Brunauer Emmett Teller Adsorption Research Articles

Hydrogen generation from sodium borohydride hydrolysis using a heterogeneous biocatalyst prepared with Zabrus tenebrionides Goeze 1777 (Coleoptera: Carabidae) chitin

Co–B/Chi, which is made up of highly distributed Co–B particles, was synthesized by impregnation and chemical reduction methods. Scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller adsorption and Fourier transform infrared spectroscopy analyses were used to describe the morphology and microstructure of Co–B/Chi. The synthesized catalyst showed high catalytic activity in the hydrolysis reaction of NaBH4. The unsupported Co–B samples were compared with the chitin-supported Co–B catalyst, and the result showed that higher catalytic activity and good cycling stability for NaBH4 hydrolysis were obtained with the chitin-supported catalyst. The reaction conditions were investigated to achieve high hydrogen production. The maximum rate of hydrogen production was obtained at 40 °C and 20 mg catalyst amount. At ideal conditions, the hydrolysis reaction’s activation energy was determined to be 51.65 kJ mol−1. It is indicate that Co–B/Chi is a viable low-cost catalyst for the hydrolysis of NaBH4 for hydrogen production.

Co-Delivery of Cisplatin and Curcumin Using Mesoporous Silica Nanoparticles to Improve their Anticancer Effects.

This study aimed to prepare and evaluate the physicochemical and anticancer properties of cisplatin and curcumin-loaded mesoporous silica nanoparticles (Cis-Cur-MSNs). In recent years, combination treatment has attained better outcomes than monotherapy in oncology. Cis-Cur-MSNs were prepared by precipitation technique. The objective of the present study was the evaluation of the physicochemical and anticancer properties of cisplatin and curcumin-loaded mesoporous silica nanoparticles (Cis-Cur-MSNs). The prepared materials were assessed in terms of physicochemical methods. The drug release pattern from the MSNs was also evaluated via ultraviolet spectrophotometry. In addition, the porosity and surface area of prepared nanoparticles were determined using the Brunauer-Emmett-Teller (BET) technique. The cytotoxicity of Cis-Cur-MSNs was evaluated on the HN5 cells as head and neck squamous carcinoma cell lines. Furthermore, ROS production of Cis-Cur-MSNs treated cells was evaluated compared with untreated cells. According to the results, prepared nanoparticles displayed nanometer size, rod morphology, and negative surface charge with mesoporous structure belonging to the MCM-41 family (twodimensional hexagonal). Regarding the results of BET adsorption and desorption isotherm analysis for Cis-Cur-MSNs and drug-free MSNs, pore diameter, pore volume, specific surface area, and drug-loaded pore area in MSNs were decreased. In the first 10 days, the prepared nanoparticles exhibited a relatively rapid release pattern for cisplatin and curcumin, and until the 35th day, the release of them from the MSNs continued slowly. The cytotoxic effect of Cis-Cur-MSNs was significantly more than Cur-MSNs and Cis- MSNs in 24 and 48 h incubation time (p < 0.05). The results suggest that Cis-Cur-MSNs may be beneficial in the development of a cancer treatment protocol. Others: The prepared nanoparticle in the present study could be a potential biomaterial for cancer treatment.

Synthesis of magnetic MFe2O4@PC (M = Fe, Cu, Co, and Mn) composites and application of heterogeneous photo-Fenton efficient removal of metronidazole under visible light

