Transmission FTIR Research Articles

Chirally-Modified Graphite Oxide as Chirality Inducing Support for Asymmetric Epoxidation of Olefins with Grafted Manganese Porphyrin

A chirality inducer was prepared by graphite oxide (GO) functionalization with enantiopure l-tartrate (GO*) and used as asymmetric support for a covalently-linked manganese porphyrine complex [Mn(TPyP)OAc]. The thereby obtained heterogeneous catalyst, GO*-[Mn(TPyP)OAc], showed excellent performance and ee-values of 92–99% for the asymmetric epoxidation of prochiral olefins with O2 as oxidant and isobutyraldehyde as co-reductant in acetonitrile; linear terminal olefins with 54–76% conversion and quantitative conversion of aromatic olefins. The GO*-[Mn(TPyP)OAc] catalyst is highly active, recyclable, and at the same time simple and inexpensive to prepare with a chiral inducer from the chiral pool. The structure of the catalyst was elucidated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET analysis, FT-IR, Raman, and photoluminescence spectroscopic methods. Graphite oxide functionalized with an enantiopure group was used as a chirality inducer and asymmetric support for a Mn-porphyrine complex. The thereby obtained heterogeneous catalyst is an excellent enantioselective catalyst for the epoxidation of prochiral olefins.

Structural, optical and electrical properties of (CdS)1-x (ZnTe)x solid solution thin films prepared by vacuum thermal evaporation method

The II-VI compounds and their solid solutions are promising source for various types of thin film devices such as thin film transistors, optoelectronic devices and solar cells. The formation of (CdS)1−x(ZnTe)x layer by interdiffusion of CdS and ZnTe during the fabrication of CdS/ZnTe heterojunction thin film was previous reported. This layer is thought to be important because it relieves strain at the CdS/ZnTe interface that would otherwise exist due to the excess 10 % lattice mismatch between the two materials. Therefore, it is essential to have a full understanding of the physical properties of (CdS)1−x(ZnTe)x alloy thin films. In this work, (CdS)1−x(ZnTe)x thin films in the entire composition range (0≤x≤1.0) were prepared by vacuum thermal evaporation on glass substrate using mixed powders of high purity of CdS and ZnTe compounds as the precursor. XRD revealed that the films exhibited a hexagonal structure with the preferred orientation of (002) plane when x ≤ 0.2. However, when x ≥ 0.8, they belonged to a cubic structure with the preferred orientation of (111) plane. For the composition 0.4 ≤ x ≤0.6, the hexagonal and cubic phases coexisted in the system and the films became less preferentially oriented. SEM and EDS were used to study the surface morphology and elemental composition of the samples. The crystallite size of the as-deposited films in the range 88–361 nm was observed by AFM image. The FTIR transmission spectra in the range 400−1,000 cm−1 revealed the characteristics of Cd-S and Zn-Te vibrational modes. Optical properties of the films were performed with UV-Vis spectrophotometer in the wavelength range 400−1,000 nm. The variation of direct energy gap with composition (x) was in good agreement with the quadratic form, giving an upward bowing parameter (b) of 1.23 eV. Electrical properties of the films were evaluated by resistivity and Hall effect measurements in the van der Pauw configuration. From transient photoconductivity measurement, the decay current data were better fitted with multiple exponential functions resulting in the several slow decay times. Density of trap states corresponding to its decay time was also evaluated from the decay current data.

MCM-41 mesoporous silica anoparticles and their adsorption for targeting drug delivery systems

MCM-41 mesoporous silica nanoparticles were successfully synthesized by the condensation of tetraorthosilicate precursor (TEOS) using cetyltrimethylammonium bromide (CTAB) as the orientation substance in alkaline (pH = 9–12), deionized water as solvent. The samples were calcinated at 550°C for 5 hours. The structural characteristics of samples were analyzed by using Small angle X-ray diffraction, transmission electron microscopy (TEM), FT-IR and isothermal adsorption of nitrogen. Optimizing the fabrication parameters, MCM-41 particles have been obtained with a spherical shape, size of 80-140 nm, pore diameter of 2–5 nm and surface area (BET) of 986,683 m2g-1. Rhodamine B adsorption of MCM-41 showed that the maximum adsorption capacity value was 299,696 mg/g, suggesting the potential of this material to design of controlled drug delivery systems.

