Character Of Absorption Research Articles

Unveiling Multiquantum Excitonic Correlations in Push-Pull Polymer Semiconductors.

Bound and unbound Frenkel-exciton pairs are essential transient precursors for a variety of photophysical and biochemical processes. In this work, we identify bound and unbound Frenkel-exciton complexes in an electron push-pull polymer semiconductor using coherent two-dimensional spectroscopy. We find that the dominant A0-1 peak of the absorption vibronic progression is accompanied by a subpeak, each dressed by distinct vibrational modes. By considering the Liouville pathways within a two-exciton model, the imbalanced cross-peaks in one-quantum rephasing and nonrephasing spectra can be accounted for by the presence of pure biexcitons. The two-quantum nonrephasing spectra provide direct evidence for unbound exciton pairs and biexcitons with dominantly attractive force. In addition, the spectral features of unbound exciton pairs show mixed absorptive and dispersive character, implying many-body interactions within the correlated Frenkel-exciton pairs. Our work offers novel perspectives on the Frenkel-exciton complexes in semiconductor polymers.

Wavelength-Independent Performance of Femtosecond Laser Dielectric Ablation Spanning Over Three Octaves

Ultrafast laser breakdown of wide bandgap dielectrics is today a key for major technologies ranging from 3D material processing in optical materials to nanosurgery. However, a contradiction persists between the strongly nonlinear character of energy absorption and the robustness of processes to the changes of the bandgap/wavelength ratio depending on applications. While various materials and bandgaps have been studied, we concentrate here the investigations on the spectral domain with experiments performed with wavelength drivers varied from deep-ultraviolet (258 nm) to mid-infrared (3.5 $\mu$m). The measured fluence thresholds for single shot ablation in dielectrics using 200-fs pulses exhibit a plateau extending from the visible domain up to 3.5-$\mu$m wavelength. This is accompanied, after ablation crater analysis, by a remarkable invariance of the observed ablation precision and efficiency. Only at the shortest tested wavelength of 258 nm, a twofold decrease of the ablation threshold and significant changes of the machining depths are detected. This defines a lower spectral limit of the wavelength-independence of the ablation process. By comparison with simulations, avalanche ionization coefficients are extracted and compared with those predicted with the Drude model. This must be beneficial to improve predictive models and process engineering developments exploiting the new high-power ultrafast laser technologies emitting in various spectral domains.

Near Infrared-II Photothermal and Colorimetric Synergistic Sensing for Intelligent Onsite Dietary Myrosinase Profiling.

Myrosinase (Myr) is a type of critical β-thioglucosidase enzyme activator essential for sustaining many functional foods to perform their health-promoting functions. An accurate and reliable Myr test is meaningful for food quality and dietary nutrition assessments, whereas the currently reported methods do not guarantee specificity and have high reliance on instrumentation, which are not suitable for rapid and onsite Myr screening especially in complex systems from various sources. Herein, we present a unique NIR-II absorption-based photothermal-responsive colorimetric biosensor for anti-interference onsite Myr determination and realization of rapid visualized outputs with the aid of smartphone calculation. Typically, assisted by glucose oxidase (GOx), Myr specifically converts the sinigrin substrate into hydrogen peroxide (H2O2) that can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) catalyzed by AuNPs to form a charge transfer complex (CTC) with NIR-II absorption and photothermal characters. Delightfully, such a proposed method is able to determine Myr within a wide range of 0 to 172.5 mU/mL with a detection limit down to 2.96 mU/mL. Moreover, simple, rapid, and real-time visual Myr identification in actual food-sourced samples could also be readily achieved by smartphone readout processing, with the promising advantages of anti-interference, high accuracy, and low cost as well as labor-saving and intelligence engagement, thus providing great feasibility for precise measurement in complex and dynamic dietary sample analysis. Overall, our proposed method presents a novel technology for onsite dietary Myr enzyme profiling, which is promising to be applied in the food industry for nutritional composition profiles, freshness evaluation, and quality assessment.

