Decrease In Absorbance Research Articles

Ru(bpy)32+ as a photoinduced oxidase mimic for colorimetric detection of biothiols

We have found that tris (2,2′-bipyridyl) ruthenium (II) (Ru(bpy)32+) possesses a high photo-induced oxidase-like activity and is capable of catalyzing the color reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) with dissolved oxygen. Ru(bpy)32+ has a catalytic constant (Kcat) that is twice as high as that of fluorescein, 170 and 275-fold higher than that of 9-mesityl-10-methyl acridine and Eosin Y, respectively. Electron spin resonance spectroscopy (ESR) and radical scavenging experiments have verified the major active radicals involved in the color reaction are •OH. A colorimetric biothiol assay has been successfully developed for the oxidase-like activity of Ru(bpy)32+ can be suppressed by sulfhydryl compounds. A linear dependence between the decrease in absorbance and the logarithm of thiol concentrations can be found ranging from 5.0 to 50 μM, with a detection limit of 1.0 μM. This work reveals a new oxidase mimic with high catalytic activity and will facilitate the utilization of this oxidase mimic in biochemical analysis.

Flow Injection Sensing Strategy for Determining Cationic Surfactants in Commodity and Water Samples

The formation of stable binary water-soluble sub-micellar aggregates of cetyltrimethylammonium bromide-copper-pyrocatechol violet complex (CTAB-Cu-PCV) diminishes the stability and absorbance of the Cu-PCV complex. A new flow injection spectrophotometric sensing strategy used for the determination of CTAB in commodity personal care antiseptics and water samples has been established relying on the above-mentioned concept. Based on the reduction of the absorption of the Cu-PCV solution by the injection of CTAB solution at pH 6.0 and 430 nm, a linear absorbance decrease was observed over the CTAB concentration range of 2.0 to 100.0 µg mL−1 (r = 0.987). The analysis method showed limits of detection (3.3 ơ) and quantification (10 ơ) of 0.08 and 0.27 µg mL−1, respectively. The precision (RSD) for five replicate determinations was 7.9 and 3.7% at 10 and 50 µg mL−1, respectively. The developed method was applied successfully to the determination of CTAB in personal care products, namely skin lotion and vaginal wash, in addition to water samples. The corresponding RSD (n = 5) values were ≤8.2%.

Direct detection of beer photodegradation in commercial bottles and introduction of a new Light-Struck Flavour Susceptibility Index

Exposure of beer to light results in the formation of undesirable flavours or complete spoilage. Photo-damaged beerhas a specific, so-called skunky or light-struck flavour (LSF). The compound responsible for LSF is 3-methylbut-2-ene-1-thiol (MBT). Riboflavin (RF) plays a key role in the formation of MBT. It absorbs light in the blue part of thespectrum and transfers excitation energy to isohumulones. This process is accompanied by the decomposition of RF,which causes a decrease in the absorbance of the sample at 450 nm. The decomposition is directly related to theformation of LSF. In this study, the decrease in absorbance associated with the defined illumination of model and realbeer directly in commercial bottles was measured. The decrease in absorbance correlated with the decrease in RFconcentration and the formation of LSF detected by the sensory panel. The Light-Struck Flavour Susceptibility Indexwas introduced as a rate of the beer susceptibility to light degradation and the formation of LSF.

Neutral red dye adsorption on carbon nano-onions: viability assay interference and adduct characterisation