Anti-betanodavirus activity of isoprinosine and improved efficacy using carbon nanotubes based drug delivery system

Viral nervous necrosis (VNN) disease has caused mass mortality in cultured marine and freshwater fish worldwide, resulting in enormous economic losses in the aquaculture industry. The causative agent of VNN is betanodavirus [also known as nervous necrosis virus (NNV)], which classified as a member of the Nodaviridae family. NNV mainly infects the central nervous system (CNS) of hosts, which is protected by an elaborate barrier system, limiting the number of drugs reaching the infected sites to tackle the infections. Therefore, it is important to develop alternative drugs and smart delivery technologies for treatment the NNV infection. In the study, the anti-NNV activity of an immunomodulatory antiviral drug, isoprinosine, was checked both in vitro and in vivo. Besides, single-walled carbon nanotubes (SWCNTs) were used as a carrier to improve the anti-NNV activity. Results showed that isoprinosine could effective protect SSN-1 cell from NNV infection, and the percentage of apoptosis was significantly decreased following isoprinosine treatment. Similarly, isoprinosine also showed a strong anti-NNV activity in zebrafish, and the IC50 (inhibitory concentration at half-maximal activity) values were 86.44 and 52.47 mg/L after exposure to isoprinosine for 3 and 5 days, respectively. The expression levels of IL-1β, IFN-γ and TNF-α were up-regulated following isoprinosine treatment, indicating that isoprinosine can improve the immune responses to against NNV infection. A smart delivery system (named as SWCNTs-I) based on SWCNTs, bovine serum albumin (BSA) and isoprinosine was constructed and characterized by transmission electron microscope, FTIR spectroscopy and UV–vis spectroscopy. SWCNTs-I was internalized inside the SSN-1 cells, and showed a systemic distribution in the zebrafish larvae. SWCNTs-I has a stronger anti-NNV activity than naked isoprinosine, and the mortality of larvae treated with SWCNTs-I was 39.3% during 7 days post infection, while that were 96.7% and 58% for the control and naked isoprinosine treatment groups, respectively. Results so far indicated that isoprinosine is a powerful anti-NNV drug, and drug delivery with SWCNTs has a potential application value to control fish viral diseases in aquaculture.

Liquid Phase Exfoliation of Two-Dimensional Materials for Sensors and Photocatalysis-A Review.

Two-dimensional (2D) materials have rewritten many disciplines of modern science and technology, both through intensive fundamental research. In this review, we will provide a comprehensive summary of the properties, synthesis, characterization, and application of 2D materials (Graphene, Hexagonal boron nitride (h-BN) and transition dichalcogenide (TMD'S) in the context of electrochemistry and related scientific fields. 2D material nanosheets have been characterized by using different techniques such as X-ray diffraction, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-Visible Spectroscopy, FT-IR Spectroscopy and Atomic Force Microscopy. 2D materials application revealed photo catalysis and sensors. Bottom-up approach and top-down methods have been proposed for exfoliation of layered materials. Graphene synthesis by chemical vapor deposition and transfer by roll-to-roll process or top-down method. Firstly, the structural, electronic, optical, and physical and chemical properties, and a variety of synthesis and characterization techniques of 2D materials are presented. Manganese dioxides (crystalline material) are significantly affected by the surface area, crystallographic structure and morphology, and synthetic route of production. Secondly, current electrochemical understanding of 2D and layered materials and their modification is discussed. Although broad in scope, this review is not an exhaustive list of facts; rather, it summarizes the established knowledge and pinpoints the most promising future trends.

Room temperature fiber optic gas sensor technology based on nanocrystalline Ba3 (VO4)2: Design, spectral and surface science

Large yields of barium vanadium oxide nanopowder were obtained by surfactant mediated solution combustion method. The structural characterization and morphological studies were done by X-ray diffraction, scanning electron microscope, transmission electron microscope, FT-IR spectra and diffuse reflectance spectra (DRS). The fiber optic gas sensing properties of the synthesized nanomaterial were tested with volatile organic compounds (VOCs) such as, ammonia, acetone, methanol and ethanol. The results reveal that nanocrystalline Ba3(VO4)2 has the highest sensitivity to ammonia and ethanol with a fast response and a recovery time of 52 and 61.5 min, respectively.

