NH Band Research Articles

Proton Transfer Processes in 2-Butenenitrile Dimer Cation Studied by Mass-Selective Infrared Spectroscopy.

2-Butenenitrile (2-Bu) is a recently discovered crucial interstellar molecule. Herein, an abnormal NH band was observed in the infrared spectrum of the 2-Bu dimer cation, suggestive of a proton transfer reaction within the cluster. Through a comprehensive theoretical analysis of the IR spectrum of (2-Bu)2+, we discovered not only the formation of a new C-N bond through the attachment of one 2-Bu to another but also the occurrence of a proton transfer reaction in the cluster. This proton was identified as originating from the methyl group of the attaching 2-Bu in the cluster based on the analysis of IR spectra of (2-Bu)+ and [2-Bu-acrylonitrile (AN)]+. Furthermore, the detailed reaction process of this ion-molecule reaction is examined with theoretical calculation. This finding contributes significantly to our deeper understanding of ion-molecule reactions in the gas phase and the formation of nitrogen-containing prebiotic molecules in the interstellar medium.

Synthesis, optical characterization and electrical behavior of chitosan/MgO/Cr2O3 nanocomposite for electrical applications

Magnesium oxide nanoparticles (MgO NPs) are straightforward, cheap, biocompatible, and biodegradable, making them one of the most popular inexpensive and non-toxic nanoparticles. In addition, Nanosized chromic oxide (Cr2O3) is a significant transition metal oxide due to its numerous exceptional attributes, it finds application in several domains. It has good electrical conductivity, excellent thermal and chemical stability. It is utilized in several industries for its ability to resist oxidation at high temperatures, as well as its application in refractory materials and catalysts. In this study, we utilized a laser ablation approach to synthesize a ternary nanocomposite composed of MgO and Cr2O3 nanoparticles as it is considered a clean method for the preparation of nanoparticles. Subsequently, these nanoparticles were integrated into Chitosan (CS) solution to create polymer nanocomposite via casting route. XRD confirmed the formation of Cr2O3 nanocrystals with size of 61 nm dispersed in chitosan/MgO matrix. FTIR verified the interactions between chitosan, MgO, and Cr2O3 nanoparticles. The broadening and shifting of the OH and NH bands with increasing Cr2O3 content confirms the interaction and complexation between Cr2O3 and Chitosan/MgO. UV–Vis analysis revealed that incorporating 7 wt% Cr2O3 reduced optical band gap from 5.59 eV for chitosan to 3.91 eV. The band gap values decreased with increasing Cr2O3 content due to polaronic defects. TGA showed improved thermal stability, with the 7 wt% Cr2O3 nanocomposite exhibiting a residual mass of 47 % at 700 °C compared to 28 % for chitosan. Dielectric studies demonstrated high dielectric constant and conductivity (10−5 S/cm at 10 Hz) values for the 7 wt% Cr2O3 nanocomposite, attributed to interfacial polarization effects and nanocapacitor formation by the conductive nanofillers. The ternary chitosan/MgO/Cr2O3 nanocomposites with tunable optical, thermal and electrical properties show promising potential for electronic applications.

Pre-perihelion monitoring of interstellar comet 2I/Borisov

ABSTRACT The discovery of interstellar comet 2I/Borisov offered the unique opportunity to obtain a detailed analysis of an object coming from another planetary system, and leaving behind material in our interplanetary space. We continuously observed 2I/Borisov between 2019 October 3 and December 13 using the 1.52-m Telescopio Carlos Sánchez equipped with Multicolour Simultaneous Camera for studying Atmospheres of Transiting exoplanets 2 instrument, and the 2.54-m Isaac Newton Telescope with Wide Field Camera. We characterize its morphology and spectro-photometric features using the data gathered during this extended campaign. Simultaneous imaging in four bands (g, r, i, and zs) reveals a homogeneous composition and a reddish hue, resembling Solar system comets, and as well a diffuse profile exhibiting familiar cometary traits. We discern a stationary trend fluctuating around a constant activity level throughout 2019 October and November. Subsequently, a reduction in activity is observed in December. Dust production and mass-loss calculations indicate approximately an average of 4 kg s−1 before perihelion, while after perihelion the net mass-loss is about 0.6 kg s−1. Our simulations indicate the most probable size of coma dust particles should be in the range 200–250 nm, and the terminal speed around 300 m s−1. The spectrum acquired with the 4.2-m William Herschel Telescope shows the presence of a strong CN line for which we find a gas production rate of 1.2 × 1024 s−1. We also detected NH2 and OI bands. The ratio between NH2 and CN productions is log (NH2/CN) = −0.2. Overall, this observing campaign provides a new understanding of 2I/Borisov’s unique characteristics and activity patterns.

