Use Of Polyacrylic Acid Research Articles

Functional regulation of organic-inorganic mesh structures for complex CaCO3-based materials

Combining biological strategies with CO2 mineralization allows for the efficient synthesis of functional CaCO3-based material with remarkable performance and efficient carbon utilization. This study found an intriguing phenomenon of increased activation energy (Ea = 52.25 kJ/mol) in the carbonation reaction caused by the complexation between calcium and carboxyl. Complexation triggered by proton transfer was the mechanism for the formation of the highly polymerized structure of polyacrylic acid (PAA)-Ca. The calcium serves as a "bridge" that connects PAA molecules, creating a spatial net structure. The abundant specific surface area of PAA-Ca leads to a shift in the kinetics to a surface coverage model. Consequently, the use of PAA resulted in an efficient synthesis of the organic-inorganic hybrid material with a high purity of CaCO3 (> 97 %). These findings have significant implications for establishing the functional regulation and efficient co-production of CaCO3 in the CO2 mineralization process under mild environmental conditions.

Enhancing dispersion stability and recyclability of ceria slurry with polyacrylic acid for improved glass polishing performance

This study aimed to enhance both the dispersion stability and recyclability of micron-sized ceria slurry in glass polishing by incorporating polyacrylic acid (PAA). PAA with a molecular weight of 240 k was very effective as a dispersant for ceria slurry due to its unique surface adsorption and its characteristics as an anionic polyelectrolyte. Using a 240 k-PAA concentration of 1.0 wt% led to significant improvements in polishing performances, as demonstrated by consistent glass removal rates across recycling cycles. Additionally, the study investigated the physico-chemical properties of polishing slurries, such as specific gravity, particle size, zeta potential, and pH. These properties were effectively maintained with the use of PAA as the dispersant, particularly when KOH was used as a pH adjuster. A 100 µm bag-type filtration system was also introduced for handling the micron-sized ceria slurry, highlighting its practical benefits in slurry management. In conclusion, employing 240 k-PAA as a dispersant in micron-sized ceria slurries for Gorilla glass polishing not only maintains quality and stability across recycling cycles but also provides notable economic advantages by enabling the recycling of the slurry.

Could Commercially Available Aqueous Binders Allow for the Fabrication of Highly Loaded Sulfur Cathodes with a Stable Cycling Performance?

In this review, the application of five commercially available aqueous-based binders including sodium carboxyl methyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), and polyethyleneimine (PEI) as well as some representative custom (or purpose) synthesized functional binders used in lithium sulfur (Li-S) batteries is summarized based on the main evaluation criteria of cycling capacity, battery lifetime, and areal sulfur loading (and, consequently, energy density of the battery). CMC with SBR (styrene butadiene rubber) has been reported with promising results in highly loaded sulfur cathodes (>5 mg cm−2 sulfur loading). PVA and PEI were confirmed to provide an enhanced adsorption of lithium polysulfides due to the interaction with hydroxyl and amine groups. No competitive advantage in electrochemical performance was demonstrated through the use of PAA and PEO. Water-based binders modified with polysulfide-trapping functional groups have complex fabrication processes, which hinders their commercial application. In general, achieving a high capacity and long cycling stability for highly loaded sulfur cathodes using commercial aqueous-based binders remains a significant challenge. Additionally, the scalability of these reported sulfur cathodes, in terms of complexity, cost, and stable electrochemical cycling, should be evaluated through further battery testing, particularly targeting pouch cell performance.

