Maximum Absorption Wavelength Research Articles

Effects of sulfonation on bis‐styrylbiphenyl fluorescent whitening agents for polypropylene

ABSTRACTThree derivatives of bis‐styrybiphenyl with different degrees of sulfonation to be used as fluorescent whitening agents (FWAs) were synthesized. Studies on their spectroscopic properties were performed using a combination of computational methods. Whitening effects of FWAs and the improved thermal stability of polypropylene (PP) were investigated. The morphology of plastic samples was examined by scanning electronic microscopy (SEM). In order to improve the compatibility between FWA and PP, PP grafted with maleic anhydride (MAH) was applied as compatibilizer. The optical properties were further clarified by the results of frontier molecular orbital modeling, which show that the presence of sulfonic sodium group leads to a red shift of maximum UV absorption wavelength and a low HOMO–LUMO energy band gap. It is observed that the addition of 0.010 wt % of the sulfonated FWA would result in the expected whitening effect as well as improved PP thermal stability, while at or above 0.015 wt %, such effects worsen sharply owing to phase separation. Furthermore, the use of MAH‐grafted PP as compatibilizer results in improvement of phase behavior and thermal stability. The study provides new insights into the effect of FWA structure on the properties of PP that are related to the whitening of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47635.

Colorimetric enzymatic determination of glucose based on etching of gold nanorods by iodine and using carbon quantum dots as peroxidase mimics.

Carbon quantum dots (CQDs) with peroxidase-mimicking activity were successfully prepared from litchi rind. A colorimetric method for glucose determination was developed based on etching of gold nanorods (GNRs) using CQDs as peroxidase mimetic. The glucose oxidase-catalyzed oxidation of glucose leads to the generation of H2O2 which oxidizes added iodide under formation of elemental iodine under the catalytic action of CQDs. Iodine then etches the GNRs along the longitudinal direction due to the higher reaction activities at the tips of GNRs. This results in a stepwise decrease in the maximum absorption wavelength of the GNRs, from initially 953nm to finally 645nm. Under the optimized conditions, the shift in the maximum absorption wavelength decreases linearly in the 0.01-2.0mM glucose concentration range, and the detection limit is 3.0μM. Importantly, this method was applied to the determination of glucose in human serum. It is perceived that the CQDs are valuable peroxidase mimics due to their ease of preparation, low costs and stable catalytic activity. Graphical abstract Carbon quantum dots were prepared from litchi rind. They can induce the oxidation of gold nanorods in the presence of I- ions and H2O2. This finding was applied to design a colorimetric assay for glucose.

Benzoxazine grafted poly(γ-Glutamic acid) functional material: Synthesis, characterization and photophysical properties

Abstract A benzoxazine grafted poly(γ-glutamic acid) (B-PGA) was successfully synthesized by esterification of poly (γ-glutamic acid) (γ-PGA) with benzoxazine (BX). Structural characterizations by FTIR, 1H-NMR, GPC and UV–Vis spectroscopy indicated that all of γ-PGA monomer units were not grafted by BX thoroughly, and the reaction time of 2 h was the optimum condition for obtaining the B-PGA product with 25% degree of conversion. After modification, the maximum absorption wavelengths (λmax) of γ-PGA was shifted from 260 to 272 nm due to the aromatic π→π* transition of BX in the B-PGA structure. For fluorescent properties, characteristic emission and excitation wavelengths of B-PGA including its fluorescence quantum yield were systematically analyzed. The results showed that the B-PGA exhibited strong fluorescence in bright green color by the influence of BX which functioned as a fluorophore. In addition, the B-PGA showed an interesting property of chemical sensing for Fe(III) ion which can be clearly observed by naked eyes from the changing of its photophysical properties such as color or fluorescence.

Hydrophilic Truxene Derivative as a Fluorescent off-on Sensor for Copper (II) Ion and Phosphate Species.

