Adsorption Analysis Research Articles

Highly Porous Nitrogen and Phosphorus Dual-Doped Carbon with Increased Phosphorus Content As an Efficient Oxygen Reduction Electrocatalyst

Highly porous nitrogen and phosphorus dual-doped carbon (NPC) was synthesized using acetylene black as a carbon source in two steps: (1) solid–gas mechanochemical treatment to prepare nitrogen-doped carbon (NC), (2) heat treatment to dope the NC with phosphorus. X-ray photoelectron spectroscopy and N2 gas adsorption analysis revealed that the solid–gas mechanochemical treatment using a ball mill incorporated nitrogen atoms into the carbon network and increased the pore volume and surface area. Furthermore, the resulting NC exhibited enhanced reactivity with ammonium dihydrogen phosphate, which was used as a phosphorus source, upon heat treatment. The phosphorus content in NPC synthesized by two-step mechanochemical and heat treatments reached 1.91 at%, a 14-fold increase compared to that of phosphorus-doped carbon synthesized by heat treatment. The NPC exhibited higher electrocatalytic activity for the oxygen reduction reaction than NC, suggesting that the additional phosphorus doping into NC can improve its electrocatalytic performance.

Investigating Discrepancies in Adsorption Enthalpy Predictions: An Analysis of CO2 Adsorption on HKUSTs

The pressing need to mitigate the presence of harmful gases in the atmosphere motivates scientific and engineering endeavors to devise effective adsorption solutions. Achieving practical and specific adsorption is essential for improving capture processes, with CO2 being a prominent target due to its significant environmental repercussions. Metal-organic frameworks (MOFs), distinguished by their high porosity and adaptable structure, have emerged as promising candidates for CO2 adsorption. Especially noteworthy are functionalized MOFs, which augment adsorption capacity, selectivity, and heat of adsorption. This research investigates CO2 adsorption on HKUST-1 modified with three amines of varying strengths, evaluating adsorption capacity and thermal impacts using direct adsorption calorimetry and Van't Hoff thermodynamic models.

Gas adsorption analysis for quantifying the edge sites of graphite

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

Facile oxygen-enriched hierarchical porous carbon particles based on biomass wastes for improving the adsorption of malachite green from aqueous solutions

The abundance of active groups and the surface areas of adsorbents used for the removal of contaminants such as dyes are very important for the effective adsorption process. For this purpose, the high surface area-activated carbon was obtained by activation of agricultural waste chestnut shells as carbon precursor(CSAC) with sodium hydroxide in the first stage of this study. In the second stage, the doping of oxygen atoms with nitric acid was carried out to further improve the surface properties of this activated carbon (O-doped CSAC). The obtained oxygen-rich activated carbon sample was used as an adsorbent to remove a cationic dye malachite green (MG). EDS, SEM, XRD, FTIR and nitrogen adsorption analyses were used for the characterisation of these activated carbon samples. FTIR, elemental analysis and EDS analyses showed a significant increase in the amount of oxygen groups on the surface. The BET surface area obtained for CSAC had a high surface area of 1548 m2/g. Kinetic, thermodynamic and isotherm parameters for the adsorption of MG with O-doped CSAC were determined. The qe values obtained for MG adsorption with O-doped CSAC showed an adsorption efficiency of about 90 %. An adsorption capacity of 284.6 mg g-1 was obtained at 298 K with the Langmuir isotherm. The adsorption mechanism of MG with O-doped CSAC was also investigated.

Thermodynamic analysis of adsorption and retention behaviors in normal-phase liquid chromatography

This study investigated the adsorption mechanisms in a normal-phase system using a cyano-based stationary phase as the sorbent. The minor disturbance method was used to measure the adsorption isotherms of acetone and alcohols with various structures. Excluding data in pure n-hexane revealed that the adsorption behaviors on cyano sites were well described by the Langmuir model. The adsorption equilibrium constants, ranging from 8.86 to 11.15 at 25 °C, showed no significant differences across alcohol structures and decreased with increasing temperature. The saturation adsorption concentration decreased with increasing alcohol molecule size, with branched-chain alcohols showing a lower saturation adsorption amount compared to straight-chain alcohols. The standard state adsorption enthalpies and entropies calculated from the equilibrium constants for various alcohols ranged from −29 to −22 kJ/mol and −78 to −55 J/K·mol, respectively, showing enthalpy-entropy compensation. A discrepancy was observed between these adsorption enthalpies and those obtained from the retention factors of alcohols using pure n-hexane as the mobile phase. This discrepancy may result from the affinity energy distribution of the adsorbent. In pure n-hexane, the adsorption behaviors of adsorbates were considerably affected by high-affinity sites. Moreover, acetone and these alcohol molecules were used as solvent modifiers to investigate the relationship between the retention factor, modifier concentration, and temperature for various solutes with distinct functional groups. The retention curves were converted to enthalpic curves using the van't Hoff equation. A theoretical model was proposed to describe the relationship between the van't Hoff enthalpy change and mobile phase composition. The proposed model effectively described the enthalpic curves, indicating that the enthalpy change follows a saturation curve with increasing modifier concentration. This trend is primarily due to competitive adsorption and complexation behaviors between the solute and modifier molecules.