Polymer-assisted enzyme induced carbonate precipitation for non-ammonia emission soil stabilization

Biocementation using enzyme induced carbonate precipitation (EICP) process has become an innovative method for soil improvement. One of the major limitations in scaling-up of biocement treatment is the emission of gaseous ammonia during the urea hydrolysis, which is environmentally hazardous. In order to eliminate this shortcoming, this paper presents a series of experiments performed to evaluate a novel approach for preventing the ammonia byproducts in the EICP process via the use of polyacrylic acid (PAA). Through the adjustment of the pH to acidic, PAA not only promotes the enzyme activity, but also averts the conversion of ammonium to gaseous ammonia and its release, thus preventing any harm to the environment. The sand samples were treated with cementation solution and assessed for improvement in strength. Calcium carbonate content measurements and X-ray powder diffraction analysis identified the calcite crystals precipitated in the soil pores. Scanning electron microscopy analysis clearly showed that calcium carbonate was precipitated connecting soil particles, thus providing a uniaxial compressive strength (UCS) of up to 1.65 MPa. Overall, the inhibition in the speciation of gaseous ammonia shows the great potential of PAA for large-scale promotion of biocement.

Iron oxide-carbon nanocomposites modified by organic ligands: Novel pore structure design of anode materials for lithium-ion batteries

• HML–iron oxide-carbon composite tailored with organic ligands successfully prepared. • Composite’s regulated pore structure depends on organic ligands’ molecular weight. • Composite shows facilitated Li + transport and reversible electrochemical kinetics. • The composite displays an excellent electrochemical performance. Iron oxide-carbon nanocomposites modified with organic ligands ( l -iron oxide-carbon) were prepared by a hydrothermal process and subsequent thermal treatments for application as lithium-ion battery anode materials. The use of polyacrylic acid as the organic ligand effectively inhibited the agglomeration and additional growth of iron oxide nanoparticles, helping to form the porous composite structure. The molecular weights of the as-employed polymeric organic ligands were further regulated (high-molecular-weight ligands (HMLs) and low-molecular-weight ligands (LMLs) were used) to control the pore structure of the composite. Interestingly, since the pore structure of the composite depended on the molecular weight (or radius of gyration) of the polymeric organic ligand, HML-based composites possessed a larger pore volume and larger pore size than those of the LML-based one. The as-formed HML-iron oxide-carbon composite contained homogeneously distributed iron oxide nanoparticles in the porous graphitic carbon matrix obtained by regulated thermal treatments involving carbonization and oxidation. In the comparative electrochemical (EC) test for the samples (HML-iron oxide-carbon and controls), HML-iron oxide-carbon exhibited superior performance (retained capacity: 835 mAh/g after 100 cycles at 1 A/g; rate capability: 628 mAh/g at 3 A/g) compared to that of the controls (LML-iron oxide-carbon, iron oxide-carbon, iron oxide, and porous carbon). HML-iron oxide-carbon also exhibited an increased capacity of 835 mAh/g at 1 A/g after prolonged cycling (after 100 cycles). This outstanding EC performance of HML-iron oxide-carbon can be attributed to its unique composite structure design obtained by the introduction of HMLs and consecutive thermal treatments.

Is prior conditioning of dentin necessary in restoration with glass-ionomer cement? A systematic review and network meta-analysis

ObjectiveTo evaluate the influence of previous conditioning with different materials on the bond strength in dentin, or clinical performance of restorations with glass-ionomer cements (GICs). Methodology: Articles published until February 04, 2020 were searched for in the PubMed and Scopus databases. Gray literature was fetched through the OpenGray platform. The references of the included articles were checked manually. Eligibility criteria(1) be about GICs; (2) test surface conditioning for GICs; (3) be about dentin; and (4) be an intervention study (clinical or laboratorial). Two reviewers participated in the entire process, independently, using structured tables in Excel spreadsheets. Direct and network meta-analyses were performed through mixed treatment comparisons (MTCs) to verify the best conditioning treatment, besides the evaluation of methodological quality and risk of bias. Results2791 articles were pre-nominated and after the eligibility criteria were applied, 30 articles were selected to perform this study. One clinical study and all in vitro studies presented a high risk of bias. Regarding direct comparisons, in restorations with self-cure GIC, the only possible comparison was between polyacrylic acid and non-previous dentin conditioning, and there was no difference between them. Regarding the use of resin-modified GIC, in the direct comparison between non-previous conditioning and use of polyacrylic acid, a favorable difference toward the use of polyacrylic acid was found. In the subgroup of comparison between non-previous treatment and primer, a favorable difference toward the use of primer was found. In the comparison subgroups between phosphoric acid and non-treatment, cavities conditioners and non-treatment, and phosphoric acid and polyacrylic acid, no statistically significant differences were verified. In the network analysis, considering direct and indirect meta-analyses for resin-modified GICs, it was found that the best conditioning for dentin prior to resin-modified GIC fillings is with phosphoric acid, followed by the cavity conditioners; and the worst is not to perform any type of conditioning. ConclusionPrior conditioning does not interfere with the bond strength of self-cure GICs to the sound dentin of permanent teeth, while conditioning dentin with phosphoric acid improves the bond strength of resin-modified GICs to the sound dentin after 24 h, used in permanent teeth. However, the risk of bias is high, the level of evidence is moderate, and the degree of recommendation is weak.