The cellulose fibers functionalized with star-like zinc oxide nanoparticles with boosted antibacterial performance for hygienic products

Bacterial infectious diseases are serious health problem which extends to economic and social complications. Moreover, bacterial antibiotic resistance, lack of suitable vaccine or emergence of new mutations is forcing the development of novel antimicrobial agents. The objective of this study is to synthesize and characterize star-like zinc oxide nanoparticles for the application of antibacterial activities in cellulose based hygiene products. ZnO NPs were in situ synthesized via precipitation method on the surface of cellulose fibers. Since bactericidal activity of nanoparticles in part depends on the concentration in the growth medium, various amount of ZnO was incorporated into cellulose matrix ranging from 1 to 3 wt%. Microscopic (TEM, SEM) and spectroscopic (FT-IR, XRD) methods were utilized to investigate the final products. The infrared absorption spectra analysis supported by theoretical finding that during the reaction, ZnO nanoparticles could be bonded with cellulose fibers via hydrogen bonding. The yield of functionalization was determined through thermogravimetric analysis. Collected data proved the successful functionalization of the cellulose fibers with nanoparticles. Static contact angle measurements were carried out showing absorptive character of as prepared fabrics. All the samples were tested for the antibacterial properties and the results were compared to the samples prepared from the pristine cellulose fibers. Moreover, mechanical tests were performed revealing that the addition of only 2 wt% of the nanofiller boosted tensile, tearing and bursting strength by a factor of 1.6, 1.4 and 2.2 in comparison to unfunctionalized paper sample, respectively. Fabricated fabric presenting high hydrophilicity and antibacterial properties have gained increased applications in fabric industry, including hygiene product industry and hence the result of this study would be a welcomed option.

Morphometric Epididymis Postnatal Development of White Rabbit Bucks Population in Algeria

The aim of this study is determinated the ultra structural morphometric changes of the epididymis during the postnatal development of rabbits of the white population. For this, 148 rabbits aged between 4 and 28 weeks were sacrificed, epididymides are fixed for the study of microscopic parameters. The morphometric study of epididymis shows that the principal cells of 4 to 12 weeks are characterized by weak morphofunctional characters. From 14 weeks, these cells acquire morphometric characters marked by high values of hcp and zsn and low values of the report by N/hcp. This is suggestive of a physiological differentiation indicating the acquisition of cellular polarity and the development of secretory and/or absorptive character. The high N/hcp ratio of young individuals between 4 and 12 weeks of age could be an indicator of the existence of cell divisions. The structural changes of the epididymis during the postnatal development is manifested by a progressive increase of the height of principal cells and the height of the zone supranuclear. The values of hcp and zsn are higher at the level of the épididyme proximal from 16 weeks which correspond in the entered in puberty.

Solar-driven aromatic aldehydes: green production from mandelic acid derivatives by a Co(ii)/C3N4 combined catalyst in aqueous media.

According to the requirements for sustainable development, reclaiming fine chemicals from wastewater under mild conditions is an extremely significant line of research. A low-cost and high-efficiency polydentate chelate- and polymeric Co(ii)-based complex (Co-L)-loaded C3N4 photocatalyst (Co-L/C3N4) was constructed and used to convert aromatic mandelic acids in wastewater at room temperature. The BET specific surface area increased from 28 m2 g−1 to 68 m2 g−1, indicating its excellent absorptive character. The light absorption range of Co-L/C3N4 reached 650 nm, while the band energy reduced to 2.30 eV, which caused a significant enhancement in photocatalytic activity. The conversion of substituted mandelic acids was more than 90% due to the photoactivity of Co-L/C3N4. Time-resolved PL spectra indicated the remarkable separation of the photogenerated electron–hole pairs in Co-L/C3N4. Furthermore, the UV-vis and in situ FTIR spectra indicated the formation of aldehyde groups in the selective oxidation process, which provided support for the plausible catalytic mechanism.

Fluorenyl Indoline as an Efficient Electron Donor for Concerted Companion Dyes: Enhanced Light-Harvesting and Photocurrent.

Concerted companion dyes (CC dyes) like XW61 have been demonstrated to be an effective platform for developing efficient DSSCs. However, the moderated phenothiazine-based electron donor in XW61 results in unsatisfactory Jsc. To address this problem, a stronger fluorenyl indoline-based electron donor has been used to construct porphyrin dye XW68 and organic dyes Y1-Y2. The stronger electron-donating character of the fluorenyl indoline unit leads to an enhanced Jsc value (20.48 mA·cm-2) for the individual dye XW68. On this basis, CC dyes XW69-XW70-C8 have been designed and synthesized by combining the frameworks of Y1 and Y2 with XW68. The complementary absorption characters of the porphyrin and the organic dye moieties lead to panchromatic absorption with a strong light-harvesting capability from 350 to 700 nm and the onset wavelength extended to ca. 840 nm in the IPCE curves. As a result, excellent Jsc values have been achieved (>22 mA·cm-2). In addition to the advantages of high Jsc, bulky octyl groups have been introduced into the donor of XW70-C8 to reduce dye aggregation and suppress charge recombination. Finally, a highest PCE of 11.1% with a satisfactory Jsc (22.25 mA·cm-2) and an enhanced Voc (750 mV) has been achieved upon coadsorption of XW70-C8 with CDCA. In addition, the CC dye XW70-C8-based solar cells exhibit excellent long-term photostability. These results provide an effective method for rationally improving the photovoltaic behavior, especially the Jsc of CC dyes, by introducing strong electron donor moieties with suitable substituents.

