Decrease In Absorption Intensity Research Articles

Effectiveness of sulfuric acid and hydrochloric acid catalysts in the esterification of frankincense cinnamic acid with ethanol and methanol

This research aims to compare the effectiveness of sulfuric acid and hydrochloric acid catalysts in the esterification of frankincense cinnamic acid (STYRAX paraleoncomud PERK). Esterification of sulfuric acid catalyst is carried out with ethanol and for hydrochloric acid catalyst with methanol. Esterification was carried out by refluxing a mixture of 1:20 cinnamic acid - ethanol and methanol, with 3 mL of each catalyst at a temperature of 60oC for one hour. The results were rinsed with 3 x 50 mL distilled water and dried with anhydrous sodium sulfate. The results were filtered and verified for functional groups using FTIR and composition analysis using GC – MS. The results of FTIR interpretation show a decrease in absorption intensity (-OH) at 3500 cm-1 as a functional group that reacts compared to the ester results as an indication of the ongoing esterification reaction. The resulting ethyl cinnamate has a high conversion of 84.42%. Methyl cinnamate also has a distinctive ester aroma but is clearer and based on GC-MS, the content of methyl cinnamate is relatively low, namely 34.40%, the remaining cinnamic acid is 37.28%, and various side products of 28.32%. Thus, the catalyst that provides better conversion is sulfuric acid, but it requires further purification by examining the appropriate absorbent and bleaching agent. The brown color of the ester product catalyzed by sulfuric acid is thought to occur due to the oxidation of the cinnamic acid double bond by the catalyst.

Characteristic of Natural and Acid-activated Clay From Hatu Village, Mollucas Province: FTIR, XRD, XRF, SEM-EDX, TEM, and BET Analysis

Research on the chemical and physical characteristics of natural and acid-activated clay from Hatu Village had been carried out using FTIR, XRD, XRF, SEM-EDX, TEM, and BET surface area analyzer instruments. The natural clay had activated with 0.25 M sulfuric acid for 3 hours using the reflux method, then calcined with 700 Watt microwave radiation for 10 minutes. Overall, FTIR data show tetrahedral and octahedral functional groups that create clay minerals. There is a decrease in absorption intensity due to acid's influence, which dissolves cations in the octahedral and interlayer clay. The XRD analysis shows the Hatu natural clay contains montmorillonite, alumina, kaolinite, quartz, and illite minerals. Broadening and decreasing the intensity of diffraction peaks due to treatment by acid and calcination. SEM images of natural clay before and after activation-calcination shows the morphology of porous and layered material, while the mapping of the surface of natural clay shows irregular and rough material topography. The EDX spectra showed four elements with the most extensive composition: O, Si, Al, and Fe. XRF data confirmed three components that have the highest mass percent, namely SiO2, Al2O3, and Fe2O3. Dealumination occurs at 0.95% due to activation by sulfuric acid along with calcination. TEM images clearly show the multilayered silicate materials. The higher nitrogen gas uptake by activated-calcinated natural clay is proportional to the large surface area and total pore volume.

Development of tellurium/cerium bimetallic nanoparticles using biological method and their detection and degradation of keratin

In the present investigation, a novel eco-friendly synthesis of TeCe BNPs is fabricated from Cinnamomum camphora-mediated leaf extract. Biofabricated TeCe BNPs mediated by C. Camphora are characterized by various studies, such as UV–visible spectroscopy, XRD, SEM, HR-TEM, AFM, and XPS. The surface morphology of bioactive TeCe BNPs is visualized through SEM and AFM studies. The average particle size of TeCe BNPs is found to be 103 nm, with a zeta potential of 0.3, which confirms the stability and dispersive nature of BNPs. The decrease in absorption intensity with an increase in light irradiation reveals the primary degradation of keratin. FTIR studies confirm the formation of a disulfide band in the region of, 1115 cm−1. Furthermore, an electrochemical biosensor based on C.Camphora mediated TeCe BNPs modified glassy carbon electrode was developed for the determination of keratin under optimal conditions. The biosensor exhibits a linear response in the potential range of 0.9–1.0 μm, with a limit of detection of 0.0562 μm and a detection limit of 4.8951E−4.