Radiolabeling of amide functionalized multi-walled carbon nanotubes for bioaccumulation study in fish bone using whole-body autoradiography

Commercial and medicinal applications of functionalized carbon nanotubes (f-CNTs) such as amidated f-CNTs are expanding rapidly with a potential risk exposure to living organisms. The effects of amidated f-CNTs on aquatic species have received a limited attention. In this work, an easy wet method to prepare [14C]-label amide multi-walled carbon nanotubes (MWNTs) is reported. Labeled carbon nanotubes were prepared by successive reactions of carboxylation, chloroacylation, and final amidation using [14C]-labeled ethanolamine. The f-CNTs were characterized using elemental analysis, electron dispersive X-ray, transmission electron microscopy, thermogravimetric analysis, and Raman and FTIR spectroscopy. An uptake experiment was carried out with juvenile Arctic char (Salvelinus alpinus) using water dispersed amidated [14C]-f-CNTs to assess their biodistribution in fish tissues using whole body autoradiography. The radioactivity pattern observed in fish head suggests that f-CNTs were accumulated in head bone canals, possibly involving an interaction with mineral or organic phases of bones such as calcium and collagen. This f-CNTs distribution illustrates how important is to consider the surface charges of functionalized carbon nanotubes in ecotoxicological studies.

Morphological/SAXS/WAXS studies on the electrochemical synthesis of graphene nanoplatelets

Recently, graphene owing to its outstanding properties such as high mechanical strength, high thermal and electrical conductivity has been introduced as a surprising material for various applications. Up to now, the introduced methods mostly have some disadvantageous, especially in term of efficiency. Electrochemical exfoliation of graphite is a cost-effective, fast and environmentally friendly method for the synthesis of graphene nanoplatelets (GNPs). Based on this fact that the properties of GNPs are greatly depend on their morphology, the aim of this study was to evaluate the morphology of the obtained powders after electrochemical exfoliation of graphite by scanning electron microscopy. In this work, the mixture of H2SO4 + NaOH + H2O2 was used as the electrolyte. Effects of three concentrations of H2SO4 on the morphology of the obtained powders was examined. After determining the optimum sample, the analyses of transmission electron microscopy, X-ray diffraction, Raman spectroscopy and FTIR were used to characterize the produced GNPs by this method. Further characterization on the optimized sample was carried out by synchrotron small and wide angle X-ray scattering (SAXS/WAXS) to understand the shape and fractality of particles which have been confirmed to the initial results. Results indicated that based on electrolyte type and concentration of H2SO4, different kinds of carbon allotropes such as expanded graphite, multi-layered GNPs and few-layered GNPs can be obtained. Results showed the efficiency of the electrochemical method was increased with decreasing the concentration of the H2SO4; the few-layered GNPs were obtained using the lowest concentration of H2SO4.

A Powerful Nanocomposite Polymer Prepared From Metal Oxide Nanoparticles Synthesized via Brown Algae as Anti-corrosion and Anti-biofilm

The chemical/microbial bio-corrosion in water pipelines are the most common problem in industry worldwide which cause damage to expensive equipment and increases the maintenance costs. In this work, the green synthesis of nanocomposite was synthesized using brown algae (Sargassum muticum) extract. This method is eco-friendly and non-toxic. The synthesized nanocomposite was characterized using UV–vis spectroscopy, Dynamic light scattering (DLS), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and FTIR analysis. The size of ZnO and CuO nanoparticles was reduced to 15nm and 20 nm respectively, after exposure to 60Co gamma-ray irradiation. The nanocomposite showed significant P-value (P<0.001) as a biofilm inhibitor and anti-adherence for Proteus mirabilis, Pseudomonas aeruginosa and Staphylococcus aureus, which were represented bio-corrosion index. The results of weight loss method showed that Proteus mirabilis caused the highest bio-corrosion rate (1.5 mpy) on mild steel coupon as examined by SEM. The nanocomposite prevented the adhesion of biofilm bacteria to carbon mild steel coupon which was confirmed by SEM examination. Finally, the nanocomposite showed highest anti-corrosion efficacy in 1M HCl at 150 ppm with high anti-corrosion efficiency (92.3%). The results of this study concludes that the green synthesized nanocomposite has multi-function to be used as anti-bacterial, anti-biofilm, anti-corrosion and anti-bio corrosion.