Tratamento Restaurador Atraumático: evolução do conhecimento e aceitação entre Cirurgiões-Dentistas da Estratégia Saúde da Família de Ponta Grossa - Paraná, Brasil ao longo de 5 anos

Objetivo: este estudo avaliou as possíveis modificações no conhecimento teórico/técnico e na aceitação da técnica restauradora atraumática (ART) entre Cirurgiões-Dentistas (CDs) da Estratégia Saúde da Família (ESF) de Ponta Grossa – PR, Brasil ao longo de 5 anos. Material e Métodos: foram utilizados dois instrumentos de avaliação: entrevistas em profundidade e questionários semiestruturados, aplicados ao mesmo grupo de 14 CDs que atuam na ESF. Durante este período, houve momentos de capacitação oferecidos pela Secretaria de Saúde do Município e Secretaria de Saúde do Estado. Resultados: Os CDs afirmaram, nas duas etapas da pesquisa, conhecer o ART e julgaram-no útil em Saúde Pública, fazendo uso das restaurações atraumáticas (RA) rotineiramente. Houve modificações nas percepções referentes ao caráter definitivo das RA; na indicação da técnica de acordo com a característica da lesão cariosa e de acordo com a idade do paciente; na utilização do ácido poliacrílico e de agentes de proteção para o cimento de ionômero de vidro (CIV), entre outras. Além disso, os dentistas passaram a reconhecer o CIV como material essencial à técnica e a aceitar a manutenção da dentina cariada. Houve modificação no hábito da leitura científica sobre o ART entre os profissionais avaliados, além do aumento do número de indivíduos que receberam capacitações sobre ART no serviço. Conclusão: concluiu-se que houve modificações positivas no conhecimento teórico/técnico e na aceitação da técnica ART entre os profissionais entrevistados, reconhecendo assim a importância das capacitações oferecidas no serviço

CMC Binding Agent for Silicon Anodes in Li-Ion Batteries : The Impact of the Formulation

Li-ion batteries using silicon (Si) as an anodic electroactive material are promising devices that are currently being investigated. However, they have a major disadvantage, which is the large volume variation (about 300%) associated with the formation of the Li-Si alloy, this expansion leading to a rapid loss of cell capacity. The usual solution to this problem is the use of a polymeric binder to maintain the cohesion of the electrode during electrochemical cycling. Carboxymethylcellulose (CMC) [1], a semi-synthetic material, has been and is still one of the most studied and used polymers for this purpose. Thus, the formulation of the negative electrode requires a mixture of silicon, CMC and a carbon additive with the "SPEX" ball milling [2] to ensure good electrical conductivity within the composite mixture. This type of mixture, which is highly energetic, reduces the size of the particles and allows the formation of a nanostructured mixture, is essential for the activation of silicon. However, as we have very recently shown in the case of the use of polyacrylic acid (PAA) as a binder [3], it also causes significant degradation of polymer chains. The objective of the work presented here is to study the effect of this mechanical grinding on CMC, in particular the effect on average molecular weights and chemical degradation and, hence, the influence of the characteristics of this modified polysaccharide on the electrochemical performance of the composite negative electrode. To answer this question, we selected three types of commercial CMCs with different molecular weights (90, 250, 700) kg/mol [4]. The formulation of the negative electrode is then modified to better define the impact of the actual molar masses on silicon capacity retention. CMC is no longer mixed with the other components in the SPEX mill, which is too energetic for the polymer binder. This new formulation allows to see the effect of grinding on CMC and to discuss the impact of molar mass variation on capacity retention. A study on the effect of grinding was therefore carried out using different characterization techniques (SEC-MALLS, FTIR, MALDI-TOF, TGA-MS).