Biological applications of nanocomposite hydrogels prepared by gamma-radiation copolymerization of acrylic acid (AAc) onto plasticized starch (PLST)/montmorillonite clay (MMT)/chitosan (CS) blends

In this work, nanocomposite hydrogels were prepared by gamma-radiation copolymerization of acrylic acid (AAc) onto plasticized starch (PLST)/montmorillonite clay (MMT)/chitosan (CS) blends. The effect of irradiation dose and MMT nanoparticle contents on the gel fraction and water absorption characters of PAAc-co-(PLST/MMT/CS) hydrogels was investigated. In addition, the structure-property behavior of the nanocomposite hydrogels was characterized by FTIR spectroscopy, thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The study showed that the appropriate dose of gamma irradiation to achieve homogeneous nanocomposite hydrogels films and the highest absorption in water was 15 kGy, regardless of composition. The introduction of MMT up to 5-wt (%) improved the physical properties and enhanced the drug uptake-release characters. The effect of the nanocomposite hydrogels on skin wound healing were evaluated by rat models, taking sulfanilamide as a model drug. The profiles of rat skin after different time intervals up 21 days revealed that wounds treated with the copolymer hydrogels were healed faster which it may considered as a potential candidate for wound dressing materials.

Study of Third-order Nonlinear Optical Properties of Basic Violet 3 Dye in Polar Protic and Aprotic Solvents.

The present work aims to study of third-order nonlinear optical (TONLO) behavior of basic violet 3 dye dissolved in polar protic and aprotic solvents, namely, ethanol, 1-propanol, acetone and dimethyl sulfonate (DMSO), respectively. The polarity of the solvent used to have a substantial impact on the linear and TONLO properties of the dye sample. The dye exhibits self-defocusing nonlinearity due to thermally induced nonlinear refractive index and nonlinear absorption coefficient reveals the character of both saturable and reverse saturable absorption (RSA). The order of magnitude of nonlinear refractive index (n2) and nonlinear coefficient of absorption (β) of dye sample was determined to be 10-7 cm2/W and 10-3cm/W, respectively. The real and imaginary factors of the TONLO susceptibility of basic violet 3 dye were measured to be the power of 10-5 esu. The obtained results reveal that the dye sample seems to have the potential candidate for use in various photonics and optoelectronics applications.

Satellite data based abundance mapping of mafic and ultramafic rocks in Mettupalayam, Tamil Nadu, India

The mafic and ultramafic rocks of Mettupalayam belong to the southern granulite terrain of India, which is concomitant with vital economic resources. The advantage of Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) data for mapping the litho units are exploited well here for differentiating the rock units with the aid of band combination (1, 3, 6), principal component analysis (5, 1, 6) and band ratioed band combination (2/3, 3/2, 1/5 and (9–8)/1, (8–6)/2, and (9–6)/3). As part of the field study, the collection of samples and ground control points were carried out and in addition to that, the generation of laboratory reflectance spectra for samples was achieved. The Spectral Angle Mapper (SAM) and Support Vector Machine (SVM) were performed using ASTER data with the aid of spectra obtained from the laboratory conditions to demarcate the abundance of mafic and ultramafic rocks of the area. The XRF method was used to retrieve the major oxides of the field-collected samples and the spectral absorption characters are validated with it. The results show a vibrant interpretation of the litho units.

ASTER mapping of gypsum deposits of Thumrait region of southern Oman

AbstractThis study demonstrates the use of ASTER data for the mapping of gypsum deposits and associated geological formations that occurred in the Thumrait region of southern Oman. The measurement of spectra over samples of gypsum in the 1,300–2,500 nm wavelength using a PIMA spectrometer showed the presence of distinct absorptions at 1400–1600, 1750, 1940, 2,100, and 2,400 nm characteristics to OH stretching, H2O combinations, and SO bending overtones and stretching, respectively. Studying the unique spectral absorption characters of gypsum samples, we developed a false color composite (FCC) and an image by decorrelation stretch using the spectral bands 7, 3, and 2 of ASTER. The results FCC showed the regions of gypsum occurrences, and the decorrelated image discriminated the gypsum occurrences from other geological formations of the area. The study of surface mineralogy of the region using the VNIR‐SWIR bands by the spectral angle mapper method showed the presence of sulfate, carbonate, and clay minerals of the geological formations in the study area. We compared the results of ASTER with the results obtained using spectral bands 12, 8, and 4 of Sentinel‐2A processed by the same methods. The study showed that the spectral bands of ASTER can be used for mapping the gypsum and associated geological formations.