Bentonite-Chitosan composites or beads for lead (Pb) adsorption: Design, preparation, and characterisation

This study investigated the efficiency of mixing bentonite with chitosan via different preparation methods, subsequently the different forms were investigated for their ability to remove Pb(II) ions from solution. The different forms of bentonite-chitosan (Bt-Ch), composites and beads, were prepared via solution blending and precipitation methods, respectively and in the weight ratios of 90%/10%, 70%/30% and 50%/50%. The beads were further subdivided, identified as “beads-A" and “beads-B", and were formed by adding either bentonite suspension or bentonite powder, respectively, to solubilised chitosan solution. The composites and beads were characterised by X-ray fluorescence (XRF), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and pH at zero point charge. XRF analysis showed a cation exchange mechanism occurred when chitosan was initially mixed with the bentonite. TGA results confirmed that beads contained more chitosan compared to their corresponding weight ratio equivalent composites. XRD results showed that chitosan was intercalated within the interlayer space of the bentonite for Bt-Ch composites and Bt-Ch beads-A and that the interlayer spacings increased with increasing chitosan loading. Though similar amounts of chitosan were present in both Bt-Ch beads-A and beads-B, there were fewer reflection shifts for beads B suggesting less intercalation of chitosan when the bentonite was added as a powder. FTIR spectra from the Bt-Ch composites and beads confirmed the presence of both chitosan and bentonite, and the NH bands of chitosan shifted to lower frequencies demonstrating their involvement in the bonding mechanism of chitosan with bentonite. The experimental adsorption data correlated well with both non-linear Langmuir and Freundlich isotherm models, and in which both chemisorption and physisorption processes played crucial roles. The Langmuir-maximum adsorption capacities of Pb(II) ions for all the analysed Bt-Ch composites and beads was found to range from 42.48 ± 4.22 to 94.60 ± 5.63 mg/g. The amount of chitosan present in the adsorbent and its distribution within or outside the interlayer space of the bentonite was shown to have pronounced effects on the Pb(II) uptake by the different Bt-Ch composites/beads, and although the chitosan greatly enhanced the adsorption of Pb(II) a cation exchange mechanism with the clay was still a dominant process. The adsorption of Pb(II) was also significantly affected by the presence of other multi-competing ions. Moreover, the developed Bt-Ch composites/beads exhibited good potential for re-use after five cycles of regeneration, thus, indicating their potential as cost-effective adsorbents for removal of Pb(II) ions from both drinking and wastewater.

Experimental study on microwave plasma discharge and combustion of premixed methane and air at atmospheric pressure

In this work, we carry out the experiments on an atmospheric-pressure premixed methane and air microwave plasma discharge combustion with premixed methane and air to study the morphology, the spatial distribution of species, and the temperature characteristics for various microwave power values and methane-to-air equivalent ratios (<i>Φ</i>) at a series of measurement positions. The experimental results show that the equivalent ratio of 0.4 corresponds to the limit value for lean-combustion of premixed methane and air. And for <i>Φ</i> < 0.4, the discharge flame is mainly characterized by the combustion induced by premixed methane and air microwave plasma discharge, while, for <i>Φ</i> ≥ 0.4, the discharge flame is constricted into filaments radially, and the natural combustion occurs in the region of low reduced electric strength and the combustion induced by plasma discharge in the region of high reduced electric strength, which affect each other. The variations of emission intensity of OH (A-X) band, NH (A-X) band and CN (B-X) band with the measuring position and the equivalent ratio <i>Φ</i> are measured by using optical emission spectrometry (OES). It is found that the discharge combustion occurs in near afterglow and the combustion in far afterglow. And the vibrational temperature and the rotational temperature of the plasma discharge combustion are determined by analyzing the emission bands of CN(B-X) and the variations of both vibrational and rotational temperatures with equivalent ratio, exhibiting very different varying tendencies for cases of <i>Φ</i> < 0.4 and <i>Φ</i> ≥ 0.4, respectively. Finally, the reaction pathway and mechanism are discussed on the basis of the comparative analyses of the emission spectra of CH<sub>4</sub> diffusion combustion flame, premixed methane and nitrogen microwave plasma discharge, and premixed methane and air microwave plasma discharge combustion.

