Ultraviolet-visible Absorption Spectra Research Articles

A Novel Hybrid Strategy for Detecting COD in Surface Water

The prediction of chemical oxygen demand (COD) by ultraviolet–visible absorption spectrum is a common method. Many researchers use the absorbance at the characteristic wavelength to establish COD prediction models. However, selecting the characteristic wavelength is a problem. In this paper, the extreme values of absorption spectrum change rate, was proposed as a new characteristic parameter to determine the characteristic wavelengths. On this basis, a novel hybrid strategy for detecting COD in surface water was proposed. We first proposed to combine the first derivative method with the permutation entropy method (FDPE) to determine the characteristic wavelengths. Then we used partial least square (PLS) to establish a COD prediction model. Experimental results demonstrated the linear correlation coefficient (R2) of the FDPE_PLS was above 0.99 without turbidity interference. Secondly, a dual-wavelength method (DWM) was proposed to determine the turbidity values. The DWM used slopes of absorbance values at 400 nm and 600 nm to predict the turbidity values. Compared with the single-wavelength method, the DWM improves the measurement accuracy of turbidity. Finally, a new turbidity compensation method was proposed to compensate for the interference in the first derivative spectrum. After compensation, FDPE_PLS can predict COD concentrations accurately, whose R2 was 0.99.

Refined standards for simulating UV–vis absorption spectra of acceptors in organic solar cells by TD-DFT

Photoexcitation property of acceptor plays a vital role to understand fundamental physical process of acceptor excitation in organic solar cells (OSCs), which should be described at a reliable level and characterized by ultraviolet-visible (UV–vis) absorption spectra. Generally, adiabatic linear-response time-dependent density functional theory (LR-TD-DFT) as a suitable framework, which requires to select exchange correlation functionals (XCFs) and basis sets to concentrate the approximation of models, is widely recognized. However, selecting reliable theoretical methods tends to consume computational cost and time, and optimal selections have not yet reached general standards. Herein, a systematic investigation including XCF, basis set, calculation density, solvation effect, and full width at half maximum (FWHM) was undertaken to quantify the photoexcitation properties of typical fullerene acceptors (FAs) and non-fullerene acceptors (NFAs). The results reveal that maximum absorption wavelength (λmax) of NFAs is strongly correlated with the fraction of “exact” Hartree-Fock exchange (EEX), thus establishing selection standards. Moreover, calculation density is the primary factor to ensure the integrity of spectra. This work provides reasonable schemes for characterization conditions, which further lays foundation for the reliability of theoretical calculations that will help to advance the theoretical characterization of optical properties of organic materials.

Photoluminescence Quenching of a Novel Electroconductive Poly(propylene thiophenoimine)-co-Poly(ethylenedioxy thiophene) Star Copolymer.

A generation 1 poly(propylene thiophenoimine)-co-poly(ethylenedioxy thiophene) (G1PPT-co-PEDOT) star copolymer, which exhibits a strong optical absorption over a broad range in the ultraviolet–visible (UV-Vis) region and with good electro/conductive properties, was chemically prepared for the first time. Synthesis of the star copolymer, G1PPT-co-PEDOT was confirmed by spectroscopic studies. Indeed, the disappearance of the very high intensity bands, C–H bending at α-position (687 cm−1), and C=N stretching (1620 cm−1) in the Fourier transform infrared spectroscopy (FTIR) of G1PPT-co-PEDOT, which were initially present in the spectrum of the thiolated starting material, G1PPT, confirmed copolymerization. Furthermore, a large bathochromic shift in the onset wavelength of the UV-Vis absorbance spectra from 367 nm in G1PPT to 674 nm in G1PPT-co-PEDOT further attests of successful copolymerization. The electrochemical analysis of G1PPT-co-PEDOT achieved a highest occupied molecular orbital (HOMO) energy level value of 5.3 eV, which is reminiscent of the value for an ideal electron-donor material. Photoluminescence quenching of up to 82% was observed in solution blends of the G1PPT-co-PEDOT star copolymer and N,N′-diisopropyl naphthalene diimide (NDI). This demonstrates the occurrence of photoinduced intermolecular charge transfer (PICT) from the electron-donating G1PPT-co-PEDOT to the electron accepting NDI, a good property, beneficial for optoelectronic and photovoltaic applications.