Carbon nano-onions (CNO) are versatile carbon nanomaterials with many potential biomedical applications. In this work, the interaction of submerged arc discharge in water (SADW) produced CNOs with the neutral red (NR) dye was studied. This dye is used in the in vitro toxicity NR assay, one of the most commonly used dye-based procedures to determine cell viability. Firstly the NR assay was carried out in murine fibroblast cell cultures exposed to CNOs. It was demonstrated that this assay produced invalid results due to the strong adsorption of NR on the CNOs. Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) studies confirmed the effective adsorption of the NR on CNOs and π-π stacking as the main interaction between them. The adsorption of NR on the CNOs was evaluated by studying the decrease of the dye solution absorbance. The influence of different experimental conditions such as pH and CNOs dosage was evaluated: absorbance was found to diminish with the CNO dosage. For the maximum dosage used of 240 μg ml−1, the highest absorbance drops of −85% at pH 7 and −78% at pH 4 were registered. The adsorption process was found to be described best by a pseudo-first order (PFO) kinetics model (R 2 = 0.99), with a kinetic adsorption constant of k 1 = 0.02 min−1 and achieving an estimated sorption capacity of 3866 mg of dye per gram of CNOs. This is one of the highest values ever reported for dyes’ adsorption on carbon materials. Lastly, density functional theory (DFT) calculations were carried out to gain further insights into the interaction. These studies suggest a CNO highest occupied molecular orbital (HOMO)/NR lowest unoccupied molecular orbital (LUMO) electron density transfer as the main orbital interaction.

How Do Intermolecular Interactions Evolve at the Nematic to Twist-Bent Phase Transition?

Polarized beam infrared (IR) spectroscopy provides valuable information on changes in the orientation of samples in nematic phases, especially on the role of intermolecular interactions in forming the periodically modulated twist–bent phase. Infrared absorbance measurements and quantum chemistry calculations based on the density functional theory (DFT) were performed to investigate the structure and how the molecules interact in the nematic (N) and twist–bend (NTB) phases of thioether dimers. The nematic twist–bend phase observed significant changes in the mean IR absorbance. On cooling, the transition from the N phase to the NTB phase was found to be accompanied by a marked decrease in absorbance for longitudinal dipoles. Then, with further cooling, the absorbance of the transverse dipoles increased, indicating that transverse dipoles became correlated in parallel. To investigate the influence of the closest neighbors, DFT calculations were performed. As a result of the optimization of the molecular cores system, we observed changes in the square of the transition dipoles, which well corresponds to absorbance changes observed in the IR spectra. Interactions of molecules dominated by pairing were observed, as well as the axial shift of the core to each other.

Lactate dehydrogenase A inhibitors with a 2,8-dioxabicyclo[3.3.1]nonane scaffold: A contribution to molecular therapies for primary hyperoxalurias

Human lactate dehydrogenase A (hLDHA) is one of the main enzymes involved in the pathway of oxalate synthesis in human liver and seems to contribute to the pathogenesis of disorders with endogenous oxalate overproduction, such as primary hyperoxaluria (PH), a rare life-threatening genetic disease. Recent published results on the knockdown of LDHA gene expression as a safe strategy to ameliorate oxalate build-up in PH patients are encouraging for an approach of hLDHA inhibition by small molecules as a potential pharmacological treatment. Thus, we now report on the synthesis and hLDHA inhibitory activity of a new family of compounds with 2,8-dioxabicyclo[3.3.1]nonane core (23–42), a series of twenty analogues to A-type proanthocyanidin natural products. Nine of them (25–27, 29–34) have shown IC50 values in the range of 8.7–26.7 µM, based on a UV spectrophotometric assay, where the hLDHA inhibition is measured according to the decrease in absorbance of the cofactor β-NADH (340 nm). Compounds 25, 29, and 31 were the most active hLDHA inhibitors. In addition, the inhibitory activities of those nine compounds against the hLDHB isoform were also evaluated, finding that all of them were more selective inhibitors of hLDHA versus hLDHB. Among them, compounds 32 and 34 showed the highest selectivity. Moreover, the most active hLDHA inhibitors (25, 29, 31) were evaluated for their ability to decrease the oxalate production by hyperoxaluric mouse hepatocytes (PH1, PH2 and PH3) in vitro, and the relative oxalate output at 24 h was 16% and 19 % for compounds 25 and 31, respectively, in Hoga1-/- mouse primary hepatocyte cells (a model for PH3). These values improve those of the reference compound used (stiripentol). Compounds 25 and 31 have in common the presence of two hydroxyl groups at rings B and D and an electron-withdrawing group (NO2 or Br) at ring A, pointing to the structural features to be taken into account in future structural optimization.

