A technique based on Fourier transform infrared (FT-IR) spectrometry was developed to detect the corresponding changes in chemical composition associated with the rapid changes in sodium and water content in 200 mm NaCl-stressed halophyte ice plants (Mesembryanthemum crystallinum). The changes in glycophyte Arabidopsis stressed with 50 mm NaCl were also examined for comparison. The obtained IR spectra were further processed by deconvolution and curve fitting to examine the chemical nature of the responding sources in the leaves. Using three stages of ice plant leaves, absorption bands corresponding to carbohydrates, cell wall pectin, and proteins were identified, with distinct IR spectra representing each developmental stage. Within 48 h of mild salt stress, the absorption band intensities in the fingerprint region increased continuously in both plants, suggesting that the carbon assimilation was not affected at the early stage of stress. The intensities of ester and amide I absorption bands decreased slightly in Arabidopsis but increased in ice plant, suggesting that the cell expansion and protein synthesis ceased in Arabidopsis but continued in ice plant. In both plants, the shift in amide I absorption band was observed hourly after salt stress, indicating a rapid conformational change of cellular proteins. Analyses of the ratio between major and minor amide I absorption band revealed that ice plant was able to maintain a higher-ordered form of proteins under stress. Furthermore, the changes in protein conformation showed a positive correlation to the leaf sodium contents in ice plant, but not in Arabidopsis.High salinity causes pleiotropic effects in plant growth such as reduced cell expansion, decreased protein synthesis, and accelerated cell death. Soil salinity is one of the major limitations of crop productivity worldwide. Halophytes are native flora of saline environments that have the characteristic to overcome the ion and osmotic imbalance caused by high NaCl concentrations. Halophytes possess a set of unique salt adaptation mechanisms. Through comparisons with glycophytes (nonhalophytes), the mechanisms of salt tolerance in halophytes have been studied at physiological, biochemical, and molecular levels (for review, see Hasegawa et al., 2000). In general, three adaptation strategies are commonly found in halophytes: compartmentation of toxic ions, accumulation of osmolytes, and conservation of water (Bohnert et al., 1995). The main strategy for glycophytes is to control of ion flux into root xylem and as the result, restrict ion movement to the shoot (for review, see Hasegawa et al., 2000).Ice plant (Mesembryanthemum crystallinum) has been used as a halophytic model because the mechanisms of salt tolerance can be induced when the plants reach a certain developmental stage. Although ice plant is not suitable for genetic manipulation, comparisons of the physiological, biochemical, and gene expression changes before and after salt stress has provided useful data. In a time course progression of salt-indu...

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In this paper, the feasibility of applying electroless displacement to prepare silver nanoparticles (AgNPs) on the surface of germanium (Ge) substrate is demonstrated, and the performances of surfaces prepared in this manner for surface-enhanced infrared absorption (SEIRA) spectroscopy are reported. The process used to produce suitable AgNPs for SEIRA by electroless deposition is simple and effective, requiring only pretreatment of the germanium surface with hot air, immersion of the substrate in a dilute solution of silver nitrate, and washing of the resulting plate. To quantify the behavior of AgNPs on a Ge substrate and to optimize the conditions for the preparation of AgNPs on Ge substrates, a monolayer of p-nitrothiophenol (PNTP) was bonded to the surface of the AgNPs by immersion of the plate in a dilute solution of PNTP and measurement of the transmission spectrum. The factors that influenced the formation of AgNPs, and hence the SEIRA signals, included the concentration of AgNO3, the reaction time and the temperature. Results indicated that stronger absorption bands in the SEIRA spectrum of a monolayer of PNTP were obtained if the reaction rate for the displacement of silver ions by Ge was slow. This condition was achieved by keeping the concentration of AgNO3 and the reaction temperature low. Under the optimal conditions found in this work, an enhancement factor of approximately 100 was achieved for commonly used probe molecules in SEIRA measurements.

