This study was performed to determine the potential of tropical intertidal biofilm bacteria as a source of novel exopolymers (EPS). A screening procedure was implemented to detect EPS-producing ...biofilm bacteria. Isolates MC3B-10 and MC6B-22, identified respectively as a Microbacterium species and Bacillus species by 16S rDNA and cellular fatty acids analyses, produced different EPS, as evidenced by colorimetric and gas chromatographic analyses. The polymer produced by isolate MC3B-10 displays significant surfactant activity, and may chelate calcium as evidenced by spectroscopic analysis. Polymer MC3B-10 appears to be a glycoprotein, while EPS MC6B-22 seems to be a true polysaccharide dominated by neutral sugars but with significant concentrations of uronic acids and hexosamines. EPS MC3B-10 possesses a higher surfactant activity than that of commercial surfactants, and given its anionic nature, may chelate cations thus proving useful in bioremediation. The chemical composition of polymer MC6B-22 suggests its potential biomedical application in tissue regeneration. This is the first report of a Microbacterium species producing EPS with surfactant properties, which expands our knowledge of the micro-organisms capable of producing these biomolecules. Furthermore, this work shows that tropical intertidal environments are a nonpreviously recognized habitat for bioprospecting EPS-producing bacteria, and that these molecules might be involved in ecological roles protecting the cells against dessication.
In this study, BiVO
4
particles were synthesized via the combustion method using orange peel powder as a fuel for photocatalytic methylene blue (MB) degradation. The novelty lies in using biomass as ...a fuel source and leveraging orange peel phytochemicals as stabilizing and complexing agents, eliminating the need for nitric acid required in conventional methods. XRD patterns showed that the orange peel promotes ternary phase formation (Dreyerite and Clinobisvanite phases), while urea supports the binary and ternary phase combination (i.e., V
6
O
13
and BiVO
4
). Raman, XPS, and FTIR analyses confirmed the BiVO
4
monoclinic phase formation using both fuels, with a band gap of approximately 2.4 eV. Increasing annealing temperature reduced structural disorder, V–O bond length, and surface area, which are more pronounced with orange peel. Photocatalytic experiments revealed the significant MB removal by adsorption with urea, while orange peel primarily drove photocatalysis in both cases, following a pseudo-first-order kinetic model. Scavenger experiments showed holes as the main reactive species promoting MB degradation. With a rise in catalyst dosage, removal is primarily enhanced through adsorption, confirmed by dark condition experiments. The BiVO
4
sample annealed at 350 ºC with orange peel fuel exhibited the best photocatalytic performance that can completely remove MB after 270 min under 200 W LED light.
In the present work, the photocatalytic efficiency of a novel system based on ZnO doped with nitrogen (ZT) and supported on graphene oxide (GO) is investigated. ZnO synthesis and their N doping were ...carried out in a microwave reactor using thiourea as nitrogen source, while the GO was prepared through a variation of the Hummers' method. Structural, morphological and photochemical characterization of the developed material was performed by X-ray diffraction (XRD), UV–Vis spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), analysis by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The compounds were used to photodegrade the methylene blue molecule, which confirms the efficiency of nitrogen doped supported system compared to pristine ZnO. The degradation percentage of MB under UV energy using nitrogen-doped ZnO/GO, in a time of 35 min, reached 98% degradation; while using visible light 93% of degradation was reached.
•N–ZnO/GO structures achieves high photocatalytic performance for MB degradation.•Nitrogen doping is efficiently carried out through thiourea and microwave heating.•GO in N–ZnO/GO systems acts as a collector and electron transporter preventing their recombination.
•Single phase CZTS thin films grown using a novel procedure.•Structural characterization through XRD and Raman measurements.•Determination of elemental composition through XPS analysis.•Stoichiometry ...of S:Sn:Zn:Cu=4.07:0.97:0.95:2.03 close to that of Cu2ZnSnS4.
This work describes a procedure to grow single phase Cu2ZnSnS4 (CZTS) thin films with tetragonal-kesterite type structure, through sequential evaporation of the elemental metallic precursors under sulphur vapor supplied from an effusion cell. X-ray diffraction analysis (XRD) is mostly used for phase identification but cannot clearly distinguish the formation of secondary phases such as Cu2SnS3 (CTS) because both compounds have the same diffraction pattern; therefore the use of a complementary technique is needed. Raman scattering analysis was used to distinguish these phases.
The influence of the preparation conditions on the morphology and phases present in CZTS thin films were investigated through measurements of scanning electron microscopy (SEM) and XRD, respectively. From transmittance measurements, the energy band gap of the CZTS films was estimated to be around 1.45eV. The limitation of XRD to identify some of the remaining phases after the growth process are investigated and the results of Raman analysis on the phases formed in samples grown by this method are presented. Further, the influence of the preparation conditions on the homogeneity of the chemical composition in the volume was studied by X-ray photoelectron spectroscopy (XPS) analysis.
