Method UV Research Articles

Well-established carbon nanomaterials: modification, characterization and dispersion in different solvents

Three different types of carbon nanomaterials, SWCNTs, MWCNTs and GNPs were prepared, modified, characterized, and their dispersibility behavior in three different solvents was evaluated. The carbon nanotubes were synthesized by using the well-known chemical vapor deposition method and the graphene nanoplatelets by wet physicochemical treatment techniques. Their characterization was accomplished by using various advanced techniques, such as powder X-ray diffraction and Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and N2 adsorption at 77 K. Furthermore, the carbon nanostructures were modified via plasma treatment and wet chemical surface modification in order to enhance their dispersion characteristics, for achieving more homogenous suspensions and therefore to be remained dispersed over a reasonable period of time without any sedimentation. The effect of treatment parameters and the use of different solvents were thoroughly studied mainly by optical methods, but also by using the DIN/EN classified ISO method of oil absorption and UV–Vis spectroscopy. The enhanced dispersion rate is observed in both CNTs and GNPs materials following their surface treatment, especially when using the solvent n-methyl-2-pyrrolidone. The aforementioned studied nanomaterials are perfect candidate fillers for preparing polymeric mixed matrix membranes.Graphical abstract

In vitro Evaluation Method of UV Protecting Ability of Sunscreens: Clarifying and Overcoming Problems to Develop New Method.

Factors influencing on in vitro evaluation of UV protecting ability of sunscreens were analyzed. It was found that any factors making the sunscreen layer spatially inhomogeneous, such as directional viscous fingering during the sunscreen application, dewetting of applied sunscreen layer, and the surface roughness of the standard PMMA plate, alter the UV transmittance. New application procedure and new type of flat hydrophilic plate were developed for inhibiting the generation of spatial inhomogeneity in applied sunscreen layer. The method created by the combination of these newly developed technologies succeeded in providing reliable and reproducible in vitro evaluation of UV protecting ability.

General method based on WKB approximation and digital holography to characterize planar waveguides

Future optical technologies are basically depending on and employing different types of optical waveguides. The fabrication of waveguides with different properties represents an expanding direction in both the industrial and scientific fields. In the current paper, we focus on studying the polymeric planar waveguides fabricated by the method of UV–excimer–laser lithography. We propose a general technique based on the WKB approximation and digital holographic interferometry to characterize slab waveguides with arbitrary refractive index profile. The necessary theoretical model is derived and the characterization method given in detail. Two samples are fabricated from polymethylmethacrylate (PMMA) polymeric material using different parameters for the used UV-laser. Then a phase-shifting digital holographic technique with the help of a Mach–Zehnder-like interferometer, is used to characterize the samples and measure their modified refractive index profiles. The resulting profiles are then fed to the proposed theoretical model and a full TE mode analysis is obtained. These results prove the ability of the proposed technique to analyze planar waveguides having any complicated refractive index profile.

Application of microextraction techniques for indirect spectrophotometric determination of fluorides in river waters

The present study is dedicated to development of improved method for determination of trace amounts of fluorides in natural waters which is based on the interaction of fluorides with ion associate (IA) of Al(III), salicylic aldehyde acylhydrazones (benzhydrazone (SABH) and 4-picolinhydrazone (SAPH)) and polymethine dye Astra Phloxine FF (AP). Comparison of analytical forms [Al(SABH)2]⋅AP and [Al(SAPH)2]⋅AP showed that the analytical system Al(III)-SAPH-AP is more effective, namely, a higher level of preconcentration of the analytical form is ensured by and extraction equilibrium is achieved faster. Based on the study, we propose a new, fast, simple, reliable, sensitive, and accurate method of the indirect UV–Vis-spectrophotometric determination of fluorides grounded on the interaction of fluorides with IA of Al(III), SAPH and AP with the utilization of vortex-assisted liquid-liquid microextraction (VALLME). The method is based on the discoloration of the microextract of IA of Al(III), SAPH and AP (Al-SAPH-AP) in presence of fluoride ions due to the formation of fluoride complexes of aluminum with higher stability. The effect of various factors has been studied. The optimal conditions of the UV–Vis-spectrophotometric determination of fluorides were defined as: pH 7.0–10.0, 1.0⋅10−6 mol⋅L−1 Al(III); 4.0⋅10−5 mol⋅L−1 SAPH; 1.0⋅10−6 mol⋅L−1 AP; λ = 560 nm. VALLME have been carried out in 250 μL of CCl4 at 20:1 vol ratios of aqueous and organic phases, with vortexing at 3000 rpm for 15 s followed by centrifugation at 2000 rpm for 2 min. The determination of fluorides is feasible in the presence of various interferences. The calibration curve shows the linear dependence in the range of 0.3–114 μg⋅L−1 of the fluorides concentration (R2 = 0.993) with the limit of detection of 0.086 μg⋅L−1 and the limit of determination of 0.284 μg⋅L−1. The accuracy of the proposed protocol of fluorides determination was verified towards a reference method on the samples of natural rivers waters (RSD 2.6–3.1%, recovery 98.3–101.4%).