Defining α-synuclein species responsible for Parkinson’s disease phenotypes in mice

Parkinson's disease (PD) is a neurodegenerative disorder characterized by fibrillar neuronal inclusions composed of aggregated α-synuclein (α-syn). These inclusions are associated with behavioral and pathological PD phenotypes. One strategy for therapeutic interventions is to prevent the formation of these inclusions to halt disease progression. α-Synuclein exists in multiple structural forms, including disordered, nonamyloid oligomers, ordered amyloid oligomers, and fibrils. It is critical to understand which conformers contribute to specific PD phenotypes. Here, we utilized a mouse model to explore the pathological effects of stable β-amyloid-sheet oligomers compared with those of fibrillar α-synuclein. We biophysically characterized these species with transmission EM, atomic-force microscopy, CD spectroscopy, FTIR spectroscopy, analytical ultracentrifugation, and thioflavin T assays. We then injected these different α-synuclein forms into the mouse striatum to determine their ability to induce PD-related phenotypes. We found that β-sheet oligomers produce a small but significant loss of dopamine neurons in the substantia nigra pars compacta (SNc). Injection of small β-sheet fibril fragments, however, produced the most robust phenotypes, including reduction of striatal dopamine terminals, SNc loss of dopamine neurons, and motor-behavior defects. We conclude that although the β-sheet oligomers cause some toxicity, the potent effects of the short fibrillar fragments can be attributed to their ability to recruit monomeric α-synuclein and spread in vivo and hence contribute to the development of PD-like phenotypes. These results suggest that strategies to reduce the formation and propagation of β-sheet fibrillar species could be an important route for therapeutic intervention in PD and related disorders.

Iron-containing magnetic nanocomposites based on polyphenoxazine

Hybrid iron-containing nanocomposite materials based on polyphenoxazine (PPOA) were synthesized for the first time via chemical transformations of PPOA in the presence of iron(III) salt (FeCl3·6H2O, Fe(NO3)3·6H2O or Fe(CH3COCH=C(CH3)O)3) in an inert atmosphere under IR radiation in the temperature range of 350–600 °С. The developed hybrid nanocomposites were characterized by means of FTIR spectroscopy, X-ray diffraction (XRD), transmission (TEM) and scanning (SEM) electron microscopy, X-Ray fluorescence spectroscopy (XRF), Inductively coupled plasma atomic emission spectroscopy (ICP-AES), atomic absorption spectrometry (AAS), elemental analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and magnetometry. The dependence of phase composition, magnetic and thermal properties of hybrid nanocomposites, as well as the size and shape of nanoparticles on synthesis temperature, Fe concentration and the nature of iron(III) salt was demonstrated.

Synthesis and characterization of a novel hydride polymer P-DSBT/ZnO nano-composite for optoelectronic applications

This paper presents the effect of nanoparticle concentration on the performance of hybrid polymer (P-DSBT)/Zinc Oxide (ZnO) thin layers. For studying the morphology, the structure and the optical behavior of the different synthesized nanocomposites, FTIR transmission spectra, scanning electron microscopy (SEM), Transmission electron microscopy, and X-ray diffractometry (XRD) were used to characterize ZnO nanostructures, atomic force microscopy, UV–Vis absorption, photoluminescence spectroscopies and contact angle measurement were used to characterize (P-DSBT)/Zinc Oxide (ZnO) nanocomposites. It has been shown that the RMS (Root Mean Square) roughness of the hybrid layers increases as a function of the percentages of ZnO in the matrix. A clear participation of nanoparticles in the nanocomposites absorption has been demonstrated in UV–Vis spectra with maintaining the absorption features of the polymer. A photoluminescence study at room temperature was been also carried out under optical excitation set as λ = 375 nm. It was confirmed that when increasing the ZnO concentration in the polymer, a shift towards red was observed and the contact angle of the composite layers decreases progressively comparing with the pure polymer. Interestingly, this confirms that polymer and polymer–ZnO hybrid nanocomposites are well adherent to the contaminated free solid surface.

