Characteristic Absorption Bands Research Articles

Effects of pretreatment applied to sugarcane bagasse on composition and morphology of cellulosic fractions

Due to the growing demand for renewable energy, the energy based on biomass plays an important role in energy policies of countries all over the world. Seven different pretreatments were performed on SCB to obtain yields, chemical composition, particle sizes and crystallinity indexes. The tools used to study the effects of pretreatments on SCB were X-ray diffraction (change in crystalline and amorphous regions) and SEM images. The application of microwave-assisted irradiation allowed the obtaining of the lowest cellulose removal with the fractions PT-6 and PT-7. FTIR spectra showed the removal of hemicellulose and lignin content during pretreatments. DP values decreased significantly suggesting higher digestibility of the seven cellulosic fractions by cellulolytic enzymes. In the present work, the presence of cellulose, hemicellulose and lignin structures in the sample of sugarcane bagasse and cellulosic fractions were indicated by the characteristic absorption bands (cm−1) of groups shown by the FTIR spectrum for hemicellulose and lignin. SEM images showed extensive degradation of the buddle of fibers of some cellulosic fractions. Mass loss (ML) obtained with SCB and cellulosic fractions were much greater under O2 atmosphere than under N2 atmosphere. The most relevant novelty of the present research was the use of chemical and physical methodologies to characterize sugarcane bagasse and their cellulosic fractions. The objective of this work was to determine the chemical composition and physical characteristics such as particle sizes as well as the removal of components resulting from seven different pretreatments. Nevertheless, future work is greatly required for improvement in this area.

Identification of inorganic oxidizing salts in homemade explosives using Fourier transform infrared spectroscopy

Recently, inorganic low explosives, such as pyrotechnic composition, black powder, and ammonium nitrate, are commonly used in improvised explosive devices (IEDs) by the rioter or terrorists since these energetic materials can be obtained easily and legally from civilian markets. Identification of inorganic oxidizing salts in these homemade explosives, including nitrates, chlorates, and perchlorates, is a necessary procedure for forensic investigators to provide criminal evidences. In this article, Fourier transform infrared (FTIR) spectroscopy was used to discriminate NO3-, CO32-, ClO3-, ClO4-, SO42-, and NH4+, whose characteristic absorption bands were explained by vibration modes of the covalent bonds. Then the spectral absorption features of nitrate salts with monovalent or divalent cations were discussed. Furthermore, it was studied whether nitrates or perchlorates can be unequivocally distinguished with the presence of carbonate and sulfate impurities through FTIR technique. Finally, the feasibility of this method was verified through an analytical case of homemade explosives.

Effects of Zn2+-Zr4+ ions on the structural, mechanical, electrical, and optical properties of cobalt ferrites synthesized via the sol–gel route

In the present study, we examined the effects of doping with Zn–Zr on the structural, optical, electrical, and mechanical properties of cobalt ferrite. Nanocrystalline cobalt ferrites comprising CoZnxZrxFe2-2xO4 (x = 0.0 to 0.4, Δx = 0.1) were prepared via the sol–gel route. X-ray diffraction analysis indicated the formation of a spinel phase in the ferrites. An additional ZrO2 phase was observed for x = 0.3. Characteristic absorption bands at frequencies of 580–610 cm−1 and 375–400 cm−1 related to spinel structures were observed in the Fourier transform infrared FTIR spectra obtained for the ferrites. The elastic constants decreased as the Zn–Zr contents increased. The longitudinal and shear velocities of ultrasound through the ferrite materials were measured using the ultrasonic pulse transmission method. The variations in the ultrasound velocities could be attributed to the changes in density. The dielectric parameters ɛ′ (dielectric constant) and tanδ (dielectric loss tangent) were analyzed as functions of the frequency and Zn–Zr composition. Both ɛ′ and tanδ decreased as the frequency and Zn–Zr contents increase. The variations in the values of parameters ɛ′ and tanδ were explained using Maxwell–Wagner interfacial polarization according to Koops phenomenological theory. The values of the activation energy and Curie temperature were calculated based on plots of the thermal variation in the direct current resistivity. The activation energy values indicated that electron hopping was the mechanism responsible for conduction in the ferrites.