Adsorption of Carbon Dioxide and Nitrogen in Co3(ndc)3(dabco) Metal-Organic Framework.

Metal-organic frameworks (MOFs) are promising materials for processes such as carbon dioxide (CO2) capture or its storage. In this work, the adsorption of CO2 and nitrogen (N2) in Co3(ndc)3(dabco) MOF (ndc: 2,6-naphthalenedicarboxylate; dabco: 1,4-diazabicyclo[2.2.2]octane) is reported for the first time over the temperature range of 273-323 K and up to 35 bar. The adsorption isotherms are successfully described using the Langmuir isotherm model. The heats of adsorption for CO2 and N2, determined through the Clausius-Clapeyron equation, are 20-27 kJ/mol and 10-11 kJ/mol, respectively. The impact of using pressure and/or temperature swings on the CO2 working capacity is evaluated. If a flue gas with 15% CO2 is fed at 6 bar and 303 K and regenerated at 1 bar and 373 K, 1.58 moles of CO2 can be captured per kg of MOF. The analysis of the multicomponent adsorption of typical flue gas streams (15% CO2 balanced with N2), using the ideal adsorbed solution theory (IAST), shows that at 1 bar and 303 K, the CO2/N2 selectivity is 11.5. In summary, this work reports essential data for the design of adsorption-based processes for CO2 capture using a Co3(ndc)3(dabco) MOF, such as pressure swing adsorption (PSA).

Adsorption-desorption mechanisms and migration behavior of fluchlordiniliprole in four different soils under varied conditions

Utilizing infrared spectroscopy coupled with batch equilibrium methods, the adsorption and desorption characteristics of the novel Insecticide fluchlordiniliprole were assessed in four different soil types. It was found that fluchlordiniliprole’s adsorption and desorption in these soils were consistent with the Freundlich isotherm, exhibiting adsorption capacities (KF-ads) ranging from 8.436 to 36.269. Temperature fluctuations, encompassing both high and low extremes, impaired the ability of soil to adsorb fluchlordiniliprole. In addition, adsorption dynamics were modulated by several other factors, including soil pH, ionic strength, amendments (e.g., biochar and humic substances), and the presence of various surfactants and microplastics. Although capable of leaching, fluchlordiniliprole exhibited weak mobility in most soils. Therefore, it appears that fluchlordiniliprole seems to pose a threat to surface soil and aquatic biota, but a minimal threat to groundwater. Synopsis StatementThis research examines the dynamics of fluchlordiniliprole in soil, an will aid in maintaining ecological safety and managing agricultural pesticides. The study's comprehensive analysis of adsorption, desorption, and soil migration patterns significantly contributes to our understanding of pesticide interactions with diverse soil types. The results of this study will enable the development of environmentally responsible agricultural practices.

Molecularly Woven Cationic Covalent Organic Frameworks for Highly Selective Electrocatalytic Conversion of CO2 to CO.

Coupling carbon capture with electrocatalytic carbon dioxide reduction (CO2R) to yield high-value chemicals presents an appealing avenue for combating climate change, yet achieving highly selective electrocatalysts remains a significant challenge. Herein, two molecularly woven covalent organic frameworks (COFs) are designed, namely CuCOF and CuCOF+, with copper(I)-bisphenanthroline complexes as building blocks. The metal-organic helical structure unit made the CuCOF and CuCOF+ present woven patterns, and their ordered pore structures and cationic properties enhanced their CO2 adsorption and good conductivity, which is confirmed by gas adsorption and electrochemical analysis. In the electrocatalytic CO2R measurements, CuCOF+ decorated with extra ethyl groups exhibit a main CO product with selectivity of 57.81%, outperforming the CuCOF with 42.92% CO at the same applied potential of 0.8 VRHE. After loading Pd nanoparticles, CuCOF-Pd and CuCOF+-Pd performed increased CO selectivity up to 84.97% and 95.45%, respectively. Combining the DFT theoretical calculations and experimental measurements, it is assumed that the molecularly woven cationic COF provides a catalytic microenvironment for CO2R and ensures efficient charge transfer from the electrode to the catalytic center, thereby achieving high electrocatalytic activity and selectivity. The present work significantly advances the practice of cationic COFs in real-time CO2 capture and highly selective conversion to value-added chemicals.