Chemical Composition and Spectroscopic Characteristics of Heat-Treated Rubies from Madagascar, Mozambique and Tanzania

The chemical composition and spectra of rubies heat-treated with high temperatures (above 1200 °C) from Madagascar, Mozambique and Tanzania were analyzed by electron microprobe, LA-ICP-MS, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-VIS spectroscopy. Compared with untreated rubies, the red hue of treated ruby intensifies while its blue tint diminishes, leading to increased cracks. The infrared spectra exhibit a distinct absorption peak at 3738 cm−1, attributed to water because of thermal treatment. After heat treatment, the absorption intensity decreases. Ultraviolet radiation reveals an enhancement in the electron transition of Cr3+ and ion transition of Fe3+ and Fe2+, with a shift towards shorter wavelengths observed in the absorption bandwidth. These can be utilized to indicate the basis of ruby identification through heat treatment.

Long-lasting stability and low-concentration SO2 gas detection aptitude of Sn-doped alumina sensors

The Sn-doping effect on the SO2 gas sensing properties has been investigated by a resistance-based measurement method. During structural analysis, the undoped aluminium oxide (Al2O3) nanoparticles display a rhombohedral phase and the Sn-doped nanoparticles reveal the orthorhombic phase which causes a diffraction shift to a higher angle. From the surface analysis, particles expose dense microstructure, which is further enhanced by doping. High-resolution scanning microscopy images confirm a non-identical orientation of particles, suggesting polycrystalline nature. Besides, the particles are interconnected through one-by-one approach by forming a necklace of bead-like structure. The optical spectroscopy measurement endows a decrease in absorption intensity followed by an increase in bandgap with increasing Sn-doping concentration (SnxAl2-xO3). In sensor investigation, Sn-doped sensor senses the SO2 gas more efficiently even at low and higher concentrations i.e. from 10 to 300 ppm. The sensor adduces an elevated sensitivity of 78.14% at 300 ppm. In addition, the sensor adsorbs the gas molecules within 17 s, depicting a fast response time. As a result of the greater sensitivity, assistive technology such as pre-concentration is no longer required. The Sn-doped sensor bestows 96.83% reproducibility, showing a practical importance.

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Experimental and Theoretical Study of the Effects of Rare Earth Elements on Growth and Chlorophyll of Alfalfa (Medicago sativa L.) Seedling.

Rare earth elements (REEs) of low concentration are usually beneficial to plant growth, while they are toxic at high concentrations. The effects of treatment with lanthanum (La) (10 and 20 μM), cerium (Ce) (10 and 20 μM), and terbium (Tb) (10 and 20 μM) on seedling growth of alfalfa (Medicago sativa L.), which is one of the most important perennial leguminous forages in the world, were studied. The results showed that all three REE treatments quickened the germination of seeds. The length of shoot under La (20 μM) treatment was significantly shortened (P < 0.05). In addition, treatment with La, Ce, and Tb had a “hormesis effect” on root length. There was a significant decrease in chlorophyll content on treatment with the three REEs, and the degree of decline was in the order of La < Ce < Tb, under the same concentration. In vitro experiments and quantum chemical calculations were further performed to explain why the treatments with REEs reduced the chlorophyll content. In vitro experiments showed that La, Ce, and Tb treatments reduced the absorbance of chlorophyll, and the decrease followed in the order of La > Ce > Tb. Quantum chemical calculations predicted that the decrease in absorption intensity was caused by the reactions between La, Ce, Tb, and chlorophyll, which formed lanthanides-chlorophyll; and there were five types of stable lanthanides-chlorophyll. In conclusion, the decrease in chlorophyll content on treatment with REEs was caused by the change in chlorophyll structure.

