Molecular Absorption Coefficient Research Articles

Analytical Method: Determination of famotidine drug using chemiluminescence method

This study involved the development of a novel, cost-effective, fast, and highly sensitive analytical technique for quantifying minimal amounts of the drug famotidine through chemiluminescence. The method is centred around the measurement of energy emitted as a result of the interaction between the drug and Luminol in an alkaline solution; this interaction generates an electronically excited intermediate state, releasing a portion of the system’s energy as photons. The method was sensitive for the analysis of famotidine. The linear calibration curve (LR) is obtained in the range 2-12 mg mL-1, with a high correlation coefficient (R2) of 0.9929. The molecular absorption coefficient (ε) was calculated at 2621×104 L mol-1 cm-1. The method displayed excellent sensitivity with a Sandell’s sensitivity of 1.287×10-5 mg cm-2, the detection limit (LOD) was found to be 0.0314 mg mL-1, and the limit of quantification (LOQ) was 0.0952 mg mL-1. This study found that recovery was obtained at 104 - 96.5 %, and the relative standard deviation (RSD%) was below 1.981%. The results showed that the proposed technique has efficient recovery for measuring famotidine in pharmaceutical preparations.

Rapid calculation of atmospheric molecular absorption characteristics in the terahertz band based on wideband K-distribution method

This paper focuses on rapidly calculating atmospheric molecular absorption properties in the 0.3–30 THz frequency range of terahertz waves. It conducts research related to spectral radiation models and fast computation model databases. Based on the latest version of the High-resolution transmission molecular absorption database-2020, in conjunction with the line-by-line (LBL) spectral radiative calculation method, the spectral absorption characteristics of nine atmospheric molecules (H2O, CO2, O3, NO, N2O, NO2, NH3, SO2, CH4) are analyzed. The relative contributions of the eight other gas molecules absorption abilities in the terahertz range are examined, with H2O molecule serving as the reference. Taking into account the non-gray absorption properties of atmospheric molecules and the need for fast computation, this study divides the frequency range of 0.3–30 THz into 24 calculation bands based on the spectral absorption distribution characteristics of atmospheric molecules. Utilizing LBL calculations with a resolution of 0.01 cm−1, a non-correlated wideband K-distribution model (WBK) is developed, which achieves nearly the same computational accuracy as LBL. Furthermore, the WBK radiation calculation model is validated under both uniform and non-uniform atmospheric conditions based on earth atmospheric environmental parameters. An exponential kernel fitting coefficient table for the rapid calculation of atmospheric molecular absorption coefficients is established based on the WBK radiation calculation model to improve computational efficiency further. This database enables fast calculation of 24 broadband absorption coefficients (corresponding to 7 Gaussian integration points) within 0–100 km altitude in earth atmosphere.

MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy.

The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of cerium's redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO2 and CeZrOx nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce3+/Ce4+ redox properties are investigated by H2-TPR experiments exploited by in situ FT-IR and Ce M5-edge AP-NEXAFS spectroscopy. In the latter case, Ce3+ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce3+ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce3+ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce3+ quantification are discussed.

Spectrum Allocation With Adaptive Sub-Band Bandwidth for Terahertz Communication Systems

We study spectrum allocation for terahertz (THz) band communication (THzCom) systems, while considering the frequency and distance-dependent nature of THz channels. Different from existing studies, we explore multi-band-based spectrum allocation with adaptive sub-band bandwidth (ASB) by allowing the spectrum of interest to be divided into sub-bands with unequal bandwidths. Also, we investigate the impact of sub-band assignment on multi-connectivity (MC) enabled THzCom systems, where users associate and communicate with multiple access points simultaneously. We formulate resource allocation problems, with the primary focus on spectrum allocation, to determine sub-band assignment, sub-band bandwidth, and optimal transmit power. Thereafter, we propose reasonable approximations and transformations, and develop iterative algorithms based on the successive convex approximation technique to analytically solve the formulated problems. Aided by numerical results, we show that by enabling and optimizing ASB, significantly higher throughput can be achieved as compared to adopting equal sub-band bandwidth, and this throughput gain is most profound when the power budget constraint is more stringent. We also show that our sub-band assignment strategy in MC-enabled THzCom systems outperforms the state-of-the-art sub-band assignment strategies and the performance gain is most profound when the spectrum with the lowest average molecular absorption coefficient is selected during spectrum allocation.