Effect of MoO3, MnO2 or mixed dopants on the spectral properties and crystallization behavior of sodium phosphate glasses containing either MgO or MgF2

Glasses from the two basic systems (Na2O–P2O5–MgO) and (Na2O–P2O5–MgF2) doped with either MoO3 or MnO2 or both of them were obtained by melting–annealing method. Characterization of both the optical and FTIR spectra for the prepared glasses were carried out together with deriving the optical band gaps and refractive indices. DTA and thermal expansion properties were investigated to reach suitable nucleation and crystallization temperatures to convert the glasses to their corresponding glass–ceramic derivatives. X-ray diffraction investigations of the glasses were primarily done to confirm their amorphous nature and then to identify the formed crystalline phases formed upon controlled thermal heat treatment with two step regime within the glass–ceramic derivatives. Optical spectra of the studied glasses reveal distinct UV absorption bands due to contaminated trace iron impurities together with the appearance of characteristic absorption bands due to molybdenum or manganese ions or both in the mixed dopants samples. FTIR spectral data indicate the appearance of vibrational peaks of phosphate groups with the interference of MgO4, MgF2 or PO3F groups. The dopants cause minor effects on the FTIR spectra. DTA and thermal expansion data support the voluminous crystallization behavior and indicating the different roles of MgO than MgF2 as reflected on the identified crystalline phases. In MgO containing glass–ceramics, the identified crystalline phase is sodium magnesium phosphate of the formula (Na3Mg2P2O16) while with MgF2–glass, two crystalline phases are identified: sodium magnesium pyrophosphate (Na2MgP2O7) beside sodium magnesium fluoride crystalline phase (NaMgF3). This refers to the compactness of the network of glasses with MgO due to its refractoriness and possibility of the formation of structural MgO4 groups. On the other hand, MgF2, is assumed to act in glass during crystallization as efficient nucleating agent as CaF2 and it is assumed to lower the melting temperature and ease of crystallization.

Infrared Spectroscopy of Large, Low‐Albedo Asteroids: Are Ceres and Themis Archetypes or Outliers?

AbstractLow‐albedo, hydrated objects dominate the list of the largest asteroids. These objects have varied spectral shapes in the 3‐μm region, where diagnostic absorptions due to volatile species are found. Dawn's visit to Ceres has extended the view shaped by ground‐based observing and shown that world to be a complex one, potentially still experiencing geological activity. We present 33 observations from 2.2 to 4.0 μm of eight large (D > 200 km) asteroids from the C spectral complex, with spectra inconsistent with the hydrated minerals we see in meteorites. We characterize their absorption band characteristics via polynomial and Gaussian fits to test their spectral similarity to Ceres, the asteroid 24 Themis (thought to be covered in ice frost), and the asteroid 51 Nemausa (spectrally similar to the CM meteorites). We confirm most of the observations are inconsistent with what is seen in meteorites and require additional absorbers. We find clusters in band centers that correspond to Ceres‐ and Themis‐like spectra, but no hiatus in the distribution suitable for use to simply distinguish between them. We also find a range of band centers in the spectra that approaches what is seen on Comet 67P. Finally, variation is seen between observations for some objects, with the variation on 324 Bamberga consistent with hemispheric‐level difference in composition. Given the ubiquity of objects with 3‐μm spectra unlike what we see in meteorites, and the similarity of those spectra to the published spectra of Ceres and Themis, these objects appear much more to be archetypes than outliers.

A simple alternative to prodrug: The hydrochloride salt monohydrate of the prostate anticancer drug abiraterone

Abiraterone acetate is a first choice prodrug to treat prostate cancer. New higher-solubility multicomponent crystal forms of the active compound abiraterone could substitute for the commonly used acetate prodrug. Here we prepare abiraterone hydrochloride monohydrate, which is the first multicomponent crystal form of this striking prostate anticancer agent. Its solid state characterization by single-crystal X-ray diffraction (SCXRD), infrared (IR) spectroscopy and thermogravimetry (TG) was performed. The only conformational difference in the molecular backbone common to the literature related crystal forms (abiraterone acetate and the free base abiraterone) and our salt resides in the 3-pyridil rotation upon protonation. If the neutral molecules found in the two literature structures are taken as references, this motif is rotated by almost exactly 180° in our protonated abiraterone. Crystal packing also follows the protonation pattern. While in both prodrug and free base there is formation of head-to-tail fashioned one-dimensional chains as the main supramolecular entities, hydrogen bonded sheets are the main supramolecular motifs of abiraterone hydrochloride monohydrate. In addition, the IR spectrum and the TG thermogram of the hydrochloride salt monohydrate are present with characteristics absorption bands and thermal events, being therefore useful as analytical data for control quality purposes of this promising active pharmaceutical ingredient.

