Size Distribution In Solution Research Articles

Synthesis and characterization of graphene oxide and graphene from coal

The present research work deals with the synthesis and characterization of the graphene oxide (GO) and graphene from coal as a precursor material. First, the collected coal was dried and converted into the finely powder forms using ball milling process. The GO was synthesized from the coal by means of strong oxidizing agents and it was further reduced in the presence of chemical reagent (sodium borohydride) and plant origins (orange peel extract (OPE)) to produce graphene nanosheets. The Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-Visible (UV-Vis) spectroscopy, dynamic light scattering (DLS) analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), simultaneous thermogravimetry (TG) method with differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were studied to investigate the synthesis of graphene oxide (GO) and graphene and their nanostructure morphology, size distribution in solution along with thermal properties. The FTIR and UV-Vis spectroscopy established the formation of GO from coal, and DLS and SEM analysis further confirm the developed methodology for synthesis of the GO and graphene from coal resources. The XRD analysis established the successful synthesis of the GO from the coal. The TG method with DTA and DSC also verified the prepared GO and graphene. The methodologies implemented here for synthesis of the GO and subsequent graphene has fulfilled the objectives of the current research works.

Influence of Mixing Intensity on Lysozyme Crystallization in a Meso Oscillatory Flow Reactor

The influence of mixing intensity on protein crystallization has been investigated for the first time in a meso oscillatory flow reactor (meso-OFR). For this, lysozyme crystallization was studied in batch at different oscillation amplitudes and frequencies. Turbidity was monitored over time to measure induction time and follow the crystallization process. Results suggest that the crystallization mechanism may be characterized by the occurrence of primary heterogeneous nucleation followed by attrition-induced secondary nucleation. Results also evidence the nonmonotonic dependence of both induction time and mean crystal size on mixing intensity. Indeed, results show that the two parameters decrease with increasing mixing intensity at Reo below 189, while for further increase of Reo both remain almost constant. Based on the literature, we suggest that such behavior may be explained by the influence of mixing intensity on protein clusters size distribution in solution. Further, induction time and mean crystal...

Effect of cryoconcentration, reverse osmosis and vacuum evaporation as concentration step of skim milk prior to drying on the powder properties

Skim milk was concentrated by cryoconcentration (CC), reverse osmosis (RO) and vacuum evaporation (VE), and the concentrated milks were spray-dried. The powder morphology and shape were observed by electron microscopy and the mean size distribution by a sieve jet method. The resulting powders were reconstituted to 25% total dry matter (TDM) to carry out different measurements such as particle size distribution in solution, zeta-potential, heat stability, color, wettability, solubility and dispersibility. The surface of the particles was smooth with small amount of visible substructures on powder surface concentrated by VE and RO. The CC and RO corresponding powders have less particle fragments than VE powder. The mean particle size was larger for CC, followed by RO and VE powders. At the size of 250nm, the CC-powder occupied three times the volume (%) occupied by the RO-powder and the VE-powder. Analysis of reconstituted powders showed that the mean size distribution of casein micelles was found 190nm, 164 and 164nm for CC, RO and VE reconstituted powders, respectively. Moreover, it has been shown that RO and VE powder produced firm gels when heated whereas the CC powder presented flocs and weak gels. As it, all powders exhibited high solubility index (˃95%). However, depending on the size, the lowest solubility in water was observed at 75nm. Regarding the powder dispersibility, they presented a good dispersibility (<90%). The powders wettability was also size-dependent and was similar for all powders at a given particle size.

Novel Copper (Cu) Loaded Core–Shell Silica Nanoparticles with Improved Cu Bioavailability: Synthesis, Characterization and Study of Antibacterial Properties