Wideband Tympanometry in Adults with Severe to Profound Hearing Loss with and without Cochlear Implants

Objectives—Cochlear implantation has been suggested to be associated with an air-bone gap, possibly secondary to increased middle- and inner-ear stiffness. To explore the effect of possible changes in mechanics due to cochlear implantation, we measured wideband tympanometry (WBT) in individuals with normal hearing and individuals with severe to profound sensorineural hearing loss who underwent unilateral or bilateral cochlear implantation. Our goal was to characterize differences in WBT patterns associated with severe to profound sensorineural hearing loss and with cochlear implantation. Design—The study participants were 24 individuals with normal hearing (48 ears) and 17 with cochlear implants, of which 15 were unilaterally implanted and two were implanted bilaterally. All the participants had normal otoscopy. In the implanted group, inner-ear anatomy was normal according to preoperative imaging. All participants underwent pure-tone audiometric assessment, standard tympanometry (226 Hz probe tone), and WBT to a click stimulus (analyzed from 226 to 8000 Hz). WBT was recorded at ambient and peak pressures. To elucidate the effect of sensorineural hearing loss on WBT, we compared normal-hearing ears with impaired non-implanted ears. The impact of cochlear implantation was assessed by comparing the WBT of the implanted and non-implanted ears of the same participants. Moreover, the effect of the ear (right vs. left) and test–retest reproducibility were evaluated. Results—WBT results for right and left ears showed no statistically significant differences in the normal hearing participants. There were no statistical differences shown between repeated measurements of WBT with removal and re-insertion of the probe in any of the groups—the normal ears, the implanted ears, and the non-implanted ears with hearing impairment. Peak compensated admittance (Ytm) in standard tympanometry was normal in 32 out of 34 (94%) ears with sensorineural hearing loss, with one CI user having bilateral negative middle-ear pressure. Compared to normal-hearing ears, ears with severe to profound SNHL, with or without cochlear implantation, showed a significant decrease in absorbance at high frequencies (4000–5000 Hz). Implanted ears, compared both to normal-hearing and contralateral-non-implanted ears, showed a significant decrease in absorbance at low frequencies (400–800 Hz) and an increase in absorbance around 1600 Hz. Conclusions—WBT analysis revealed that the implanted ears showed a significant decrease in absorbance at low frequencies (400–800 Hz) and an increase at 1600 Hz. This finding is likely a result of an increased stiffness due to the implantation surgery and the presence of the implant in the inner ear. In contrast, the specific decrease in absorbance around 4000–5000 Hz in the implanted and non-implanted ears compared to the normal ears is likely either due to aging or the impact of the severe-to-profound SNHL on the input impedance of the cochlea. The structural and functional changes of both the conductive system and the cochlea associated with aging and SNHL may change the wideband acoustic immittance of the ear and these alterations might be correlated with the hearing loss severity. Additional research is needed to determine how much hearing loss and age influence wideband acoustic immittance of the ear.

Molecular and spectroscopic changes of peat-derived organic matter following photo-exposure: Effects on heteroatom composition of DOM.

The temporal evolution of molecular compositions and changes in structural features of Hillsboro Canal (Florida, USA) dissolved organic matter (DOM) was studied with an emphasis on nitrogen and sulfur containing molecules, after a 13 day time-series exposure to simulated sunlight. The Hillsboro Canal drains from the ridge and slough wetland environment underlain by peat soils from the northern extent of the Greater Everglades Ecosystem. The Hillsboro Canal-DOM was characterized by combining ultrahigh-resolution mass spectrometry (FT-ICR-MS), high-field nuclear magnetic resonance spectroscopy (1H NMR), size exclusion chromatography (SEC) with UV detection, and ultraviolet/visible (UV/vis) absorbance and excitation emission matrix (EEM) fluorescence spectroscopy. Size exclusion chromatography (SEC) demonstrated progressive depletion of higher mass molecules and a concomitant decrease of absorbance during photo-irradiation. NMR and FT-ICR-MS revealed nonlinear temporal evolution of DOM. In fact, FT-ICR-MS showed an initial depletion of supposedly chromophoric molecules often carrying major unsaturation accompanied by an uneven evolution of numbers of CHO, CHOS and CHNO compounds. While CHNO compounds continually increased throughout the entire photo-exposure time, CHO and CHOS compounds temporarily increased but declined after further light exposure. Progressive loss of highly unsaturated compounds was accompanied by production of low mass CHO and CHNO compounds with high O/C ratios. Area-normalized 1H NMR spectra of DOM in water and of the water insoluble fraction (~5%) in methanol revealed clear distinctions between irradiated and non-irradiated samples and congruent evolution of DOM structural features during irradiation, with more uniform trends in methanolic-DOM. Photoirradiation caused initial photoproduction of oxygenated aliphatic compounds, continued depletion of phenols and oxygenated aromatics, substantial change from initial natural product derived olefins to photoproduced olefins, and uneven evolution of carboxylated and alkylated benzene derivatives. This study demonstrates longer-term heteroatom-dependent photochemistry of DOM, which will affect the speciation of N and S heteroatoms, their connections to inorganic nutrients, and potentially their bioavailability.