Impact of scene-specific enhancement spectra on matched filter greenhouse gas retrievals from imaging spectroscopy

Matched filter techniques have been widely used for retrieval of greenhouse gas enhancements from imaging spectroscopy datasets. While multiple algorithmic techniques and refinements have been proposed, the greenhouse gas target spectrum used for concentration enhancement estimation has remained largely unaltered since the introduction of quantitative matched filter retrievals. The magnitude of retrieved methane and carbon dioxide enhancements, and thereby integrated mass enhancements (IME) and estimated flux of point-source emitters, is heavily dependent on this target spectrum. Current standard use of molecular absorption coefficients to create unit enhancement target spectra does not account for absorption by background concentrations of greenhouse gases, solar and sensor geometry, or atmospheric water vapor absorption. We introduce geometric and atmospheric parameters into the generation of scene-specific unit enhancement spectra to provide target spectra that are compatible with all greenhouse gas retrieval matched filter techniques. Specifically, we use radiative transfer modeling to model four parameters that are expected to change between scenes: solar zenith angle, column water vapor, ground elevation, and sensor altitude. These parameter values are well defined, with low variation within a single scene. A benchmark dataset consisting of ten AVIRIS-NG airborne imaging spectrometer scenes was used to compare IME retrieved using a matched filter algorithm. For methane plumes, IME resulting from use of standard, generic enhancement spectra varied from −22 to +28.7% compared to scene-specific enhancement spectra. Due to differences in spectral shape between the generic and scene-specific enhancement spectra, differences in methane plume IME were linked to surface spectral characteristics in addition to geometric and atmospheric parameters. IME differences were much larger for carbon dioxide plumes, with generic enhancement spectra producing integrated mass enhancements −76.1 to −48.1% compared to scene-specific enhancement spectra. Fluxes calculated from these integrated enhancements would vary by the same percentages, assuming equivalent wind conditions. Methane and carbon dioxide IME were most sensitive to changes in solar zenith angle and ground elevation. We introduce an interpolation approach that can efficiently generate scene-specific unit enhancement spectra for given sets of parameters. Scene-specific target spectra can improve confidence in greenhouse gas retrievals and flux estimates across collections of scenes with diverse geometric and atmospheric conditions.

Molecular engineering of triphenylamine‐based metal‐free organic dyes for dye‐sensitized solar cells

AbstractIn this study, the photovoltaic properties of the organic dyes based on triphenylamine having a D‐π‐A structure including TC201, TC202, TC203, TC601, H‐P, F‐P, FF‐P, T‐F, and P1B were investigated theoretically. In this model, triphenylamine was used as an electron donor, cyanoacrylic acid, and benzoic acid as the electron acceptors, and anthracene phenyl, anthracene vinyl phenyl, anthracene ethynyl phenyl, ethynyl anthracene phenyl, styryl phenyl, styryl‐2‐fluorophenyl, styryl‐2,6‐difluorophenyl, styryl furan, and styryl as the π‐conjugated systems. The results show that a change in the π‐conjugated system and electron acceptor affect the properties of the dye‐sensitized solar cell (DSSC). Also, TC601 dye having the ethynyl anthracene phenyl π‐conjugated system shows the highest charge transfer distance (DCT) and the least overlap of the electron–hole distribution (S) in comparison with other dyes. Moreover, the presence of a triple bond in the vicinity of triphenylamine increases the resonance effect of the π‐electrons that facilitates the process of charge transfer in this dye. Spectroscopic analysis shows that H‐P and F‐P dyes have the higher molecular absorption coefficients and TC202, TC203, F‐P, and T‐F dyes show a red shift in comparison with other dyes. Moreover, the voltage–current curve of the studied dyes shows that the highest values of the open circuit voltage and short circuit current density are related to P1B and TC601 dyes, respectively. Finally, TC601 and P1B are proposed as the best candidates to be used in the DSSCs due to their maximum incident photon to current conversion efficiency.

Theoretical Investigation of the Circularly Polarized Luminescence of a Chiral Boron Dipyrromethene (BODIPY) Dye.