A terahertz multi-band metamaterial absorber and its synthetic evaluation method based on multivariate resonant response fusion for trace pesticide detection

A synthetic multivariate response evaluation of a multi-band terahertz (THz) metamaterial absorber (MMA) for highly sensitive and accurate detection of trace pesticides including indole-3-acetic acid, thidiazuron, benomyl, and chlorpyrifos in solution is presented. The THz spectral response of the prepared MMA sensor illustrated that with an increase in pesticide concentration (10∼520 ng/L), all absorption bands (0.91, 1.59, 1.99, and 2.42 THz) exhibited a red-shift in frequency, part of which showed a decrease in absorption intensity. The modeling results between the pesticide concentrations and spectral responses demonstrated that the proposed multivariate resonant response fusion (MRRF) framework outperformed all the univariate regressions in improving accuracy and simplifying evaluation through the effective multivariate selection and statistical fusion. The highest detection accuracy was achieved for chlorpyrifos (CPF). Consequently, trace CPF in four vegetable extracts was detected to further verify the stability and reliability of the multi-band MMA combined with MRRF. The results indicated that the predicted recoveries using our approach were accurate, and the detection limits of all pesticide solutions reached 10 ng/L. This work presents a new prospect for highly sensitive detection of trace hazardous materials and the potential application of THz metamaterial technology in food safety inspection.

Sensing Applications of Triazole Conjugated Silver Nanoparticles

This study involves synthesis and physicochemical evaluation of triazole conjugated silver nanoparticles (TBS-AgNPs). The triazole derivative (TBS) was synthesized via click reaction followed by its conjugation with silver nanoparticles through the chemical reduction method. The TBS-AgNPs were characterized by various spectroscopic techniques, for instance, UV-Visible, atomic force microscopy (AFM), Fourier transform infrared (FTIR),and dynamic light scattering (DLS). TBS-AgNPs showed maximum absorption at 400 nm with an average particle size of 60-80 nm. Sensitivity and selectivity of TBS-AgNPs towards metal ions were evaluated using UV-Visible spectroscopy and the addition of Pd2+ produced a significant decrease in absorption intensity of TBS-AgNPs. Whereas, all other tested metal ions such as Sn2+, Ni2+, Ca2+, Bi3+, NH4+, K+, Mg2+, Na+, Co2+, Mn2+, and Ba2+ did not alter the optical properties of TBS-AgNPs for Pd2+. TBS-AgNPs nanoparticles are highly selective for Pd2+ as no interference was observed in competitive experiments. Job's plot indicated a 1:1 binding ratio between Pd2+ and TBS-AgNPs. Furthermore, TBS-AgNPs were effectively used for the detection of Pd2+ ion in laboratory tap water.

The Use of Green Spectroscopy for Analysis of Quetiapine

Three green (eco-friendly), inexpensive and simple spectrophotometric methods for quetiapine fumarate (QTF) analysis have been developed and validated. Method I was based on the measurement of the oxidation product of QTF at 610 nm. Potassium permanganate was used as oxidant. Method II was also relay on oxidation of the drug with ceric ammonium sulfate and the decrease in absorption intensity at 315 nm was measured. Method III involved complexation of the analyte with 2´,7´-bis (acetoxy mercury) fluorescein and quantitative analysis depended on determination of the reduction in absorption intensity of the used reagent at 502 nm. Different reaction conditions affecting intensity of measurement were carefully studied, optimized and validated. In all proposed methods, no need for extraction procedures and there were linear relationships between the absorbance readings and concentrations of QTF in the range of 5-35, 1-6 and 30-100 μg/mL with LOD values 1.11, 0.12 and 2.68 μg/mL for methods I, II and III respectively. The suggested methods were successfully applied to QTF analysis in pure form and in drug tablets.

Enhanced LSPR performance of graphene nanoribbons-silver nanoparticles hybrid as a colorimetric sensor for sequential detection of dopamine and glutathione

In the present study, a novel plasmonic sensing platform was proposed for sequential colorimetric detection of dopamine (DA) and glutathione (GSH) in human serum sample by taking advantage of plasmon hybridization in graphene nanoribbons/sliver nanoparticles (GNR/Ag NPs) hybrid. DA was detected based on etching strategy and morphology transition of label-free Ag NPs hybridized with GNR. As a result of the etching process, hexagonal Ag NPs were changed to smaller corner-truncated nanoparticles and a blue shift was observed in its plasmonic band, accompanied by the color change from green to red. Sequentially, GSH induced aggregation of Ag NPs which resulted in a decrease in absorption intensity of Ag NPs plasmonic band and a color change from red to gray. By employing GNR/Ag NPs hybrid as a sensitive colorimetric sensor, DA and GSH were successfully detected in low concentrations of 0.04 μM and 0.23 μM, respectively. The same experiment was carried out in the absence of GNR and the detection limits were obtained 0.46 and 1.2 μM for DA and GSH, respectively. These results confirmed the effective role of GNR on the sensitivity improvement of GNR/Ag NPs hybrid. The proposed simple and sensitive sensing approach offered a beneficial and promising platform for sequential detection of DA and GSH in the biological samples.