Effects of Polyacrylic Acid Pre-Treatment on Bonded-Dentine Interfaces Created with a Modern Bioactive Resin-Modified Glass Ionomer Cement and Subjected to Cycling Mechanical Stress.

Objectives: Resin-modified glass ionomer cements (RMGIC) are considered excellent restorative materials with unique therapeutic and anti-cariogenic activity. However, concerns exist regarding the use of polyacrylic acid as a dentine conditioner as it may influence the bonding performance of RMGIC. The aim of this study was to evaluate the effect of different protocols for cycling mechanical stress on the bond durability and interfacial ultramorphology of a modern RMGIC applied to dentine pre-treated with/without polyacrylic acid conditioner (PAA). Methods: The RMGIC was applied onto human dentine specimens prepared with silicon-carbide (SiC) abrasive paper with or without the use of a PAA conditioner. The specimens were immersed in deionised water for 24 h then divided in 3 groups. The first group was cut into matchsticks (cross-sectional area of 0.9 mm2) and tested immediately for microtensile bond strength (MTBS). The second was first subjected to load cycling (250,000 cycles; 3 Hz; 70 N) and then cut into matchsticks and tested for MTBS. The third group was subjected to load cycling (250,000 cycles; 3 Hz; 70 N), cut into matchsticks, and then immersed for 8 months storage in artificial saliva (AS); these were finally tested for MTBS. The results were analysed statistically using two-way ANOVA and the Student–Newman–Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMCGIC-bonded dentine specimens were aged as previously described and used for interfacial ultramorphology characterisation (dye nanoleakage) using confocal microscopy. Results: The RMGIC applied onto dentine that received no pre-treatment (10% PAA gel) showed no significant reduction in MTBS after load cycling followed by 8 months of storage in AS (p > 0.05). The RMGIC–dentine interface created in PAA-conditioned SiC-abraded dentine specimens showed no sign of degradation, but with porosities within the bonding interface both after load cycling and after 8 months of storage in AS. Conversely, the RMGIC–dentine interface of the specimens with no PAA pre-treatment showed no sign of porosity within the interface after any of the aging protocols, although some bonded-dentine interfaces presented cohesive cracks within the cement after prolonged AS storage. However, the specimens of this group showed no significant reduction in bond strength (p < 0.05) after 8 months of storage in AS or load cycling (p > 0.05). After prolonged AS storage, the bond strength value attained in RMGIC–dentine specimens created in PAA pre-treated dentine were significantly higher than those observed in the specimens created with no PAA pre-treatment in dentine. Conclusions: PAA conditioning of dentine prior to application of RMGIC induces no substantial effect on the bond strength after short-term storage, but its use may increase the risk of collagen degradation at the bonding interface after prolonged aging. Modern RMGIC applied without PAA dentine pre-treatment may have greater therapeutic synergy with saliva during cycle occlusal load, thereby enhancing the remineralisation and protection of the bonding interface.

Synthesis and characterization of Si nanoparticles wrapped by V2O5 nanosheets as a composite anode material for lithium-ion batteries

The preparation and the structural, morphological and electrochemical characterization of a Silicon/V2O5 nanosheets composite (Si@V2O5), as an active anode material for Li-ion batteries, are here reported. The nanocomposite material, aimed at mitigating the morphological instability issues commonly plaguing Si-based anodes, is prepared by a H2O2-based low-impact synthesis, while the electrode processing involves the use of Polyacrylic Acid (PAA) binder. The electrolyte formulation is optimized as well, by employing Vinylene Carbonate (VC) additive, in order to maximize cycling stability and performance. Preliminary results report specific capacities of 932 mAhg−1 and 759 mAhg−1 after 50 cycles at 500 mA g−1 and 1000 mA g−1, respectively. The Si@V2O5 electrode also shows remarkable rate capability performance.