Ortho to para hydrogen conversion over bimetallic iron and cobalt catalysts

The catalytic conversion of ortho-hydrogen (o-H2) to para-hydrogen (p-H2) serves as a crucial step in the storage of liquid hydrogen. A variety of iron-cobalt bimetallic catalysts (FCO) were synthesized using a precipitation method, incorporating diverse levels of Co doping into Fe-based catalysts. The effects of Co doping on the crystal structure, porosity, and magnetism of FCO catalysts were studied by XRD, N2 physical adsorption, FTIR, XPS, and VSM analyses. The efficiency of ortho-para hydrogen conversion over FCO at 77 K was evaluated. It was found that the catalyst’s lag coefficient was significantly improved by Co doping, leading to an increase of magnetic moment. The catalyst of FCO-5 with a Fe/(Fe + Co) molar ratio of 0.5 exhibited the highest activity in ortho-para hydrogen conversion. The corresponding conversion rate, outlet p-H2 content, and the reaction rate constant were 99.2%, 49.7% and 291.7 mol·L−1·s−1, respectively, under a gas hourly space velocity of 5400 h−1.

Biodiesel production from agricultural biomass wastes: Duroc breed fat oil, Citrillus lanatus rind, and Sorghum Bagasse

This research study synthesized a base catalyst from the waste Citrullus lanatus rind (WCLR) for the synthesis of biodiesel from the waste pig fat oil. The high-acid-value oil (high free fatty acid: FFA) was converted to low-acid-value oil through adsorption in sorghum bagasse ash with high particle sizes. The developed base catalyst was obtained from the WCLR and was characterized via thermogravimetric analysis (TGA), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD-FT), and Brunauer-Emmett-Teller (BET) adsorption analysis. The properties of biodiesel were compared with the recommended standard.Results reflected that the duroc breed pig fat is rich in oil, and the oil is unsaturated. Sorghum bagasse proved to be a good bio-adsorbent for the unsaturated fat FFA reduction. The catalyst produced from WCLR was found to be rich in potassium-calcium-magnesium (K-Ca-Mg) base salts. The predicted yield of 98.69 % (wt./wt.) at 69.96 min, 79.93 °C, 3.15 % (wt.), and 8.57 (vol.) at desirability of 100 % was validated as 98.52 % (wt./wt.). Catalytic strength can be recycled in five cycles. The cost implications indicated that the cost of producing 25 L of biodiesel is $2.61.This study proved to be the most economical way of producing biodiesel that is environmentally friendly, cost-effective, and easy to produce for future energy needs.•Oil was obtained via rendering from duroc breed waste fat oil.•Sorghum bagasse was used as adsorbent for acid reduction of high FFA pig fat oil.•Base catalyst used was obtained from calcined waste Citrullus lanatus rind.

Modulation of triplet quantum coherence by guest-induced structural changes in a flexible metal-organic framework

Quantum sensing has the potential to improve the sensitivity of chemical sensing by exploiting the characteristics of qubits, which are sensitive to the external environment. Modulation of quantum coherence by target analytes can be a useful tool for quantum sensing. Using molecular qubits is expected to provide excellent sensitivity due to the proximity of the sensor to the target analyte. However, many molecular qubits are used at cryogenic temperatures, and how to make molecular qubits respond to specific analytes remains unclear. Here, we propose a material design in which the coherence time changes in response to a variety of analytes at room temperature. We used the photoexcited triplet, which can be initialized at room temperature, as qubits and introduce them to a metal–organic framework that can flexibly change its pore structure in response to guest adsorption. By changing the local molecular density around the triplet qubits by adsorption of a specific analyte, the mobility of the triplet qubit can be changed, and the coherence time can be made responsive.