APPLICATION OF OPTICAL METHODS OF ANALYSIS FOR DETERMINATION OF TOXICANCES

Introduction: Among medicines which exhibit antidepressant effect, Syndnocarb is widely used. It is used in psychiatry, in narcological practice it is prescribed to patients with chronic alcoholism, in pediatrics – children with diseases of the central nervous system. In case of overdose, it has a toxic effect and may be the cause of poisoning. Therefore, it is necessary to have the express methods of its analysis sensitive and reliable. Purpose: To develop a method of spectrophotometric analysis of a siderine in the UV region of a spectrum suitable for its rapid detection in solutions and tablets. Methods: UV spectrophotometry method. Results: The method of identification of a drug of antidepressant action of Sydnocarb is proposed by the method of molecular absorption spectroscopy in the UV region of the spectrum. Selected optimal conditions for the development of analysis techniques. The character of spectra in various solvents (inorganic and organic) in acid, alkaline and neutral media is studied. The maxima of light absorption are determined, molar and specific light absorption coefficients are calculated in all the solvents studied, by which it can be quantified. The developed method is used to identify the syndocard in tablets. Conclusion: The elaborated procedure enables to quickly and reliably identify the Syndnocarb in solutions and tablets by the method of UV spectrophotometry in the nearrange region of the spectrum. The maxima of light absorption, molar and specific coefficients in such solvents are determined: potassium hydroxide, nitric acid, water, dichloroethane, ethanol and phosphate buffer solution. It has been established that Sydnocarb has two stripes of dressing in acidic, alkaline and neutral media, as well as in organic solvents. In the longwave region of the spectrum, a hypochromic effect (decrease in absorption intensity) is observed in all of these solvents. The molar and specific coefficients of light absorption are determined, which make it possible to carry out the quantitative determination of the sidecar in various objects.

Preparation and Characterization of Cellulose Acetate from Pineapple (&lt;i&gt;Ananas comosus&lt;/i&gt;) Leaves

Pineapple leaves was utilized for the fabrication of cellulose acetate. It underwent a series of process that includes alkaline treatment using sodium hydroxide aqueous solution, bleaching treatment using acetate buffer and aqueous sodium chlorite, and acetylation using acetic anhydride. The preparation of cellulose acetate was done in different acetylation times (8, 16, 24 and 32 hours). The cellulose acetate samples were then characterized using fourier transform infrared spectroscopy (FTIR) to elucidate the vibrational move, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) to investigate the thermal property of the material and scanning electron microscopy (SEM) to examine the surface morphology. FTIR result showed significant decrease in absorption intensity of the O-H stretch after the acetylation which indicates the substitution of hydroxyl group by acetyl group. On the other hand, the emergence of C=O stretch of the ester group and C-O stretch of acetyl group can be observed which indicates the formation of cellulose acetate. TGA and DTA also shows enhanced thermal stability of cellulose acetate prepared in 16 hrs acetylation period. Increasing the reaction time to 24 hrs and 32 hrs resulted to significant decrease in thermal stability. SEM images revealed the deterioration on the physical structure of cellulose after 24 hrs acetylation.

Quadruple-signaling (PET, ICT, ESIPT, [sbnd]C[dbnd]N[sbnd] rotation) mechanism-based dual chemosensor for detection of Cu2+ and Zn2+ ions: TRANSFER, INH and complimentary OR/NOR logic circuits

Herein, we have designed and synthesized o-phenylenediamine-based 4-in-1 dual chemosensor DAU, for simultaneous detection of Cu2+ and Zn2+ through modulation of PET, ICT, ESIPT and CN rotation mechanisms. The binding of first Cu2+ ion with NEt2 group causes red shift of absorption band from 372 nm to 420 nm and fluorescence enhancement due to keto- form at 480 nm (∼20 fold). When concentration of Cu2+ further increased from 1 to 10 equivalents, it results in decrease in absorption intensity at 420 nm and increase in absorption intensity at 300 nm and fluorescence quenching at 480 nm followed by enhancement due to enol- form at 410 nm. In contrary higher concentrations of Zn2+ causes only red shift from 372 to 420 nm however fluorescence remained low due to PET quenching effect. Significantly, when Cu2+ is added to DAU–Zn2+ (1:5) complex, it results in decrease of absorption intensity at 420 nm and increase in fluorescence at 480 nm followed by a 7-fold increase of the emission intensity at 410 nm. The multiple outputs of DAU can be used for fabrication of INHIBIT, TRANSFER logic devices and complementary OR/NOR logic circuit.