In Vivo Antimalarial Test of Artocarpin and in vitro Antimalarial Test of Artonin M Isolated from Artocarpus

The derivative of flavonoid compounds, artocarpin (1) and artonin M (2), were isolated from the root wood of Artocarpus altilis and from the root bark of A. kemando, respectively. Both plants originated from Lampung, Indonesia. The structure of the two compounds has been carefully determined by physical method and spectroscopy techniques of UV, IR, and NMR. The in vivo antimalarial test of artocarpin showed very good Plasmodium activity in female mice, with ED50 value of 34.88 mg/kg body weight (kgBW), whereas the in vitro antimalarial test of artonin M showed very strong activity with IC50 of 0.3 μg/mL (5.967 x 10-7 M).

Evaluating a Combined Method of UV and Washing for Sanitizing Blueberries, Tomatoes, Strawberries, Baby Spinach, and Lettuce

We assessed a fresh produce decontamination system using a combined method of UV and washing (water-assisted UV [WUV]) in different scales. The system used tap water to wash fresh produce while exposing it to UV light. First, the reduction of Salmonella in tap water under UV treatment (1 to 1,740 mJ/cm2) was determined. Increasing the UV dose significantly (P < 0.05) increased the Salmonella reduction in wash water, and UV intensity of more than 2 mW/cm2 could reduce Salmonella in tap water to below 1 CFU/mL given enough processing time (more than 1 min; UV dose of 120 mJ/cm2). Then, the decontamination effectiveness of a small WUV system was tested on blueberries (50 g). Blueberries were spot or dip inoculated with a Salmonella cocktail and treated by the small WUV system (200 mL of water). In general, WUV treatments achieved significantly better Salmonella inactivation than tap water wash; tap water wash (10 min) and 2 mW/cm2 WUV treatment (with a UV dose of 1,200 mJ/cm2) reduced populations of spot-inoculated Salmonella on blueberries by 2.44 and 5.45 log, respectively. Compared with spot-inoculated Salmonella on blueberries, dip-inoculated Salmonella was more difficult to be inactivated by WUV treatments. Then, the decontamination effectiveness of WUV treatments was tested on blueberries (170 g), tomatoes (290 g), strawberries (170 g), baby spinach (60 g), and lettuce (60 g) using a larger WUV system. In general, 10 min of 29 mW/cm2 WUV treatment (a high UV dose of 17,400 mJ/cm2) resulted in significantly better Salmonella inactivation than tap water wash (for 10 min) regardless the inoculation method, agreeing with the results of the small-scale study. For both spot- and dip-inoculated lettuce, no significant difference (P > 0.05) in Salmonella inactivation by WUV treatments was observed when the quantity of lettuce increased from 50 to 100 g.

Self-Association of the Macromolecules of Aldrich Humic Acid in Aqueous Solutions Using Ultraviolet-Visible (UV-Vis) Absorption Spectroscopy.

The ultraviolet-visible (UV-Vis) spectra of the aqueous solutions of humic acids (HA) Aldrich were obtained within the concentration range 1-20 mg/L (0.1-2ċ10-6 mol/L). A conclusion on the existence of the self-association (dimer formation) of HA macromolecules is based on the deviation of the concentration dependence of optical density (OD) from the linear one at [HA] > 10 mg/L (>10-6 mol/L). An original, mathematical algorithm is proposed to determine a dimerization constant K and a molar coefficient of dimer absorption The value of K was (2.56 ± 0.07) ċ 106 L/mol. The calculated molar coefficients of HA macromolecule dimer absorption, , indicate an increase in the dimer extinction coefficient compared to the double value of the molar monomer absorption 2 . It was established that the spectral dependence of the value β = / exhibits a minimum within a wavelength range of 300-450 nm, which is due to the difference in the efficiency of the interaction of various sites upon HA macromolecule dimerization. Thus, an approach of studying the processes of self-association is proposed using the method of UV-Vis absorption spectroscopy. This method is implemented for molecules that do not have characteristic absorption bands. The proposed method can also be successfully applied to molecules with characteristic absorption bands.