Over the last decade, molecules capable of emitting circularly polarized light have attracted growing attention for potential technological and biological applications. The efficiency of such devices depend on multiple parameters, in particular the magnitude and wavelength of the peak of emitted light, and also on the dissymmetry factor for chiral applications. In light of these considerations, molecular systems with tunable optical properties, preferably in the visible spectral region, are particularly appealing. This is the case of boron dipyrromethene (BODIPY) dyes, which exhibit large molecular absorption coefficients, have high fluorescence yields, are very stable, both thermally and photochemically, and can be easily functionalized. The latter property has been extensively exploited in the literature to produce chromophores with a wide range of optical properties. Nevertheless, only a few chiral BODIPYs have been synthetized and investigated so far. Using a recently reported axially chiral BODIPY derivative where an axially chiral BINOL unit has been attached to the chromophore unit, we present a comprehensive computational protocol to predict and interpret the one-photon absorption and emission spectra, together with their chiroptical counterparts. From the physico-chemical properties of this molecule, it will be possible to understand the origin of the circularly polarized luminescence better, thus helping to fine-tune the properties of interest. The sensitivity of such processes require accurate results, which can be achieved through a proper account of the vibrational structure in optical spectra. Methodologies to compute vibrationally-resolved electronic spectra can now be applied on relatively large chromophores, such as BODIPYs, but require more extensive computational protocols. For this reason, particular attention is paid in the description of the different steps of the protocol, and the potential pitfalls. Finally, we show how, by means of appropriate tools and approaches, data from intermediate steps of the simulation of the final spectra can be used to obtain further insights into the properties of the molecular system under investigation and the origin of the visible bands.

Interference and Coverage Analysis in Coexisting RF and Dense TeraHertz Wireless Networks

This letter develops a stochastic geometry framework to characterize the statistics of the downlink interference and coverage probability of a typical user in a coexisting terahertz (THz) and radio frequency (RF) network. We first characterize the exact Laplace Transform (LT) of the aggregate interference and coverage probability of a user in a THz-only network. Then, for a coexisting RF/THz network, we derive the coverage probability of a typical user considering biased received signal power association (BRSP). The framework can be customized to capture the performance of a typical user in various network configurations such as THz-only, opportunistic RF/THz, and hybrid RF/THz. In addition, asymptotic approximations are presented for scenarios where the intensity of THz BSs becomes large or molecular absorption coefficient in THz approaches to zero. Numerical results demonstrate the accuracy of the derived expressions and extract insights related to the significance of the BRSP association compared to the conventional reference signal received power (RSRP) association in the coexisting network.

2-Thiohydantoin Moiety as a Novel Acceptor/Anchoring Group of Photosensitizers for Dye-Sensitized Solar Cells.

Very recently, we have reported the synthesis and evaluation of biological properties of new merocyanine dyes composed of triphenylamine moiety, π-aromatic spacer, and rhodanine/2-thiohydantoin-based moiety. Interestingly, 2-thiohydantoin has never been studied before as an electron-accepting/anchoring group for the dye-sensitized solar cells (DSSCs). In the presented study, we examined the applicability of 2-thiohydantoin, an analog of rhodanine, in DSSC technology. The research included theoretical calculations, electrochemical measurements, optical characterization, and tests of the solar cells. As a result, we proved that 2-thiohydantoin might be considered as an acceptor/anchoring group since all the compounds examined in this study were active. The most efficient device showed power conversion efficiency of 2.59%, which is a promising value for molecules of such a simple structure. It was found that the cells’ performances were mainly attributed to the dye loading and the ICT molecular absorption coefficients, both affected by the differences in the chemical structure of the dyes. Moreover, the effect of the aromatic spacer size and the introduction of carboxymethyl co-anchoring group on photovoltaic properties was observed and discussed.

A nano-spectral study of charge transfer complexes to alizarin dye with electronic acceptors (TiO2)

The research involves the preparation of the nano-accepters, titanium dioxide (TiO2). It is diagnosed by different techniques such as IR, AFM, SEM, XRD and EDX, which illustrated the topographic features and features of the nano-crystalline prepared in terms of crystalline level, size of minute, pore shape, and elements analysis and et al. The study also includes a spectroscopic study of the transfer complexes of the charge using nano-TiO2 as the accepter’s electron with the alizarin dye extracted as donor electrons using absolute ethanol as a solvent. The Bensi-Hildebrand equation is applied to calculate the equilibrium constant and the molecular absorption coefficient of the resulting complex. The linear relationship resulting from the application of the equation showed that the forward ratio of the talent to the receiver is 1: 1. The effect of temperature change at the range (293-313 °K) was study on the equilibrium constants calculated from the Bensi-Hildebrand equation and used in the calculation of thermodynamic functions ΔH°, ΔS° and ΔG°. Negative values ​​ΔG° showed that the reaction was automatic and the positive values ​​ΔH° Indicate that the interaction of the composition of the complex is endothermic, while the positive values ​​ΔS° are indicative of the random reaction. The stability energy of the complex complexes is calculated and is equal to (2.24 eV) as well as the calculation of the ionization Potential and the dissociation energy of the excitation state of these complexities and other physical properties. The kinetics of the transition of the prepared charge complexes were studied in the absolute ethanol solvent. The results of the study showed that the kinetics of the formation and decomposition of the complexes are first order.

