Silver-coated Filter Paper Research Articles

A comparative study on the adsorption behaviors of PABA in the silver nano-particles

Surface-enhanced Raman scattering (SERS) spectra of P-Aminobenzoic Acid (PABA) adsorbed on the silver nano-particles were studied, respectively, in the silver colloidal solution and on the dried silver-coated filter paper. To further study the adsorption behaviors of PABA on the different substrates, we analyze the problem by means of theoretical calculation. Five models of PABA adsorbed on the surfaces of silver nano-particles were established. The Raman spectra of these five models using DFT-B3PW91 with lanl2dz were calculated. By comparing the theoretical values with the experimental values, we found that the calculated Raman frequencies of the models were in good agreement with experimental values, respectively. So we can believe that the simplified models are probably reasonable to describe some surface- enhanced Raman experiments.

Determination of acetylsalicylic acid in commercial tablets by SERS using silver nanoparticle-coated filter paper

In this work, filter paper was used as a low cost substrate for silver nanoparticles in order to perform the detection and quantification of acetylsalicylic acid by SERS in a commercial tablet. The reaction conditions were 150mM of ammonium hydroxide, 50mM of silver nitrate, 500mM of glucose, 12min of the reaction time, 45°C temperature, pretreatment with ammonium hydroxide and quantitative filter paper (1–2μm). The average size of silver nanoparticles deposited on the paper substrate was 180nm. Adsorption time of acetylsalicylic acid on the surface of the silver-coated filter paper was studied and an adsorption time of 80min was used to build the analytical curve. It was possible to obtain a calibration curve with good precision with a coefficient of determination of 0.933. The method proposed in this work was capable to quantify acetylsalicylic acid in commercial tablets, at low concentration levels, with relative error of 2.06% compared to the HPLC. The preparation of filter paper coated with silver nanoparticles using Tollen’s reagent presents several advantages such as low cost of synthesis, support and reagents; minimum amount of residuals, which are easily treated, despite the SERS spectroscopy presenting fast analysis, with low sample preparation and low amount of reactants as in HPLC analysis.

Comparison of Surface-Enhanced Raman Scattering Spectra of Azo Dye Sudan III on Several Substrates

ABSTRACT On several substrates, including dried silver-coated filter paper, electro-polishing aluminum foils, and anodic aluminum oxide (AAO) nanometer array templates, surface-enhanced Raman scattering (SERS) spectra of Azo Dye Sudan III molecules were studied, and high-quality SERS spectra were obtained, which indicated that electro-polishing aluminum foils and AAO nanometer array templates were also active SERS substrates. A number of additional modes were presented, as well as some split peaks, which were especially obvious on electro-polishing aluminum foil and AAO nanometer array template. The enhancement mechanisms were discussed and the enhancement factors G were calculated as 104, 106, and 105, respectively.

Silver nanoparticle-treated filter paper as a highly sensitive surface-enhanced Raman scattering (SERS) substrate for detection of tyrosine in aqueous solution

Highly sensitive SERS substrates based on deposition of silver nanoparticles on commercially available filter paper were prepared in this work, and used to overcome problems found in analyses of aqueous samples. To prepare silver nanoparticle- (AgNP) doped filter substrates, a silver mirror reaction was used. The procedures for substrate preparation were systematically optimized. Pretreatment of filter paper, reaction time, temperature, and concentration of reagents for silver mirror reactions were studied. The morphologies of the resulting substrates were characterized by field-emission scanning electron microscopy (FE-SEM) and correlated with the SERS signals by probing with p-nitrothiophenol (pNTP). Filter papers with different pretreatments were found to have different sizes and distributions of AgNPs. The best performance was found when filter paper was pre-treated with ammonia solution before growth of AgNPs. Based on the SEM images, the resulting AgNPs had roughly spherical shape with a high degree of uniformity. The silver-coated filter paper substrates provide much higher SERS signals compared to glass substrates and the reproducibility was improved significantly. Based on statistical analyses, the relative standard deviations for substrate-to-substrate and spot-to-spot were both were less than 8% and the enhancement factors for the substrates were, in general, higher than 107. The SERS substrates were used to selectively detect tyrosine in aqueous solution. Results indicate that filter-based SERS substrates are highly suited to detection of tyrosine. Compared to glass-based SERS substrates, 50 times more SERS signal was observed in detection of tyrosine. The linear range can be up to 100 μM with a detection limit of 625 nM (S N −1 = 3).