Novel poly(2-ethyl-2-oxazoline) and poly(diallyldimethylammonium chloride) polymer functionalized montmorillonite: Physicochemical aspects and near-IR study of hydration properties

The novel functionalized montmorillonites (Mts) with non-ionic poly(2-ethyl-2-oxazoline) (PEtOx) and cationic poly(diallyldimethylammonium) (PDDA) were created via an intercalation method with different loading ratio of both polymers. A comprehensive investigation into their physicochemical properties was conducted using Carbon analysis (CA), Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), Simultaneous thermal analysis (TGA/DSC) and BET-N2 adsorption analysis. The impact of hydration on PEtOx-Mts and PDDA-Mts was assessed through gravimetric analysis and near-infrared spectroscopy (NIR) spectroscopy. PXRD analysis revealed a significant increase in 001 diffraction of PDDA-Mt corresponding to a PDDA interlayer with a basal spacing ranging from 1.47 to 1.49 nm. Conversely, the basal spacing exceeding 2 nm for PEtOx suggested, that the PEtOx polymer was intercalated in a larger amount and packed in a less compact manner compared to PDDA. After modification of Na-Mt with PEtOx polymer, FTIR spectroscopy confirmed the presence of the carbonyl CO group (3265 and 1641 cm-1) and the stretching (2982, 2942 and 2883 cm-1) and bending (1480–1200 cm-1) vibrations of the CH2 and CH3 groups. The vibrations of CH groups were further verified following PDDA modification. NIR spectroscopy also confirmed the vibrational bands attributed to both modifiers after intercalation of PEtOx and PDDA. The results of BET-N2 adsorption revealed a significant decrease in the specific surface area (SSA) after intercalation with a non-ionic PEtOx polymer. On the contrary, in the case of saturation of Na-Mt with polycation PDDA, SSA increased slightly in two instances. TGA analysis confirmed greater weight loss for PEtOx-Mts compared to PDDA-Mts. Derivative thermogravimetry (DTG) revealed the release of physisorbed bound water around 100 °C, decomposition of the organic phase within the 250–550 °C range and dehydroxylation of OH groups around 550–800 °C in both cases. The results obtained from the gravimetry and NIR analysis indicated a greater hydrophobic nature for PEtOx-Mts compared to PDDA-Mts. These findings hold substantial potential for enhancing the properties of novel organo-montmorillonites, thereby facilitating their application as adsorbents for pollutants, surface coatings, biodegradable materials, fillers in polymer nanocomposites, drug carriers, anticancer agents and various other significant applications.

Development and characterization of a zeolite based drug delivery system: Application to cannabidiol oral delivery

The growing interest in the therapeutic potential of cannabidiol (CBD) has led to the need for effective and reliable delivery methods that overcome its low oral absorption. Zeolites, a class of porous nanoparticles, offer unique advantages as drug carriers due to their high surface area and adjustable pore size. In this study, a zeolite-based drug delivery system was developed for the encapsulation of CBD. The zeolite particles were characterized using various techniques such as Scanning Electron Microscopy (SEM), N2 adsorption analysis, Solid-state Fourier Transform Infrared (FTIR), Direct Light Scattering (DLS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) before and after the loading. The drug encapsulation efficiency, and the release profile of CBD from the zeolite matrix were evaluated in addition to in vitro dissolution experiments in the intestinal and gastric simulated fluids. The results showed that the loaded zeolite particles exhibited high encapsulation efficiency of 73.5 %. XRD analysis proved that the USY structure remained intact after loading with CBD. DLS and N2 adsorption analysis indicated that CBD was successfully loaded into the zeolite matrix. When compared to CBD containing particles in a commercialized capsule, the in-vitro dissolution rate of CBD loaded zeolite was significantly higher after 30 min in the simulated stomach (pH 1.8) and the intestinal (pH 6.8) fluids, 67.8 % versus 43.6 % and 62.6 % vs 38.4 % respectively. Our findings open new avenues for the use of zeolites as an efficient drug delivery system for drugs with low bioavailability like CBD.

Comparative Analysis of Locally Sourced Adsorbents for Iponda and Idominasi, Abandoned Gold Mine Wastewater Bioremediation in Osun State, Nigeria