Optical, conductivity and dielectric properties of plasticized solid polymer electrolytes based on blends of sodium carboxymethyl cellulose and polyethylene oxide

Solid polymer electrolytes (SPEs) based on plasticized sodium carboxymethyl cellulose/polyethylene oxide (CMC/PEO) were successfully prepared using solution casting method. The prepared SPEs were investigated using different spectroscopic techniques. Ultraviolet–Visible absorption spectra (UV–Vis) revealed that changing PEO content in the polymer matrix causes the optical band gap energy to change and decrease. These changes indicate that there is a transfer of charge carriers within the polymer matrix. The variations occurring in the major structural units within the prepared CMC/PEO SPEs are retraced using Fourier transform infrared spectroscopy (FTIR). FTIR results revealed that the polymeric materials suffer changes in their chemical structures and that complexation occurred between the individual polymers due to blending. Correlation between UV–Vis optical band gap and FTIR outcomes is established. Electrical impedance spectroscopy (EIS) was used to study the conduction mechanism for the prepared SPEs. Impedance results showed that the CMC/PEO sample with blending ratio of 80/20 wt% (sample named B2) possesses the highest ionic conductivity of 1.18E−06 S/cm and the lowest activation energy of approximately 0.67 eV at ambient temperature.

A Conjugated Copolymer Bearing Imidazolium-based Ionic Liquid: Electrochemical Synthesis and Electrochromic Properties

An imidazolium-based ionic liquid (IL) modified triphenylamine derivative, namely 1-(4-((4-(diphenylamino)benzoyl) oxy)butyl)-3-methyl imidazole tetrafluoroborate (TPAC6IL-BF4), was designed and synthesized, and further applied with 3,4-ethylene dioxythiophene (EDOT) to prepare conjugated copolymer P(EDOT:TPAC6IL-BF4) via electrochemical polymerization. The cyclic voltammetry curves show that the copolymer P(EDOT:TPAC6IL-BF4) possesses two pairs of redox peaks, which should be ascribed to the redox behaviors of EDOT and triphenylamine. The ultraviolet-visible (UV-Vis) absorption spectrum of P(EDOT:TPAC6IL-BF4) exhibits one maximum absorption peak at 580 nm and a small shoulder characteristic peak at 385 nm under neutral state which are assigned to π-π* conjugated structure of EDOT and triphenylamine. After being applied at the positive voltage, the copolymer color changes from dark blue to light blue, which is close to the color of poly(3,4-ethylenedioxythiophene) (PEDOT). Surprisingly, the copolymer P(EDOT:TPAC6IL-BF4) shows shorter switching time of 0.37 s, 0.30 s at 580 nm and 0.38 s, 0.45 s at 1100 nm compared with PEDOT. It is more intriguing that the copolymer P(EDOT:TPAC6IL-BF4) exhibits electrochromism even in free supporting electrolyte. The results confirm that the existence of imidazolium-based ionic liquid has an improvement on the ion diffusion properties and the switching time of conjugated polymer, which may provide a potential direction for the preparation of high-performance electrochromic materials.

Optical bandgap and luminescence in Er3+ doped oxyfluoro-germanate glass-ceramics

We determine the optical bandgap energy and the Urbach energy in trivalent erbium (Er3+) doped oxyfluoro-germanate glass-ceramics from the ultraviolet-visible absorption spectra. The glass-ceramics are produced by subjecting the as-prepared glass to heat treatment at various temperatures above Tg (494 °C) for 1 hour. The calorimetric measurements show that the nanocrystals formed during heating are stable and the composition of the remaining glass matrix remains unchanged. It is found that both the density and the bandgap energy of the glass ceramics vary non-linearly with increasing heat-treatment temperature. This non-linear trend accords with that for the upconversion luminescence of these materials. Furthermore, the indirectly allowed transition in bandgap is observed in all the studied glass ceramics. An exponential dependence of absorption coefficient on the photon energy is observed, indicating that the Urbach rule is obeyed. The results derived from this study will be potentially useful for designing the rare earth ion doped glass-ceramics with a strong luminescence effect.