Surface-enhanced Raman scattering of a series of n-hydroxybenzoic acids ( n = P, M and O) on the silver nano-particles

Surface-enhanced Raman scattering (SERS) spectra of a series of n-hydroxybenzoic acids ( n-HBA, n = P, M and O) adsorbed on the silver nano-particles were studied, respectively, in the silver colloidal solution and on the dried silver-coated filter paper. On the same substrate, the different molecules’ SERS spectra were different, while on the different substrates the same molecules’ SERS spectra were also different. Significant changes were found in the SERS spectra of PHBA molecules adsorbed on the two substrates, and the changes found in MHBA’s spectra on two substrates were next to PHBA’s, while almost no changes were found in the spectra of OHBA molecules. Moreover, it was found, on the filter paper, that the SERS spectra of the same molecules would change with the coverage density of the silver nano-particles. The analyses showed that the origins of these changes were the different adsorption behavior of molecules adsorbed on the silver nano-particles. Because in these three molecules the relative positions of the carboxyls and hydroxyls on the benzenes are different, the adsorption behaviors of these three molecules adsorbed on the silver surfaces are also different. The experimental results suggest that the surface characteristic of the substrate and the surface configuration of the adsorbate could exert a great influence on the adsorption behavior of the adsorbates on the substrates.

The adsorption behavior of p-hydroxybenzoic acid on a silver-coated filter paper by surface enhanced Raman scattering

On dried filter paper coated with silver nanoparticles, surface-enhanced Raman scattering (SERS) spectra of p-hydroxybenzoic acid (PHBA) were studied, and high-quality SERS spectra were obtained, indicating that the silver-coated filter paper is a highly SERS-active substrate. The analysis showed that the adsorption behavior of PHBA molecules on silver nanoparticles coated on filter paper was different from that in silver aqueous colloids. On the filter paper, it was found that the SERS spectra of PHBA changed with the proportion of PHBA molecules and silver nanoparticles, indicating that the adsorption behavior of PHBA molecules changed with the proportion. The probable reasons are given.

A disposable biosensor for urea determination in blood based on an ammonium-sensitive transducer

A potentiometric urea-sensitive biosensor using a NH + 4-sensitive disposable electrode in double matrix membrane (DMM) technology as transducer is described. The ion-sensitive polymer matrix membrane was formed in the presence of an additional electrochemical inert filter paper matrix to improve the reproducibility in sensor production. The electrodes were prepared from one-side silver-coated filter paper, which is encapsulated for insulation by a heat-sealing film. A defined volume of the NH + 4-sensitive polymer matrix membrane cocktail was deposited on this filter paper. To obtain the urea-biosensor a layer of urease was cast onto the ion-sensitive membrane. Poly (carbamoylsulfonate) hydrogel, produced from a hydrophilic polyurethane prepolymer blocked with bisulfite, served as immobilisation material. The disposable urea-sensitive electrode was combined with a disposable Ag/AgCl reference electrode to obtain the disposable urea biosensor. The sensor responded rapidly and in a stable manner to changes in urea concentrations between 7.2×10 −5 and 2.1×10 −2 mol/l. The detection limit was 2×10 −5 mol/l urea and the slope in the linear range 52 mV/decade. By taking into consideration the influence of the interfering K +- and Na +- ions the sensor can be used for the determination of urea in human blood and serum samples (diluted or undiluted). A good correlation was found with the data obtained by the spectrophotometric routine method.