The near-infrared (NIR) spectra of powdered calcite in the 3–121 μm mode particle size range

The near-infrared (NIR) spectra of powdered carbonate minerals is of significant multidisciplinary interest. However, there is a paucity of accounts of the behaviour of NIR bands as a function of particle size in well-constrained experimental settings, although such studies may hold promise in revealing band-specific traits and identifying spectral features amenable to quantified measurement of particle size fractions. To these ends, this study examines the NIR spectral response in the 2.5 to 1.66μm wavelength (4000–6000cm−1 wave number) region from powdered calcite in size fractions ranging from 3 to 121μm mode particle sizes.Results show that the behavioural response of the NIR spectra is varied. Those assigned to 3v3: 2.34μm (4270cm−1) and 2.3μm (4350cm−1) wavelengths show a linear relationship (r2=0.9992), with decreasing particle size and absorption intensity. Bands at 2μm (5007cm−1), 1.96μm (5109cm−1) and 1.87μm (5336cm−1) assigned to combinations between v3 overtones and v1 and its overtone show an initial decrease in absorption intensity, but an increase in absorption intensity in the 3μm mode particle size powder relative to the 5μm mode powder. The differing behaviours of 3v3 overtone related bands with respect to combinations containing v1 or its overtone occur at particle size ranges in which the optical thick to thin transition occurs at mid-infrared (MIR) frequencies. The separate NIR behavioural responses of specific bands are qualitatively reminiscent of MIR types 1 and 2 behaviour of [CO32−] anion internal modes at the optical thick to thin transition.

Polymer/clay nanocomposites based on aliphatic–aromatic polyamide containing thiazole ring and new organomodified nanosilicate layers: Synthesis, characterization, and thermal properties study

New polyamide/clay nanocomposites (PACN) were produced using semicrystalline polyamide (PA) containing thiazole ring and new organoclay (OC) through solution intercalation technique. For further study, PA/Cloisite‐15A nanocomposites (PAAN) were also prepared using PA and Cloisite‐15A. X‐ray diffraction (XRD), field emission‐scanning electron microscopy (FE‐SEM), and transmission electron microscopy (TEM) results showed a good dispersion for OC in the PA matrix. A meaningful decrease in intensity of absorption from ultraviolet–visible spectra as well as from fluorescence emissions of resulted PACN were observed. As thermogravimetric analysis (TGA) in nitrogen atmospheres showed, the T5 and T10 increased by about 57% and 36%, respectively for PACN containing 5 mass% of OC, as the char yield enhanced greatly, which was about 16.3% higher than the neat PA. Also the TGA results showed that PACN had higher thermal stability than PAAN. Differential scanning calorimetry (DSC) analysis exhibited higher glass‐transition temperature values (Tg) for PACN as compared to the neat PA. POLYM. COMPOS., 39:E1407–E1420, 2018. © 2017 Society of Plastics Engineers

Band bending effect induced non-enzymatic highly sensitive glucose sensing in ZnO nanoparticles

We report band bending effect assist the enhancement of green fluorescence in ZnO nanoparticles surrounded by glucose molecules. Optical absorption measurements show free exciton absorption of ZnO around 377nm and consistent decrease in absorption intensity while adding glucose. Room temperature photoluminescence study under excitation at 330nm shows very strong emission in the ultra violet (UV) and visible wavelength regions. Enhancement in green emission intensity is observed while increasing concentration of glucose from 60 to 480nM, which is attributed for decreasing depletion layer width near the surface as a result of electrons donating by glucose. Recorded time resolved emission spectra of prepared nanoparticles in the presence and absence of glucose proves that there is no energy transfer process occurs during ZnO-glucose interaction and the enhanced green emission are due to glucose molecules adsorbed on the surface of ZnO which can be applied for non-enzymatic glucose sensing applications.