Dual-mode colorimetric and fluorescence sensing system for the detection of captopril based on Fe/NC nanozymes and carbon dots

Metal nitrogen-doped carbon (MNC) nanozymes have received increasing attention in bio-catalysis filed due to adequate catalytic activity, outstanding stability and reusability. Herein, the Fe/NC nanozymes (Fe/NC NZs) with peroxidase-like activity was successfully synthesized and a fluorescence turn on and colorimetric dual-mode sensing system was developed for quantification of captopril (CP) based on Fe/NC NZs and orange-emitting carbon dots (O-CDs). The Fe/NC NZs as an enzyme mimic can efficiently catalyze the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction, forming blue-colored oxidized TMB product (oxTMB) with the presence of H2O2, leading to the fluorescence quenching of O-CDs simultaneously via the inner filter effect (IFE). When CP was present, the blue oxTMB was reduced to colorless TMB, resulting in the inhibition of IFE and the recovery of fluorescence of O-CDs. The fluorescence increase of O-CDs and absorbance decrease of oxTMB depended on CP concentration. Good linear relationships of fluorescence and colorimetric sensing towards CP were obtained in the range from 1 to 50 μM, and the detection limits were 0.47 and 0.56 μM, respectively. Moreover, this as-constructed dual-mode sensor was used to detect CP in pharmaceutical products with satisfactory results.

Effect of gamma rays on Zn/Cu doped strontium borate glass system for dosimetric applications

Abstract Two alkali strontium borate glasses containing Cu2+ or Zn2+ ions (0.15 mol%) has been prepared by melting annealing method. Some of the glasses dosimetric measurements have been performed; they were checked by ultraviolet-visible light measurement showing the specific peaks of Cu+/Cu2+ and Zn2+ ions. Upon γ-rays, glasses are sensitive to the absorbed dose in the range 0.4–15 kGy, revealing their light absorption. A gradual decrease in optical absorbance and DC electrical conductivity was detected with progressive irradiation. While a gradual increase in optical energy bandgap (Eopt) and electron paramagnetic resonance (EPR) was observed. The presence of transition metal ion (TM) with their variable configurations helps to trap the radiolytic electrons or holes during the color center recovery rates. UV–Vis and EPR dosimetric characteristics have high color stability with excellent short and long-term stability revealing their possible use as glass dosimeters in medical sterilization and food irradiation processing.

Free radical scavenging actions of virgin coconut oil

Natural antioxidants are quite popular in beauty products. In further product development, natural antioxidants are needed from local products of the NTB community. This study aims to optimize the antioxidant activity of local products Virgin Coconut Oil (VCO) from Cocos nucifera L. grown in Lombok. This type of research is experimental laboratory research using the DPPH method. VCO was isolated by conventional methods, namely standing and layered filtration. Data were obtained from the results of the UV-Vis spectroscopy test. The results showed that the free radical inhibition of VCO was strong, with an IC50 value of 51.57 and an inhibition of 48% at a 5% VCO concentration. The absorbance of DPPH decreased with increasing reaction time. The decrease in absorbance from every 5 minutes indicates the antioxidant activity continues to a stationary point. A color change indicates the stationary point to yellow. The strong antioxidant activity of VCO is used as the basis for its use as an active ingredient in various cosmetic products. VCO is also believed to have a function as a natural moisturizer.