IR cavity ringdown spectroscopy and density functional theory calculation of pyrrole-diethyl ketone clusters: impacts of carbon-chain flexibility on the diversity of N-H⋯OC hydrogen bonds.

The N-H⋯OC hydrogen bond (H-bond) plays a key role in stabilizing the geometry and energy of biomolecules such as protein folding and DNA double strand. To investigate N-H⋯OC H-bonds in a microscopic view, we apply IR cavity ringdown spectroscopy (IR-CRDS) and density functional theory (DFT) calculation to pyrrole-diethyl ketone (Py-Dek) clusters in the gas phase. Dek exhibits a pentane carbon chain, which provides various conformations such as anti, gauche, and their mixtures. An introduction of the carbon-chain flexibility to Py-Dek clusters is expected to cause a diversity of the N-H⋯OC H-bond formation. In the observed IR spectra, there are seven prominent bands of the NH stretches due to Py-Dek clusters. These bands are classified into three groups: one for Py1-Dek1, two for Py1-Dek2, and four for Py2-Dek1. Stable structures and their harmonic frequencies obtained by DFT calculations provide the proper NH band assignments and appropriate cluster structures. Py1-Dek1 exhibits a single isomer, which is formed by an ordinary N-H⋯OC H-bond between Py and anti-conformation of Dek (Dek(a)) with a linear carbon-chain. Py1-Dek2 shows two isomeric structures, in which both isomers are commonly constructed by the N-H⋯OC H-bond for the first Dek and by the stacking interaction between π electrons of Py and the second Dek. Both isomers exhibit the Dek(a) for the stacking interaction, but are distinguished between Dek(a) and gauche-conformation Dek (Dek(g)) for the N-H⋯OC H-bond. Py2-Dek1 shows a triangular cyclic structure, which is formed by the N-H⋯OC H-bond, the N-H⋯π H-bond, and the stacking interaction between Py and Dek. The observed four bands are assigned to two N-H⋯OC and two N-H⋯π H-bonds for two isomeric structures due to Dek(a) and Dek(g). Not only smaller clusters but also higher hetero-tetramers are characterized based on the architecture of smaller clusters. In particular, Py2-Dek(a)2(I) was the first to be found with a highly symmetric (Ci) cyclic structure. Calculated potential energy surfaces of Py-Dek clusters shed light on the impact of Dek flexibility on N-H⋯OC H-bond diversity. Selective formation of isomeric structures for Py-Dek clusters is discussed in terms of a mechanism of a two- and three-body collision process in a supersonic expansion.

In-situ degradation of Amphotericin B in a microbial electrochemical cell containing wastewater

Antimicrobial resistance raises serious medical implications and is primarily caused by indiscriminate usage and environmental contamination with antimicrobial agents. To prevent microbes from developing resistance against antimicrobial agents, they must be effectively degraded. This is the first study that investigates the degradation of Amphotericin B(AmB) with simultaneous wastewater treatment in a Microbial Peroxide producing cell (MPPC). Two sets of MPPCs (A and B) were used to degrade AmB oxidatively, one with H2O2 and the other with the microbial electro Fenton process in a catholyte containing 0.1% AmB. MPPC A and B had voltage outputs of 0.356 ± 3 V and 0.411 ± 2 V, producing 26 ± 0.04 mM and 44 ± 0.8 mM of H2O2 respectively. The structural changes of treated samples were analyzed using Fourier Transformed Infrared Spectroscopy, which revealed the disappearance of major characteristic bands such as the NH band (1556 cm−1), the CH band Polyene ring (3358 cm−1), and others, implying the disruption of multiple double bonds in polyene, resulting in the structure's lactone ring breakdown. Liquid chromatography quadrupole time-of-flight revealed the changes in retention time and peak area of treated samples in comparison to native AmB which also confirmed its structural changes. Such structural disruption induced the drug to lose its antifungal action since no zones of inhibition were detected in an antimicrobial susceptibility test against Candida albicans. The degradation of 57.05% and 69.83% of AmB by H2O2 and the Fenton process was also correlated with a reduction in COD. Simultaneously the anodic wastewater treatment in both the MPPCs had COD removal efficiency of 78% and 82% and the BOD removal efficiency was 75.38% and 90% respectively. The MPPC system's process conditions and reactor design could be optimized further to enhance antimicrobial degradation and wastewater treatment. This research offers a sustainable and efficient method for expediting antimicrobial degradation while simultaneously treating wastewater.