Occurrence of stable and mobile organic matter in the clay-sized fraction of shale: Significance for petroleum geology and carbon cycle

Stability and mobility of organic matter (OM) in shale is of great significance for the carbon cycle and petroleum exploration and exploitation. To examine the stability and mobility of OM occurrence in shales, clay-sized fractions (<2μm) were separated from shales physically and chemically treated with different reagents. These fractions were followed by pyrolysis and measurements of specific surface area (SSA) and Fourier transform infrared spectrophotometry (FTIR). It is revealed that after wet chemical oxidation and organic solvent extraction, there exist: a) changes in total organic carbon (TOC), hydrogen index (HI) and oxygen index (OI); b) appreciable decrease in absorption intensity of –CH2– stretching vibration bands at 2924 and 2853cm−1; and c) dramatic increase of SSAs after wet chemical oxidation. These characteristics suggest that the TOC in the clay-sized fraction can be categorized into physical mobile-OC (PmOC), chemical mobile-OC (CmOC) and stable-OC (SOC), which account for 43.3%, 17.1% and 39.6% of TOC on average in the studied samples, respectively. The OM in the clay-sized fraction mainly occurs on mineral internal surface, and the occurrence of OM determines the stability and mobility of OC. The PmOC mainly accumulates in the pores and at the mouth and/or edge of the interlayer spaces of clay minerals, the CmOC chiefly adsorbs on the mineral external surface, and the SOC mainly occurs on the mineral internal surface. These occurrence characteristics of different OCs indicate that the mobility and stability of OM occurrence in a sample have different levels. The occurrence of stable and mobile OM in the clay-sized fraction of shale as investigated can improve the understanding of the occurrence of OM in shales, and provide a new insight for carbon cycle research and petroleum exploration and exploitation.

Benzimidazole based ratiometric chemosensor for detection of CN− and Cu2+ ions in protic/aqueous system: Elaboration as XOR logic operation

ESIPT based benzimidazole derivative probe 1 with electron withdrawing group has been synthesized and investigated their photophysical behavior towards various anions. The probe 1 has been used for selective estimation of CN− and signaled the binding event through formation of new absorption band at 380nm and emission band at 430nm with CN−. The addition of various metal ions to probe 1 in aqueous system showed selectivity towards Cu2+ and Hg2+ ions as compared to other metal ions, and signal the binding event through formation of new absorption band at 375nm and decrease in absorption intensity respectively. Thus, probe 1 act as chemosensor for CN− ions which restricts the ESIPT emission at 485nm due to H-bonding interactions between OH to nitrogen of benzimidazole moiety to release its enol emission. The chemical inputs of CN− and Cu2+ ions to probe 1 mimicked a sequence dependent operation of an exclusive-OR (XOR) logic gate. The binding behavior of probe 1 towards CN− and Cu2+ has also been confirmed through DFT calculations.

Polyether precursors of molecular recognition systems based on the 9,10-anthraquinone moiety

A series of novel polyether derivatives of 9,10-anthraquinone (AQ) was synthesized and characterized by means of UV–Vis spectroscopy, acid-base titration and complexometric titration. The results were compared with 1-NEt2AQ and 1-NHEtAQ – model compounds of alkylaminoanthraquinones. Acetonitrile and methanol were used as solvents for determination of spectroscopic and acid-base properties. Complexometric titrations were carried out exclusively in acetonitrile. Spectral characteristic of these compounds strongly depends on pH. Addition of acid causes the decrease of absorption intensity and in some cases also a shift of the visible range band. The weakest base is the compound (2), and the strongest – compound (1), both in methanol and acetonitrile solution. The introduction of an additional substituent in the position 8 of the anthraquinone compound increases its basicity. The presence of metal ions causes changes in intensity of absorption (decrease for compounds (2) and (3) and increase with bathochromic shift for (1) and (4)). For the determination of the coordination properties aluminum (III) ions were chosen. The highest complex stability constant with Al (III) ions is observed for compound (1), and the weakest for compound (3). The elongation of the polyether chain decreases the stability of the complex formed.