We report synthesis of a novel core-shell silica based antimicrobial nanoparticles where the silica shell has been engineered to accommodate copper (Cu). Synthesis of the core-shell Cu-silica nanoparticle (C-S CuSiO2NP) involves preparation of base-hydrolyzed Stöber silica "seed" particles first, followed by the acid-catalyzed seeded growth of the Cu-silica shell layer around the core. The Scanning Electron Microscopy (SEM) and the Transmission Electron Microscopy (TEM) measured the seed particle size to be -380 nm and the shell thickness to be -35 nm. The SEM particle characterization confirms formation of highly monodispersed particles with smooth surface morphology. Characterization of particle size distribution in solution by Dynamic Light Scattering (DLS) technique was fairly consistent with the electron microscopy results. Loading of Cu to nanoparticles was confirmed by the SEM-Energy Dispersive X-Ray Spectroscopy (EDS) and Atomic Absorption Spectroscopy (AAS). The Cu loading was estimated to be 0.098 microg of metallic copper per mg of C-S CuSiO2NP material by the AAS technique. Antibacterial efficacy of C-S CuSiO2NP was evaluated against E. coli and B. subtilis using Cu hydroxide ("Insoluble" Cu compound, sub-micron size particles) as positive control and silica "seed" particles (without Cu loading) as negative control. Bacterial growth in solution was measured against different concentrations of C-S CuSiO2NP to determine the Minimum Inhibitory Concentration (MIC) value. The estimated MIC values were 2.4 microg metallic Cu/mL for both E. coli and B. subtilis. Bac-light fluorescence microscopy based assay was used to count relative population of the live and dead bacteria cells. Antibacterial study clearly shows that C-S CuSiO2NP is more effective than insoluble Cu hydroxide particles at equivalent metallic Cu concentration, suggesting improvement of Cu bioavailability (i.e., more soluble Cu) in C-SCuSiO2NP material due to its core-shell design.

Characteristics of Calcium Carbonate Crystal Structure and Size Distribution in Solution under the Electromagnetic Field

Various non-chemical water treatment methods have been utilized to solve fouling problems. All of these methods have never been scientifically proven to be a valid tool for controlling scales, and one of reasons could be the lack of understanding of the operational principle and treatment mechanisms. The present study focuses on characteristics of calcium carbonate crystal size distribution in solution and crystal structure on the surface under the electromagnetic field in order to comprehend the mechanisms of the Electromagnetic treatment device (ETD). An electromagnetic treatment setup was built for treating scaling water, and a series of fouling tests were carried out with and without ETD, analyzing the particles size distribution in solution by Dynamics Light Scattering (DLS) technology and making Scanning Electron Microscope (SEM) photos. The main results were as follows：The number of precipitate nucleation in solution was few and the particle growth was slow without ETD. In opposition to the case untreated, a rapid particle growth was observed and the number of nucleation was expected to be more, due to the ETD effectively increasing the ions and crystals collision frequency and effectiveness by utilizing the induced electric field. It was implied that the particle growth was promoted mainly by coagulation process but not nucleation growth in all the experimental temperature range. In the high temperature, the crystal phase of calcium carbonate could be changed from aragonite type without ETD to calcite with ETD. In the lower temperature, all the precipitated crystals in solution were calcite and there were little differences between with ETD and without ETD.

