-dopa) and poly(ethylenimine) (PEI) self-assembled into multilayer films were used to load and for sustained release of antibiotics. The obtained multilayer films were immersed in tris-buffered saline containing gentamicin sulfate (GS) to load the antibiotics and were cross-linked via catechol chemistry of dopa. Through raising pH value, more carboxyl groups of PAA were protonated and combined with GS through electrostatic forces. After cross-linking, the multilayer films were used as a drug delivery system to embed GS in the matrices which showed a two-stage sustained release profile. In vitro, the release of GS into phosphate-buffered saline (PBS) from the multilayer films, as well as the antibacterial activity, was determined. The drug-loaded multilayer films showed excellent bactericidal function against Staphylococcus aureus...

Synthesis of magnetite nanoparticles coated with poly(acrylic acid) by photopolymerization

Magnetite nanoparticles were coated with poly(acrylic acid) layer by a simple and efficient method of photopolymerization. Structure and morphology of prepared nanoparticles were characterized by ATR-FT IR, XRD and TEM analysis. Moreover, thermal stability and content of magnetite in nanoparticles has been determined by thermogravimetry (TGA). It was found that resulting nanoparticles were covered by a thin, durable shell of crosslinked PAA (thus, insoluble in water). Nanoparticles were characterized by a very small size (in range of 6–13nm) and high content of the magnetite (81%). The protective coating on the magnetite surface is a result of interactions between carboxyl groups of PAA and Fe3O4 particles.

Patterned Poly(acrylic acid) Brushes Containing Gold Nanoparticles for Peptide Detection by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry.

Patterned poly(acrylic acid) (PAA) brushes was successfully generated via photolithography and surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid as verified by water contact angle measurements and FT-IR analysis. The carboxyl groups of PAA brushes can act as reducing moieties for in situ synthesis of gold nanoparticles (AuNPs), without the use of additional reducing agent. The formation of AuNPs was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. The glass surface-modified by PAA brushes and immobilized with AuNPs (AuNPs-PAA) can be used as a substrate for SALDI-MS analysis, which is capable of detecting both small peptides having m/z ≤ 600 (glutathione) and large peptides having m/z ≥ 1000 (bradykinin, ICNKQDCPILE) without the interference from matrix signal suggesting that AuNPs were stably trapped within the PAA brushes and the carboxyl groups of PAA can serve as internal proton source. By employing AuNPs as the capture probe, the AuNPs-PAA substrate can selectively identify thiol-containing peptides from the peptide mixtures with LOD as low as 0.1 and 0.05 nM for glutathione and ICNKQDCPILE, respectively. An ability to selectively detect ICNKQDCPILE in a diluted human serum is also demonstrated. The patterned format together with its high sensitivity and selectivity render this newly developed substrate a potential platform for high-throughput analysis of other biomarkers, especially those with low molecular weight in complex biological samples.

A New Concept for Development of Quartz Crystal Microbalance Fire Prevention Sensors Modified with Nano-Assembled Thin Films

In this report, we describe a new concept for the development of quartz crystal microbalance (QCM) fire prevention sensors modified with nano-assembled thin films. The first example is the fabrication of QCM gas sensors based on alternate adsorption of TiO2and poly(acrylic acid) (PAA) for the sensitive detection of amine odors. The QCM sensors showed a linear response to ammonia at concentrations of 0.3--15 ppm, depending on the deposition cycle of the alternate TiO2/PAA layers. Ammonia binding is based on acid--base interaction with the free carboxylic acid groups of PAA, and the limit of detection of the 20-cycle TiO2/PAA400film under exposure to ammonia was estimated to be 0.1 ppm. The second example, monitoring of relative humidity, used porphyrin-based nano-assembled thin films prepared by a layer-by-layer approach on QCM resonators. These films were also used to detect significant environmental changes (due to smoke, humidity, or hazardous material release), and the results revealed that QCM-based real-environment monitoring devices can be implemented.

Dual stimuli-responsive copolymers comprising poly(N-isopropylacrylamide) and poly(cyano malachite green)

Abstract This article describes synthesis and stimuli-responsive behavior of dual stimuli-responsive copolymers (PNIMG) composed of temperature-responsive poly( N -isopropylacrylamide) (NIPAAm) and photo-responsive poly(cyano malachite green) (CMG). The PNIMG copolymer was regularly and uniformly layer-by-layer deposited with poly(acrylic acid) (PAA) onto solid substrates via hydrogen bonding between carboxylic acid group of PAA and amide hydrogen of PNIPAAm in PNIMG, leading to multilayered films composed of PNIMG/PAA bilayers. Upon UV irradiation, the colorless electrically neutral CMG involved in PNIMG copolymer in solution and multilayer films was converted to the light green cationic form through the release of cyanide ion. The initial photoionization rates of PNIMG-3, PNIMG-6 and PNIMG-10 (numbers denote the mol% CMG composition in PNIMG) in solution were determined to 6.54 × 10 −3 , 1.88 × 10 −2 and 3.22 × 10 −2 s −1 , respectively, indicating the strong dependency of the photoionization rate on the CMG compositions of PNIMG. The photoionization rates of CMG in (PNIMG-3/PAA) 10 and (PNIMG-6/PAA) 10 multilayer films were determined to be 6.50 × 10 −5 and 1.25 × 10 −4 s −1 , respectively, which were slower by two orders of magnitude, compared to those in solution. The thermal-responsive behavior of PNIMGs in solution was manifested from clear identification of their lower critical solution temperature (LCST), which was dependent on the CMG composition of PNIMG. The LCST of PNIMG-3, PNIMG-6 and PNIMG-10 copolymers (29, 28 and 27.5 °C, respectively) decreased gradually, as the CMG composition increased. By contrast, the PNIMG copolymers positively-charged after the UV irradiation exhibited very slow and weak phase transition behavior in acetate buffer solution, leading to no clear identification of their LCSTs. The multilayer film composed of PNIMG/PAA bilayers involving the net and fixed positive CMG charges acts as a Donnan membrane, which exerts either weak electrostatic repulsion or attraction effects for cations and anions. The selectivity of K + /Ca 2+ by (PNIMG-6/PAA) 10 membrane increased nearly by twofold compared to that of (PNIMG-3/PAA) 10 , exhibiting the influence of CMG density on the Donnan effect of the membranes. Furthermore, the selectivity of K + /Ca 2+ by (PNIMG/PAA) 10 membranes showed 2–3 fold increase after UV irradiation due to the enhanced Donnan effect. These photo-responsive membranes would find potential applications in designing sophisticated modern materials for biotechnology, filtration systems, and sensors, which could require a remote, clean and focused photocontrol over ions or particle-transports.