Dissociative Excitation of Nitromethane Induced by Electron Impact in the Ultraviolet - Visible Spectrum.

The excitation of nitromethane (CH3 NO2 ), which is an important propellant and prototypic molecule for large class of explosives, has been investigated by electron impact and subsequent emission of photons in the UV-VIS spectral region between 300 nm and 670 nm. Emission spectrum of nitromethane was recorded at an electron energy of 50 eV. New dissociative excitation channels were observed through the appearance of different CH, CN, NH, OH and NO bands, and the Balmer series of atomic hydrogen. In addition, relative emission cross sections were recorded for the transitions of selected fragments. The emission spectrum was captured with significantly higher resolution in comparison to previous studies.

Influence of Fluorine Substitution on Nonbonding Interactions in Selected Para-Halogeno Anilines.

A series of 4-halogeno aniline derivatives was studied employing combined theoretical and experimental methods (i. e. crystal structure analysis and vibrational spectroscopies). This simplified model system was selected to shed light on the impact of fluorine substitution on the formation of noncovalent interactions such as halogen bonds (XBs) and hydrogen bonds (HBs), which are key interactions in fluorinated/halogenated drug-protein complex formation. Comparative analysis of three previously reported and five newly determined crystal structures indicated that, in most cases, 2-fluoro and 2,6-difluoro substitution of 4-X anilines increases the ability of adjacent amine to form strong N-H⋅⋅⋅N HBs. Additionally, fluorine substituents in the difluorinated derivatives are competitive and attractive HB and XB acceptors and increase the probability of halogen-halogen contacts. A peculiar observation was made for 4-iodoaniline and 2,6-difluoro-4-iodoaniline, which form distinct interaction patterns compared to the corresponding 4-Cl and 4-Br analogs. The observed intramolecular N-H⋅⋅⋅F interactions lead to additional NH bands in the FT-IR spectra.

Synthesis and characterization of a novel benzothiazole functionalized chitosan and its use for effective adsorption of Cu(II)

Contamination of water with the copper(II) ions leads to serious diseases such as liver damage and cancer. This deadly effect prompted us to target the synthesis of a novel functionalized chitosan (Cs-BT) to be used as an adsorbent for removing the copper(II) ions from the aqueous solution. The functionalization was done by introducing benzothiazole moiety into the chitosan (Cs) chain and confirmed by the full disappearance of the NH2 band in the FT-IR spectrum of the adsorbent. The TGA-DTG analysis revealed that the functionalization reduced the thermal stability of the adsorbent (Cs-BT) as compared with pure chitosan. The adsorption was evidenced by SEM and EDX analysis. The adsorption study demonstrated that the optimal adsorption conditions were 120 min contact time, pH = 6, and initial Cu(II) concentration 200 mg/L. At these conditions, the Cs-BT achieved a maximum copper adsorption capacity of 1439.7 mg/g. Consequently, Cs-BT could be a promising and efficient Cu adsorbent in water treatment. Study the adsorption kinetics and isotherms manifested that the pseudo-first-order was better than pseudo-second-order and Temkin isotherm was better than Langmuir, Freundlich, and Dubinin–Radushkevich for explaining the adsorption process. The calculated thermodynamic parameters implied the spontaneity and the endothermic nature of the adsorption process.

Plasma-Induced Defects Enhance the Visible-Light Photocatalytic Activity of MIL-125(Ti)-NH2 for Overall Water Splitting.