The eggs of Mugil cephalus were significantly larger than those of Epinephelus malabaricus, and E. coioides, while those of Sciaenops ocellatus were intermediate between E. coioides and M. cephalus. The distribution density of pores in the egg envelope of S. ocellatus was significantly different from that of E. malabaricus and E. coioides. The micropyle diameters were significantly different in the four species. The ultrastructure of the zona radiata surface, the distribution density of pores and the size of eggs were also useful characters for distinguishing among the four species, but the ultrastructural features of the micropyles were the most important of all for egg identification. 2000 The Fisheries Society of the British Isles

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A germanium disk on which silver nanoparticles have been deposited by galvanic displacement is shown to be an inexpensive substrate for surface-enhanced Raman spectroscopy (SERS). The preparation, which is based on spontaneous reduction of silver cations at the surface of a germanium disk, is quick and requires nothing more than a Petri dish. The SERS enhancement of silver and gold substrates prepared in this way was measured using benzenethiol and was compared to enhancement of Klarite, a commercially available gold-coated nanoengineered SERS substrate. The enhancement provided by electrolessly deposited metals was found to be superior over Klarite and the reproducibility was generally below 15%. Furthermore, unlike the case for nanoengineered substrates, germanium disks can be polished and reused.

In this study, we integrated zinc oxide nanomaterials, which possess a high surface-to-volume ratio and take part in specific interactions with organic functional groups, into infrared sensing devices to improve both the sensitivity and selectivity of the detection of volatile organic compounds (VOCs). An annealing method was developed to modify ZnO nanoparticles directly onto the surface of an IR internal reflection element. The ZnO nanoparticles produced this way are spherical (diameters, approximately 20 nm). When this modified sensing element was used to detect VOCs, intense IR signals for compounds bearing polar functional groups were observed. The conditions for preparing the ZnO nanoparticles for IR sensing of VOCs were optimized by varying such factors as the volume of the coating zinc solution, the calcination temperature, and calcination time. After mapping the IR signals obtained with respect to these factors, the optimal IR signal from this modified IR sensing element occurred when using 100 microL of zinc solution and performing the calcination at 400 degrees C for at least 30 min. VOCs having different functional groups were used to characterize the behavior of the ZnO-modified sensing element; our results indicate that the selectivity of this device favors polar compounds. Based on detection of several polar VOCs, the results indicate that quantitative analysis is possible when using the ZnO nanoparticle-modified sensor; in some cases, the detection limit was below an injected sample volume of 0.5 nL (approximately 2.2 ppm), with a linear regression coefficient (R2) above 0.99 when up to 0.3 microL of sample (approximately 1400 ppm) was injected to a 100 mL of sample cell.

A facile photoreduction strategy to attach silver nanoparticles on filter paper (AgNPs@FP) to form surface‐enhanced Raman scattering (SERS) substrate array was proposed and examined. As prepared, SERS substrate array was applied to detect low concentration of adenine and other nucleobases in aqueous solutions. In addition, the formed SERS substrate array allows mass analysis of aqueous samples with a requirement of only 10 μL in sample volume. To optimize and understand the parameters in preparations, factors such as the concentrations of citrate and silver nitrate, photoreduction time, and concentration of sodium hydroxide were varied and examined. Para‐nitrothiophenol was used as a Raman probe molecule and scanning electron microscope (SEM) images of the substrates were used to explore the influences of experimental factors in the preparation of SERS array. Results indicated that silver ions could be effectively reduced and deposited in/on filter paper with the presence of citrate. The formed AgNPs@FP exhibits a three‐dimensional structure as the particles formed on and beneath the surface of the cellulosic fibers could be observed. Deposition of analyte on restricted substrate array rendered reproducible results and the spot‐to‐spot SERS intensity varied within 8%. At optimal conditions, the substrate enhancement factor approached 107. We demonstrated that the filter paper‐based SERS substrates can be used as a suitable tool for biological analysis, and a limit of detection better than 160 nM was obtained in detection of adenine molecules in aqueous solutions with a linear range up to 20 μM. Copyright © 2014 John Wiley & Sons, Ltd.