Unraveling the Impact of Halide Mixing on Crystallization and Phase Evolution in CsPbX3 Perovskite Solar Cells

Summary All-inorganic perovskite solar cells (PSCs) have attracted wide attention for their excellent thermal stability. However, the detailed crystallization process and complicated phase-transition mechanism of the CsPbX3 film with different halide compositions (I, Br, Cl) remain mysterious. In this study, systematic investigations are performed via state-of-art in situ grazing-incidence wide-angle X-ray scattering to understand the role of the halide elements in all-inorganic perovskite crystallization kinetics, phase-transition, and stabilization mechanism as well as how film morphology and grain size are affected. Based on these results, we were able to fabricate high-performance ternary halide (I, Br, Cl) all-inorganic PSCs through a precise compositional engineering. Our results provide guidance for an in-depth understanding of all-inorganic perovskite materials and pave the way to obtain high-performance all-inorganic PSCs.

Facile synthesis and characterisation of green luminescent carbon nanodots prepared from tender coconut water using the acid‐assisted ultrasonic route

In the present investigation, the authors have adopted a simple and economical method for the synthesis of bright green photoluminescent carbon nanodots (CNDs) from tender coconut water via acid-assisted ultrasonic route. Tender coconut water is used as a less expensive and eco-friendly carbon precursor to produce well-dispersed CNDs possessing a hybrid structural behaviour of both nanocrystalline and amorphous carbon phases. The monodispersed CNDs with spherical morphology and particle size (4 ± 1 nm) were confirmed with the aid of high-resolution transmission electron microscopy. The functional groups attached to CNDs are held responsible for the fluorescence nature and mono-dispersion that were assessed using Fourier transform infrared spectroscopy. The green fluorescence nature of CNDs was evaluated at a maximum emission at 510 nm with an excitation wavelength of 450 nm, using ultraviolet–visible absorption spectrum and photoluminescence spectra. The CNDs with a carbon core and chemical groups over their surface exhibited a fluorescence quantum yield of 60.18%. The stability, low-cost precursor, rapid reaction and uniform dispersion without chemical functionalisation makes these CNDs synthesised from tender coconut water more advantageous than other sources. This research mainly emphasis on synthesis and characterisation of CNDs with a detailed mechanism for CND formation.

Comparison between the gold nanoparticles prepared by chemically and laser ablation method

Noble metal gold nanoparticles were prepared by tow method. The first method gold nanoparticles (AuNPS) synthesised by the reduction of chloroauric acid ( HAuCl4) with a solution for sodium borohydride. The second method the gold mineral plates were ablation by pulsed laser when it was immersed in filtered H2O. The synthesized nanoparticles are characterized by using UV–Visible absorption spectroscopy, X-ray diffraction and transmission electron microscopy (TEM).The Ultraviolet-Visible absorption spectra in the visible regions of the gold nanoparticles appear intense absorptions a result of surface plasmon resonance (spr) vibrations in noble mineral nanoparticles. From X-ray diffraction and TEM tests the particle size for the laser ablation method calculated was found to be lie between (15- 20 nm) and for chemical method approximately lie between (13-16 nm).

Change of Phase Transition Temperature in Band Engineered Ferroelectric Lanthanum-Modified Bismuth Titanates.

The ferroelectric material chosen for a solar cell has to absorb as much of the solar spectrum as possible, therefore a low band gap is desirable, but it is rarely known for phase transition temperature on the bandgap engineered ferroelectric materials. The phase transition temperature of a ferroelectric material can be determined by monitoring its dielectric constant with increasing temperature, as the dielectric constant changes abruptly at the phase transition temperature. Here, we inform the measurement of the phase transition temperature of the ferroelectric complex oxide Bi3.25La0.75Ti₃O12 as well as cobalt and iron doped Bi3.25La0.75Ti₃O12 bulk ceramics for photovoltaic cells based on dielectric monitoring with changing temperature. We synthesized lanthanum-modified bismuth-titanate-based ceramics with various doping concentrations transition metal to Ti. X-ray diffraction analysis revealed that all the compounds crystallized in an orthorhombic structure. Their morphologies and size distributions were observed using scanning electron microscopy. From the ultraviolet-visible spectroscopy absorption spectra of the synthesized powder, bandgaps were checked. An inductance-capacitance-resistance meter was used to obtain the relationship between dielectric responses and the temperature of the targets in a tube furnace. We observed that the dielectric constant increases gradually with increasing temperature, until the transition temperature and subsequently decreases, and we were able to determine the phase transition temperatures of the tested materials. Furthermore, the results revealed that all the doped bismuth titanates keep their phase transition temperatures, which were sufficiently high, to maintain their ferroelectric properties above room temperature.