A new symmetrical truxene derivative (TP3) containing three dipicolylamino peripheral groups is successfully synthesized in four synthetic steps with an overall yield of 42%. This hydrophilic fluorescent compound exhibits a maximum absorption wavelength at 375nm, an emission maximum at 474nm with an outstanding 58% quantum efficiency in THF-HEPES buffer mixture. The compound shows a highly selective fluorescence quenching towards Cu(II) ion with a detection limit of 0.06ppm. The results from mass spectrometry and Job plot indicate that a 1:1 complex between TP3 and Cu(II) ion is responsible for the signal quenching. Interestingly, this TP3-Cu complex can be used as a turn-on sensor for hydrogen phosphate and nucleoside phosphates. The limit of detection for hydrogen phosphate is estimated at 8.7nM. The signal restoration involves a displacement of TP3 in the complex by the phosphates which have strong coordination abilities with Cu(II) ion.

PEWARNA ALAMI EKSTRAK MASERASI BUNGA ROSELLA (Hibiscus sabdariffa L.)

Rosella contains anthocyanin compounds that can be used as natural red dyes. This flower is also known to have many benefits (functional benefits) for health. Aside from being a dye, rosella (Hibiscus sabdariffa L.) can be used as a preservative, because it contains antioxidants and antibacterial. This research is a laboratory experiment study, which was carried out by maceration extraction method by giving an intervention at the temperature and pH of the carrier, using maceration extraction method, and the resulting extract was then isolated by anthocyanin and organoletically tested, pH and color absorption carried out by testing with UV-Vis spectrophotometry. The results of this study obtained absorbance values with the maximum absorption wavelength for the roselle natural red color sample was 510 nm. The best value of type B with intervention at acid pH with 1% citric acid content with emphasis at room temperature or 250C with an absorbance value of 1.544 Keywords: Rosela, Anthocyanin, Maserasi

Effects of microwave and water bath heating on the interactions between myofibrillar protein from beef and ketone flavour compounds

AbstractThis paper presents the effects of microwave on the structure changes of myofibrillar protein compared with traditional water bath heating method. Under microwave or water bath heating conditions, α‐helix conformation of myofibrillar protein was converted into β‐turn, β‐sheet and randomly coiled structures gradually. T he fluorescence intensity of myofibrillar protein exhibited a marked red shift of the maximum absorption wavelength after microwave or water bath treatment. Total sulfhydryls groups and surface hydrophobicity contents were increased with progressing microwave or water bath treatment time. Results indicated that the thermal effects of microwave dominated the structure changes of myofibrillar protein, and microwaving also had an apparent influence on myofibrillar protein structure compared with water bath heating due to its nonthermal effects, and thus affecting the retention and release of ketone flavour compounds.

Pilot-scale evaluation of bio-decolorization and biodegradation of reactive textile wastewater: An impact on its use in irrigation of wheat crop

In the present investigation, a number of experiments have been conducted for mineralization of wastewater containing methyl orange (MO) in integrated biofilm bioreactor with coconut fiber as natural bio-material. The color removal expected from the standard curve of dye versus optical density at its maximum absorption wavelength (460 nm) were 87% and COD removals were 69%. Pseudomonas putida showed a strong ability to decolorize methyl orange under aerobic conditions at pH 7.0 and ambient temperature were considered to be the optimum decolorizing conditions under static state. The spectral analysis of UV–Visible spectroscopy, Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (1H NMR) corrugated the metabolic products formed during the degradation. The nutritional profile of wheat grains irrigated with TTW has enhanced with respect to Energy 241%, Carbohydrate 212% and Protein 402% in comparison to grains obtained on irrigation with Textile wastewater (TWW).