Direct Energy Transfer from a pH Glass Electrode to a Liquid Crystal Display.

Self-powered sensors are attractive because the lack of a dedicated battery makes them environmentally friendly and allows them to be more easily miniaturized. Unfortunately, the development of self-powered potentiometric sensors is challenging because only very limited energy can be harvested from this measurement principle. For the first time, the potential of a high impedance glass pH electrode (130 M Ω) is shown here to be directly read out optically. This is accomplished by a liquid crystal display (LCD) as the electrochromic transducer, which changes its transmission upon imposing an external voltage in the range of 2-3 V. Importantly, owing to its low capacitance of about 50 pF, this process requires a very small transient charge on the order of 100 pC, which may be spontaneously imposable even across pH glass electrodes. For the LCD to be turned on, the cell voltage is boosted by additional Zn2+/Zn elements placed in series. The LCD is found to give a time-dependent absorbance decrease, which is mitigated by adding a high resistance element to attenuate the associated decay. The approach gives repeatable LCD absorbance values that allows one to directly visualize pH with a precision of about 0.01 pH units. The absorbance value depends inversely on pH in a much wider range (pH 1-13) than what is normally observed with optical sensors while based on the same underlying measurement as a potentiometric pH probe.

A Modification of the ABTS• Decolorization Method and an Insight into Its Mechanism

A modification of the ABTS• decolorization assay for plate readers is presented. In our modification, 200 µL of ABTS solution of absorbance 1.0 at 734 nm was added with an antioxidant and decreased absorbance resulted. For comparison of antioxidant activities in the kinetic assay of absorbance decrease, concentration dependence of absorbance decrease and of area under curve are recommended. “Fast” and “slow” antioxidants were distinguished: while the reactions of “fast” antioxidants ABTS• were completed within seconds, the reactions of “slow” antioxidants were not finished after 6 min. We recommend reaction time of 60 min for assays of such antioxidants, blood plasma and plant extracts. Sub-additive interactions between some antioxidants (ascorbate and Trolox, hispidulin and Trolox, and glutathione and ascorbate) were found in the ABTS• decolorization; possible reasons for such interactions are discussed.

Spectroscopic Characteristics and Speciation Distribution of Fe(III) Binding to Molecular Weight-Dependent Standard Pahokee Peat Fulvic Acid.

Peat-derived organic matter, as powerful chelators, is of great significance for the transport of Fe to the ocean and the enhancement of dissolved Fe. However, the iron binding capacity of molecular weight (MW)-fractionated dissolved organic matter is variable, due to its structure and composition heterogeneity. In this work, we used the standard Pahokee Peat fulvic acid (PPFA) as an example, and investigated the spectroscopy properties and Fe(III) binding ability of PPFA and different molecular weight fractions by UV–Vis absorbance and fluorescence spectroscopy and the Donnan Membrane Technique (DMT). The results showed binding sites for Fe(III) at the 263 nm and >320 nm regions in differential absorbance spectra. Upon increasing the iron concentration to 18.00 μmol·L−1, the critical binding capacity was exceeded, which resulted in a decrease in absorbance. Fe(III) was found to prefer to bind to humic-like components, and ultraviolet humic-like fluorophores displayed stronger binding strength. High molecular weight PPFA fractions (>10 kDa) possessed more aromatic and hydrophobic components, displayed a higher degree of humification, and exhibited higher metal binding potential. Furthermore, the speciation analysis and stability constant (cK) were calculated using Donnan membrane equilibrium. The correlation between cK values and PPFA spectral properties demonstrated that aromaticity, hydrophobicity, molecular weight and humification degree were crucial indices of PPFA–Fe(III) affinity. Significantly, the humification degree, represented by HIX, showed the strongest correlation (r = 0.929, p = 0.003), which could be used to estimate the binding strength. This study provides further understanding of the complexation mechanism of iron and DOM in the peat environment and identifies the considerable effect of molecular weight.

