Molecular Diameter Research Articles

Effects of the Wettability of a Probing Tip on the Hydration Layer Imaged in Atomic Force Microscopy

Utilizing a fully atomistic molecular dynamics simulation, we uncovered the molecular structure of a hydration layer formed on a hydrophobic carbon sample. By varying the wettability of a probe tip, we investigated how the hydration layer manifests as an image (force) measured in atomic force microscopy. With approaching a tip within 1 nm, the intrinsic hydration layer was significantly perturbed. A hydrophobic tip eventually evaporated the hydration layer at a closer distance, giving an attractive force characteristic of a hydrophobic force. With a hydrophilic tip, the hydration layer persisted with some compression, giving an oscillating force with a period close to the molecular diameter of water.

Production of Cyclic Anhydride-Modified Starches

Modified starches offer a biodegradable, readily available, and cost-effective alternative to petroleum-based products. The reaction of alkenylsuccinic anhydrides (ASAs), in particular, is an efficient method to produce amphiphilic starches with numerous applications in different areas. While ASAs are typically derived from petroleum sources, maleated soybean oil can also be used in an effort to produce materials from renewable sources. The reaction of gelatinized waxy maize starch with octenylsuccinic anhydride (OSA), dodecenylsuccinic anhydride (DDSA), a maleated fatty acid (TENAX 2010), phthalic anhydride (PA), 1,2,4-benzenetricarboxylic acid anhydride (trimellitic anhydride, TMA), and three maleated soybean oil samples, was investigated under different conditions. To minimize the reaction time and the amount of water required, the outcome of the esterification reaction was compared for starch dispersions in benchtop dispersed reactions, for starch melts in a heated torque rheometer, and for reactive extrusion in a pilot plant scale twin-screw extruder. The extent of reaction was quantified by 1H NMR analysis, and changes in molecular weight and diameter were monitored by gel permeation chromatography (GPC) analysis. The outcome of the reactions varied markedly in terms of reaction efficiency (RE), molecular weight distribution, and average hydrodynamic diameter, for the products derived from the different maleated reagents used, as well as for the different reaction protocols.

One-step Ethylene Purification from an Acetylene/Ethylene/Ethane Ternary Mixture by Cyclopentadiene Cobalt-Functionalized Metal-Organic Frameworks.

The separation of ethylene (C2 H4 ) from a mixture of ethane (C2 H6 ), ethylene (C2 H4 ), and acetylene (C2 H2 ) at normal temperature and pressure is a significant challenge. The sieving effect of pores is powerless due to the similar molecular size and kinetic diameter of these molecules. We report a new modification method based on a stable ftw topological Zr-MOF platform (MOF-525). Introduction of a cyclopentadiene cobalt functional group led to new ftw-type MOFs materials (UPC-612 and UPC-613), which increase the host-guest interaction and achieve efficient ethylene purification from the mixture of hydrocarbon gases. The high performance of UPC-612 and UPC-613 for C2 H2 /C2 H4 /C2 H6 separation has been verified by gas sorption isotherms, density functional theory (DFT), and experimentally determined breakthrough curves. This work provides a one-step separation of the ternary gas mixture and can further serve as a blueprint for the design and construction of function-oriented porous structures for such applications.

One‐step Ethylene Purification from an Acetylene/Ethylene/Ethane Ternary Mixture by Cyclopentadiene Cobalt‐Functionalized Metal–Organic Frameworks

AbstractThe separation of ethylene (C2H4) from a mixture of ethane (C2H6), ethylene (C2H4), and acetylene (C2H2) at normal temperature and pressure is a significant challenge. The sieving effect of pores is powerless due to the similar molecular size and kinetic diameter of these molecules. We report a new modification method based on a stableftwtopological Zr‐MOF platform (MOF‐525). Introduction of a cyclopentadiene cobalt functional group led to new ftw‐type MOFs materials (UPC‐612andUPC‐613), which increase the host‐guest interaction and achieve efficient ethylene purification from the mixture of hydrocarbon gases. The high performance ofUPC‐612andUPC‐613for C2H2/C2H4/C2H6separation has been verified by gas sorption isotherms, density functional theory (DFT), and experimentally determined breakthrough curves. This work provides a one‐step separation of the ternary gas mixture and can further serve as a blueprint for the design and construction of function‐oriented porous structures for such applications.