Biodegradable segmented polyurethanes (BSPUs) were prepared with poly(caprolactone) as a soft segment, 4,4′-methylene bis (cyclohexyl isocyanate) and either butanediol (BSPU1) or dithioerythritol ...(BSPU2) as a chain extender. BSPU samples were characterized in terms of their physicochemical properties and their hemocompatibility. Polymers were then degraded in acidic (HCl 2
N), alkaline (NaOH 5
M) and oxidative (H
2O
2 30
wt.%) media and characterized by their mass loss, Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Undegraded BSPU1 and BSPU2 exhibited different properties, such as the glass transition temperature
T
g of the soft segment (−25 vs. 4
°C), mechanical properties (600% vs. 900% strain to break) and blood coagulating properties (clotting time
=
11.46 vs. 8.13
min). After acidic and alkaline degradation, the disappearance of the 1728
cm
−1 band of polycaprolactone (PCL) on both types of BSPU was detected by FTIR. However, the oxidative environment did not affect the soft segment severely as the presence of PCL crystalline domains were observed both by DSC (melting temperature
T
m
=
52.8
°C) and XRD (2
θ
=
21.3° and 23.7°). By TGA three decomposition temperatures were recorded for both BSPU samples, but the higher decomposition temperature was enhanced after acidic and alkaline degradation. The formation of the porous structure on BSPU1 was observed by SEM, while a granular surface was observed on BSPU2 after alkaline degradation.
Microwave hydrothermal synthesis, using an experimental 2
3
factorial design, was used to produce tunable ZnO nano- and microstructures, and their potential as photocatalysts was explored. ...Photocatalytic reactions were conducted in a microreactor batch system under UV and visible light irradiation, while monitoring methylene blue degradation, as a model system. The variables considered in the microwave reactor to produce ZnO nano- or microstructures, were time, NaOH concentration and synthesis temperature. It was found that, specific surface area and volume/surface area ratio were affected as a consequence of the synthesis conditions. In the second stage, the samples were plasma treated in a nitrogen atmosphere, with the purpose of introducing nitrogen into the ZnO crystalline structure. The central idea is to induce changes in the material structure as well as in its optical absorption, to make the plasma-treated material useful as photocatalyst in the visible region of the electromagnetic spectrum. Pristine ZnO and nitrogen-doped ZnO compounds were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET), XPS, and UV–Vis diffuse reflectance spectroscopy. The results show that the methodology presented in this work is effective in tailoring the specific surface area of the ZnO compounds and incorporation of nitrogen into their structure, factors which in turn, affect its photocatalytic behavior.
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•N-ZnO/GO achieved high photocatalytic performance for lignin degradation.•N-doping was efficiently carried out using ethylenediamine, urea or thiourea.•GO in N-ZnO/GO acts as ...electron transporter preventing recombination.
The present work reports the results of the lignin molecule degradation studies using nitrogen-doped ZnO photocatalysts supported on graphene oxide. Three different nitrogen precursors were used to achieve the nitrogen doping in ZnO, namely urea, ethylenediamine, and thiourea, using a microwave-assisted hydrothermal method. Our purpose is to demonstrate that different nitrogen precursors give rise to different amounts of doping in ZnO, which in turn, favorably affects their photocatalytic behavior. The synthesized compounds were tested on the lignin degradation reaction, under visible (Vis) and ultraviolet (UV) energy irradiation. Structural and physicochemical properties of prepared samples were investigated to provide explanation of the photocatalytic behavior observed in samples. XPS analyses were developed to determine differences in nitrogen content, as well to determine the proportion of N-N or O-Z-N binding in samples. Remarkable structural and photocatalytic differences were found for every sample as effect of the nitrogen precursor. Photocatalytic activity tests revealed that the percentage of lignin degradation under UV irradiation was 80 %; while using Vis energy the degradation value was 61 %.
The United Nations Organization (UNO) has revealed that approximately 2.1 billion people do not have access to treated water. Methylene blue (MB) and rhodamine B are produced as water pollutants in ...textile, plastic, and dye industries. In this study, oxalic acid or lactic acid surface-modification were applied to TiO2/ZnO nanoparticles aiming to improve antibacterial and adsorption properties. The mixtures containing the corresponding acid and nanoparticles in 0.25 : 1/0.5 : 1 ratios of ZnO and TiO2 correspondingly were subjected to ultrasonic treatment with a catenoidal ultrasonic probe coupled to a homemade ultrasonic generator with an output power of 750 W, wave amplitude of 50% and variable frequency in the range of 15–50 kHz. To verify the influence of the ultrasonic treatment, different treatment times of 30, 45, 60, and 90 min were applied. Unmodified and modified TiO2/ZnO nanoparticles were characterized by FTIR, TGA, XRD, SEM, and XPS. From the results, obtained from the physicochemical characterization, in the ZTO90 and ZTL90 samples a greater modification was shown. The SEM images showed that a coating was present on the surface of the ceramic particles of the ZTL90 sample. The O 1s deconvolution in the XPS spectra indicates a greater presence of C=O bonds in the ZTL90 sample. In parallel, the sample ZTL90 presented 85 and 89% adsorption efficiency for MB and rhodamine B dyes in a time of 12 min, and important antibacterial activity against E. coli and S. epidermis could be evidenced.
Control of the recombination process and improvement of transport charge carriers could be achieved in photocatalysts by modifying the catalytic support. In the present study, our goal was to study ...the effect of nitrogen doping on graphene oxide sheets using doping sources such as urea, thiourea, or ethylenediamine to produce GO-N catalytic supports which were used to form ZnO/GO-N systems. The synthesis of ZnO and GO-N was carried out through a hydrothermal process under microwave heating. The ZnO/GO-N compounds were tested to study the degradation of the lignin molecule under UV irradiation. A set of characterization techniques were used to study the ZnO/GO-N compounds, including XPS analyses which confirmed the N-doping in the samples. The ZnO compound reached 40% of lignin degradation in 70 min, while the ZnO/GO-N compound produced 79% of lignin degradation, also in 70 min evidencing the positive effect of the GO-N support. The best results of degradation were obtained when thiourea was used as the N-doping media.
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