Defect engineering in metal-organic frameworks is commonly performed by using thermal or chemical treatments. Herein we report that oxygen plasma treatment generates structural defects on MIL-125(Ti)-NH2 , leading to an increase in its photocatalytic activity. Characterization data indicate that plasma-treated materials retain most of their initial crystallinity, while exhibiting somewhat lower surface area and pore volume. XPS and FT-IR spectroscopy reveal that oxygen plasma induces MIL-125(Ti)-NH2 partial terephthalate decarboxylation and an increase in the Ti-OH population. Thermogravimetric analyses confirm the generation of structural defects by oxygen plasma and allowed an estimation of the resulting experimental formula of the treated MIL-125(Ti)-NH2 solids. SEM analyses show that oxygen plasma treatment of MIL-125(Ti)-NH2 gradually decreases its particle size. Importantly, diffuse reflectance UV/Vis spectroscopy and valence band measurements demonstrate that oxygen plasma treatment alters the MIL-125(Ti)-NH2 band gap and, more significantly, the alignment of highest occupied and lowest unoccupied crystal orbitals. An optimal oxygen plasma treatment to achieve the highest efficiency in water splitting with or without methanol as sacrificial electron donor under UV/Vis or simulated sunlight was determined. The optimized plasma-treated MIL-125(Ti)-NH2 photocatalyst acts as a truly heterogeneous photocatalyst and retains most of its initial photoactivity and crystallinity upon reuse.

Controlling N and C-atom densities in N2/H2 and N2/CH4 microwave afterglows for selective TiO2 surface nitriding

Radiative states of N2/<5% H2 and N2/<50/00 CH4 HF(microwave) flowing afterglows of microwave plasmas at reduced gas pressures (4–20 Torr) have been analyzed by emission spectroscopy. The N2 1st pos (580 nm), 2nd pos (316 nm), N2+ 1st neg (391.4 nm), NH (336 nm) and CN (386 nm) bands in the pink (early) and the late afterglows were measured and the NO titration was used to determine the concentrations of N-atoms, O-atoms in impurity, N2(X,v > 13) and N2(A) metastable molecules, N2+ ions. Introduction of small percentages of H2 (or CH4) into N2 lead to a size reduction of the early afterglow region which was followed by a late afterglow zone where the N + N recombination is the dominant process. In addition, it also gave an effect of reducing the densities of N atoms (as well as the N2 excited states) in the afterglow regions. At the same time, it introduced other active species such as H (or C) atoms, of which the densities strongly vary depending on the percentage of H2 (or CH4) in the mixture. Such changes in the densities of active species such as N and C atoms in the afterglow region had a strong influence on the incorporation characteristics of N atoms into the surface of TiO2 films introduced into the afterglow region. These results deliver an important meaning in devising process conditions especially for selective nitrogen or carbon doping into a skin-depth layers of oxide materials, which is desired in the case of preparing a few nm-thick functional films for photovoltaic and photocatalytic applications.

Probing the vibrational dynamics of amide bands of N-methylformamide, N, N-dimethylacetamide, and N-methylacetamide in water

We report the vibrational dynamics of amide modes of N-methylformamide (NMF), N-methylacetamide (NMA), and N, N-dimethylacetamide (DMA) in water using first principles molecular dynamics simulations. The solvent-mediated dynamics and stretching profile of CO, NH, and CN modes of amide molecules were analyzed in terms of vibrational spectral and second-order reorientational dynamical properties. The maximum redshift is observed for the amide I band of DMA due to stronger DMA-water hydrogen bonding interaction; a blue shift is observed for NMF. The calculations also reveal that the amide-A band of NMF exhibits a redshift as compared to NMA. Multiple peaks are located for the CN band of DMA, and this feature gradually decreases for NMA and NMF. Spectral dynamics of amide bands were investigated by calculating the frequency-frequency correlation functions. Slowest spectral diffusion is found for the CO band of DMA. However, NMA shows slower dynamics for NH band than that of NMF.

Interaction dust – plasma in Titan's ionosphere: An experimental simulation of aerosols erosion

Organic aerosols accumulated in Titan's orange haze start forming in its ionosphere. This upper part of the atmosphere is highly reactive and complex ion chemistry takes place at altitudes from 1200 to 900 km. The ionosphere is a nitrogen plasma with a few percent of methane and hydrogen. Carbon from methane enables the formation of macromolecules with long organic chains, finally leading to the organic aerosols. On the other hand, we suspect that hydrogen and the protonated ions have a different erosive effect on the aerosols.Here we experimentally studied the effect of hydrogen and protonated species on organic aerosols. Analogues of Titan's aerosols were formed in a radiofrequency capacitively coupled plasma (RF CCP) discharge in 95% N2 and 5% CH4. Thereafter, the aerosols were exposed to a DC plasma in 99% N2 and 1% H2. Samples were analysed by scanning electron microscopy and in situ infrared transmission spectroscopy. Two pellet techniques – KBr pressed pellets and thin metallic grids - were compared to confirm that modifications seen are not due to the material used to make the pellet.We observed that the spherical aerosols of ~500 nm in diameter were eroded under N2-H2 plasma exposure, with the formation of holes of ~10 nm at their surface. Aerosols were globally removed from the pellet by the plasma. IR spectra showed a faster disappearance of isonitriles and/or carbo-diimides compared to the global band of nitriles. The opposite effect was seen with β-unsaturated nitriles and/or cyanamides. Double bonds as CC and CN were more affected than amines and CH bonds. NH and CH absorption bands kept a similar ratio in intensity and their shape did not vary.Therefore, it seems that carbon and hydrogen play opposite roles in Titan's ionosphere: the carbon from methane leads to organic growth while hydrogen and protonated species erode the aerosols and react preferentially with unsaturated chemical functions.