Sepiolite / poly-3-hydroxyoctanoate nanocomposites: Effect of clay content on physical and biodegradation properties

Vinlytrimethoxy silane (VTMS) was grafted onto the pristine sepiolite. This VTMS containing sepiolite (VTMS-g-Sep) was used to prepare sepiolite/poly-3-hydroxyoctanoate (Sep/PHO) nanocomposites sheets by melt blending technique. Fourier transform infrared (FTIR) spectroscopy showed the formation of siloxane linkages in nanocomposites. Wide angle x-ray diffraction analysis indicated the formation of new crystal in nanocomposites. Thermal analysis demonstrated an increase in melting temperature of nanocomposite sheets. An increase of 1.4 and 16 folds in tensile strength and elongation at break of Sep/PHO nanocomposites was observed in comparison to PHO alone. The degradation studies of Sep/PHO nanocomposite were carried out both under in-vitro conditions and soil. Scanning electron microscopy showed the formation of agglomerates, grooves, and pits on the surface of Sep/PHO nanocomposite sheets buried in soil. FTIR analysis of the Sep/PHO nanocomposite sheets buried in soil showed a decrease in the intensities of the characteristic absorption bands at 2948 cm−1 (anti-symmetric stretching vibrations of the CH bonds) and 1730 cm−1 (carbonyl CO stretching vibration). While, intensities of absorption bands at 3670–3070 cm−1 (OH stretching vibrations) and 1050–1150 cm−1 (CO bending vibration) were increased after 90 days of soil burial.

Cr3+ doped nanoporous anodic alumina: Facile microwave assisted doping to realize nanoporous ruby and phase dependent photoluminescence

Microwave-assisted solution technique (MAST) was used for the homogeneous doping of Cr3+ in nanoporous anodic alumina (NAA) which when heat-treated transforms into nanoporous ruby. The rise in annealing temperature led to the phase transition in the sequence: amorphous- δ- θ- α-alumina as evidenced by XRD. The dopant was homogenously distributed as seen from the elemental mapping and the Cr3+ content was 0.5 at%. Diffuse reflectance spectroscopy (DRS) displayed the characteristic blue and green absorption bands and the color-tone varied from light-green at 700 °C to the pink appearance at 1350 °C owing to the dopant diffusion. Two broad photoluminescence (PL) excitation bands centered at ∼550 nm and ∼400 nm were observed whose intensity increased with the annealing temperature. All the alumina phases exhibited characteristic phase dependent PL showing variation in the luminescence intensity and peak position. The characteristic R-line for α-phase was intense and observed at 694 nm with 4 m s lifetime in accordance with that expected for Ruby. Crystal field parameters were obtained from the PL excitation spectra and Dq/B values were found to be higher than 2.3 for all the phases of NAA confirming the presence of Cr3+ ions in the strong crystal field. With annealing, the CIE coordinates moved towards the red region. The presented work shows a promising easy and inexpensive method for dopant incorporation into alumina and explores the understanding of phase-dependent emission of Cr3+ doped NAA for their potential applications in the areas of nano-optics and composite luminescent nanomaterials.