Nanoscale magnetic spinel ferrite composites with the general formula MFe2O4@PC (M = Fe, Cu, Co, and Mn; PC = biochar) were prepared by a facile impregnation and pretreatment method. MFe2O4@PC particles were deliberated by X-ray Diffractometer (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), Brunauer–Emmett–Teller adsorption–desorption isotherm (BET), X-ray Photoelectron Spectroscopy (XPS) and Vibrating Sample Magnetometer. The results showed that MFe2O4 coating, which is evenly distributed on the surface of HNO3-pretreated biochar, can provide more active sites to enable MFe2O4@PC to be activated by visible light. The XRD confirmed that the crystallite sizes of MFe2O4 ranged from 10.0 to 27.9 nm. With the help of surface-OH, PCoF has a rapid adsorption performance on metronidazole (MNZ) and can degrade 99% of MNZ within 20 minutes at an optimal pH of 3.0. Meanwhile, the PCuF composites showed excellent photo-Fenton catalytic performance for the degradation of MNZ under neutral pH conditions, and 96.0% of MNZ (300 mg/L) could be removed within 120 min. This study confirmed OH is the main reactant, while O2− and h+ contributed to the degradation of MNZ during photocatalysis. MFe2O4@PC composite can be separated easily by an external magnetic field. The synthesized PCoF was reused for 5 cycles and it was clear that it had no significant loss, indicating its excellent ability to remove MNZ from wastewater.

Estimation of Mineral Accessible Surface Area from Mineral Abundance and Clay Content

The mineral reactive surface area is often quantified through a wide range of approaches (e.g., Brunauer–Emmett–Teller adsorption, geometry approximation, and imaging techniques). As such, values vary 1–5 orders of magnitude which can result in large discrepancies when used in reactive transport models to simulate geochemical reaction rates. Simulations carried out using mineral accessible surface areas (ASAs) determined from a coupled 2D and 3D imaging approach have shown better match with reaction rates measured in core-flood experiments. However, such image processing requires large amounts of time and resources. In this work, the possibility of estimating mineral ASAs from easily measured properties like mineral abundance and porosity is explored. Six sandstone samples of varying compositions were studied along with data from three additional samples from the previous literature. Mineral ASAs were quantified using a combined 2D scanning electron microscopy and 3D X-ray nano-computed tomography imaging approach. Sample properties like mineral accessibility, mineral ASAs, connected porosity, and clay content were compared to explore potential correlations between properties. Overall, it was observed that mineral accessibility can be predicted where feldspar mineral accessibility generally increases with increasing abundance and quartz accessibility decreases with increasing clay content. Mineral ASAs vary between samples, depending on the relative abundance of minerals and overall pore connectivity. While the ASA of quartz decreases with abundance, albite and carbonate mineral ASAs increase with abundance. Quantitative observations, including predictive relationships for ASAs from porosity and mineral volume fraction, are developed. Estimations of ASAs and mineral accessibility from more easily quantifiable properties can largely reduce the required extent of image analysis.

Synthesis of “needle-cluster” NiCo2O4 carbon nanofibers and loading of Co-B nanoparticles for hydrogen production through the hydrolysis of NaBH4

Hydrogen production through chemical processes has received considerable attention. Replacing precious-metal-based catalysts in NaBH4 hydrolysis entails challenges such as the low durability and efficiency of non-precious metals. Here, carbon nanofiber (CNF)-supported NiCo2O4 and CoB were synthesized to form a burr-shaped rod-like catalyst (CNF-NiCo2O4-CoB). The morphology and microstructure of the catalyst were characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller adsorption analysis. Then, NaBH4 hydrolysis was catalyzed using CNF-NiCo2O4-CoB. At 303 K, the hydrogen production rate and activation energy of the hydrolysis reaction were 5225 mL min−1 g−1 and 38.32 kJ mol−1, respectively. The maximum hydrogen production rate achieved using this composite catalyst was significantly higher than that of a pure CoB catalyst. The composite catalyst also exhibited high durability, maintaining 82.5% of its initial catalytic activity even after nine hydrolysis cycles. The magnetic nature of the catalyst improved its recyclability. This work provides a new method for synthesizing composite-structured catalysts, exhibiting considerable potential in the hydrolysis of NaBH4.