Diffusion in dense supercritical methane from quasi-elastic neutron scattering measurements

Methane, the principal component of natural gas, is an important energy source and raw material for chemical reactions. It also plays a significant role in planetary physics, being one of the major constituents of giant planets. Here, we report measurements of the molecular self-diffusion coefficient of dense supercritical CH4 reaching the freezing pressure. We find that the high-pressure behaviour of the self-diffusion coefficient measured by quasi-elastic neutron scattering at 300 K departs from that expected for a dense fluid of hard spheres and suggests a density-dependent molecular diameter. Breakdown of the Stokes–Einstein–Sutherland relation is observed and the experimental results suggest the existence of another scaling between self-diffusion coefficient D and shear viscosity η, in such a way that Dη/ρ=constant at constant temperature, with ρ the density. These findings underpin the lack of a simple model for dense fluids including the pressure dependence of their transport properties.

Pervaporative Dehydration of Organic Solvents Using High-Silica CHA-Type Zeolite Membrane.

A high-silica chabazite (CHA) type zeolite membrane was prepared on the porous α-Al2O3 support tube by the secondary growth of seed particles. The dehydration performances of the membrane were determined using methanol, ethanol, 2-propanol, acetone, acetic acid, methyl ethyl ketone (MEK), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrolidone (NMP) at 303–373 K. As a result, the dehydration performances of the membrane were categorized to following three types: (1) 2-propanol, acetone, THF, and MEK; (2) ethanol and acetic acid; and (3) methanol, DMF, and DMSO, and NMP. The adsorption isotherms of water, methanol, ethanol, and 2-propanol were determined to discuss the influences of the organic solvents on the permeation and separation performances of the membrane. For 2-propanol, acetone, MEK, and THF solutions, the high permeation fluxes and separation factors were obtained because of the preferential adsorption of water due to molecular sieving. In contrast, the permeation fluxes and separation factors were relatively low for methanol, DMF, and DMSO, and NMP solutions. The lower dehydration performance for the methanol solution was due to the adsorption of methanol. The permeation fluxes for ethanol and acetic acid solution were ca. 1 kg m−2 h−1. The significantly low flux was attributed to the similar molecular diameter to the micropore size of CHA-type zeolite.

Development of thermodynamic frameworks for modeling of clathrate hydrates stability conditions in porous media

A thermodynamic approach based on dissociation enthalpy of clathrate hydrate and water activity in porous medium is introduced. The dissociation enthalpy of clathrate hydrate is correlated as a function of mean pore radius, and mean molecular diameter of the guest molecule. The constants of the proposed correlation were obtained by minimizing the objective function and using 30% of available experimental data of simple clathrate hydrates. In this model, the water activity in the porous medium is calculated considering the effects of capillary pressure, porous medium properties, and geometric constraints. Subsequently, the solid solution theory of van der Waals-Platteeuw is extended to predict the stability conditions of clathrate hydrate in porous medium by modifying water activity. Both proposed approaches are capable of predicting / estimating the dissociation conditions of simple and mixed- clathrate hydrates in various porous media and under a wide ranges of operating conditions. The results confirm that as pore diameter decreases, the inhibition effect of porous medium increases.

Adsorption of 17α-Ethinyl Estradiol and Bisphenol A to Graphene-Based Materials: Effects of Configuration of Adsorbates and the Presence of Cationic Surfactant

Endocrine-disrupting chemicals (EDCs) have attracted much attention in recent years. Graphene-based materials (GMs) have been deemed as excellent adsorbents for the removal of EDCs. The objective of the present study was to understand how the cationic surfactants (CTAB; cetyltrimethylammonium nitrate) affect the adsorption of EDCs (17 α-ethinyl estradiol (EE2) and bisphenol A (BPA)) on graphene oxide (GO), reduced graphene oxides (RGOs), and the few-layered commercial graphene (CG). It was observed that the presence of CTAB showed different effects on the adsorption of EDCs to different GMs. The adsorption of EDCs on GO was enhanced because of the enhanced hydrophobicity of GMs after the adsorption of CTAB and the newly formed hemimicelles by the adsorbed CTAB, which could serve as the partition phase for EDCs. Moreover, the electron donor-acceptor interaction and cation bridging effect of the –NH4 + group of the adsorbed CTAB between EDCs and GMs could also enhance the adsorption of EDCs to GMs. With the increase of the extent of GM reduction, the adsorption enhancement by the presence of CTAB weakened. This could be attributed to the competition and pore blockage effect caused by the adsorbed CTAB. It is worth noting that the enhancement of CTAB on the adsorption of BPA to GMs was more profound than that of EE2. This is likely because the pore blockage effect plays a less important role in the adsorption of BPA due to its smaller molecular diameter and deformable structure.