This study investigates and compares the effects of Neem leaf (NL) and coconut husk (CCH) adsorbents in reducing the levels of heavy metal concentration and elemental content in wastewater from two specific abandoned gold mining sites, namely Iponda (Iponda wastewater- IPWW) (longitude 4°43'18''E, Latitude 7°43'57''N ) and Idominasi (Idominasi wastewater -IDWW) (longitude 4°42'0''E, Latitude 7°40'59''N). Preparation of locally sourced adsorbents, bioremediation process through adsorption and physico-chemical analysis of the treated wastewater samples were carried out. Adsorbents were prepared from washed, air-dried neem leaves, grinded to 40 microns size to facilitate penetration of the adsorbate. In addition, washed and airdried CCH was carbonized in an electric muffle furnace at between 300 0C and 350 0C over a period of 30 minutes, and then granulated and sieved with a mesh size of 40 µm to ensure uniform size. Measured dosages of adsorbent (0.5 g, 0.75 g, and 1 g) were added to a 50 ml volume of wastewater and the mixture was agitated at different speeds ranging from 30 rpm to 120 rpm. The treated wastewater samples were then subjected to various physico-chemical analytical tests to determine the effect of the adsorbents on the reduction of the heavy metal concentration and elemental content of the wasted water samples. The results of this study demonstrate that both NL and CCH adsorbents have a significant impact on the wastewater from the two abandoned gold mining sites, IPWW and IDWW. This impact is reflected in the reduction of heavy metal and other element concentrations in the wastewater. Furthermore, it can be concluded that the bioremediation process is more effective when utilizing NL compared to carbonized CCH. Locally sourced cheap non-edible biomass materials hitherto considered as wastes have proved to be highly effective and efficient when used as adsorbents in the treatment of wastewater from abandoned gold mining sites. This is evident from the results obtained from this study.

Kinetics and thermodynamics analysis of the polybenzimidazole adsorption onto carbon materials using adsorption isotherm measurements

Kinetics and thermodynamics analysis of the polybenzimidazole adsorption onto carbon materials using adsorption isotherm measurements

Microscopic and macroscopic analysis of hexavalent chromium adsorption on polypyrrole-polyaniline@rice husk ash adsorbent using statistical physics modeling

This paper contributed with new findings to understand and characterize a heavy metal adsorption on a composite adsorbent. The synthesized polypyrrole–polyaniline@rice husk ash (PPY–PANI@RHA) was prepared and used as an adsorbent for the removal of hexavalent chromium Cr(VI). The adsorption isotherms of Cr(VI) ions on PPY–PANI@RHA were experimentally determined at pH 2, and at different adsorption temperatures (293, 303, and 313 K). Multi-layer model developed using statistical physics formalism was applied to theoretically analyze and characterize the different interactions and ion exchanges during the adsorption process for the elimination of this toxic metal from aqueous solutions, and to attribute new physicochemical interpretation of the process of adsorption. The physicochemical structures and properties of the synthesized PPY–PANI@RHA were characterized via Fourier transform infrared spectroscopy (FTIR). Fitting findings showed that the mechanism of adsorption of Cr(VI) on PPY–PANI@RHA was a multi-ionic mechanism, where one binding site may be occupied by one and two ions. It may also be noticed that the temperature augmentation generated the activation of more functional groups of the composite adsorbent, facilitating the interactions of metal ions with the binding sites and the access to smaller pore. The energetic characterization suggested that the mechanism of adsorption of the investigated systems was exothermic and Cr(VI) ions were physisorbed on PPY-PANI@RHA surface via electrostatic interaction, reduction of Cr(VI) to Cr(III), hydrogen bonding, and ion exchange. Overall, the utilization of the theory of statistical physics provided fruitful and profounder analysis of the adsorption mechanism. The estimation of the pore size distribution (PSD) of the polypyrrole-polyaniline@rice husk ash using the statistical physics approach was considered stereographic characterization of the adsorbent (here PPY–PANI@RHA was globally a meso-porous adsorbent). Lastly, the mechanism of Cr(VI) removal from wastewater using PPY-PANI@RHA as adsorbent was macroscopically investigated via the estimation of three thermodynamic functions.

Methylamine Separations Enabled by Cooperative Ligand Insertion in Copper-Carboxylate Metal-Organic Frameworks.

Monomethylamine (NH2CH3), dimethylamine (NH(CH3)2), and trimethylamine (N(CH3)3) are important chemical feedstocks that are produced industrially as an azeotropic mixture and must be separated using an energy-intensive thermal distillation. While solid adsorbents have been proposed as alternatives to distillation for separating various industrial gas mixtures, methylamine separations remain largely unexplored in this context. Here, we investigate two isoreticular frameworks Cu(cyhdc) (cyhdc2- = trans-1,4-cyclohexanedicarboxylate) and Cu(bdc) (bdc2- = 1,4-benzenedicarboxylate) as prospective candidates for this challenging separation, motivated by the recent discovery that Cu(cyhdc) reversibly captures ammonia through a unique framework-to-coordination polymer phase change. Through a combination of gas adsorption and powder X-ray diffraction analyses, we find that Cu(cyhdc) and Cu(bdc) reversibly bind large quantities of mono- and dimethylamine through framework-to-coordination polymer phase change mechanisms, although both frameworks adsorb only moderate amounts of trimethylamine via physisorption. Single-crystal X-ray diffraction analysis of select mono- and dimethylamine containing phases suggests that the number of hydrogen bond donors available and the linker donor strength are key factors influencing amine uptake. Finally, investigation of the tricomponent adsorption behavior of both materials reveals that Cu(cyhdc) is selective for the capture of monomethylamine from a range of mono-, di-, and trimethylamine mixtures.