Synthesis and Characterization of SnO2-TiO2 Nanocomposites Photocatalysts

Background: The photocatalytic activity of SnO2-TiO2 nanocomposites was successfully assessed after synthesis by Sol-Gel method, deposition on porous silicon material and annealing at 400, 600 and 800oC temperatures, with surface grain size in the range between 5 and 12 nm. The photocatalyst was characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (SEM), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG) and mass spectroscopy (MS). The photocatalytic assessment suggests that this SnO2-TiO2 photocatalyst presents important photocatalytic efficiency to methyl blue (MB) at low annealing temperature. </P><P> Methods: In this work, sol-gel method is used to prepare SnO2-TiO2 nanocomposites; which were deposited on porous silicon, annealed at different temperatures and investigated to understand their structural, morphological, optical and physical properties. Their photocatalytic activity was evaluated by using the degradation of MB under irradiation with UV light. </P><P> Results: The intensity of the characteristic absorption band of methyl blue at 655 nm decreased significantly with the increasing irradiation time. Meanwhile, a change in color of the solution occurred; turning from blue to colorless after 20 min of irradiation, and thus indicating the gradual decomposition of methyl blue molecules during UV light irradiation in the presence of the prepared SnO2-TiO2. As expected, no degradation of the SnO2-TiO2 nanocomposites occurred under control experimental conditions. The MB degradation efficiency was reported by C/C0 quantity; where C and C0 correspond respectively to its concentration at time t and initial concentration. In the presence of photocatalysts, it can be clearly deduced that after irradiation for 20 min, the C/C0 of the MB value was about 0% with the prepared and untreated nanocomposites of SnO2-TiO2 and remains constant when using a SnO2-TiO2 nanocomposite treated at 800°C. </P><P> Conclusion: This research has successfully synthesized the SnO2-TiO2 nanocomposite photocatalysts by Sol-Gel process and deposited by spin–coating technique on porous silicon substrates. Besides, all structural, optical and catalytic properties were studied and CO related. The obtained material was annealed at three different temperatures 400°C, 600°C and 800°C. It is denoted that its grain size increases from about 5 nm to 12 nm with the annealing temperature. The photocatalytic effect has been tested on the MB solution, which demonstrates that the nanometric grain size enhances the adsorption properties and achieves a good photocatalytic performance at a low temperature.

Isaria fumosorosea-based zero-valent iron nanoparticles affect the growth and survival of sweet potato whitefly, Bemisia tabaci (Gennadius).

Nanoparticles can be used for effective pest management as a combined formulation of metal and some other material that has proven efficacy against a given pest. This study reports the synthesis, characterization and efficacy of Isaria fumosorosea-based zero-valent iron (ZVI) nanoparticles against sweet potato whitefly Bemisia tabaci (Gennadius). The I. fumosorosea-ZVI nanoparticles showed a characteristic surface plasmon absorption band at 470 nm during UV-visible spectroscopy. The scanning electron micrographs of nanoparticles showed spherical shaped nanoparticles with sizes ranging between 1.71 and 3.0µm. The EDX analysis showed the characteristic peak of iron at 0.6 and 6.8KeV. The XRD analysis showed characteristic peaks at 44.72°, 65.070°, 82.339° and 82.65°. The bioassay results indicated that the percentage of larval mortality of B. tabaci challenged with I. fumosorosea ZVI nanoparticles was both concentration and age dependent. Isaria fumosorosea ZVI nanoparticles showed high pathogenicity against second and third instar nymphs, and pupae with LC50 values of 19.17, 26.10 and 37.71 ppm, respectively. The LT50 was lowest for second instar nymphs (3.15 days) and highest for pupae (4.22 days) when inoculated with a concentration of 50 ppm. Isaria fumosorosea ZVI nanoparticles can be an eco-friendly tool for effective B. tabaci management. © 2019 Society of Chemical Industry.

NiII -ATCUN-Catalyzed Tyrosine Nitration in the Presence of Nitrite and Sulfite.

The nitration of tyrosine residues in proteins represents a specific footprint of the formation of reactive nitrogen species (RNS) in vivo. Here, the fusion product of orange protein (ATCUN-ORP) was used as an in vitro model system containing an amino terminal Cu(II)- and Ni(II)-binding motif (ATCUN) tag at the N-terminus and a native tyrosine residue in the metal-cofactor-binding region for the formation of 3-NO2 -Tyr (3-NT). It is shown that NiII -ATCUN unusually performs nitration of tyrosine at physiological pH in the presence of the NO2 - /SO3 2- /O2 system, which is revealed by a characteristic absorbance band at 430 nm in basic medium and 350 nm in acidic medium (fingerprint of 3-NT). Kinetics studies showed that the formation of 3-NT depends on sulfite concentration over nitrite concentration suggesting key intermediate products, identified as oxysulfur radicals, which are detected by spin-trap EPR study by using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). This study describes a new route in the formation of 3-NT, which is proposed to be linked with the sulfur metabolism pathway associated with the progression of disease occurrence in vivo.