Study on thermodynamics, dynamics and reverse shape separation selectivity of mesoporous UiO-66 for nHEP/MCH

UiO-66-Z with uniform mesopores using 2-aminoterephthalic acid and terephthalic acid as mixed ligands was synthesized by hydrothermal method in this paper. Thermodynamic and dynamic properties of UiO-66-Z were discussed. Dynamic separation performance and adsorption selectivity of UiO-66-Z for the equimolar n-heptane/methylcyclohexane (nHEP/MCH) binary mixture were investigated. Results show that UiO-66-Z has complete tetrahedral cages with uniform mesopores of 38 Å. Adsorption rate constant of MCH on UiO-66-Z (14.5 × 10 −3 S −1 ) is twice that of UiO-66 (6.7 × 10 −3 S −1 ), while nHEP does not significantly change at 323K with the pressure of 0.05–0.1 kPa. Effective adsorption diffusion coefficient of nHEP and MCH on the UiO-66-Z is about 25 times higher than that on the UiO-66. Compared with UiO-66, the desorption activation energy (Ed 1 ) of the first desorption peak of nHEP and MCH on the UiO-66-Z is reduced by 53.75% and 76.66%, respectively. The separation selectivity of MCH to nHEP on the UiO-66-Z reaches up to 3.13 at 473 K. Results indicate that the introduction of mesopores in the UiO-66-Z can enhance mass transfer of nHEP and MCH in the pores, especially which is more obvious mass transfer effect for MCH with a larger molecular dynamics diameter under low partial pressure. The retention of most tetrahedral cages in the UiO-66-Z is conducive to improving its inverse shape separation selectivity for MCH/nHEP. Compared with UiO-66, nHEP and MCH have higher desorption efficiency on UiO-66-Z at the same temperature and time. • Mesoporous UiO-66 was synthesized by dual mixed ligands for enhancing mass transfer performance. • The retention of most tetrahedral cages in the UiO-66-Z is conducive to improve separation selectivity for methylcyclohexane/n-heptane. • Separation selectivity of UiO-66-Z to MCH/nHEP reaches up to 3.13 at 473 K. • MCH and nHEP have higher desorption efficiency on UiO-66-Z at the same temperature and time.

(Invited) Parametrization of Gaussian Disordered Model with Fully Spatial and Energetic Disorders for Organic Thin Film Transistors