Highly stiff yet elastic microcapsules incorporating cellulose nanofibrils.

Microcapsules with high mechanical stability and elasticity are desirable in a variety of contexts. We report a single-step method to fabricate such microcapsules by microfluidic interfacial complexation between high stiffness cellulose nanofibrils (CNF) and an oil-soluble cationic random copolymer. Single-capsule compression measurements reveal an elastic modulus of 53 MPa for the CNF-based capsule shell with complete recovery of deformation from strains as large as 19%. We demonstrate the ability to manipulate the shell modulus by the use of polyacrylic acid (PAA) as a binder material, and observe a direct relationship between the shell modulus and the PAA concentration, with moduli as large as 0.5 GPa attained. These results demonstrate that CNF incorporation provides a facile route for producing strong yet flexible microcapsule shells.

Use of Polyacrylic Acid and Polydimethylsiloxane Mixture for In‐Needle Microextraction of Volatile Aroma Compounds in Essential Oils

A prototype stainless steel needle (Hamilton 90022, 22 gauge, 718 µm o.d., 413 µm i.d., 51 mm length, bevel tip) packed with polyacrylic acid (PAA) and polydimethylsiloxane (PDMS) mixture (7:3 ratio) having a micro‐bore tunnel (290 µm i.d., ca. 61.5 µm thickness, 10 mm length) was newly prepared as a device of headspace in‐needle microextraction (HS‐INME). Design of the needle, optimization of adsorption, desorption parameters, and validation of analytical methods were conducted to evaluate the HS‐INME efficiency for volatile organic compounds. The optimized adsorption conditions were 60 °C for 20 min and desorption conditions were 240 °C for 2 min. The calibration curves showed good linearity with the squared correlation coefficient value (r2) over 0.99. The limit of detection for linalool, (+)‐limonene, and eugenol were 13.5, 10.9, and 9.1 ng while limit of quantification were 45.1, 36.4, and 30.5 ng, respectively. The recovery results showed the acceptable range between 95.6 and 115.3%. The relative standard deviations for intra‐ and inter‐assay showed the values less than 10%. It was applied to analyze seven essential oils for polar and nonpolar volatile aroma compounds successfully. From the results obtained in this study, HS‐INME was advantageous to low cost due to ease of fabrication, reuse without loss of absorbent or reduction of extraction efficiency, and no use of solvent. In conclusion, a needle packed with PAA and PDMS mixture having a micro‐bore tunnel is a new development of INME that may complement the shortcomings of the current headspace extraction methods.

A simple and rapid method for high-resolution visualization of single-ion tracks

Prompt determination of spatial points of single-ion tracks plays a key role in high-energy particle induced-cancer therapy and gene/plant mutations. In this study, a simple method for the high-resolution visualization of single-ion tracks without etching was developed through the use of polyacrylic acid (PAA)-N, N’-methylene bisacrylamide (MBAAm) blend films. One of the steps of the proposed method includes exposure of the irradiated films to water vapor for several minutes. Water vapor was found to promote the cross-linking reaction of PAA and MBAAm to form a bulky cross-linked structure; the ion-track scars were detectable at a nanometer scale by atomic force microscopy. This study demonstrated that each scar is easily distinguishable, and the amount of generated radicals of the ion tracks can be estimated by measuring the height of the scars, even in highly dense ion tracks. This method is suitable for the visualization of the penumbra region in a single-ion track with a high spatial resolution of 50 nm, which is sufficiently small to confirm that a single ion hits a cell nucleus with a size ranging between 5 and 20 μm.