Decorating untreated carbon nanotubes with Fe3O4@SiO2 nanoparticles and its microwave absorption property

In order to decorate carbon nanotubes, we must pass through the functionalization stage. Acid treatment is a common method of modifying the surface of carbon nanotubes to make them suitable for accepting other nano-objects. Since, acidic functionalization of carbon nanotubes creates many defects in its structure, leads to lose most of their superior physical properties such as thermal conductivity, electrical conductivity and mechanical strength. On another hand, untreated multi-walled carbon nanotubes (UTCNTs) have a weak ability to be decorated with other nanomaterials due to the absence of a sufficient amount of functional groups. Therefore, it is very important to plan some strategy to solve this problem. Here, we propose a new approach to decorate non-functionalized carbon nanotubes by magnetic attraction. First, UTCNTs are decorated by small amounts of Fe3O4 nanoparticles (Fe3O4-UTCNTs). Next, the magnetically modified MWCNTs (Fe3O4-UTCNTs) are decorated by Fe3O4@SiO2 core-shell nanoparticles via magnetic attraction between these two magnetic components (Fe3O4-UTCNTs and Fe3O4@SiO2). We prepared three Fe3O4@SiO2/Fe3O4-UTCNTs samples with different weight ratios of Fe3O4-UTCNTs to Fe3O4@SiO2 core-shell nanoparticles, named S1 [1:0.5], S2 [1:1], and S3 [1:2.5]. The saturation magnetization of S1, S2 and S3 are 35.27, 44.45 and 57.68 emu/g, respectively. All samples which were characterized by FT-IR spectroscopy, X-Ray diffraction, scanning and transmission electron microscopy, applied as a microwave absorber. After measuring the electromagnetic parameters of each sample and calculating their reflection losses (RLs), we found that all samples exhibit strong RLs (between −33 and −50 dB) and wide absorption bands (between 7.2 and 8.1 GHz), with low thicknesses of 1–3 mm, at the range of 2–12 and 8–12 GHz. The results also show that, by increasing the weight ratio of Fe3O4@SiO2 core-shell in the composite, the minimum RL increases for some thicknesses of samples, while the absorption band widths are broadened for all thicknesses.

Investigation of the densification mechanisms and corrosion resistance of amorphous silica films

The barrier properties of the technologically attractive amorphous silica films depend on their structural characteristics at the atomic level, which, in turn are strongly influenced by the deposition conditions. In this paper, we propose an investigation of the poorly investigated densification mechanism of amorphous SiO2 films processed by CVD from TEOS and O2 between 400 and 550 °C. Based on literature survey and our original experimental results, we show that the densification process of these films, occurring with increasing the deposition temperature, is highlighted by a decrease of the water and silanol content, probed by transmission FTIR. We discuss the evolution of Si-O-Si related vibration signatures and we use the central force model to correlate the LO2 and LO3 shifts with the decrease of the Si-O-Si bond force constant, when the deposition temperature increases. Nuclear analysis reveals that films processed below 525 °C present hydrogen content between 5 ± 0.3 and 7 ± 0.3%at. Ellipsometry measurements attest that films processed at 550 °C are close to O/Si silica stoichiometry and hydrogen free. We show that application of the P-etch test results in particularly low erosion rate of 10 Å.s−1 for dense films processed at 550 °C.