WO3/TiO2 Nanotubes with Strongly Enhanced Photocatalytic Activity

Initiated by the work of Fujishima and Honda in 1972, over the past decades, the use of particulate or colloidal semiconductors in solutions has extensively been studied for the photocatalytic oxidation of organic waste and pollutants in water. By far the most studied material is TiO2, as it is considered to represent the most suitable photocatalyst, in view of effectiveness and stability against photodecomposition. Typically these photocatalytic systems are used in form of nanoparticles, either freely suspended in solution or compacted to a robust photoelectrode. Earlier studies mainly focused on geometric parameters of the particles that influence the photocatalytic activity, such as surface area, size distribution in solution, as well as the TiO2 crystal structure, which was found to play a crucial role. Later, various approaches were reported to enhance the photocatalytic activity of TiO2, for example, by decorating the surface of TiO2 nanoparticles with noble metals such as Pt, Pd, Ag, Au, and so forth. More recently, improved photocatalytic activity was reached by modifying TiO2 particles with other oxides (such as CrxOy, FexOy, VxOy, MoOx, WOx, etc.). The effect of noble particle decoration was mainly interpreted in terms of a facilitated contribution of the photoexcited electrons in the photocatalytic reaction producing, for example, superoxide from O2 dissolved in aqueous electrolytes, while decoration with other oxides particles may influence the rate of charge transfer to the environment via surface states or junction formation. In general, two main reactions are considered to be relevant for the photocatalytic activity of TiO2: 1) the generation of valence-band holes that upon ejection to the environment (electrolyte) have an oxidative power sufficient to oxidize almost any organic material and 2) conduction-band electrons ejected to the electrolyte that may form reactive superoxides. Most recently, advanced geometries of TiO2 have been increasingly explored, in particular self-ordered TiO2 nanotubes (TiNT) have attracted wide attention due to the high level of geometrical definition combined with a high surface area (for an overview see references [23–26]). Such self-ordered TiO2 nanotubular layers can easily be grown on Ti metal sheets by a simple but optimized electrochemical anodization in F containing electrolytes. 28] Investigations of their photocatalytic properties have shown that these tubular layers can be more efficient than classical nanoparticulate layers of a comparable thickness. Self-ordered oxide nanotubes cannot only be grown on pure Ti, but also on other transition metals such as Mo, W, Ta, Nb, and so forth, and a full range of Ti alloys including TiW, TiNb, TiAl, TiMo, TiTa. In the present work, we demonstrate a very strong effect of tungsten addition to the TiO2 nanotubes in terms of their photocatalytic activity. For this, different TiW alloys (Ti0.2at%W (Ti0.2W) and Ti9at%W (Ti9W)) as well as pure Ti were anodized to form 2 mm-long self-organized tube layers as shown in Figure 1. To achieve these self-organized layers different anodization conditions had to be applied as outlined in the Supporting Information. For all cases, comparable dimensions of nanotubular layers with a tube length between 2.2 mm to 2.6 mm and a diameter (obtained from SEM cross sections) between 85 nm to 100 nm were used. For the TiW alloys (Figure 1a–d), a thin porous initiation layer is present on the top of the highly ordered nanotubes, as visible in the cross-sectional images of Figure 1b and d. Figure 1e and f show for comparison, the top view and cross section of pure TiO2 nanotube layers. The top layer can be removed, but this was found to not affect the results strongly. [a] I. Paramasivam, Y.-C. Nah, C. Das, N. K. Shrestha, Prof. Dr. P. Schmuki Department of Materials Science WW-4 Institute of Corrosion and Surface Science (LKO) University of Erlangen—N rnberg Martensstr.7, 91058 Erlangen (Germany) Fax: (+49)9131-852-7575 E-mail : schmuki@ww.uni-erlangen.de Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000397. It contains experimental descriptions, XRD patterns of TiO2-WO3 nanotubes at 350 8C and 550 8C, and EDX of elemental compositions for Ti9W and Ti0.2W.

Electromagnetic anti-fouling technology for prevention of scale

An electromagnetic anti-fouling technology (EAFT) was developed further. The operating principle of the EAFT was presented using fundamental physics laws. To validate the effect of EAFT and identify the mechanism, a circulating flow setup was built. A series of fouling tests were carried out with and without EAFT, measuring fouling thermal resistance as function of time, making scanning electron microscope images and analyzing the particles size distribution in solution by dynamics light scattering technology. The main results were as follows: 1) All the precipitated crystals in solution were calcite and there were little differences between with EAFT and without EAFT in the experimental range. 2) The number of precipitate nucleation in solution was small and the particle growth was slow without EAFT. In opposition to the case untreated, a rapid particle growth was observed and the number of nucleation was expected to be large, due to the fact that the EAFT effectively increases the ions and crystals collision frequency and effectiveness by utilizing the induced electric field. It is indicated that the particle growth is promoted mainly by coagulation process but not nucleation growth. 3) The EAFT could prolong the delay time of fouling greatly, and after the delay time, the thermal resistance quickly increased. Therefore, in order to mitigate scale significantly, the floccules in solution should be deposited beforehand in a low-lying area of the exchangers and let off in time.