Structural and magnetic studies on Co-Zn nanoferrite synthesized via sol-gel and combustion methods

Abstract Co–Zn nanocrystalline ferrites with chemical composition Co0:5Zn0:5Fe2O4 were synthesized by sol-gel and combustion methods. The sol-gel method was carried out in two ways, i.e. based on chelating agents PVA and PEG of high and low molecular weights. In auto-combustion method, the ratio of citric acid to metal nitrate was taken as 1:1, while in sol-gel method the chelating agents were taken based on oxygen balance. All the three samples were studied by thermogravimetric and differential thermal analysis for the identification of phase formation and ferritization temperature. The synthesized samples were characterized by powder X-ray diffraction and FT-IR spectroscopy without any thermal treatment. The measured lattice constants and observed characteristic IR absorption bands of the three samples are in good agreement with the reported values showing the formation of a cubic spinel structure. The crystallite sizes of all samples were determined using high intensity peaks and W-H plot. Size-Strain Plot method was also implemented since two of the samples showed low crystallite sizes. The least crystallite size (5.5 nm) was observed for the sample CZVP while the highest (23.8 nm) was observed for the sample CZCA. Cation distribution was proposed based on calculated and observed intensity ratios of selected planes from X ray diffraction data. All structural parameters were presented using experimental lattice constant and oxygen positional parameter, and they correlated with FT-IR results. Magnetic measurements were carried out using vibrating sample magnetometer at room temperature to obtain the characteristic parameters such as saturation magnetization, coercivity, remanence, squareness ratio and Bohr magnetons. Among all, the sample synthesized via citric acid autocombustion method displayed a remarkably higher magnetization of 53 emu/g and the remaining two samples displayed low magnetization values owing to their smaller crystallite sizes.

Transient absorption spectroscopic studies on 4-nitroquinoline N-oxide: From femtoseconds to microseconds timescale.

The singlet excited state of 4-nitroquinoline N-oxide (1NQNO*) has been characterized by different spectroscopic techniques, combining transient absorption with steady state and time-resolved emission spectroscopy. The energy of 1NQNO* has been established as 255 kJ/mol from the fluorescence spectrum, whereas its lifetime has been found to be 10 ps in the femto-laser flash photolysis (LFP) experiments, where a characteristic S1Sn absorption band with maximum centered at 425 nm is observed. In a first stage, the triplet excited state of NQNO (3NQNO*) has also been characterized by emission spectroscopy in solid matrix, at low temperature. Thus, from the steady-state phosphorescence spectrum the triplet energy has been estimated as 183 kJ/mol, whereas the setup with time resolution has allowed us to determine the phosphorescence lifetime as 3 ms. Formation of 3NQNO* by intersystem crossing in solution at room temperature, has been monitored by femto-LFP, which shows the appearance of a band with maximum at 560 nm (T1-Tn). It increases with the decreasing intensity of its precursor 425 nm (S1Sn) band, giving rise to an isosbestic point at 500 nm. The characterization of 3NQNO* has been completed by nano-LFP, using xanthone as photosensitizer and oxygen as well as β-carotene as quenchers. In addition, quenching of 3NQNO* by electron donors (DABCO) is also observed in aprotic solvents, leading to the radical anion of NQNO (-NQNO). If there is a proton source in the medium (Et3N as electron donor or MeCN:H2O/4:1 as solvent system) protonation of the radical anion results in formation of the neutral radical of NQNO (NQNOH). In general, all processes are slower in protic solvents because of the solvation sphere. Overall, this information provides a deeper insight into the formation and behavior of excited states and radical ionic species derived from the title molecule NQNO.