Facile synthesis and characterization of covalently colored polyurethane latex based on the chain extension of water-soluble dye monomer

In this work, a new method for facile synthesis of covalently colored polyurethane latex was developed. A series of blue dye monomers were synthesized via one-step reaction of a reactive dye and amino compounds, and then employed as chain extenders to react with polyurethane prepolymer in the emulsification process to prepare the covalently colored polyurethane latexes. The chemical structures and the properties of dye monomers and the corresponding polymers were investigated, and the UV–Vis spectra of covalently colored polyurethane featured fairly consistent with dye monomers with maximum absorption wavelength at 620 nm and 580 nm, since the chemical structure of chromophore maintained unchanged. The conversion of dye monomer reached more than 92% with 1.0 wt% dye content, whereas the conversion decreased with the increase of the dye amount and the adding time. Compared with the noncovalently latex film, the light fastness of the covalently colored latex film was greatly promoted due to the chemical bonding of chromophores with polymer matrix.

Sensitive spectrophotometric determination of trace-level Co2+ in water based on acetate enhanced catalysis of Co2+

A sensitive spectrophotometric method was developed for the determination of trace-level Co2+ in water based on the acetate enhanced catalytic decolorization of methylene blue (MB) with Co2+ as a catalyst and peroxymonosulfate (PMS) as an oxidizing agent. This indirect spectrophotometric method was easy to operate due to the strong absorption of MB at a maximum absorption wavelength of 664 nm with a molar absorptivity of 5.88 × 104 L mol−1 cm−1. Under the selected reaction conditions of 10.0 mg L−1 MB, 60.0 mg L−1 PMS and 100.0 mg L−1 Ac−, the depletion extent of MB was linearly correlated with the concentration of Co2+ from 0.20 to 7.0 μg L−1 (R2 = 0.986) and then from 7.0 to 50.0 μg L−1 (R2 = 0.991), with a detection limit (3 s/k) of 0.10 μg L−1. It was found that this method possessed excellent anti-interference capability to various coexisting ions including similar transitional metals. The developed method was used to determine the Co2+ concentration in practical samples with satisfactory results.

Enhanced nonlinear optical properties of porphyrin with an extended π-conjugated bridge

In this work, a series of molecules with an extended π-conjugated bridge have been theoretically designed based on porphyrin, where -(CH=CH)n- (n = 1–4, 8, 12) chain is served as an extended π-conjugated bridge. It is found that all molecules exhibit large energy gaps in the range of 3.484–4.151 eV for porphyrin-(CH=CH)n-NH2, and 3.624–4.250 for porphyrin-(CH=CH)n-NO2. The maximum absorption wavelengths of all molecules show a red shift trend with increasing -(CH=CH)n- length, which leads to small transition energy. It is observed that long chain brings these molecules the large first hyperpolarizability, which are 1.04 × 105 au for porphyrin-(CH=CH)12-NH2, 1.26×105 au for porphyrin-(CH=CH)12-NO2. Moreover, compared with -(CH=CH)n-NH2 with the same chain length, -(CH=CH)n-NO2 chain can achieve larger nonlinear optical response. It is hoped that the research in this paper can provide a new strategy for the experimental design of nonlinear optical materials.

UV-ANALYTICAL METHOD DEVELOPMENT AND VALIDATION FOR SIMULTANEOUS ESTIMATION OF DAPOXETINE HYDROCHLORIDE AND SILDENAFIL CITRATE IN TABLET DOSAGE FORM

Objective: The objective of this research was to develop and validate a simple ultraviolet (UV) spectrophotometric method for simultaneous determination of sildenafil citrate and dapoxetine hydrochloride in a pharmaceutical formulation.Methods: Two simple UV spectrophotometric methods have been developed for simultaneous determination of sildenafil citrate and dapoxetine hydrochloride. For both methods, stock solutions were prepared in methanol followed by the further required dilutions with methanol. Proposed dual-wavelength method and ratio derivative method, the wavelength of maximum absorption for sildenafil citrate and dapoxetine hydrochloride was 292 nm and 231 nm, respectively.Results: In both methods, the linearity range lies between 10 and 60 μg/ml for sildenafil citrate and 2–12 μg/mL for dapoxetine hydrochloride with their respective wavelengths. By dual-wavelength method, the percentage of sildenafil citrate and dapoxetine hydrochloride was found to be 101.3% and 100.3%, respectively.Conclusion: Result obtained in this research work clearly indicated that both these methods were found to be accurate, precise, stable, and robust as indicated by low values of percentage relative standard deviation. Thus, the present study gives an excellent method for the determination of both the drugs in combined tablet formulation.