Adsorption of Selected Herbicides on Activated Carbon from Single- and Multi-Component Systems-Error Analysis in Isotherm Measurements.

The aim of this study is to examine the influence of various factors on the precision and repeatability of the experimental determination of herbicide adsorption isotherms. Studies were conducted for the activated carbon RIB as an adsorbent and three herbicides as adsorbates: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chlorophenoxyacetic acid (4-CPA), and 3-chlorophenoxypropionic acid (3-CPP). The herbicide adsorption process was carried out in single-component and multi-component modes (the herbicide was adsorbed in the presence of an accompanying substance, i.e., 4-nitroaniline (4-NA)). Due to the significant contribution of the competition phenomenon in the adsorption process, which is important, e.g., in multi-component environmental systems, a qualitative and quantitative analysis of herbicide adsorption in the presence of a competing substance was presented. This work presents, among other things, the influence of adsorbent heterogeneity (grain size) on measurement uncertainties. The spread of standard deviations for solutions requiring dilution during spectrophotometric measurements was discussed, indicating that dilutions contribute to increasing measurement uncertainties. The heterogeneity parameters of the Freundlich equation for the studied adsorption systems were analyzed; the 2,4-D/RIB system was indicated as the most energetically heterogeneous. Differentiation of the experimental conditions (pH, temperature) allowed us to assess their impact on the efficiency and mechanism of adsorption. A high repeatability of experimental isotherms was obtained for the multi-component system. The accuracy of quantitative determination of equilibrium concentrations for the tested two-component systems was assessed based on the measured UV-Vis spectra, and the adsorption of herbicides from single- and multi-component systems was compared.

Real-time monitoring of voltage-responsive biomolecular binding onto electro-switchable surfaces.

Voltage-responsive biosensors capable of monitoring real-time adsorption behavior of biological analytes onto electroactive surfaces offer attractive strategies for disease detection, separations, and other adsorption-dependent analytical techniques. Adsorption of biological analytes onto electrically switchable surfaces can be modelled using neutravidin and biotin. Here, we report self-assembled monolayers formed from voltage-switchable biotinylated molecules on gold surfaces with tunable sensitivity to neutravidin in response to applied voltages. By using electrochemical quartz crystal microbalance (EQCM), we demonstrated real-time switchable behavior of these bio-surfaces and investigate the range of sensitivity by varying the potential of the same surfaces from -400 mV to open circuit potential (+155 mV) to +300 mV. We compared the tunability of the mixed surfaces to bare Au surfaces, voltage inert surfaces, and switchable biotinylated surfaces. Our results indicate that quartz crystal microbalance allows real-time changes in analyte binding behavior, which enabled observing the evolution of neutravidin sensitivity as the applied voltage was shifted. EQCM could in principle be used in kinetic studies or to optimize voltage-switchable surfaces in adsorption-based diagnostics.

Mesoporous silica thin film as effective coating for enhancing osteogenesis through selective protein adsorption and blood clotting

The role of blood clots in tissue repair has been identified for a long time; however, its participation in the integration between implants and host tissues has attracted attention only in recent years. In this work, a mesoporous silica thin film (MSTF) with either vertical or parallel orientation was deposited on titania nanotubes surface, resulting in superhydrophilic nanoporous surfaces. A proteomic analysis of blood plasma adsorption revealed that the MSTF coating could significantly increase the abundance of acidic proteins and the adsorption of coagulation factors (XII and XI), with the help of cations (Na+, Ca2+) binding. As a result, both the activation of platelets and the formation of blood clots were significantly enhanced on the MSTF surface with more condensed fibrin networks. The two classical growth factors of platelets-derived growth factors-AB and transformed growth factors-βwere enriched in blood clots from the MSTF surface, which accounted for robust osteogenesis bothin vitroandin vivo. This study demonstrates that MSTF may be a promising coating to enhance osteogenesis by modulating blood clot formation.