Fast spatially resolved surface-enhanced Raman spectrometry on a silver coated filter paper using charge-coupled device detection

This paper describes the performance of surface-enhanced Raman spectroscopy (SERS) on a silver-coated filter paper using a charge-coupled device (CCD) detector. It is demonstrated that spatially resolved SER spectrometry with satisfactory spectral resolution can be performed with a low integration time. When the analytical information is distributed in space, CCD-SERS provides an effective solution for rapid analysis. For instance, binary mixtures separated by paper chromatography on a silver-coated filter paper can be studied in situ by SERS. The effect of binning on the spatial resolution and on the analytical figures of merit is discussed. Binning improves the sampling efficiency and improves the limits of detection by two orders of magnitude.

Potentiometric biosensor in double matrix membrane technology

A throw-away urea sensor is described. A pH-sensitive disposable sensor constructed using double matrix membrane technology was used as a transducer. Double matrix membrane technology describes a process where an ion-sensitive polymer matrix membrane is formed in the presence of an additional inert matrix for to improve the reproducibility of sensor production. In this case one-side silver-coated filter paper was used as the inert matrix which was encapsulated by a heat sealing film. A pH-sensitive membrane was casted into this filter paper and on the surface of this membrane a urease containing layer was deposited. The sensor responded to between 10 −2 mol/l and 10 −4 mol/l urea, the response slope was 32·7 mV/decade. The concentration range in which the sensor responds is important for clinical analysis. The main advantages of this pH-based urea electrode include miniature size as well as simple and low cost fabrication in a batch process.

Mixture analysis and quantitative determination of nitrogen-containing organic molecules by surface-enhanced Raman spectrometry.

Surface-enhanced Raman spectrometry (SERS) on a silver-coated filter paper substrate of nitrogen-containing organic molecules is reported. A correction procedure for standardization of measurements is proposed and evaluated to solve the difficult problem of quantitation of adsorbate in SERS. The relative standard deviation obtained through this procedure is around 15%. Linearity (r = 0.999) was achieved up to 50 micrograms/mL aminoacridine. A limited dynamic range is observed, however, due to the limited number of SERS active sites in the substrate. Spectral fingerprinting of three-component mixtures by concentration-dependent selective molecular adsorption on the substrate is also reported.

Analysis by surface enhanced Raman spectroscopy on silver hydrosols and silver coated filter papers

Surface enhanced Raman spectrometry (SERS) is an analytical technique with a sensitivity comparable to that of conventional molecular absorption or fluorescence spectroscopy, with the additional major advantage of selectivity inherent in vibrational spectroscopies. The analytical application of flowing silver hydrosols is described. Under the controlled experimental conditions of flow injection analysis, it was possible to detect as low as 30 ng of p-aminobenzoic acid. The linear range was two orders of magnitude (1–100 μg ml −1) with a signal reproducibility of 3.2%. Silver coated filter paper is another SERS active substrate that is simple to prepare and handle. The SERS spectra of several nitrogen-containing molecules were obtained on these substrates. The effects of laser power and paper hydration are described. The relative advantages of both substrates are compared.

Surface-enhanced Raman spectrometry on a silver-coated filter paper substrate

The production, morphology, and optical properties of silver-coated filter paper as a new active substrate for surface-enhanced Raman spectrometry (SERS) are reported. The procedure involves a simple, one-stage reduction of filter-paper-supported silver nitrate with sodium tetrahydroborate. Intense and reproducible spectra of a variety of ionic and molecular adsorbates including p-aminobenzoic acid, acridine, 9-aminoacridine, 2-aminoanthracene, 6-nitroquinoline and 5-aminoquinoline are obtained. Simplicity, low cost, speed and availability are salient features of the substrate, which extend the applicability of the SERS technique to more practical situations.