Sub-terahertz vibrational spectroscopy of ovarian cancer and normal control tissue for molecular diagnostic technology.

We introduce here recently developed highly resolved Sub-Terahertz resonance spectroscopy of biological molecules and cells combined with molecular dynamics (MD) computational analysis as a new approach for optical visualization and quantification of the presence of microRNAs, particularly the mir-200 family, as potential biomarkers in samples from tissue of epithelial ovarian cancers for disease early detection, analysis, prognosis and treatment.METHOD: A set of samples for this study was prepared from anonymized archival formalin-fixed, paraffin-embedded ovarian epithelial tissue containing regions of invasive neoplastic cells from cases of high-histologic grade serous papillary ovarian carcinoma. Control samples were normal mucosa from fallopian tubes of patients with no known malignancy. Spectroscopic characterization of tissue samples in this study was performed using a continuous wave, frequency domain automated spectrometer operating at room temperature in the spectral region of 310-500 GHz. The spectral results were compared with molecular dynamics simulations and absorption coefficient calculations utilized to predict the absorption spectra.RESULTS: The characteristic spectroscopic features in absorption spectra, particularly the presence of absorption peaks near 13cm-1 have been identified as cancer indicators. Tissue samples heterogeneity, reflected by diverse spectral signatures, provides additional, very specific information that may be used for identification of cancer subtypes, clinical behavior or sensitivity to specific therapies. Further work is warranted to determine if this signature can be detected in bio-fluids from ovarian cancer patients. If strongly correlated with cancer burden, it may then be investigated as a potential new biomarker for disease monitoring, and also perhaps as a biomarker for cancer screening.

Software system for numerical simulation of broadband laser gas analysis of the atmosphere

Introduction: Successful monitoring of environmental parameters requires the development of flexible software complexes with evolvable calculation functionality. Purpose: Developing a modular system for numerical simulation of atmospheric laser gas analysis. Results: Based on differential absorption method, a software system has been developed which provides the calculation of molecular absorption cross-sections, molecular absorption coefficients, atmospheric transmission spectra, and lidar signals. Absorption line contours are calculated using the Voigt profile. The prior information sources are HITRAN spectroscopic databases and statistical models of the distribution of temperature, pressure and gas components in the atmosphere. For modeling lidar signals, software blocks of calculating the molecular scattering coefficient and aerosol absorption/scattering coefficients were developed. For testing the applicability of various laser sources in the problems of environmental monitoring of the atmosphere, a concentration reconstruction error calculation block was developed for the atmospheric gas components, ignoring the interfering absorption of laser radiation by foreign gases. To verify the correct functioning of the software, a program block was developed for comparing the results of the modeling of atmospheric absorption and transmission spectra by using the standard SPECTRA information system. The discrepancy between the calculation of the atmospheric transmission spectra obtained using the developed system as compared to the SPECTRA results is less than 1%. Thus, a set of the presented program blocks allows you to carry out complex modeling of remote atmospheric gas analysis. Practical relevance: The software complex allows you to rapidly assess the possibilities of using a wide range of laser radiation sources for the problems of remote gas analysis.

UV-Spectrometric Determination of Total Phenols Using Diazotized Sulfanilic Acid

Phenolic compounds, including nitro- and chlorophenols, in neutral aqueous solutions react with diazotized sulfanilic acid. The molecular absorption coefficients of azo dyes obtained from various phenols in the range 360‒380 nm are quite close, which ensures the determination of the total concentration of phenols as C6H5OH. Under optimized conditions, the systematic errors in the analysis of model mixtures did not exceed 30 rel. %. They may be due to either the difference in molar absorption coefficients, or the delayed formation or instability of some azo dyes, and also due to the influence of reducing agents and arylamines. The procedure may become a good alternative to the determination of the phenolic index of sewage waters by the reaction with 4-aminoantipyrine.