Hydrogen isotopic analysis using molecular emission from laser-induced plasma on liquid and frozen water

The hydrogen isotopes in liquid and frozen water samples were analyzed by laser ablation molecular isotopic spectrometry (LAMIS), which employs the molecular emission from laser-induced plasma for isotope analysis. Molecular emission bands of OH and NH radicals were observed, and their spectral features were characterized in accordance with sample matrix and measurement conditions. The OH and NH bands exhibit different emission behavior, which was attributed to formation kinetics and thermodynamic factors. Under optimized condition, isotopic shift between hydrogenated (OH and NH) and deuterated (OD and ND) species was measured at individual rotational branches. By using these molecular bands, the partial least squares regression (PLSR) structure was established for quantitative analysis of hydrogen isotope and evaluated by cross-validation in terms of accuracy and precision. The PLSR result was good with root mean square error of prediction (RMSEP) of 0.3–0.7% for all species. Particularly, the case using OH/OD emission from liquid water revealed the most accurate result with RMSEP of 0.33%. It was affected by the quality and reproducibility of spectral data determined by utilized species. This study not only supports the behavioral understanding of molecular radicals in laser-induced plasma, but also identifies the feasibility of LAMIS for real-time application to quantitative analysis in various sample matrices.

Impact of soft segment size on physicochemical and antimicrobial properties of waterborne polyurethane dispersions for textile applications

The waterborne polyurethane dispersions (WPUDs) have substituted solvent borne systems due to strong environmental concerns. In this study, a series of WPUDs synthesized to evaluate the impact of size of soft segment (Polyethylene glycol; PEG) on their properties. The Fourier Transform Infrared spectroscopy (FTIR), dynamic light scattering, rheometer and gravimetric determination of total solid content were used to assess the physicochemical properties of dispersions. The appearance of characteristic NH and CO urethane bands in FTIR spectra demonstrated the proposed synthesis of WPUDs. An increase in the molecular weight of hydrophilic soft segment ensued a decrease in average particle size of dispersions along with a parallel increase in viscosity and total solid content of dispersions. The textile testing and SEM analyses supported the finishing of cotton fabric with slight improvement in tear strength. However, no significant correlation was observed between tear strength and size of soft segment. Furthermore, the dispersions showed antimicrobial activity against gram −ve and +ve bacteria though the effect was diminishing with increase in the molecular weight of soft segment.

NH and CN radical emission from corona post discharge region in high density nitrogen plasma

The corona post discharge region in high-density nitrogen plasma has been investigated. We observed the emission band (0-0) of NH located at 336 nm corresponding to the transition A3Π-X3Π− which is particularly intense at low pressure. The possibility would be that NH is formed from a radiative recombination between a hydrogenated compound present in trace amounts (as CmHn) and nitrogen. Outside the (0-0) NH band, only the band (1-1) at 337.00 nm (i.e. 1 nm from the previous one) was detected. Since its transmission probability is lower than that of the band (0-0) and is located very close to the intense 2S+ band (0-0) (337.13 nm), detection is not possible. A very weak emission of the CN violet system ((B2Σ+-X2Σ) has been identified in the discharge zone with excitation threshold in the order of 3.37 eV. The most intense bands are between 385 nm and 388.34 nm. This radical can only come from a reaction in the discharge between the nitrogen and an organic compound of the CnHm type. Although the purification system is very sophisticated, traces of hydrocarbons can be introduced either by contamination by oil vapours from the pumping system or by their presence in the starting gas (0.01 ppm). The radical CN is observed only with a discharge in negative polarity.