An ordered copper nanowell-array film with near-perfect broadband absorption from ultraviolet to near-infrared light

A copper film with the well arrays structure is prepared by magnetron sputtering in an anodic aluminum oxide (AAO) template. The ultraviolet–visible absorption spectra indicate that the light absorbance of the film is as high as 99.6% in the wavelength range of 200–2500 nm. The copper nanowell-array film exhibits a strong absorptance at the spectral range of 200–2500 nm owing to light trapped in the nanowell-array structures, the interband transition of copper, and the surface plasmon resonances of copper nanowell-arrays. This near-perfect broadband light absorption from UV–vis–NIR might improve greatly the utilization of light.

A novel luminol chemiluminescence system induced by black phosphorus quantum dots for cobalt (II) detection

Black phosphorus quantum dots (BP QDs) were prepared through a solvothermal exfoliation method in alkaline N-methyl-2-pyrrolidinone. The BP QDs induce distinct chemiluminescence (CL) of alkaline luminol directly. A possible reaction mechanism is proposed by the study of CL spectrum, ultraviolet–visible absorption spectra, electron paramagnetic resonance spectra as well as radical scavenging experiments. The presence of BP QDs significantly increases generation of active oxygen species, which oxidize luminol and lead to intense CL emission at 425 nm. The reaction of luminol with BP QDs are specifically catalyzed by cobalt (II) ion, this presents a sensitive CL method for cobalt (II) ion. A linear response range extends from 2.5 to 2000.0 pmol/L cobalt (II) ion and a detection limit of 0.7 pmol/L (3sb) is acquired. The method displays a good precision approved by a relative standard deviation of 1.9% at 100.0 pmol/L cobalt (II) ion solution (n = 11). A preliminary application of the method was conducted by successful determination of cobalt amount in silica gel and rain water samples.

Spectroscopic, quantum chemical and molecular docking studies on 2,4-dimethoxy-1,3,5-triazine: a potent inhibitor of protein kinase CK2 for the development of breast cancer drug

ABSTRACT The theoretical calculations of the 2,4-dimethoxy-1,3,5-triazine (DMT) molecule were performed with the help of density functional theory (DFT) calculations using 6-311++G(d,p) basis set. The conformational analysis of the DMT molecule was carried out and the most stable molecular structure was predicted. The structural parameters and vibrational wavenumbers of the title molecule were also calculated. Fourier transform-infrared (FT-IR) and Fourier transform-Raman (FT-Raman) spectra of the molecule were observed and simulated. The ultraviolet-visible (UV-Vis) absorption spectra of the molecule were simulated in the gas phase as well as in the liquid phase. The frontier molecular orbitals of the molecule were simulated, which confirms the bio-active nature of the molecule. The molecular electrostatic potential surface was visualized to confirm the reactive regions of the molecule. The natural bond orbital analysis reveals the bio-activity of the molecule. The thermodynamic functions of the molecule were computed. The molecular docking analysis confirms that the title molecule could act as a potent inhibitor of protein kinase, casein kinase (CK2), which is a key protein for breast cancer. The obtained results show that the title molecule is a potential bio-active agent which may be valuable for the designing of drugs for the treatment of breast cancer.