So far, the most widely addressed hopping transport model for organic disordered semiconductors (ODSs) is the so-called extended Gaussian disordered model (EGDM) [1] based on numerical simulations within the cubic lattice without spatial disorder. As known since 1973 [2] and confirmed recently [3], the EGDM is based on the parametrization of transport coefficients in the framework of the irrelevant set of parameters. Parameters responsible for the effects are not in the equations, while parameters in the equations are not responsible for the effects [3]. The deficiencies of the EGDM are particularly pronounced for systems with spatial disorder. Therefore, the study of Gaussian disordered model (GDM) with spatial disorder is necessary to provide a simulation tool for transport coefficients of charge carriers in real organic thin film transistors (OTFTs) and organic light-emitting diodes (OLEDs) based on materials with spatial disorder.In this study, we examine the GDM which contains both spatial and energetic disorders and propose a physical parametrization for OTFTs. We determine all the parameters by adjusting the localization length and the attempt-to-escape frequency to satisfy experimentally measured mobility. For the localization length, the concept of effective localization length [4] is adopted which has the order of a molecular diameter, because assumption of the very low localization length (commonly order of 10-8 cm) induces very low mobility due to the strong localization of the each state. The large effective localization length can alleviate the strong localization and so it can predict the similar scale of mobility with experimentally measured one. In addition, the proper value of the attempt-to-escape frequency is estimated from comparison between a direct calculation of Miller-Abrahams (MA) transition rate and theoretical estimations of the hopping transition rate based on MA and Marcus theories. We show that its value should be increased by more than two orders of magnitude than conventional value to simulate high mobility device.Then, we validate our parametrization of GDM through comparison between experimentally measured and numerically calculated transfer curves and charge carrier mobility of OTFTs at various temperature (Fig. 1). The staggered pentacene-based OTFT device was fabricated and measured at different temperatures T = 329, 293, 258 and 233 K. The charge carrier mobility was extracted by the transmission line method (TLM). For numerical simulation, we implemented the GDM by Baranovskii [3] into the commercial TCAD simulation tool, Silvaco ATLAS. Then, the numerical solver calculated Poisson’s, continuity and drift-diffusion equations in a self-consistent manner with characteristics of ODSs such as Gaussian density-of-states, generalized Einstein relation and GDM by Baranovskii. Numerical simulation with a single set of parameters makes an accurate fit with experimentally measured transfer curves (Fig. 1a) and charge carrier mobility (Fig. 1b) at every temperature condition.In conclusion, we propose physically based parametrization of GDM with fully spatial and energetical disorder for OTFTs. It is confirmed that the localization length and the attempt-to-escape frequency are key parameters for the practical fitting with experimental result. In addition, we can expect that the electronic design automate (EDA) industry can be promoted by providing rigorous transport model and its parametrization for OTFTs within commercial simulation software.[1] W. F. Pasveer, J. Cottaar, C. Tanase, R. Coehoorn, P. A. Bobbert, P. W. M. Blom, M. De Leeuw, and M. A. J. Michels, Phys. Rev. Lett. 94, 206601 (2005).[2] B.I. Shklovskii Sov. Phys.-Semicond. 6, 1964 (1973).[3] S. D. Baranovskii, Phys. Status Solidi Appl. Mater. Sci. 215, 1700676 (2018).[4] A. V Nenashev, J. O. Oelerich, and S. D. Baranovskii, J. Phys. Condens. Matter 27, 093201 (2015). Figure 1

Boiling-up of a superheated Lennard-Jones liquid in a channel with solid smooth walls

Nucleation of bubbles in a stretched Lennard-Jones liquid located between two flat smooth solid walls has been investigated by the molecular dynamics method. A dense monomolecular liquid layer is maintained on the wall surface during near-wall boiling-up at the moment of bubble origin. The centers of bubbles are located mainly at a distance of (1.5–3) molecular diameters from the walls. The nucleation rate in the near-wall layer is two orders of magnitude higher than in a homogeneous liquid. Liquid boiling-up in the presence of smooth wettable walls proceeds by the mechanism of homogeneous nucleation, independently of the bubble formation location.

Effects of protein concentration during ultrasonic processing on physicochemical properties and techno-functionality of plant food proteins

Plant proteins have been increasingly recognized as very relevant food ingredients, due to concerns related to ecology, health and even religion. However, compared to food proteins from animal sources, the former ones have considerably lower dispersibility. Because of this, exploring techno-functional properties of plant proteins in formulations is much more difficult. Ultrasound has been explored in food processing for different purposes and represents a strategic non-thermal operation to enhance the dispersibility (and, consequently, several techno-functionalities) of food proteins. During ultrasonic processing in aqueous medium, the concentration of protein material may favour or impair the action of ultrasound waves, but this fact has been only marginally addressed in literature. Hence, this study investigated the effects of different protein concentrations during ultrasonic processing on techno-functional properties of soy protein isolate (SPI), rice protein isolate (RPI), and pea protein concentrate (PPC). Ultrasonic treatments (USt) at 20 kHz were designed using a Box–Behnken experimental planning, varying ultrasound power (562.5, 637.5 or 712.5 W), application time (120, 360 or 600 s), and concentration of the proteins in aqueous medium [1.0%, 3.0% or 5.0% (w/v)]. Hydrophobic surface index (H0), molecular mass profile, hydrodynamic diameter (dh), and ζ-potential of these three protein materials after USt were evaluated and discussed. Moreover, Response surface methodology was applied to evaluate and to optimize the following techno-functionalities of SPI, RPI, and PPC: water and oil holding capacity (WHC and OHC), and foaming, emulsifying, and gelling properties. After USt, OHC increased for the three protein materials. For SPI, dispersibility and FC at 712,5 W | 600 s | 1.0 % w/v were improved. The WHC (562.5 W | 120 s | 5.0 % w/v), OHC (562,5 W | 120 s | 1.0 % w/v) of SPI were also increased. For PPC, USt led to enhanced dispersibility (712.5 W | 360 s | 3.0 % w/v), WHC (712.5 W | 600 s | 5.0 % w/v), OHC (637,5 W | 120 s | 3.0 % w/v). On the other hand, none of the USt was efficient to significantly modify neither physicochemical nor techno-functional properties of RPI, which remains a challenge. In summary, the present study showed that USt may effectively improve the technological functionality of SPI and PPC. However, concentrations of these protein materials should be kept < 5% (w/v) during ultrasonic processing, otherwise the ultrasound waves are attenuated, and their desirable effects too.