Quantitative analysis of free water in ionic liquid-water mixtures

The purpose of this paper is to determine the amount of water in ionic liquid aqueous solutions that does not form hydrogen bonds (that is to say, free water). Here, the amount of free water was determined in mixtures of water and four ionic liquids based on the imidazolium cation: 1-Butyl-3methylimidazolium acetate, 1-Butyl-3methylimidazolium bromide, 1-Butyl-3methylimidazolium chloride, and 1–3, dimethyl-imidazolium chloride. Their ionic liquid mass fraction was between 0% and 80%. The amount of free water in the mixtures was determined from the concentration profiles obtained by analysing the near infrared spectra of the mixtures between 800 and 1070 nm using multivariate curve resolution-alternating least squares. The absorption band characteristic of the OH- group in the water is present in the spectral region considered. The analysis was done at three temperatures: 298.15, 313.15 and 333.15 K. The major conclusions obtained from a comparative analysis of the results are these: a) the length of the alkyl chain significantly affects the hydrophobicity of the cations when the molality of the ionic liquid in the solutions is higher than 1.435 mol/kg. b) for the solutions with the same cation, the amount of free water in the chloride solutions is lower than in the acetate and bromide solutions when the temperature is lower than 333.15 K. At this temperature, the capacity of acetate and bromide solutions to interact with water is the same. Between 298.15 and 333.15 K, the ionic liquid concentration at which there is no free water in the solutions ranges between 62.70% and 59.59% for the 1–3, dimethylimidazolium chloride, 66.72% and 87.75% for the 1-Butyl-3methylimidazolium chloride, 69.76% and 78.36% for the -1-Butyl-3methylimidazolium bromide and between 69.77% and 78.26% for the 1-Butyl-3methylimidazolium acetate. So, the ionic liquid with the greatest capacity to retain water is the 1–3, dimethylimidazolium chloride.

Preparation, characterization, and antibacterial activity of organo-sepiolite/chitosan/silver bionanocomposites

Bionanocomposites with different loadings of silver (Ag) were prepared via synthesis of Ag nanoparticles (AgNPs) using the wet chemical reduction method in the lamellar space layer of the organo-sepiolite/chitosan (O-SEP/CS). The prepared O-SEP/CS/Ag bionanocomposites were characterized using various analysis methods for their structure, morphology, and optical properties. The characteristic absorption bands from the UV–visible absorption spectrum confirmed the formation of AgNPs. The antibacterial activities of O-SEP/CS/Ag bionanocomposites were investigated against gram-positive and gram-negative bacteria using the disc diffusion method. The results suggest that O-SEP/CS/Ag bionanocomposites can be useful in wide range of bio-medical applications because of high antibacterial activity.

Features of diazo dye photodecomposition in aqueous solutions containing zinc, aluminum and erbium salts

Subject of research.The features of diazo dye Chicago Sky Blue 6B photodecomposition in aqueous solutions containing the salts of zinc, aluminum and erbium were studied. The paper presents the research of effect of the type and concentration of salts of these metals on the spectral properties of solutions and kinetic dependencies of the decomposition processes of a diazo dye under the action of UV radiation from DRT-240 high-pressure mercury lamp. Method. The methodology of the studies consisted in the sequential measurement of the absorption spectra of the solutions on a Perkin-Elmer Labda 650 spectrophotometer in the UV and visible parts of the spectrum after UV irradiation of various durations and analysis of the observed spectral changes. Main results. Based on the research carried out, it was shown that the absorption spectrum of the dye changes in the presence of metal salts in solutions and an additional maximum appears on the characteristic broad and intense absorption band of the dye in the visible part of the spectrum (λ = 540–680 nm). That fact suggests the behavior of dye molecular structuring. When metal salts are introduced into the solution, the mechanism of its decomposition under the action of UV radiation also changes significantly. In the presence of metal salts, along with a decrease in the intensity of the absorption band of the dye in the visible part of the spectrum, its substantial shift to the shortwave region is also observed. Studies of the dye decomposition kinetics under UV irradiation showed that the rate of the dye photodegradation sharply increases in the presence of metal nitrates in solutions. The introduction of zinc nitrate into the solution has particularly strong effect on the dye photodegradation in an aqueous solution. Practical relivance.The experimental results obtained can be used in the development of photochemical processes for the purification of water from organic pollutants.

Pharmaceutical Cocrystal Formation of Pyrazinamide with 3-Hydroxybenzoic Acid: A Terahertz and Raman Vibrational Spectroscopies Study.

Vibrational modes of pyrazinamide (PZA), 3-hydroxybenzoic acid (3-hBA), and their cocrystal were characterized using terahertz time-domain (THz-TDS) and Raman vibrational spectroscopic techniques. In experimental THz spectra, the cocrystal has characteristic absorption bands at around 0.81, 1.47, and 1.61 THz, respectively, meanwhile the raw materials are absolutely different in this region. Raman spectra also show similar results about differences between the cocrystal and corresponding starting parent materials. Density functional theory (DFT) was used to simulate both optimized structures and vibrational modes of the cocrystal formed between PZA and 3-hBA. The vibrational modes of such cocrystal are assigned through comparing the simulation DFT frequency results with experimental vibrational spectra. The calculation of the theoretical THz spectrum shows that the hydrogen bonding effect established between H11–N12–H13 and the carboxyl group -COOH makes contributions to the formation of absorption peaks in 0.49, 0.62, 0.83, and 1.61 THz, which agrees pretty well with experimental results. The theoretical Raman result also matches well with experimental observations. The results provide a fundamental benchmark for the study of pharmaceutical cocrystal formation and also inter-molecular hydrogen bonding interactions between active pharmaceutical ingredients and various cocrystal coformers based on Raman and terahertz vibrational spectroscopic techniques combined with theoretical simulations.