Calcium oxide modifier stimulated intense luminescence from Dy3+ doped in sulfophosphate glasses

The role of varied CaO concentration (as modifier) on the visible light emission traits of dysprosium ions (Dy3+) doped in sulfophosphate glasses was evaluated. These glasses were prepared and spectroscopic features of synthesized glasses were characterized. The amorphous nature of these glasses was studied by X-ray diffraction method. The Ultraviolet-Visible absorption spectra of glasses revealed the existence of thirteen characteristic peaks. Two emission peaks centered at 483 (blue) and 573 nm (yellow) assigned to the 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+ ion, respectively. The Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6) and radiative properties of glasses were calculated which applied to predict radiative properties. Values of Ω2 for glasses were significantly augmented with the increase in CaO contents which denotes to more symmetry of the ligand surroundings in the vicinity of Dy3+ ion. The measured yellow to blue (Y:B) emission intensity ratio suggested the possibility of achieving bright white light using the proposed glasses. Present glasses indicated higher effectiveness for white LED applications than the reported ones.

Synthesis of magnesium nitride films with BN as protective layers by reactive radio-frequency magnetron sputtering

Magnesium nitride films were synthesized on silicon substrates by reactive radio-frequency magnetron sputtering (13.56 MHz) with a high-purity magnesium target and nitrogen as the working gas. The effects of the sputtering power and the growth temperature on the qualities of Mg3N2 films were investigated. As for Mg3N2 films synthesized at 773 K for 2 h with the sputtering power of 200 W, the intense Raman peak at 381 cm-1 with the Full width at half maximum of 8.3 cm-1 and the sharp X-Ray Diffraction peak of Mg3N2 (222) at 2θ=31.1° were observed, and the ultraviolet-visible absorption spectra showed that the prepared Mg3N2 films have the intrinsic absorption edges of about 480 nm and the optical bandgap of 2.62 eV. Moreover, it was demonstrated that Boron nitride films can be used as not only protective layers to effectively prevent Mg3N2 films from being hydrolyzed, but also good optical windows.

Room temperature ferromagnetism in ZnS and ZnO nanoparticles

This article deals with the structural and optical properties of zinc oxide and zinc sulfide nanoparticles synthesized by chemical precipitation method. X-ray diffraction study confirmed the wurtzite structure of zinc oxide and the cubic structure of zinc sulfide. The average crystallite size, the lattice constant, and unit cell volume were calculated from the x-ray diffraction study. The ultraviolet-visible absorption spectra and the Tauc’s plot were confirmed the energy gap of zinc sulfide and zinc oxide samples to be 5.1 eV and 3.73 eV, respectively. Fourier Transformation Infrared spectra confirmed the formation of zinc oxide and zinc sulfide through the appearance of peaks between 618 cm−1- 439 cm−1. The photoluminescence spectra confirmed the violet emission from ZnO and UV from ZnS. The transmission electron microscope study also confirmed the existence of particles in nanometer size. Composition analysis confirmed the existence of zinc, sulfur, and oxygen. The vibrating sample magnetometer results depict that the zinc sulfide and zinc oxides are ferromagnetic at room temperature. Electron paramagnetic resonance spectra also confirmed the ferromagnetic nature of zinc sulfide and zinc oxide samples.

Separation of cobalt and lithium from spent lithium-ion battery leach liquors by ionic liquid extraction using Cyphos IL-101

The eventual fading and scrapping of lithium (Li)-ion batteries will result in the formation of a huge urban mine of spent batteries. Hydrometallurgy and further extraction/separation are effective ways in which to recover the valuable metal ions from such batteries. Herein, extraction and recovery of spent lithium cobalt oxide (LiCoO2) battery leach liquors using Cyphos IL-101 is proposed. Based on the optimization of extraction conditions, continuous circulating extraction, and thermodynamic analysis, Cyphos IL-101 effectively extracted cobalt (Co) ions with excellent stability and high extraction capacity (35.25 g/L). The separation factor of Co and Li (βCo/Li) was 102.11 in 0.5 M HCl at 60 °C under the optimal operation condition. Moreover, an increase in temperature increased Co extraction in the spent Li-ion battery leach liquors. The extractants before and after use were characterized using ultraviolet-visible (UV–Vis) absorption spectra, Fourier transform infrared (FTIR) spectra, and nuclear magnetic resonance (NMR) spectra. The extraction mechanism of cobalt ions by Cyphos IL-101 was suggested as that cobalt transferred to the organic phase from the aqueous phase in the form of [CoCl4]2−. 90.5% of Co and 86.2% of Li were recovered by precipitation after extraction separation in the forms of cobalt oxalate and lithium carbonate with the purity 87.4% and 74.2%. This suggested method might provide a promising strategy for recycling spent lithium cobalt oxide batteries.