UV-ANALYTICAL METHOD DEVELOPMENT AND VALIDATION FOR SIMULTANEOUS ESTIMATION OF DAPOXETINE HYDROCHLORIDE AND SILDENAFIL CITRATE IN TABLET DOSAGE FORM

Objective: The objective of this research was to develop and validate a simple ultraviolet (UV) spectrophotometric method for simultaneous determination of sildenafil citrate and dapoxetine hydrochloride in a pharmaceutical formulation.Methods: Two simple UV spectrophotometric methods have been developed for simultaneous determination of sildenafil citrate and dapoxetine hydrochloride. For both methods, stock solutions were prepared in methanol followed by the further required dilutions with methanol. Proposed dual-wavelength method and ratio derivative method, the wavelength of maximum absorption for sildenafil citrate and dapoxetine hydrochloride was 292 nm and 231 nm, respectively.Results: In both methods, the linearity range lies between 10 and 60 μg/ml for sildenafil citrate and 2–12 μg/mL for dapoxetine hydrochloride with their respective wavelengths. By dual-wavelength method, the percentage of sildenafil citrate and dapoxetine hydrochloride was found to be 101.3% and 100.3%, respectively.Conclusion: Result obtained in this research work clearly indicated that both these methods were found to be accurate, precise, stable, and robust as indicated by low values of percentage relative standard deviation. Thus, the present study gives an excellent method for the determination of both the drugs in combined tablet formulation.

Cloud Point Extraction Coupled with Liquid Ion Exchange for Separation and Determination Mn (VII) in real samples

Spectrophotometric study about ion-pair association complex of Mn(VII) as MnO4- by using (4-hydroxyphenylazo)-4-Benzennaphthol HPABN as organic reagent shows wave length for maximum absorbance was ?max= 292nm, so the study about determination the optimum condition of extraction shows the extraction method need presence 0.2 M HCl and 100 µg of Mn (VII) as MnO4-, so 0.5 mL of TritonX-100, and necessary heating the solution at 80oC for 20min with existence 0.1 M of NaCl as electrolyte, so that stoichiometry exhibits the most feasible extracted structure of ion-pair complex with 1:1 (organic reagent: MnO4-). The research involved many other studies such as interferences, surfactant kinds organic reagents kind so that spectrophotometric determination of Mn (VII).

Spectroscopic Investigation of the Mixture of Ascorbic Acid and Sodium Benzoate

UV spectroscopy was employed to understand the possible interaction between ascorbic acid (AA) and sodium benzoate (SB). The absorbance of each of the preservatives was taken singly (285 and 291nm for SB and AA, respectively) and the spectrum of a common drink that contained the two preservatives was recorded. Then the interaction of AA with SB was monitored by varying the concentration of AA in SB, reaction temperature and exposure to sunlight. The peaks of AA and SB disappeared and a new peak emerged at higher wavelength upon addition of AA to SB, suggesting a redshift and incorporation of AA in SB. Sunlight and temperature (≤body temperature) did not cause AA and SB to react or changes in the wavelength of maximum absorbance. Addition of AA into a typical fizzy drink did not result in new peak suggesting AA did not create any new products by its addition to this product, which already contained AA and SB at the recommended level. However, the addition of a higher amount of AA into the fizzy drinks cause a noticeable red shift from 287.5 to 295nm. Thus caution should be taken when taking AA with SB containing products.