Recovery of lithium from alkaline brine by solvent extraction with functionalized ionic liquid

Lithium recovery from alkaline brine was carried out by solvent extraction (SX) using a hydroxyl-functionalized ionic liquid, 1-hydroxyethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([OHEMIM][NTf2]) and a neutral ligand, trialkyl phosphine oxide (Cyanex923) as the extractants. Effect of extraction parameters, i.e. concentration of ionic liquid, extraction time, pH value of aqueous phase, phase ratio and mole ratio of sodium to lithium, on lithium extraction efficiency have been studied. Under the optimal parameters, over 93% of lithium was extracted in one single run. The extraction mechanism of lithium was investigated by the combination method of experiment and UV–visible spectroscopic characterization, and it was found that the ion exchange predominated during the extraction process. The extraction complex was determined by a slope analysis method, indicating that Cyanex923, Li+ and [NTf2]- formed a 2:1:1 complex. The thermodynamic study indicated that lithium extraction reaction was spontaneous. Based on the above results, [OHEMIM][NTf2]-Cyanex923 extraction system showed a promising application in the recovery of lithium from alkaline brine.

Computational model of bladder tissue based on its measured optical properties.

Urinary bladder diseases are a common problem throughout the world and often difficult to accurately diagnose. Furthermore, they pose a heavy financial burden on health services. Urinary bladder tissue from male pigs was spectrophotometrically measured and the resulting data used to calculate the absorption, transmission, and reflectance parameters, along with the derived coefficients of scattering and absorption. These were employed to create a "generic" computational bladder model based on optical properties, simulating the propagation of photons through the tissue at different wavelengths. Using the Monte-Carlo method and fluorescence spectra of UV and blue excited wavelength, diagnostically important biomarkers were modeled. Additionally, the multifunctional noninvasive diagnostics system "LAKK-M" was used to gather fluorescence data to further provide essential comparisons. The ultimate goal of the study was to successfully simulate the effects of varying excited radiation wavelengths on bladder tissue to determine the effectiveness of photonics diagnostic devices. With increased accuracy, this model could be used to reliably aid in differentiating healthy and pathological tissues within the bladder and potentially other hollow organs.

СРАВНЕНИЕ РАДИАЦИОННОЙ СТАБИЛЬНОСТИ ХЛОРОФИЛЛОВЫХ ФРАКЦИЙ В СПИРТОВЫХ И АЦЕТОНОВЫХ ЭКСТРАКТАХ ВОДОРОСЛЕЙ LAMINARIA JAPONICA (МЬЯНМЫ)

В работе выделены этанольные и ацетоновые экстракты из бурых водорослей Laminaria Japonica Jemo (D) и Jenit (M). Методом UV-VIS спектрофотометрии зарегистрированы спектры оптического поглощения исходных экстрактов и их изменения при различном разбавлении растворителями. Показано, что природа водорослей, способ их культивирования, природа растворителей влияют на эффективность экстракции ценных биологически активных соединений (БАС), включая наиболее важные из них – каротиноиды и хлорофиллы. Особое внимание в этой работе было уделено изучению радиационно-химических превращений спиртовых (этанол), ацетоновых, водно-этанольных (50%) и водно-ацетоновых (50%) растворов экстрактов водорослей при различных условиях моделирования окислительно-восстановительных реакций за счет насыщения облучаемых растворов разными газами: кислородом воздуха, аргоном или закисью азота. Определена радиационно-химическая стабильность хлорофилловых фракций в разных видах водорослей в зависимости от условий радиолиза. Известно, что хлорофиллы часто используются в фармакологии, в качестве пищевого красителя, а в настоящее время в качестве компонентов светочувствительных слоев в нанофотонике. Данные по радиационной чувствительности биологических соединений из морских водорослей можно использовать для оценки их стабильности при радиационной стерилизации сырья и медицинских препаратов.

Defect evolution and photoluminescence in anion-defective alumina single crystals exposed to high doses of gamma-rays

A method of luminescent UV and VUV spectroscopy was used to study the evolution of color centers in anion-defective alumina single crystals exposed to high doses of gamma-radiation. A sharp drop in the intensity of the emission bands and, therefore, the concentration of F+ and F-centers associated with the formation of aggregate F2-type centers was found. The aggregate centers create an additional emission band in the range of (1.8–2.8) eV. When the crystals are exposed to middle and high doses, the photoluminescence (PL) intensity is the highest in the emission band of F22+-centers, which indicates a high concentration of the aggregates from singly charged oxygen vacancies (of F+-centers). When PL of the crystals exposed to high doses is excited with synchrotron radiation of the VUV range, a wide emission band in the red and near infrared (NIR) regions is registered. The centers related presumably to impurity defects, their aggregates and clusters consisting of several oxygen vacancies are responsible for this emission band.