Exceptional photodecomposition activity of heterostructure NiTiO3–TiO2 catalyst

Mesoporous TiO 2 mixed with NiTiO 3 at various concentrations was synthesized by combining sol–gel and eco-friendly hydrothermal methods. The properties of the NiTiO 3 –TiO 2 (NTO–Ti) photocatalyst were characterized using Χ-ray diffraction, Raman spectroscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller adsorption, energy dispersive X-ray, and UV–vis absorption spectra techniques. The photocatalytic activity of NTO–Ti catalysts was assessed by way of the photodegradation of cinnamic acid (CA) under UV-A irradiation. The effects of the operating parameters, including catalyst dosage, airflow, and initial solution pH on the photodecomposition efficiency of CA were also investigated. Research results confirm that NTO–Ti heterostructure catalysts are synthesized in the crystalline phase with high crystallinity. Compared with pure TiO 2 , the NTO–Ti catalysts have a smaller particle size and average crystallite size (8.6–9.0 nm versus 34.8 nm) and lower band gap energy (3.02–3.08 eV versus 3.20 eV). The catalysts also enable a redshift in the absorption band from UV (λ = 385 nm) to UV-A light (λ = 404–412 nm). The study showed that the physicochemical and photochemical properties and the photocatalytic performance of the NTO–Ti catalysts are controlled by the NiTiO 3 loading. NTO–Ti with NiTiO 3 1.0 wt.% was found to maximize CA photodegradation. Under the most favorable conditions, CA removal of 82.8% was obtained after 120 min, which is higher than for pure TiO 2 (68.7%) and NiTiO 3 (3.8%) catalysts under the same conditions. • Mesoporous TiO 2 nanomaterials mixed with NiTiO 3 of various concentrations were synthesized. • The heterostructured NiTiO 3 -TiO 2 nanomaterials had advantages of properties and photocatalytic performance over the pure TiO 2 . • 1.0%NiTiO 3 -TiO 2 was found to be the most effective catalyst with the 120 min TOS removal efficiency of CA reached 82.8%.

Envirronmentally friendly fabrication of Fe2TiO5-TiO2 nanocomposite for enhanced photodegradation of cinnamic acid solution

In this study, Fe2TiO5-TiO2 heterostructured composites (FTO-Ti) were synthesised via a simple combination of the sol-gel and hydrothermal methods in a neutral medium of water. Various techniques were used to investigate the characteristics of the FTO-Ti samples, including X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller adsorption (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and point of zero charges (PZC). Compared to TiO2, the combination of FTO and TiO2 significantly reduces crystal and particle size and increases surface area six-fold, while simultaneously reducing the band gap energy of the catalyst and extending the region of photon absorption zone toward visible wavelengths (407 versus 395 nm). The photocatalytic activity of the FTO-Ti samples was studied using the batch method for the photodegradation of cinnamic acid (CA). The FTO content was found to strongly influence the photocatalytic performance of the FTO-Ti composites. Of the samples studied, 10% FTO-TiO2 nanocomposite exhibits the highest activity for CA decomposition. In the optimum conditions, its maximum 90 min CA conversion reaches 89.0%, which is much higher than both bare Fe2TiO5 (8.5%) and TiO2 (74.8%). Moreover, the catalyst can easily be recovered and reused for at least eight reaction cycles. The results show that hybridising the small band gap Fe2TiO5 pseudobrookite with a large band gap TiO2 semiconductor is a promising approach for the fabrication of highly active photocatalysts.