Collaborative design of cement-based composites incorporated with cooper slag in considerations of engineering properties and microwave-absorbing characters

“Waste materials” possess “new utilization” for that the application of copper slag (CS) instead of natural sand can impart excellent engineering properties and exceptional microwave absorption characters to cement-based composites. In this work, natural sand was replaced in volume by copper slag to design and prepare cement mortars with different copper slag contents (10%, 30%, 50%, 70% and 100%). The mechanical properties, workability, durability and microwave-absorbing characters of mortars were tested and evaluated by the response surface methodology (RSM) and grey entropy correlation analysis to perform a collaborative analysis; and finally, optimal copper slag content was recommended. The prediction model constructed by RSM shows that mechanical properties can be mostly optimized when the conditions were set to water/cement ratio of 0.6, copper slag content of 46% and copper slag fineness modulus of 2.77. Copper slag can obviously affect workability and durability of mortars, which can be mainly due to its irregular shape and low water absorption rate. Furthermore, the microwave-absorbing characters of mortars can vary with copper slag content. The mortar with 50% copper slag content achieves the minimum reflectivity and the maximum effective bandwidth. The roughness, water absorption and content of copper slag should be given priority when applied in microwave-absorbing building engineering. Copper slag makes a dominant contribution to mortars when its content reached 50%, which can be recommended as the optimal copper slag content incorporating into cement-based composites.

Prediction of a new 2D B2CO monolayer from density functional theory

In this study, a novel two-dimensional (2D) B2CO monolayer is theoretically predicted. According to our results 2D B2CO monolayer indicates significant structural, energetically and kinetically stabilities. These stabilities are confirmed by calculating its cohesive energy and phonon dispersion spectra. It is found that fully relaxed and optimized unit cell of the predicted monolayer possesses a buckled hexagonal crystal structure (space group: 156_P3m1) and is an indirect semiconductor with a band gap of 1.69 eV (2.81 eV) calculated by DFT-PBE (HSE06) level of theory. We further examined the effects of biaxial strains on the electronic properties of the monolayer and found its electronic properties can be effectively modulated by external strain effects. The optical aspects of the monolayer and found that proposed 2D material were also investigated. It has been shown that the monolayer shows very low absorption in visible region of electromagnetic spectra while it exhibits high absorption and reflection characters in UV region. These obtained results propose that the monolayer can be considered as a transparent material for the visible lights and a useful shielding material in ultra violet region.

Mapping and accuracy assessment of siltation of recharge dams using remote sensing technique

This study demonstrates the use of ASTER data to map the siltation of the Al-Khod Dam constructed at the lower reaches of Samail Catchment area, north Muscat, Sultanate of Oman. In this study, the decorrelated image of spectral bands 6, 3, and 1 clearly discriminated the distribution of siltation. The occurrence of siltation is confirmed by the detection of minerals using the VNIR-SWIR bands by the Spectral Angle Mapper (SAM) method. In addition, the siltation of the dam is studied for the years 1987 to 2018 using Landsat satellite images. Interpretation of images showed a gradual increase of the siltation. Mapping accuracy for the occurrence of siltation is assessed by a confusion matrix which produced an overall accuracy of 97.88% and Kappa coefficient of 0.98 in the Maximum Likelihood method. Results of image analyses are verified in the field and confirmed through laboratory analyses. The study of spectral absorption characters of field samples using a Portable Infrared Mineral Analyzer (PIMA) showed the presence of OH molecule bearing minerals (clays, serpentines, etc.) and carbonate minerals (calcite and dolomite) in the silt deposits. The occurrence of these minerals is confirmed further by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analyses.

Acoustic Oscillations of Aluminum Membranes Laser-Excited by a Thermoelastic Mechanism

A theoretical model of photoacoustic response signal formation from laser-irradiated metal membranes is proposed with allowance for the excitation of defect states. Theoretical results obtained for 197-μm-thick aluminum membranes in a frequency range from 20 Hz to 7 kHz are compared to experimental data for membranes excited by laser radiation at a 660-nm wavelength. The proposed theoretical model provides quite adequate coincidence with experiment for membrane oscillations under the assumption of a purely surface character of laser radiation absorption.