Significantly Improved Electrical Breakdown Strength of Natural Ester Liquid Dielectrics by Doping Ultraviolet Absorbing Molecules

In this paper, we experimentally demonstrate that molecules with maximum absorption wavelength corresponding to the first excitation energy of base liquid molecules are able to significantly improve the electrical performances of natural ester oils. The positive lightning impulse breakdown and acceleration characteristics, ac breakdown characteristics, and streamer structure of the natural ester oils, as well as the electronic properties of the molecules, are presented. The molecules with different absorptions in ultraviolet lights were doped into the natural ester oil. The positive lightning impulse breakdown characteristics of natural ester oil with different doped molecules indicated that the doped molecule with great absorption in the medium wavelength ultraviolet irradiation was able to significantly enhance the positive lightning impulse breakdown and acceleration voltages of natural ester oil by 15% and 60%, respectively. In addition, it also enhanced the ac breakdown voltage by 17%. The base liquid molecules exhibited first excitation energy of 4 eV, which corresponds to the maximum absorption wavelength of such molecules, indicating that the improved electric breakdown strength was a result of the reduced the number of excited molecules and weakened ionization of molecules during the streamer propagation.

Hydrothermal Synthesis of Boron Nitride Quantum Dots/Poly(Luminol) Nanocomposite for Selective Detection of Ascorbic Acid

Boron nitride quantum dots (BNQDs) were synthesized hydrothermally using boric acid and urea. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the formation of BN quantum dots with the lattice size of 0.227 nm. Fourier-transform infrared (FT-IR) and Ultraviolet–visible (UV-Vis) spectroscopies revealed the B-N, O-H and N-H bond formation in the BNQDs and the maximum absorption wavelength at 269 nm. BNQDs exhibited strong fluorescence emission at a wavelength of 330 nm. Furthermore, BNQDs were coated onto a glassy carbon electrode (GCE). Followed by, poly(luminol) (Plu) was electrochemically deposited onto BNQDs/GCE from 0.1 M H2SO4 containing 0.5 mM luminol in order to prepare nanocomposite (hybrid film) coated electrode with improved stability and electrochemical activity. Due to unique nature and synergetic effect between BNQDs and Poly(luminol), as-prepared hybrid Plu/BNQDs film coated GCE showed improved electrocatalytic activity for vitamin C (ascorbic acid, AA) oxidation at 0.2 V. The calibration graph was obtained from 10 to 100 μM AA by amperometry and limit of detection (LOD) was found to be 1.107 μM. The interference effects were also carried out in the presence of uric acid (UA), dopamine (DA) and glucose (Glu). Interestingly, UA, DA and Glu did not produce significant responses on the Plu/BNQDs/GCE which indicated good selectivity of the sensor for AA. Moreover, Plu/BNQDs/GCE based sensor showed reproducible and repeatable analytical performances. We propose that the Plu/BNQDs based hybrid film can be used as a selective sensor probe for the detection of the AA.

Milk oligopeptide inhibition of (α)-tocopherol fortified linoleic acid oxidation

ABSTRACT This study investigated the effect of milk oligopeptides and (α)-tocopherol on inhibition of linoleic acid oxidation using Fe2+-vitamin C induced linoleic acid oxidation model through analysis of malondialdehyde, peroxide value, and conjugated diene and triene in the model. The alteration of milk oligopeptides maximal absorption wavelength, fluorescent feature, and secondary structure were further investigated to elucidate the interactions between milk oligopeptide and (α)-tocopherol that altered the inhibitory effect of linoleic acid oxidation. Results showed that Pro-Tyr-Tyr-Ala-Lys (PYYAK) and Ile-Pro-Ile-Gln-Tyr (IPIQY) with (α)-tocopherol significantly inhibited the oxidation of linoleic acid and reduced the formation of malondialdehyde by 38% and 41%, respectively. Additionally, Ile-Pro-Ile-Gln-Tyr-Val (IPIQYV) and (α)-tocopherol synergistically reduced the peroxide value in the model by 36.8%. Milk oligopeptides exhibited a blue shift on its maximal absorption wavelength, and their absorbance value decreased with the increase of the (α)-tocopherol concentration. The fluorescent intensity of milk oligopeptides was reduced with the addition of (α)-tocopherol and such fluorescent intensity reductions resulted from the static quenching process through the formation of milk oligopeptide-(α)-tocopherol complex. Fourier transform infrared spectroscopy analysis revealed that (α)-tocopherol significantly altered the secondary structure of milk oligopeptides and the percentage of β-turn obviously increased in milk oligopeptide-(α)-tocopherol complex. These indicated that the inhibition of linoleic acid oxidation might result from complex formed between milk oligopeptide and (α)-tocopherol through inter-molecular interactions.