N-Layer BET adsorption isotherm modeling for multimeric Protein A ligand and its lifetime determination

Langmuir and other single-layer adsorption isotherms show the binding behavior of natural Protein A ligands immobilized on a column. However, no models have been shown in literature to explain the adsorption phenomena on the recombinant high binding capacity Protein A resins. This study has characterized the Protein A binding domain distribution across the ligand with multi-layer adsorption isotherms for a recombinant Protein A resin. The adsorption data was analyzed using the Langmuir, Freundlich, Brunauer–Emmett–Teller (BET) and various other mathematical equations. The best fit of experimental data was obtained with n-layer BET model wherein the isotherms of Protein A exhibited Type IV behavior according to BET classification. Furthermore, the binding capacity was studied throughout the shelf life using the multi-layer adsorption isotherm model. Antibody adsorption isotherms of Protein A resin were obtained at preset duration of caustic incubation. The experiments were carried out for two conditions of sanitization agent, namely, caustic and caustic with salt. Static and dynamic isotherm analysis showed that a new resin had a lower binding capacity and the initial sanitization improved the binding capacity, probably by making the binding domains more accessible. The binding capacity at equilibrium, dynamic breakthrough and batch were also evaluated and reported in this paper. The study modeled the multimeric Protein A ligand and established the requirement of optimization for cleaning regime. This study provides a fundamental understanding of the binding patterns in the recombinant Protein A ligands through a working mathematical equation and improves the current knowledge of Protein A resin lifetimes.

Controlling Phase Composition, Properties and Activity of TiO₂ Nano-Photocatalyst Synthesized by Hydrothermal Technique in the Degradation of Cinnamic Acid Solution.

In this work, titanium oxide catalysts were synthesized by the hydrothermal method from titanium isopropoxide (TTIP) as a precursor under acidic (Ti-A1 and Ti-A2), neutral (Ti-W) and alkaline (Ti-B) media. Characteristics of the catalysts were identified by various methods including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, UV-Vis diffuse reflectance spectroscopy, transmission electron microscopy, and Raman spectroscopy. The phase composition and PZC value of the obtained catalysts depended on the hydrothermal medium and the amount of TTIP: pure anatase and brookite phase formed at neutral and alkaline medium, respectively; whereas acidic medium favored the formation of anatase/rutile mixed phase and anatase phase decreased with the increasing amount of TTIP. The band gap energy of the synthesized catalysts was approximately 3.08-3.23 eV. Photocatalytic activity of synthesized catalysts was surveyed in the degradation of cinnamic acid (CA) solution at various pH in the region from 3.8 to 9.0 under UV irradiation. Photocatalytic oxidation was favorable in an acidic environment. At acidic pH values (3.8 and 5.0), the CA conversion was in the order of Ti-A2 ≥ Ti-A1 > Ti-P25 > Ti-W ≫ Ti-B, whereas it followed Ti-P25 > Ti-A1 > Ti-A2 ≈ Ti-W > Ti-B at pH 7.0 as well as pH 9.0.

Fabrication of TiO&lt;SUB align="right"&gt;2/Al&lt;SUB align="right"&gt;2TiO&lt;SUB align="right"&gt;5 nanocomposite photocatalysts

In this work, TiO2/Al2TiO5 (Ti/ATO) heterostructure catalysts with the different content of TiO2 were successfully synthesised by sol-gel-based hydrothermal method. Characteristics of the synthesised catalysts were determined by various methods including X-ray diffraction (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller adsorption (BET), UV-Vis diffuse reflectance spectroscopy (DRS), and scanning electron microscopy (SEM). The results showed that the addition of TiO2 to Al2TiO5 significantly reduced the particle size, shifted the absorption band above 404 nm, and increased the specific surface area of the hybrid catalysts. The value of the anatase/rutile ratio can be controlled by TiO2 content changing on hybrid samples. The sample containing 33% TiO2 (33Ti/ATO) had the highest activity for cinnamic acid (CA) remove under irradiation of UV-visible light due to the proportion of TiO2 anatase and rutile phases, more hydroxyl groups on the catalyst surface, small nanoparticle size, and high the specific surface area. The optimum reaction conditions including the catalyst dosage, the airflow, and the initial pH solution in the photocatalytic degradation of cinnamic acid at 25°C were determined on 33Ti/ATO catalyst. In the most favourable conditions, the CA removal efficiency reached 88.5% after 60 min, much higher than that on the Al2TiO5 sample with the removal efficiency of 38.0%.