Synthesis and Study of New Luminescent Carbon Particles with High Emission Quantum Yield

Luminescent carbon nanoparticles (CNPs) having a high mass yield of carbon material and emission quantum yield are synthesized from lentil grain flour via thermal carbonization, followed by treatment in nitric acid, and by the hydrothermal method. The luminescent and optical properties, solubility, and stability of solutions of various CNPs during interaction between particles and electromagnetic radiation are studied and analyzed by photoluminescence and optical absorption methods. When carbonization temperatures are 400 and 500°C, the mass yields of carbon materials are 34.6 and 29.7%, respectively. The amount of CNPs whose sizes are less than 50 nm is 7.2–12.5%, whereas the proportion of particles soluble in pure water is no more than 0.8% of the weight of a carbon material. New particles having a mass yield of 81–104% and high solubility of CNPs in water are formed as a result of special treatment of carbon material powders in HNO3. The solubility of CNP powders is strongly dependent on temperature and pH of a solvent; some samples achieve 30.3 g/L at 96.9°C. The energy of the direct band gap of CNPs is 3.325–3.445 eV, and the carbon nuclei of the particles contain structural defects and various surface groups of high concentration. Some absorption bands, including those at 271 (NH1) and 370 nm (NH2), appear in the optical absorption spectra after hydrothermal treatment of all CNPs in the presence of ammonia or urea. The structural features of the NH1 and NH2 bands, the photoluminescence spectra, and the magnitudes and the stability of quantum yields of different CNPs are thoroughly studied depending on temperature and duration of hydrothermal treatment. The maximum quantum yield of the best CNP samples during excitation with 406 nm laser radiation is 39.3%, which is a promising indicator for practical use.

Synthesis, structural characterization, and computational study of (E)-N′-(3,4-dimethoxybenzylidene)furan-2-carbohydrazide

An efficient synthesis of the new (E)-N′-(3,4-dimethoxybenzylidene)furan-2-carbohydrazide is described. Its molecular structural features have been characterized by FTIR, 1H NMR, 13C NMR and MS, then have been confirmed by single crystal X-ray diffraction. Quantum chemical calculations including molecular geometry, intermolecular H-bonds and vibrational frequencies were carried out for the structures to explain stability and geometry using the hybrid density functional (DFT/B3LYP) in conjunction with 6-311 + G(d,p) basis set. The calculated structural and vibrational parameters are presented and compared with their experimental X-ray and FTIR counterparts. The global minimum and local minima ground states characteristics of the title compound and its rotamers have been theoretically established through 2D potential energy scan and vibrational frequencies. Computational analysis predicted that head-to-tail E/E-dimer of the observed E-isomer has significantly stronger intermolecular hydrogen bonding in solution rather than in the gaseous state. It is found that NH and CO vibrational bands suffering blue-shift due to intermolecular hydrogen bonds (IHBs). Weak intramolecular hydrogen bonds that have been detected in the monomeric form in the gaseous state and in solution are lacking in trimers and tetramers due to loss of planarity in the molecular structure. Optimization in solution clearly shows that the strength of the IHBs decreased exponentially with dielectric continuum of the solvent used. Inexistence of solvent/monomer intermolecular hydrogen bonds has been explained in terms of Condensed Fukui Functions.

Water adsorption with relative humidity changes for keratin and collagen as studied by infrared (IR) micro-spectroscopy.

Natures and amounts of water retained at the surface of stratum corneum (SC) of human skins, affecting skin health and penetration of chemical components, remain unclear. A keratin film, a main component of human SC surface, was measured by IR micro-spectroscopy combined with a quartz crystal microbalance (QCM) and a relative humidity (RH) control system. Water contents increased with RH up to about 19 wt% and were correlated linearly with the OH + NH band areas in IR spectra of the keratin film. The OH + NH band areas for the triple helix collagen film are about twice as large as those for the keratin film (double helix). The free water component increases with RH by keeping the bound water component minor for the keratin film. About twice of water retention capacity of the collagen film can be due to increasing adsorption of free water, interacting possibly with hydrophobic aliphatic CH surfaces. The present results suggest relatively low water contents less than about 19 wt% of outermost SC layers of human skin composed mostly of keratin exposed to ambient RH conditions. The triple helix collagen can be used as an effective moisturizing agent.