Theoretical studies on D-A-π-A and D-(A-π-A)2 dyes with thiophene-based acceptor for high performance p-type dye-sensitized solar cells

Eight p-type dyes with D-A-π-A or D-(A-π-A)2 structures were designed to investigate the effect of thiophene derivatives acting as acceptors on the properties of the sensitizers. Structure optimizations were performed by the density functional theory (DFT) method, and the electronic and absorption characters were obtained with the time-dependent DFT (TD-DFT). The results show that all the eight dyes have an excellent light harvesting efficiency (LHE) performance (0.99–1.00). And the driving forces of hole injection (ΔGinj) and dye regeneration (ΔGreg) of all dyes are more negative than −0.2 eV, resulting in an efficient hole injection and dye regeneration. Furthermore, the dyes with 2,3-dimethylpyrazine thiophene moiety (DMPZT-1) have the narrowest energy gaps. Importantly, the dyes with DMPZT-1 moiety display red shifts of the UV–vis absorption and enhanced absorptions of visible light (400–800 nm) in comparison to their prototype. In addition, the charge recombination (ΔGCR) performance of A1 and B1 is improved by DMPZT-1. Compared with the D-A-π-A dyes, the additional -A-π-A chain in D-(A-π-A)2 could decrease energy gap further and improve the visible light adsorption, LHE, and driving forces for hole injection and charge regeneration (ΔGinj and ΔGreg). Replacing thiophene with DMPZT-1 acceptor is an effective way to improve the performance of the dyes.

Sound absorption properties for multi-layer of composite materials using nonwoven fabrics with kapok

Kapok fiber with high degree of hollow and small fiber diameter has excellent sound absorption. To optimize the sound absorption characters at the low frequency, sound absorption coefficients and specific surface impedance of two-layer, three-layer, and four-layer materials as polyethylene film-reinforced kapok fiber nonwoven fabrics have been studied by using the impedance tube method in the frequency range of 100–2500 Hz. The layering sequence, the polyethylene films thickness, and the gradient thickness structure of nonwoven fabrics affected the sound absorption properties at the low frequency for multi-layer materials that have been analyzed. The results show that the multi-layer composite materials have better sound absorption than a single-layer nonwoven fabrics at the low frequency. The elastic vibration of polyethylene film contributes to sound absorption improvement at the low frequency. The sound absorption at the low frequency of multi-layer materials can be further improved by changing polyethylene film position or increasing polyethylene film thickness. In addition, the gradient thickness structure of nonwoven fabrics can effectively improve sound absorption at the low frequency, and the gradient change direction also exhibits remarkable effects on the sound absorption of multi-layer materials.

Magnetic resonance imaging of water absorption by highly porous ceramic materials

By using the magnetic resonance imaging method the nontrivial character of water absorption was demonstrated for the first time in highly porous ceramic materials. The effect of hygroscopic memory was found out which is that the preferable concentration of absorbed water in certain areas within the sample persists regardless the subsequent sample wetting history. Coating the oxide fibres with fluorine-containing hydrocarbons in supercritical CO2 in order to hydrophobize the material has been shown to affect substantially the water transport within the sample that can be referred to as an effective approach to protect the porous materials from humid environment. The results obtained demonstrate the advantages of the magnetic resonance imaging in studying the water absorption processes and visualization of water pathways in highly porous ceramic materials.

Absorption of laser radiation by metals at formation superficial nanostructure

The absorption mechanism of laser radiation is offered by a metal surface at the formation of superficial nanostructure. Principally, the heterogeneous character of such absorption depends on formation in the old, excited structure of zones of absorption. It is shown herein that the absorption process of laser radiation by metals can have a nonlinear character.

Magnetic Resonance Imaging of Water Absorption by Highly Porous Ceramic Materials

By using the magnetic resonance imaging method the nontrivial character of water absorption was demonstrated for the first time in highly porous ceramic materials. The effect of hygroscopic memory was found out which is that the preferable concentration of absorbed water in certain areas within the sample persists regardless the subsequent sample wetting history. Coating the oxide fibres with fluorine-containing hydrocarbons in supercritical CO 2 in order to hydrophobize the material has been shown to affect substantially the water transport within the sample that can be referred to as an effective approach to protect the porous materials from humid environment. The results obtained demonstrate the advantages of the magnetic resonance imaging in studying the water absorption processes and visualization of water pathways in highly porous ceramic materials.