Novel glycosylated mycosporine-like amino acid, 13-O-(β-galactosyl)-porphyra-334, from the edible cyanobacterium Nostoc sphaericum-protective activity on human keratinocytes from UV light

A UV-absorbing compound was purified and identified as a novel glycosylated mycosporine-like amino acid (MAA), 13-O-β-galactosyl-porphyra-334 (β-Gal-P334) from the edible cyanobacterium Nostoc sphaericum, known as “ge xian mi” in China and “cushuro” in Peru. Occurrence of the hexosylated derivative of shinorine (hexosyl-shinorine) was also supported by LC-MS/MS analysis. β-Gal-P334 accounted for about 86.5% of total MAA in N. sphaericum, followed by hexosyl-shinorine (13.2%) and porphyra-334 (0.2%). β-Gal-P334 had an absorption maximum at 334nm and molecular absorption coefficient was 46,700 at 334nm. Protection activity of β-Gal-P334 from UVB and UVA+8-methoxypsoralen induced cell damage on human keratinocytes (HaCaT) was assayed in comparison with other MAA (porphyra-334, shinorine, palythine and mycosporine-glycine). The UVB protection activity was highest in mycosporine-glycine, followed by palythine, β-Gal-P334, porphyra-334 and shinorine in order. β-Gal-P334 had highest protection activity from UVA+8-methoxypsoralen induced cell damage followed by porphyra-334, shinorine, mycosporine-glycine and palythine. We also found an antioxidant (radical-scavenging) activity of β-Gal-P334 by colorimetric and ESR methods. From these findings, β-Gal-P334 was suggested to play important roles in stress tolerant mechanisms such as UV and oxidative stress in N. sphaericum as a major MAA. We also consider that the newly identified MAA, β-Gal-P334 has a potential for use as an ingredient of cosmetics and toiletries.

Plasmon-Coupled Resonance Energy Transfer.

In this study, we overview resonance energy transfer between molecules in the presence of plasmonic structures and derive an explicit Förster-type expression for the rate of plasmon-coupled resonance energy transfer (PC-RET). The proposed theory is general for energy transfer in the presence of materials with any space-dependent, frequency-dependent, or complex dielectric functions. Furthermore, the theory allows us to develop the concept of a generalized spectral overlap (GSO) J̃ (the integral of the molecular absorption coefficient, normalized emission spectrum, and the plasmon coupling factor) for understanding the wavelength dependence of PC-RET and to estimate the rate of PC-RET WET. Indeed, WET = (8.785 × 10-25 mol) ϕDτD-1J̃, where ϕD is donor fluorescence quantum yield and τD is the emission lifetime. Simulations of the GSO for PC-RET show that the most important spectral region for PC-RET is not necessarily near the maximum overlap of donor emission and acceptor absorption. Instead a significant plasmonic contribution can involve a different spectral region from the extinction maximum of the plasmonic structure. This study opens a promising direction for exploring exciton transport in plasmonic nanostructures, with possible applications in spectroscopy, photonics, biosensing, and energy devices.

Impact of Diradical Spin State (Singlet vs Triplet) and Structure (Puckered vs Planar) on the Photodenitrogenation Stereoselectivity of 2,3-Diazabicyclo[2.2.1]heptanes.

Versatile transformations of azo compounds are utilized not only in synthetic organic chemistry but also in materials science. In this study, a hitherto unknown stereoselectivity was observed by low-temperature in situ NMR spectroscopy for the photochemical denitrogenation of a cyclic azoalkane (2,3-diazabicyclo[2.2.1]heptane) derivative. Direct (singlet) photodenitrogenation at 188 K afforded two products, the configurationally retained ring-closed compound (ret-CP) and the inverted compound (inv-CP), in a ratio of 82/18 (±3) (ret-CP/inv-CP), with an overall yield of >95%. Triplet-sensitized denitrogenation at 199 K using benzophenone ((3)BP*) or xanthone ((3)Xan*) selectively produced inv-CP, with a ret-CP/inv-CP ratio of 7/93 (±3). Thermal isomerization of inv-CP into ret-CP was observed by low-temperature NMR spectroscopy. Transient absorption spectroscopy revealed that two distinct singlet diradicals are involved in the formation of CP during direct photodenitrogenation, that is, puckered puc-(1)DR and planar pl-(1)DR diradicals. The former produces ret-CP, whereas the latter affords inv-CP. Kinetic analysis using the integrated profiles method was used to determine the molecular absorption coefficient of pl-(1)DR (ε560 = 4900 ± 250 M(-1) cm(-1)) for the first time. The involvement of the puckered singlet diradical resolves the mechanistic puzzle of stereoselective denitrogenation of diazabicycloheptane-type azoalkanes.