Co2TiO4/Reduced Graphene Oxide Nanohybrids for Electrochemical Sensing Applications.

For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer–Emmett–Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology.

Kinetic Simulation of Adsorption Isotherms

The possibilities of calculating adsorption equilibria by simulating a set of kinetic stages of sorption and desorption are considered. An approach is proposed in which an adsorption isotherm is obtained by scanning the concentration of the adsorbed substance in a simulation program as a linear function of time. The principal possibility of obtaining the adsorption isotherms of five types out of the six approved by IUPAC (except for the multistage one of type VI) is shown. To obtain undistorted adsorption isotherms, it is necessary and sufficient to use a scanning step larger than the time constant for establishing the adsorption equilibrium. It is shown that the polymolecular Brunauer–Emmett–Teller adsorption isotherm can be simulated with high accuracy using a simple kinetic scheme.

Sulfonic acid-functionalized poly(4-styrenesulfonic acid) mesoporous graphene oxide hybrid for one-pot preparation of coumarin-based pyrido[2,3-d]pyrimidine-dione derivatives

Sulfonic acid-functionalized poly(4-styrenesulfonic acid) mesoporous graphene oxide hybrid (PSSA-MGO) is prepared by polymerization of 4-styrenesulfonic acid on the surface of mesoporous graphene oxide. The catalyst is fully characterized by several methods including Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller adsorption–desorption analysis, scanning and transmission electron microscopy. PSSA-MGO is used as an efficient acidic catalyst for the one-pot preparation of some novel chromenopyridopyrimidine-dione derivatives via the three-component reaction of 4-aminocoumarin, thiobarbituric acid and aromatic aldehydes. All the obtained products were also characterized. This synthetic procedure presents some advantages including an eco-friendly procedure, high yield of the products and recyclability of the catalyst.

Measuring the specific surface area (SSA) of freeze-dried biologics using inverse gas chromatography

The specific surface area (SSA) of freeze-dried biologics (FD) is usually measured via a Brunauer–Emmett–Teller (BET) analysis of volumetric nitrogen adsorption isotherms. However, this technique has accuracy limitations for materials <0.5 m2/g, requires dry samples, must be measured at 77 K and has slow sample preparation times (drying/degassing). Inverse gas chromatography (IGC) is chromatographic characterization technique which can be used to analyse the SSA (down to ≈0.1 m2/g) of various solid-state materials including powders using organic molecules such as octane at ambient temperatures/pressure for a range of relative humidities. This study presents a comprehensive comparison between the N2 BET adsorption versus octane BET adsorption using IGC methods for determining the SSA’s for a range of freeze dried biological materials. These include IgG 5% w/w, an influenza antigen standard, sucrose 5% w/w and trehalose 5% w/w. IGC provided comparable SSA values to the N2 BET method with better reproducibility (lower RSDs %). Large variations in average SSA within manufactured FD batches were observed for both IGC and volumetric determinations. IGC was also used to measure the change in SSA with increasing humidity, with FD cakes shrinking and losing their structural integrity with increasing moisture content. Such information highlights the importance of moisture content in determining the physical stability of FD cakes as exemplified by their SSA. In conclusion, IGC is a suitable alternative method for determining the SSA of freeze-dried biological materials which are generally strongly dependent on their moisture content.

Bimetallic Nanoparticles Anchored on Core-Shell Support as an Easily Recoverable and Reusable Catalytic System for Efficient Nitroarene Reduction.