Efficacy of Concanavalin-A conjugated nanotransfersomal gel of apigenin for enhanced targeted delivery of UV induced skin malignant melanoma

The aim of present study was to develop the efficient targeting of Concanavalin-A conjugated nanotransfersomal gel to bind directly to melanocytes gel layer against UVB induced skin carcinoma. Carbopol loaded nanotransfersomal gel have prepared by modified rotary evaporation sonication technique & conjugated synthesized by carbodiimide method and they were characterized the morphology, zeta potential, penetration and cell viability. In vitro release studies & skin permeation have determined using Franz diffusion cell and confocal laser scanning microscope (CLSM). The conjugated formulation showed vesicles size, polydispersity index, zeta potential and % conjugation efficiency of 179.0 ± 0.32 nm, 0.197 ± 0.07, 35.1 ± 0.21 mV and 89.73 ± 1.29% respectively. The surface morphology was confirmed by transmission electron microscopy (TEM) and FTIR to make sure the compatibility among its ingredients. Con-A conjugated nanotransfersomal gel showed toxicity on melanoma (A375) in a concentration range of 0.4–2.0 mg/mL, but less toxicity toward HaCaT cells. The MTT assay has analyzed against two different cell lines, to determine their anti-cancer potentials and their targeting ability. Conjugated formulation were found to decrease the cell viability, higher skin targeting efficacy in in-vitro & in-vivo. Concanavalin conjugated nanotransfersomal gel of apigenin promise an efficient and economic approach for the skin cancer.

Catalytic and antibacterial properties of gold nanoparticles synthesized by a green approach for bioremediation applications.

In this work, we are proposing the green synthesis of gold nanoparticles (AuNPs) using aqueous extracts of A. triphylla and evaluating their antibacterial and catalytic properties. Characterization was performed by UV-Vis and FT-IR spectroscopies, X-ray diffraction, and transmission electron microscopy (TEM). Antibacterial activity of AuNPs was analyzed using E. coli and S. Aureus and catalytic activity was determined by the degradation of methylene blue and congo red. UV-Vis analysis showed an increase in AuNPs concentration by increasing the extract concentration, volume extract, and precursor salt concentration. The crystalline nature of AuNPs was corroborated by X-ray diffraction. TEM analysisshowed nanoparticles with spherical morphology (mostly) and size between 40 and 60nm. These results are novel because they showed a homogeneous morphology and a narrow size distribution which is difficult to obtain in green synthesis processes. Results of antibacterial activity showed inhibition zones of 11.3mm and 10.6mm for S. Aureus and E. coli, respectively, indicating the bactericidal capacity of the nanoparticles. The degradation periods for methylene blue and congo red were 5 and 11min, respectively, which are very short compared with previous reports. These results are of great significance for catalytic applications. Therefore, A. triphylla extracts made possible AuNPs synthesis and the nanoparticles obtained can be used as catalytic and antibacterial materials for water remediation.

Ultrasound assisted dispersive solid phase extraction of triazole fungicides by using an N-heterocyclic carbene copper complex supported on ionic liquid-modified graphene oxide as a sorbent.

An ultrasound-assisted method is described for dispersive solid phase extraction of trace levels of triazole fungicides. A sorbent was prepared from an N-heterocyclic carbene copper complex that was supported on ionic liquid-modified graphene oxide. The sorbent was characterized by scanning electron microscopy, transmission electron microscopy, Raman and FT-IR spectroscopy, energy-dispersive X-ray spectroscopy and elemental mapping. The capability of sorption and extraction is mainly based on complexation with Cu (I) ions. The variables affecting extraction were optimized. Following desorption with ethanol, the fungicides were quantified by corona discharge ion mobility spectrometry. Under optimized conditions (solution pH value: 7.0; amount of sorbent: 10mg; extraction time: 3min; desorption agent: ethanol), the technique provides good linearity (>0.994), repeatability (RSD < 4.1%), low limits of detection (0.18ng.mL-1), excellent preconcentration factors (468-476) and high recoveries from spiked environmental water samples (92-94%). The sorbent can be reused over five cycles without significant loss of its activity. Graphical abstract Schematic presentation of design and synthesis of the N-heterocyclic carbene copper complex supported on ionic liquid-modified graphene oxide as a sorbent for triazole fungicides and its application in ultrasound-assisted dispersive solid phase extraction with ion mobility spectrometric detection.