Investigation on the Electromagnetic Anti‐Fouling Technology for Scale Prevention

AbstractAn electromagnetic anti‐fouling (EAF) device was built for treating scale containing water. In order to validate the effect and identify the mechanisms of EAF technology, a series of experiments were carried out, both with and without, an EAF device. The fouling thermal resistance was measured as a function of time. Scanning electron microscope (SEM) images of the fouling layers were obtained and the particle size distribution in solution was analyzed by dynamic light scattering (DLS) technology. The main results were as follows: (1) With EAF treatment, the crystal phase of calcium carbonate was changed to calcite from the aragonite type which exists without EAF treatment; (2) A rapid particle growth was observed under EAF treatment conditions. This rapid growth was due to that the EAF treatment results in an induced electric field inside the bulk flow, and can effectively increase collision frequency of the ions and crystals along with the effectiveness of collision. This implies that the particle growth was promoted mainly by a coagulation process, and not by nucleation growth; (3) The EAF treatment greatly reduced the fouling resistance within the time period tested.

Whey protein adsorption onto steel surfaces—effect of temperature, flow rate, residence time and aggregation

Whey protein adsorption on stainless steel surfaces was investigated by in situ ellipsometry under well-defined flow conditions and protein solution residence times. The size distribution in solution of the protein aggregates formed under the same conditions was determined by dynamic light scattering. The adsorption was performed at 72 °C and 85 °C, which is below and above the unfolding temperature of β-lactoglobulin (75 °C). The effect of increasing the Reynolds number on the aggregation process was evident only for the longest protein solution residence time, when larger aggregates were produced. At the higher temperature, higher flow turbulence decreased the amount of protein adsorbed on the surface, which was attributed to shear-induced removal of protein from the surface. At both temperatures, longer protein solution residence times decreased both the adsorption kinetics and the amount of protein adsorbed. This could be related to the concentration of native protein available in solution. Based on the experimental results, a model of the formation of a protein monolayer and multilayers on solid surfaces was developed. The model takes into account the dependence of the adsorption process on both protein solution residence time and flow rate and predicts the evolution of adsorbed mass of protein per unit surface area with operating time. Surface-induced aggregation was identified as the main mechanism responsible for the formation of multilayers, based on experimental data. To reduce the amount of protein adsorbed/deposited on the surface an increase in protein solution residence time was found to be more effective than an increase in the Reynolds number.

Synthesis and Self-Assembly of the Organic−Organometallic Diblock Copolymer Poly(isoprene-b-ferrocenylphenylphosphine): Shell Cross-Linking and Coordination Chemistry of Nanospheres with a Polyferrocene Core

Narrow polydispersity samples of the organic-organometallic diblock copolymer, poly(isoprene-b-ferrocenylphenylphosphine) (PI-b-PFP), have been synthesized by sequential living anionic polymerizations in tetrahydrofuran. These block copolymers form “starlike” spherical micelles in hexane with a dense PFP core surrounded by a swollen corona of PI chains as characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. Although the TEM results indicated a very narrow micelle core size distribution, DLS studies indicated a monomodal, but relatively broad distribution of the overall hydrodynamic size of the micelles in solution. The hydrodynamic size of the micelles and the broad size distribution in solution suggest that DLS measurements might be detecting aggregates of individual micelles. The PI corona chains were found to undergo a cross-linking reaction under UV irradiation in the presence of the radical initiator AIBN. The micelle solution concentration and UV irradiation time affect this cross-linking reaction. Furthermore, the phosphorus sites in the block copolymers could be coordinated to a transition metal, such as Au. The resulting Au-containing block copolymers still form spherical micelles, but with a different size and size distribution.

Fractionation of trace metals in surface water with screen filters

Size fractionation of solid particulate phases serving as carriers of trace elements (e.g. Al, Cd, Cu, Fe, Mn and Zn) in surface waters was conducted by pressure filtration using screen filters with defined pore sizes in the range 5-0.015 μm. The particle size distribution in solution was determined by Photon Correlation Spectroscopy. The accumulation of solids on the filter surface was demonstrated, leading to a successive reduction of the efficient pore size (‘clogging’). Thus, filters with a defined pore size of 0.40 μm and a diameter of 47 mm had an apparent separation efficiency corresponding to a pore size of 0.015 μm after filtration of 100 ml containing approximately 100 mg/l of suspended solids. Aluminium and iron were almost exclusively present in the particle size range 5-0.20 μm. Copper and manganese were retained to 45% and zinc and cadmium to 30% by the 0.015-μm pore size filter.