A chemical profiling strategy for semi-quantitative analysis of flavonoids in Ginkgo extracts

Flavonoids analysis in herbal products is challenged by their vast chemical diversity. This work aimed to develop a chemical profiling strategy for the semi-quantification of flavonoids using extracts of Ginkgo biloba L. (EGB) as an example. The strategy was based on the principle that flavonoids in EGB have an almost equivalent molecular absorption coefficient at a fixed wavelength. As a result, the molecular-contents of flavonoids were able to be semi-quantitatively determined by the molecular-concentration calibration curves of common standards and recalculated as the mass-contents with the characterized molecular weight (MW). Twenty batches of EGB were subjected to HPLC-UV/DAD/MS fingerprinting analysis to test the feasibility and reliability of this strategy. The flavonoid peaks were distinguished from the other peaks with principle component analysis and Pearson correlation analysis of the normalized UV spectrometric dataset. Each flavonoid peak was subsequently tentatively identified by the MS data to ascertain their MW. It was highlighted that the flavonoids absorption at Band-II (240–280nm) was more suitable for the semi-quantification purpose because of the less variation compared to that at Band-I (300–380nm). The semi-quantification was therefore conducted at 254nm. Beyond the qualitative comparison results acquired by common chemical profiling techniques, the semi-quantitative approach presented the detailed compositional information of flavonoids in EGB and demonstrated how the adulteration of one batch was achieved. The developed strategy was believed to be useful for the advanced analysis of herbal extracts with a high flavonoid content without laborious identification and isolation of individual components.

Analysis of Disperse Dyes Using Liquid Chromatography/Linear Ion Trap Mass Spectrometry (LC/LIT-MSn) and Database Construction.

Liquid chromatography/linear ion trap mass spectrometry (LC/LIT-MS(n)) was used to construct a database of disperse dyes. Fifty-three standard dyes were subjected to LC/LIT-MS(n) and characterized based on their mass spectra (MS, MS(2), and MS(3)), values of λmax (maximum absorption wavelength in the UV-visible spectrum), and retention times. The results demonstrate that it is possible to reliably identify coexisting dyes that cannot be separated by LC or detected by diode array detection due to their low molecular absorption coefficients. In addition, the by-products included in the standard dyes were found to provide important information for the identification and discrimination of dyestuffs synthesized using different processes. The confirmation of the effectiveness of LC/LIT-MS(n) analysis in detecting small amounts of disperse dyes in this study shows its potential for use in the discrimination of dyed fibers obtained at crime scenes.

Simple and Versatile Molecular Donors for Organic Photovoltaics Prepared by Metal-Free Synthesis

Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers (1-5) were synthesized from mono- or dialdehydes by a simple metal-free procedure. Cyclic voltammetry and UV/Vis absorption spectroscopy show that the extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. Compared to solutions, the optical spectra of spin-cast thin films of compounds 1-3 show a broadening and red shift of the absorption bands, consistent with the formation of J-aggregates. In contrast the blue shift observed for the EDOT-containing compounds 4 and 5 suggests the presence of H-aggregates. Solution-cast and vacuum-deposited films of donors 1-5 were evaluated in solar cells with fullerene C60 as acceptor. A power-conversion efficiency among the highest reported for bilayer devices of basic configuration was obtained with compound 2. On the other hand, the results obtained with 4 and 5 suggest that the presence of EDOT in the structure can have deleterious effects on the organization and performances of the donor material.

Small Molecular Donors for Organic Solar Cells Obtained by Simple and Clean Synthesis

A small donor-acceptor molecule is synthesized in a two-step procedure involving reaction of N,N-diphenylhydrazine on 2,5-diformylthiophene and Knoevenagel condensation. Results of UV/Vis absorption spectroscopy and cyclic voltammetry show that replacement of the phenyl ring bridge of a reference compound 2 by an azo group produces a slight red-shift of λmax, an enhancement of the molecular absorption coefficient, and a decrease of the energy level of the frontier orbitals. A preliminary evaluation of the potentialities of compound 1 as donor material in a basic bilayer planar heterojunction cell of 28 mm(2) active area using C60 as acceptor gave a short-circuit current density of 6.32 mA cm(-2) and a power conversion efficiency of 2.07 %.