Researching the possibility of formation of the ion associates of food azo dye carmoisine (E122) with organic amines

PURPOSE : Carmoisine is the synthetic food dye used in the manufacture of some medicals and food products. Previously, we had already established, that it is able to form the ion associates with chlorpheniramine maleate and in this way can be extracted from water solution with chloroform. The aim of the work is establishment of partition coefficients of the associate for water and different organic solvents, and research the interaction of the carmoisine with certain organic amines. MATERIAL AND METHODS : As the object of research the synthetic food dye carmoisine was selected. Analytical studies were performed by the method of UV and visible spectrophotometry. RESULTS AND CONCLUSIONS : As the result of the work performed, the partition coefficients of the associate of carmoisine and chlorpheniramine maleate for various systems water-organic solvent were spectrophotometrically established and it was shown, that the associate is better soluble in cyclohexanol, 2-octanol, and butanol. The formation of ion associates between carmoisine and some organic amines was established experimentally. The partition coefficients for the obtained ion associates were calculated. It was shown, that the associate of carmoisine with myramistine has the highest partition coefficient.

Photoluminescence of anion-defective alumina single crystals exposed to high-dose gamma-radiation

The method of UV and VUV spectroscopy with synchrotron radiation was used to measure photoluminescence (PL) spectra and photoluminescence excitation (PLE) spectra in anion-defective alumina single crystals exposed to high doses of gamma-radiation. A change in the intensity of the excitation band of F-centers near the fundamental absorption edge (8.8eV) was found to depend on doses and temperatures. New wide bands with µs–ms decay kinetics of emission were registered in the PL spectra at excitations with VUV and UV photons. The obtained results show that high-dose irradiations of the crystals under study lead to appearance of F2-type aggregate centers in different charged states. These centers are additional traps of charge carriers. Emission bands of other aggregate and impurity centers, which form an experimental PL spectrum in the crystals exposed to high doses, were also identified. The evolution of the centers, produced by oxygen vacancies and impurities, creates the features of dose responses of dosimetric α-Al2O3:С single crystals exposed to high doses of radiations.

Researching the possibility of formation the ion associates of food azo dye carmoisine (e122) with organic amines

PURPOSE : Carmoisine is the synthetic food dye used in the manufacture of some medicals and food products. Previously, we had already established, that it is able to form the ion associates with chlorpheniramine maleate and in this way can be extracted from water solution with chloroform. The aim of the work is establishment of partition coefficients of the associate for water and different organic solvents, and research the interaction of the carmoisine with certain organic amines. MATERIAL AND METHODS : As the object of research the synthetic food dye carmoisine was selected. Analytical studies were performed by the method of UV and visible spectrophotometry. RESULTS AND CONCLUSIONS : As the result of the work performed, the partition coefficients of the associate of carmoisine and chlorpheniramine maleate for various systems water-organic solvent were spectrophotometrically established and it was shown, that the associate is better soluble in cyclohexanol, 2-octanol, and butanol. The formation of ion associates between carmoisine and some organic amines was established experimentally. The partition coefficients for the obtained ion associates were calculated. It was shown, that the associate of carmoisine with myramistine has the highest partition coefficient.

Synthesis and ultrasonic investigations of titanium oxide nanofluids

Titanium oxide (TiO2) nanoparticles (NPs) were synthesized by means of sol–gel method. Crystalline nature of synthesized TiO2 NPs was confirmed by the X-ray powder diffractometry (XRD). The surface morphology and the size of particle of NPs were analyzed by high resolution scanning electron microscopic method (HRSEM). Phase composition in TiO2 was identified by FT-Raman spectroscopy. TiO2 NPs were dispersed into water and mixed thoroughly by using ultrasonication process to obtain nanofluid sample. The dispersion of nanoparticles in nanofluids is studied with the unique method of UV–visible spectrometer, which confirms that dispersion stability has prepared nanofluids. Ultrasonic velocity and the values of density were measured for different concentrations of titanium oxide nanofluids. The acoustical parameter such as adiabatic compressibility, intermolecular free length, and acoustic impedance was calculated from the experimental data. It was observed that ultrasonic velocity was made visible on linearity with particle concentration and the results were discussed.