Metal complexes of azo compounds: Synthesis, characterization, molecular modeling and degradation study by gamma radiation

The Fe(III), Co(II) and Cu(II) complexes of three azo compounds namely, 2-(phenylazo)-1-naphtllol (Sudan I) (HL1) a, 4-(phenylazo)-1-naphthol (HL2) b and 2,4-bis(phenylazo)-1-naphthol (HL3) c were prepared and characterized on the basis of their elemental analysis, molar conductance, UV–VIS and FT IR spectroscopic studies. Besides, density functional theory (DFT) computations were conducted to study structures and energetics of the ligands and their complexes. Molecular Electrostatic Potential was also calculated by the DFT method and predicts the most reactive part in the molecule. The isolated complexes are found to have the formulas [Cu(L1)2] a1, [Co(L1)2] a2, [Fe(L1)3] a3, [Cu(HL2)2Cl2].H2O b1, [Co(HL2)(NO3)2].H2O b2, [Fe(HL2)Cl3].H2O b3, [Cu(HL3)Cl2].H2O c1, [Co(HL3)(NO3)2].H2O c2 and [Fe(HL3)Cl3].H2O c3. The IR result showed that the ligand a was chelated with the metal ions in a monobasic bidentate manner, with NO donor sites of the azo nitrogen and the deprotonated phenolic oxygen. While the ligand c was chelated with the metal centers in a neutral bidentate manner and the ligand b was bound with the metal ions as a neutral monodentate donor by azo nitrogen atom. The molecular docking results indicated that the ligands HL1a, HL2b and HL3c may possess significant anti-inflammatory activity. Gamma irradiation of variable concentrations of the ligand solutions HL1a and its complexes [Cu(L1)2] a1, [Co(L1)2] a2 and [Fe(L1)3] a3 was investigated. The color bleaching of the dyes solutions was increase gradually with increasing absorbed dose in the dose range of 3, 5 and 10 kGy.

Effect of UV, pH and solvent on the photophysical properties of novel xanthylium fluorophore in solid and liquid state

The current work describes the comparative study of the photophysical properties of new series of xanthylium fluorophore in different organic solvents, the effect of pH, and the effects of UV light irradiation and stability. The designed molecule plays a significant role in the stability. We disclosed the synthesized molecule's stability from UV–Vis, fluorescence, theoretical studies, the molecule sensitivity to solvent polarity, and pH due to its structural nature. The decrease in absorbance and fluorescence intensity with UV–visible light irradiation for the solid and liquid samples were studied. The dye discoloration rate was estimated. The mechanism for the same has been explored, and the information is given in detail. The electrostatic potential, surface mapping analysis, and the stability of the synthesized dye molecules were studied theoretically and compared with the experimental outcome. The stability study and other factors allowed us to predict the suitable application of the synthesized xanthylium fluorophore.

Will paper microzones become the greenest chemistry method for electrolytic analysis?

Methods of electrochemical correlation are becoming more complex and costly with the lack of a simple electrolytic analysis method. Herein, an interesting analysis of the performance of electrocatalytic degradation of different dyes was carried out using a modified paper microzones method (PMZs) performed with a smartphone, and data from spectrophotometers were used for comparative analysis. At the same voltage and in the same reaction cell, the same mass of sodium sulphate, acetic acid and pure water were added according to the strength of the electrolyte to degrade methyl orange(MO), fuchsin basic(FB), methylene blue(MB) and the mixture of these dyestuffs. When measured by the PMZs method, the correlation coefficients were above 0.9 in the concentration range of 5–50 mg/L, the range of variation of LOD values was 3.843–9.561 mg/L and the range of variation of LOQ was 11.646–28.973 mg/L. When measured by the spectrophotometric method, some of the dyes only had a greater correlation in the range of 5–40 mg/L. The range of variation of LOD values was 0.900–9.213 and the range of variation of LOQ was 2.727–27.917 mg/L. When FB was used as a degradation object, the decrease in absorbance at 80 min was 21.83%, 35.93%, 60.90% and the increase in grey value was 0.40%, 3.04%, 3.25% under the conditions of electrolytes only water, CH3COOH, Na2SO4, respectively, and maintained P less than 0.05 at different moments. Hence, the related results contribute to the further application and development of green chemistry PMZs in electrochemical analysis and environmental science.