Deciphering the grounds of the suitability of acylhydrazones as efficient photoswitches.

Many efforts are currently being devoted to designing molecular photoswitches with specific properties. In this sense, a recent publication [D. J. van Dijken et al., J. Am. Chem. Soc., 2015, 137, 14982-14991] has synthesized and analyzed the photochromic properties of a large set of acylhydrazones (ACHs), a relatively unexploited class of potential photoswitches with two stable E and Z isomers. This study has revealed a very diverse and complex pattern of the absorption/emission properties of ACHs depending on the substituents attached to the ACH motif. In this work, high level theoretical calculations are performed on a representative set of the experimentally studied ACHs in order to analyze, at the molecular level, the reasons behind the different photochemistries experimentally observed. This systematic study allows for the classification of the full set of ACHs into just four categories. The two more common groups display a small, either positive or negative, shift of the maximum wavelength of absorption between the E and Z isomers. Less common, but far more interesting from a practical point of view, are the compounds that show a large (>100 nm) Stokes shift. This behavior may arise from two different situations. The most common one implies the possibility of an intramolecular proton transfer in the excited electronic state of the less stable Z isomer. The less likely scenario would also involve a loss of the azidic proton through an intermolecular proton transfer that would take place with the aid of the solvent.

Spectrophotometric Determination of the Ionization Constants for the Oximes – Cholinesterases Reactivators at Different Temperatures

The goal of study was the determination of the ionization constants for the oximes – cholinesterases reactivators in aqueous solutions at different temperatures. The wavelengths of absorption maxima of the protonated and deprotonated oxime groups, the molar extinction coefficients of the various oximes species, and the ionization constants for the oxime cholinesterases reactivators (isonitrosin, pralidoxime, dipyroxime, toxogonin, methoxime, carboxime and asoxime) were obtained using spectrophotometric data (wavelength 190 to 450 nm) in solutions (pH 5 – 12) at 20°C, 25°C and 37°C. The proportion of nucleophilic forms involved in the oxime-induced reactivation of phosphorylated cholinesterases was shown to be is positively dependent on the incubation medium pH value and temperature. A hypothesis that the temperature affects the oximes ability to reactivate phosphorylated cholinesterases has been proposed.

Spectrophotometric Determination of Captopril in Pharmaceutical Sample by Phosphomolybdic Blue

In the sulfuric acid medium, ammonium molybdophosphate can be reduced to phosphomolybdic blue by hydrosulfuryl(-SH) in captopril molecule, and the content of captopril can be obtained based on the absorbance of the phosphomolybdic blue. A novel method for the spectrophotometric determination of captopril by phosphomolybdic blue has been established. The various effect factors on the spectrophotometry determination of captopril by silicomolybdenum blue are investigated in detail. The results show that the maximum absorption wavelength of chromogenic system is 711.8 nm. Beer’s law is obeyed between the concentration of captopril and the absorbance in the range of 0.08024∼0.2728 mg/mL, the linear regression equation is A = -0.2635+5.0469C (mg/mL), with the linear correlation coefficient is 0.9991. This proposed method has been applied to determinate of captopril in captopril tablets, and the results agree well with pharmacopoeial method.