Structural, Optical and Electrical Properties of MnO2 / MWCNTs/PVA Nanocomposite

Manganese dioxide/multi-walled carbon nanotubes MnO2/ MWCNTs nanocomposite are synthesized by hydrothermal method. The crystallographic information of the acid-treated MWCNTs and the MnO2/ modified MWCNTs nanocomposite were characterized by X-ray diffraction (XRD),Transmission electron microscope (TEM )and FT-IR spectra. Optical and electrical properties of MnO2 / MWCNTs / PVA nanocomposite thin film with different concentration were studied .UV-VIS absorption spectra shift, at different exposing time , indicated the sensitivity to UV radiation. Optical band gap decreases with increasing time of radiation. Electrical properties of MnO2 / MWCNTs / PVA nanocomposite thin films with different concentration according to different frequency and exposing time of UV radiation showed semiconducting properties and sensitivity to UV radiation.

Water adsorption and hygroscopic growth of six anemophilous pollen species: the effect of temperature

Abstract. Hygroscopicity largely affects environmental and climatic impacts of pollen grains, one important type of primary biological aerosol particles in the troposphere. However, our knowledge of pollen hygroscopicity is rather limited, and the effect of temperature in particular has rarely been explored before. In this work three different techniques, including a vapor sorption analyzer, diffusion reflectance infrared Fourier transform spectroscopy (DRIFTS) and transmission Fourier transform infrared spectroscopy (transmission FTIR) were employed to characterize six anemophilous pollen species and to investigate their hygroscopic properties as a function of relative humidity (RH, up to 95 %) and temperature (5 or 15, 25 and 37 ∘C). Substantial mass increase due to water uptake was observed for all the six pollen species, and at 25 ∘C the relative mass increase at 90 % RH, when compared to that at &lt;1 % RH, ranged from ∼30 % to ∼50 %, varying with pollen species. It was found that the modified κ-Köhler equation can well approximate mass hygroscopic growth of all the six pollen species, and the single hygroscopicity parameter (κ) was determined to be in the range of 0.034±0.001 to 0.061±0.007 at 25 ∘C. In situ DRIFTS measurements suggested that water adsorption by pollen species was mainly contributed to by OH groups of organic compounds they contained, and good correlations were indeed found between hygroscopicity of pollen species and the number of OH groups, as determined using transmission FTIR. An increase in temperature would in general lead to a decrease in hygroscopicity, except for pecan pollen. For example, κ values decreased from 0.073±0.006 at 5 ∘C to 0.061±0.007 at 25 ∘C and to 0.057±0.004 at 37 ∘C for Populus tremuloides pollen, and decreased from 0.060±0.001 at 15 ∘C to 0.054±0.001 at 25 ∘C and 0.050±0.002 at 37 ∘C for paper mulberry pollen.

Scaling up of levan yield in Bacillus subtilis M and cytotoxicity study on levan and its derivatives

This study focused on kinetics of levan yield by Bacillus subtilis M, in a 150L stirred tank bioreactor under controlled pH conditions. The optimized production medium was composed of (g/L): commercial sucrose 100.0, yeast extract 2.0, K2HPO4 3.0 and MgSO4⋅7H2O 0.2; an increase in both carbohydrates consumption and cell growth depended on increasing the size of the stirred tank bioreactor from 16L to 150L. The highest levansucrase production (63.4 U/mL) and levan yield of 47g/L was obtained after 24h. Also, the specific levan yield (Yp/x) which reflects the cell productivity increased with the size increase of the stirred tank bioreactor and reached its maximum value of about 29.4g/g cells. These results suggested that B.subtilis M could play an important role in levan yield on a large scale in the future. Chemical modifications of B.subtilis M crude levan (CL) into sulfated (SL), phosphorylated (PL), and carboxymethylated levans (CML) were done. The difference in CL structure and its derivatives was detected by FT-IR transmission spectrum. The cytotoxicity of CL and its derivatives were evaluated by HepGII, Mcf-7 and CaCo-2. In general most tested levans forms had no significant cytotoxicity effect. In fact, the carboxymethylated and phosphrylated forms had a lower anti-cancer effect than CL. On the other hand, SL had the highest cytotoxicity showing SL had a significant anti-cancer effect. The results of cytotoxicity and cell viability were statistically analyzed using three-way ANOVA.