Production of high quality green textile filaments from carboxymethylated cellulose covalently cross‐linked by reactive green 19 dye

AbstractHuge quantities of wastewaters are produced during dyeing of textile, which is why wastewater treatment plants are required in textile industries in which, in most cases, non‐dyed filaments are produced first and dyeing of these filaments is performed at a later stage. Here, carboxymethylated cellulose (CMC) with the COOH group content of 1.3 mmol/g CMC was covalently crosslinked through reactive green 19 dye in the dope solution (0.09 wt% dye with reference to CMC) from which green textile filaments were spun. The incorporation of dye in the dope solution has the advantage of obtaining dyed filaments without using an additional step for dying of the fabricated textile filaments and, moreover, it can be done in such a way that clean, no dye containing wastewater is produced. The filaments also demonstrated an increase in mechanical strength (tenacity ~ 0.96 cN/dtex) and a decrease in water absorbency (water absorbency ~ 0.63 g water/g filament) due to chemical crosslinking of cellulose chains through the dye. Owing to covalent bond formation between the CMC and the dye, excellent color fastness properties were obtained for the fabricated filaments.

Preparation and Enzyme Degradability of Spherical and Water-Absorbent Gels from Sodium Carboxymethyl Cellulose.

To synthesize a biodegradable alternative to spherical polyacrylic acid absorbent resin, spherical hydrogel particles were prepared from carboxymethyl cellulose (CMC) dissolved in an aqueous solution, using ethylene glycol diglycidyl ether (EGDE) as a crosslinking agent. The effect of varying the initial CMC concentration and feed amount of EGDE on the shape, water absorbency, water-holding capacity, and enzyme degradability of the resultant CMC hydrogels was determined. The reaction solution was poured into fluid paraffin, and spherical hydrogel particles were obtained via the shear force from stirring. The shape and diameter of the spherical hydrogel particles in the swollen state depended on the CMC concentration. The spherical hydrogel particles obtained by increasing the amount of EGDE resulted in a decrease in absorbency. Additionally, all the spherical hydrogel particles were degraded by cellulase. Thus, spherical biodegradable hydrogel particles were prepared from CMC, and the particle size and water absorption of the hydrogel could be controlled in the range of 5–18 mm and 30–90 g·g−1 in the swollen state, respectively. As an alternative to conventional superabsorbent polymers, the spherical CMC hydrogels are likely to be useful in industrial and agricultural applications.

Absorption and Resonance Rayleigh Scattering Spectra of Ag(I) and Erythrosin System and Their Analytical Application in Food Safety.

In pH 4.4∼4.6 weakly acidic media, erythrosine (Ery) can react with Ag(I) to form hydrophobic ion-association complex, which can further aggregate to form nanoparticles with an average particle size of about 45 nm under the action of water phase extrusion and van der Waals force. As a result, it could lead to a decrease of absorbance, a significant enhancement of resonance Rayleigh scattering (RRS) and the appearance of a new emission spectrum. Based on these Phenomena, two new methods (spectrophotometry and RRS) were established for the determination of trace Ag(I). The detection limits for Ag(I) by spectrophotometry and RRS are 9.74 and 0.12 ng/ml, respectively. In this paper, we have investigated the formation of nanoparticles, the optimum reaction conditions, the influence factors, explored the reason for enhancement of the scattering intensity and the effect of coexisting substance. This research shows that RRS method not only has good selectivity and high sensitivity, but also is simple and rapid. Analyzing of actual samples and standard samples, the determination result of this method is consistent with that of standard methods (Flame atomic absorption spectroscopy). Thus the method had potential feasibility to analysis for Ag(I) in the environmental water samples, pharmaceutical, and food industries.