Deducing the Conformational Properties of a Tyrosine Kinase Inhibitor in Solution by Optical Spectroscopy and Computational Chemistry.

Dacomitinib (PF-00299804) was recently approved by the Food and Drug Administration (FDA) as a tyrosine kinase inhibitor (TKI). Unfortunately, side effects and disease resistance eventually result from its use. Off-target effects in some kinase inhibitors have arisen from drug conformational plasticity; however, the conformational states of Dacomitinib in solution are presently unknown. To fill this gap, we have used computational chemistry to explore optimized molecular geometry, properties, and ultraviolet-visible (UV-Vis) absorption spectra of Dacomitinib in dimethyl sulfoxide (DMSO) solution. Potential energy scans led to the discovery of two planar and two twisted conformers of Dacomitinib. The simulated UV-Vis spectral signatures of the planar conformers reproduced the two experimental spectral bands at 275 and 343 nm in solution. It was further discovered that Dacomitinib forms conformers through its three flexible linkers of two C–NH–C bridges, which control the orientations of the 3-chloro-4-fluoroaniline ring (Ring C) and the quinazoline ring (Rings A and B) and the 4-piperidin-1-yl-buten-2-nal side chain, and one C–O–C local bridge which controls the methoxy group locally. When in isolation, these flexible linkers form close hexagon and pentagon loops through strong intramolecular hydrogen bonding so that the “planar” conformers Daco-P1 and Daco-P2 are more stable in isolation. Such flexibility of the ligand and its ability to dock and bind with protein also depend on their interaction with the environment, in addition to their energy and spectra in isolation. However, an accurate quantum mechanical study on drug/ligand conformers in isolation provides necessary reference information for the ability to form a complex with proteins.

Optical properties of two-dimensional semi-conductive MXene Sc2COx produced by sputtering

Semi-conductive MXene Sc2COx is synthesized by using magnetron sputtering. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) is performed to determine the composition of sample. The bandgap of Sc2COx sample is determined by ultraviolet-visible (UV–VIS) range absorption and photoluminescence (PL) spectrum. The Tauc plot indicates that Sc2COx is a direct bandgap material. The high sensitivity of scandium to oxygen makes the sample contain both scandium carbide and scandium oxide. Thermal annealing introduces more oxidation into the sample. Structure of MXene will be broken when the annealing temperature is higher than 600 °C.

Characterization of landfill leachate by spectral-based surrogate measurements during a combination of different biological processes and activated carbon adsorption.

Surrogate measurements based on excitation-emission matrix fluorescence spectra (EEMs) and ultraviolet-visible absorption spectra (UV-vis) were used to monitor the evolution of dissolved organic matter (DOM) in landfill leachate during a combination of biological and physical-chemical treatment consisting of partial nitritation-anammox (PN-Anammox) or nitrification-denitrification (N-DN) combined with granular active carbon adsorption (GAC). PN-Anammox resulted in higher nitrogen removal (81%), whereas N-DN required addition of an external carbon source to increase nitrogen removal from 24% to 56%. Four DOM components (C1 to C4) were identified by excitation-emission matrix-parallel factor analysis (EEM-PARAFAC). N-DN showed a greater ability to remove humic-like components (C1 and C3), while the protein-like component (C4) was better removed by PN-Anammox. Both biological treatment processes showed limited removal of the medium molecular humic-like component (C2). In addition, the synergistic effect of biological treatments and adsorption was studied. The combination of PN-Anammox and GAC adsorption could remove C4 completely and also showed a good removal efficiency for C1 and C2. The Thomas model of adsorption revealed that GAC had the maximum adsorption capacity for PN-Anammox treated leachate. This study demonstrated better removal of nitrogen and fluorescence DOM by a combination of PN-Anammox and GAC adsorption, and provides practical and technical support for improved landfill leachate treatment.