We report an easily recoverable and reusable versatile magnetic catalyst (Fe3O4@CS_AgNi, where CS = chitosan) for organic reduction reactions. The catalytic system is prepared by dispersing AgNi bimetallic nanoparticles on the magnetite core–shell (Fe3O4@CS). The as-synthesized catalyst has been characterized by spectroscopic techniques, such as IR, UV–vis, and X-ray photoelectron spectroscopy (XPS), and analytical tools, such as thermogravimetric analysis, powder X-ray diffraction, Brunauer–Emmett–Teller adsorption, FEG–scanning electron microscopy, high-resolution transmission electron microscopy (HR-TEM), inductively coupled plasma-atomic emission spectroscopy, and magnetic measurements. HR-TEM studies indicate the core–shell structure of Fe3O4@CS and confirm the presence of AgNi nanoparticles on the surface of Fe3O4@CS spheres. IR spectral and XPS studies lend evidence for the occurrence of a strong chemical interaction between the amino groups of CS and AgNi nanoparticles. The nano-catalyst Fe3O4@CS_AgNi rapidly reduces p-nitrophenol to p-aminophenol using NaBH4 as the reductant within a few minutes under ambient conditions (as monitored by UV–visible spectroscopy). The utility of this catalytic system has also been extended to the reduction of other nitroarenes. A strong interaction between Fe3O4@CS and AgNi nanoparticles impedes the leaching of AgNi nanoparticles from the core–shell support, leading to excellent reusability of the catalyst.

ADSORPTION ISOTHERM STUDY FOR THE REMOVAL OF NICKEL IONS FROM AQUEOUS SOLUTION USING THERMAL POWER PLANT FLY ASH

In the present study, the adsorption of nickel ions on the surface of fly ash was investigated. The batch adsorption experiments were performed at constant room temperature 25±1 0 C using Atomic Absorption Spectroscopy (AAS) Technique. Three adsorption isotherms such as Temkin, Harkins Jura and Brunauer-Emmett-Teller (BET) were used to analyze the results obtained from the experiments. The coefficient of correlation (R 2 ) was determined for each isotherm model to establish the best fit adsorption isotherm model. To carry out the error analysis of the three adsorption isotherm models Chi-square test (Ʃχ 2 ) was used. It was concluded from the laboratory investigations and analysis that BET adsorption isotherm is best-fit adsorption isotherm as per linear coefficient of correlation and by nonlinear Chi-square test. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.93104 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Study on the Effect of Demulsification Speed of Emulsified Asphalt based on Surface Characteristics of Aggregates

Aggregate is an indispensable raw material for emulsified asphalt construction. For the purpose of explaining the influence of aggregate characteristics on the demulsification speed of emulsified asphalt, the surface energy and specific surface area (SSA) characteristics of aggregates were calculated based on the capillary rise method and the BET (Brunauer-Emmett-Teller) adsorption test. Afterwards, the effect of the surface energy and specific surface area of the aggregate on the emulsified asphalt demulsification speed was systematically studied by using ultraviolet spectroscopy as well as the orthogonal test. Experimental results indicate that the specific surface energy parameter of the aggregate is certainly related to the particle size of the aggregate. That is, the surface free energy of the unit system is proportional to the surface area A and the density of the interface unit. The specific surface area parameter of aggregates increases with the decrease of particle size, when the particle size is reduced to 600 mesh, the specific surface area parameters of the three aggregates selected in this paper tend to be consistent. Orthogonal experimental analysis demonstrates that the surface energy and specific surface area have an impact on the emulsion breaking speed and they are proven to be positively correlated. Meanwhile, in the case of small particle sizes, there is no statistically significant correlation between the physical properties of aggregates and the demulsification speed of emulsified asphalt, and the physical property of aggregates is not the main factor that affects the demulsification speed of the emulsified asphalt. On the contrary, the material properties of the aggregate, such as acid-base property and chargeability, are the dominant factors.