Operando XAS and UV-Vis Characterization of the Photodynamic Spiropyran-Zinc Complexes.

Thermal and photoinduced processes accompanying complexation of photochromic spiropyrans (SPP) with Zn ions in acetone solution were characterized by means of UV-vis and X-ray absorption spectroscopies in operando regime. SPP ligands are usually transparent at λ > 350 nm, but after mixing with Zn ions, they produce a stable colored (ε = 32 000-38 000 M-1 cm-1) complex with maximum absorption at 525 nm, which makes them a powerful tool for monitoring metal-ion concentration in solution. The complex revealed fluorescence and photochromic behavior under static irradiation with visible light with constant photoreaction quantum yield across its characteristic absorption band. Zn K-edge X-ray absorption spectra show prominent changes in Zn local atomic structure between free Zn ions and Zn complex. The pump-flow-probe scheme was adapted to measure operando changes in Zn coordination upon light irradiation. Within experimental time resolution, we have determined that 20 μs after light irradiation, Zn ion is released out of the complex. This is the first example of the direct spectroscopic probe of the Zn photorelease from the spiropyran complex.

Lightweight SrM/CCTO/rGO nanocomposites for optoelectronics and Ku band microwave absorption

In this research, nanocomposites comprising M-type strontium hexaferrites (SrM) SrFe12−xCsxO19 (x = 0.0, 0.05, 0.10), calcium copper titanate (CCTO) CaCu3Ti4−yAlyO12 (y = 0.0, 0.1, 0.2) and reduced graphene oxide (rGO) have been prepared. XRD patterns shows the presence of single phase nanocrystalline SrM and CCTO which is further supported by Raman spectroscopy and FTIR analysis. The presence of secondary phase such as α-Fe2O3, CaTiO3, and CuO has not been observed. Characteristics absorption bands of Cs-substituted SrM and Al-substituted CCTO were observed at 446, 551 and 605 cm−1, these peaks gives the idea of the formation of SrM and CCTO phase. The D and G bands of GO were observed at 1358 and 1604 cm−1 respectively, while that of the rGO were respectively observed at 1351 and 1595 cm−1. FESEM micrograph show the incorporated SrM nanoparticles, CCTO nanoparticles and rGO sheets, reduction in surface energy and magnetic dipolar interaction prompt the SrM nanoparticles to surround the CCTO nanoparticles and decorate the surface of the rGO sheets. The non-magnetic CCTO phase in the nanocomposites causes the tuning of the magnetic properties. The band gap obtained from UV–vis NIR spectroscopy is within the range of UV-blue LED application. The sample SCR3 shows a maximum reflection loss of − 16.0 dB at 18.0 GHz and matching thickness of 2 mm. The obtained reflection loss is attributed to multiple absorption mechanism as a result of improved impedance matching between the dielectric and magnetic loss absorbents.

Growth of Gold Nanoparticles in a Glass Matrix by Continuous Laser Irradiation for Efficient Surface Enhanced Raman Scattering

The synthesis of a soda‐lime glass doped by gold nanoparticles (Nps) is achieved using successively thermal poling and continuous wave (cw) ultraviolet (UV) laser exposure. The formation of gold Nps is undoubtedly proved by an absorption band characteristic of their surface plasmon resonance (SPR), and by scanning electron microscopy, which reveals Nps of about 40 nm in diameter, located in the very near surface region of the glass. Absorption spectroscopy also suggests the formation of bimetallic silver‐gold Nps in systems prepared by using thermal poling and laser exposure of a glass previously doped by silver ions using ion exchange. Finally, the low detection limit of Rhodamine 6G (R6G) measured by surface‐enhanced Raman spectroscopy proves the potential of our gold‐doped glass as an efficient Raman substrate, which offers an alternative to silver Nps doped glass.