Electrochemical characterization of carbon coated bundle-type silicon nanorod for anode material in lithium ion secondary batteries

Nanostructured silicon synthesis by surface modification of commercial micro-powder silicon was investigated in order to reduce the maximum volume change over cycle. The surface of micro-powder silicon was modified using an Ag metal-assisted chemical etching technique to produce nanostructured material in the form of bundle-type silicon nanorods. The volume change of the electrode using the nanostructured silicon during cycle was investigated using an in-situ dilatometer. Our result shows that nanostructured silicon synthesized using this method showed a self-relaxant characteristic as an anode material for lithium ion battery application. Moreover, binder selection plays a role in enhancing self-relaxant properties during delithiation via strong hydrogen interaction on the surface of the silicon material. The nanostructured silicon was then coated with carbon from propylene gas and showed higher capacity retention with the use of polyacrylic acid (PAA) binder. While the nano-size of the pore diameter control may significantly affect the capacity fading of nanostructured silicon, it can be mitigated via carbon coating, probably due to the prevention of Li ion penetration into 10nano-meter sized pores.

Effect of Dentin Surface Modification on the Microtensile Bond Strength of Self‐Adhesive Resin Cements

To explore the potential to modify human dentin surface as a means of improving the microtensile bond strength (μTBS) of resin cement to dentin. Sound human molars were collected, and their occlusal surfaces were ground flat to expose polished dentin. Indirect composite resin cylinders were cemented to the teeth with RelyX Unicem or G-Cem self-adhesive cements following dentin surface treatments: 6.5% grape-seed extract, 5% glutaraldehyde, or 25% polyacrylic acid and control (no pretreatment). After 24 hours, the teeth were sectioned into beams to produce a cross-sectional area of 1.0 mm(2). Specimens of each group (n = 25) were individually mounted on a jig and placed on a tensile testing machine. A tensile force was applied to failure at a 1 mm/min crosshead speed. The use of polyacrylic acid on dentin prior to cementation with RelyX Unicem resulted in a statistically significant increase in μTBS compared to the control group (p= 0.0282). Polyacrylic acid (p= 0.0016) or glutaraldehyde (p= 0.0043) resulted in a statistically significant increase in μTBS of G-Cem to dentin when compared to the control group. Treatment with grape-seed extract did not result in a statistically significant increase in μTBS for either cement (p > 0.05). Priming dentin surfaces prior to the use of self-adhesive resin cements may be a promising means of improving μTBS. In addition, it was concluded that the results of this study are material dependent as well as being dependent of the type of dentin primer.

Hierarchical and non-hierarchical mineralisation of collagen

Biomineralisation of collagen involves functional motifs incorporated in extracellular matrix protein molecules to accomplish the objectives of stabilising amorphous calcium phosphate into nanoprecursors and directing the nucleation and growth of apatite within collagen fibrils. Here we report the use of small inorganic polyphosphate molecules to template hierarchical intrafibrillar apatite assembly in reconstituted collagen in the presence of polyacrylic acid to sequester calcium and phosphate into transient amorphous nanophases. The use of polyphosphate without a sequestration analogue resulted only in randomly-oriented extrafibrillar precipitations along the fibrillar surface. Conversely, the use of polyacrylic acid without a templating analogue resulted only in non-hierarchical intrafibrillar mineralisation with continuous apatite strands instead of discrete crystallites. The ability of using simple non-protein molecules to recapitulate different levels of structural hierarchy in mineralised collagen signifies the ultimate simplicity in Nature’s biomineralisation design principles and challenges the need for using more complex recombinant matrix proteins in bioengineering applications.

A chemical phosphorylation-inspired design for Type I collagen biomimetic remineralization