Solvent effects on the retention mechanisms of an amylose-based sorbent

The mobile phase, when used in combination with a polysaccharide-based sorbent, often contains hydrocarbons with polar modifiers. Studies have investigated the effect of solvent on the recognition mechanism of polysaccharide-based sorbents, but it remains unclear how these modifier molecules affect solute retention behavior. This study used an amylose 3,5-dichlorophenylcarbamate–based sorbent to systematically investigate the retention behavior of various solutes as a function of the concentration of four polar modifiers: ethanol, isopropanol, methyl tert-butyl ether, and acetone. The thermodynamic properties of adsorption for the four modifiers were thoroughly investigated using retention factor data, van’t Hoff plots, and adsorption isotherms of the modifier molecules. The adsorption data of acetone and isopropanol followed the Langmuir isotherm, whereas the bi-Langmuir isotherm more accurately fit the ethanol data. For methyl tert-butyl ether, the Brunauer–Emmett–Teller adsorption isotherm indicated multilayer adsorption with a low saturation capacity of the first adsorption layer. A multivalent retention model interpreted slopes of the plots of the logarithm of the retention factor versus the logarithm of the modifier concentration. Because the molecular polarity of acetone is stronger than that of methyl tert-butyl ether, the limiting absolute slope values of tetrahydrofuran at a very high acetone modifier concentration were smaller than that when methyl tert-butyl ether was used as the polar modifier. The higher absolute value of the slope for tert-butanol suggested the potential of CO groups of acetone molecules to form bifurcated H bonds on a tert-butanol molecule. When alcohol was employed as the polar modifier, the results suggested that the effect of isopropanol self-association on the retention factor was stronger than the effects of solute–IPA complexation and isopropanol adsorption. For alcohol modifiers, U-shaped retention curves were obtained for all aromatic solutes. When acetone or methyl tert-butyl ether was used, the absence of a U-shaped curve indicated the weak polarity of those modifiers.

Kelvin Probe Force Microscopy and Calculation of Charge Transport in a Graphene/Silicon Dioxide System at Different Relative Humidity.

The article shows how the dynamic mapping of surface potential (SP) measured by Kelvin probe force microscopy (KPFM) in combination with calculation by a diffusion-like equation and the theory based on the Brunauer-Emmett-Teller (BET) model of water condensation and electron hopping can provide the information concerning the resistivity of low conductive surfaces and their water coverage. This is enabled by a study of charge transport between isolated and grounded graphene sheets on a silicon dioxide surface at different relative humidity (RH) with regard to the use of graphene in ambient electronic circuits and especially in sensors. In the experimental part, the chemical vapor-deposited graphene is precisely patterned by the mechanical atomic force microscopy (AFM) lithography and the charge transport is studied through a surface potential evolution measured by KPFM. In the computational part, a quantitative model based on solving the diffusion-like equation for the charge transport is used to fit the experimental data and thus to find the SiO2 surface resistivity ranging from 107 to 1010 Ω and exponentially decreasing with the RH increase. Such a behavior is explained using the formation of water layers predicted by the BET adsorption theory and electron-hopping theory that for the SiO2 surface patterned by AFM predicts a high water coverage even at low RHs.

Chitosan-mediated Co–Ce–B nanoparticles for catalyzing the hydrolysis of sodium borohydride

Highly dispersed Co–Ce–B nanoparticles supported on chitosan-derived carbon (Co–Ce–B/Chi–C) were synthesized through chemical reduction and carbonization. The morphology and microstructure of the Co–Ce–B/Chi–C nanocomposite were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller adsorption analysis. This nanocomposite had uniform morphology and large surface area, and it showed high catalytic activity for NaBH4 hydrolysis and good cycle stability. Compared with unsupported Co–Ce–B particles, this nanocomposite showed greatly increased catalytic activity for NaBH4 hydrolysis. A remarkably high hydrogen generation rate of 4760 mL−1 min−1 g−1 at 30 °C was achieved with low activation energy of 33.1 kJ mol−1. These results indicate that the Co–Ce–B/Chi–C nanocomposite is a promising catalyst for on-demand hydrogen generation via NaBH4 hydrolysis.