Synthesis and characterization of CNTs using egg albumin &amp; Metal (Cr+3)

The growing need for analytical devices requiring smaller sample volumes, decreased power consumption and improved performance have been driving forces behind the rapid growth in nanomaterials research. Due to their dimensions, nano structured materials display unique properties not traditionally observed in bulk materials. Due to the vast application of CNTs, it is necessary to develop new methods for the synthesis of CNTs. In this method, complexes of transition metal Cr(III) with amino acid present in egg albumin have been synthesized. The complex so formed, is analyzed on the basis of spectroscopic method of UV, IR and NMR spectroscopy. The amino acid metal complex is decomposed at higher temperature in muffle furnace to obtain metal carbon nano tubes.

Study on the contribution of different molecular weight species to the absorption UV–Visible spectra of flame-formed carbon species

A reconstruction method of UV–Visible spectra, recently developed for discriminating the contribution of different molecular weight (MW) species to the spectral properties of carbonaceous species formed in a premixed ethylene flame, was applied to a benzene flame. The reliability and sensitivity of the technique in detecting specific structural features of the carbonaceous species was demonstrated.The flame-formed carbon species were deposited on quartz plates inserted in the soot formation region of a premixed fuel-rich benzene flame. The dichloromethane-soluble (DCM-soluble) and dry soot fractions were separated in a very wide MW range, from 200 to 1E11u, by Size Exclusion Chromatography (SEC) coupled with on-line UV–Visible spectroscopy. The optical band gap (Eg) and the UV peak position of each MW-segregated fraction were evaluated by means of a spectral reconstruction procedure, to get details on the carbon network structure in terms of sp2 and sp3 sites and size and stacking of the aromatic units. Moreover, the MW-segregated fractions of the species soluble in DCM were also analyzed by fluorescence emission spectroscopy and by atmospheric pressure laser desorption ionization–mass spectrometry for determining their aromatic character.The output of the spectral reconstruction procedure provided insights in the chemical structure and evolution of carbonaceous species from Polycyclic Aromatic Hydrocarbons (PAH) to soot nuclei and finally to soot aggregates. The comparison with data obtained in a premixed ethylene flame burning in similar temperature conditions showed some structural differences in flame-formed carbonaceous species due to the effect of the different chemical environment in which soot precursor are formed.

Photoactivity of brookite–rutile TiO 2 nanocrystalline mixtures obtained by heat treatment of hydrothermally prepared brookite

Pure brookite phase was prepared by hydrothermal synthesis of titanium peroxo-complex in the presence of glycolic acid at 220 °C. The structure of prepared brookite samples was determined by X-ray powder diffraction (XRD) and selected area electron diffraction (SAED). The prepared brookite was studied by in situ high temperature XRD in air. The morphology and microstructure characteristics were also obtained by transmission electron microscopy (TEM). The nitrogen adsorption–desorption was used for determination of surface area (BET) and porosity. The method of UV–vis diffuse reflectance spectroscopy was employed to estimate band-gap energies of prepared brookite. The photocatalytic activity of the prepared titania samples were assessed by photocatalytic decomposition of Orange II dye in an aqueous slurry under UV irradiation at 365 nm wavelength. The photocatalytic activity of the prepared sample brookite heated to 800 °C in air was higher than nanocrystalline unheated brookite powder.

Process analytical technology applied for end-point detection of pharmaceutical blending by combining two calibration-free methods: Simultaneously monitoring specific near-infrared peak intensity and moving block standard deviation

Here, we describe a combination approach using Two Calibration-Free Methods with reflectance near-infrared (TCFM-NIR), which involves detecting end-points for active pharmaceutical ingredients (APIs) blending by simultaneously monitoring specific NIR peak intensity of APIs and calculating moving block standard deviation (MBSD). After determining the specific NIR peak range of nicaldipine hydrochloride, conditions for TCFM-NIR were established by monitoring the differential intensity of the second peak (1136 nm) while MBSD was calculated from the NIR peak intensity between 1100 and 1150 nm. In comparison with the validated reference method of UV–VIS spectroscopy, which is particularly destructive, TCFM-NIR was found to be useful in detecting end-points for blending of nicaldipine hydrochloride. TCFM-NIR monitors two important factors for estimation of blend uniformity: API concentration, using specific NIR peak intensity for APIs, and blend homogeneity, using MBSD. Also, the conditions of TCFM-NIR were confirmed to be adequate by using Partial Least Square (PLS). Further, simultaneously monitoring these two blend uniformity factors is more useful in preventing estimation errors for nondestructive monitoring of blend homogeneity than monitoring only one factor, as with NIR spectroscopy.

Influence of Defects on Low Temperature Diffusion of Boron in SiC

The low temperature diffusion of Boron in bulk SiC crystals is investigated and simplified model of such diffusion is presented. The method of UV stimulated etching by aqueous solution of KOH is proposed and some experimental data on influence of defects on quality of prepared p-n junctions are presented.