Objectives Type I collagen alone cannot initiate tissue mineralization. Sodium trimetaphosphate (STMP) is frequently employed as a chemical phosphorylating reagent in the food industry. This study examined the feasibility of using STMP as a functional analog of matrix phosphoproteins for biomimetic remineralization of resin-bonded dentin. Methods Equilibrium adsorption and desorption studies of STMP were performed using demineralized dentin powder (DDP). Interaction between STMP and DDP was examined using Fourier transform-infrared spectroscopy. Based on those results, a bio-inspired mineralization scheme was developed for chemical phosphorylation of acid-etched dentin with STMP, followed by infiltration of the STMP-treated collagen matrix with two etch-and-rinse adhesives. Resin–dentin interfaces were remineralized in a Portland cement-simulated body fluid system, with or without the use of polyacrylic acid (PAA) as a dual biomimetic analog. Remineralized resin–dentin interfaces were examined unstained using transmission electron microscopy. Results Analysis of saturation binding curves revealed the presence of irreversible phosphate group binding sites on the surface of the DDP. FT-IR provided additional evidence of chemical interaction between STMP and DDP, with increased in the peak intensities of the P O and P–O–C stretching modes. Those peaks returned to their original intensities after alkaline phosphatase treatment. Evidence of intrafibrillar apatite formation could be seen in incompletely resin-infiltrated, STMP-phosphorylated collagen matrices only when PAA was present in the SBF. Significance These results reinforce the importance of PAA for sequestration of amorphous calcium phosphate nanoprecursors in the biomimetic remineralization scheme. They also highlight the role of STMP as a templating analog of dentin matrix phosphoproteins for inducing intrafibrillar remineralization of apatite nanocrystals within the collagen matrix of incompletely resin-infiltrated dentin.

Low Light CMOS Contact Imager with an Integrated Poly-Acrylic Emission Filter for Fluorescence Detection

This study presents the fabrication of a low cost poly-acrylic acid (PAA) based emission filter integrated with a low light CMOS contact imager for fluorescence detection. The process involves the use of PAA as an adhesive for the emission filter. The poly-acrylic solution was chosen due its optical transparent properties, adhesive properties, miscibility with polar protic solvents and most importantly its bio-compatibility with a biological environment. The emission filter, also known as an absorption filter, involves dissolving an absorbing specimen in a polar protic solvent and mixing it with the PAA to uniformly bond the absorbing specimen and harden the filter. The PAA is optically transparent in solid form and therefore does not contribute to the absorbance of light in the visible spectrum. Many combinations of absorbing specimen and polar protic solvents can be derived, yielding different filter characteristics in different parts of the spectrum. We report a specific combination as a first example of implementation of our technology. The filter reported has excitation in the green spectrum and emission in the red spectrum, utilizing the increased quantum efficiency of the photo sensitive sensor array. The thickness of the filter (20 μm) was chosen by calculating the desired SNR using Beer-Lambert’s law for liquids, Quantum Yield of the fluorophore and the Quantum Efficiency of the sensor array. The filters promising characteristics make it suitable for low light fluorescence detection. The filter was integrated with a fully functional low noise, low light CMOS contact imager and experimental results using fluorescence polystyrene micro-spheres are presented.

Size-controlled synthesis of highly water-soluble silver nanocrystals

We describe a modified polyol process for the synthesis of silver nanocrystals with uniform sizes ranging from several nanometers to ∼20 nm. The use of polyacrylic acid, in place of polyvinylpyrrolidone in the conventional polyol process, significantly limits the growth of silver nanocrystals, prevents the interparticle aggregation and fusion, and leads to a uniform population of samples with high water solubility. The size of nanocrystals can be conveniently tuned by controlling the reaction time, the concentration and chain length of the polymeric surfactants, and the reaction temperature. Uniform silver nanocrystals within sizes below 20 nm are preferred candidates over larger particles for applications where high density of optical absorption is required, for example, for photothermal conversion in cancer therapy.

In Situ Ophthalmic Gel of Ciprofloxacin Hydrochloride for Once a Day Sustained Delivery

This article focuses on preparation and evaluation of a once a day ophthalmic delivery system for ciprofloxacin hydrochloride based on the concept of pH-triggered in situ gelation. The in situ gelling system involves the use of polyacrylic acid (Carbopol® 980NF) as a phase transition polymer, hydroxypropyl methylcellulose (Methocel® K100LV) as a release retardant, and ion exchange resin as a complexing agent. Ciprofloxacin hydrochloride was complexed with ion exchange resin to avoid incompatibility between drug and polyacrylic acid. The developed formulation was stable, and nonirritant to rabbit eyes and in vitro drug release was found to be around 98% over a period of 24 hours.