Metabolism and Distribution of Novel Tumor Targeting Drugs In Vivo.

As a new tumor therapy, targeted therapy is becoming a hot topic due to its high efficiency and low toxicity. Drug effects of targeted tumor drugs are closely related to pharmacokinetics, so it is important to understand their distribution and metabolism in vivo. A systematic review of the literature on the metabolism and distribution of targeted drugs over the past 20 years was conducted, and the pharmacokinetic parameters of approved targeted drugs were summarized in combination with the FDA's drug instructions. Targeting drugs are divided into two categories: small molecule inhibitors and monoclonal antibodies. Novel targeting drugs and their mechanisms of action, which have been developed in recent years, are summarized. The distribution and metabolic processes of each drug in the human body are reviewed. In this review, we found that the distribution and metabolism of small molecule kinase inhibitors (TKI) and monoclonal antibodies (mAb) showed different characteristics based on the differences of action mechanism and molecular characteristics. TKI absorbed rapidly (Tmax ≈ 1-4 h) and distributed in large amounts (Vd > 100 L). It was mainly oxidized and reduced by cytochrome P450 CYP3A4. However, due to the large molecular diameter, mAb was distributed to tissues slowly, and the volume of distribution was usually very low (Vd < 10 L). It was mainly hydrolyzed and metabolized into peptides and amino acids by protease hydrolysis. In addition, some of the latest drugs are still in clinical trials, and the in vivo process still needs further study. According to the summary of the research progress of the existing targeting drugs, it is found that they have high specificity, but there are still deficiencies in drug resistance and safety. Therefore, the development of safer and more effective targeted drugs is the future research direction. Meanwhile, this study also provides a theoretical basis for clinical accurate drug delivery.

Pressure regulated basis for gene transcription by delta-cell micro-compliance modeled in silico: Biphenyl, bisphenol and small molecule ligand models of cell contraction-expansion.

Molecular diameter, lipophilicity and hydrophilicity exclusion affinity limits exist for small molecule carrier-mediated diffusion or transport through channel pores or interaction with the cell surface glycocalyx. The molecular structure lipophilicity limit for non-specific carrier-mediated transmembrane diffusion through polarity-selective transport channels of the cell membrane is Lexternal structure ∙ Hpolar group-1 of ≥ 1.07. The cell membrane channel pore size is > 0.752 and < 0.758 nm based on a 3-D ellipsoid model (biphenyl), and within the molecular diameter size range 0.744 and 0.762 nm based on a 2-D elliptical model (alkanol). The adjusted van der Waals diameter (vdWD, adj; nm) for the subset of halogenated vapors is predictive of the required MAC for anesthetic potency at an initial (-) Δ Cmicro effect. The molecular structure L ∙ Hpolar group-1 for Neu5Ac is 0.080, and the L ∙ Hpolar group-1 interval range for the cell surface glycocalyx hydrophilicity barrier interaction is 0.101 (Saxitoxin, Stx; Linternal structure ∙ Hpolar group-1) - 0.092 (m-xylenediamine, Lexternal structure · Hpolar group). Differential predictive effective pressure mapping of gene activation or repression reveals that p-dioxin exposure results in activation of AhR-Erβ (Arnt)/Nrf-2, Pparδ, Errγ (LxRα), Dio3 (Dio2) and Trα limbs, and due to high affinity Dio2 and Dio3 (OH-TriCDD, Lext · H-1: 1.91–4.31) exothermy-antagonism (Δ contraction) with high affinity T4/rT3-TRα-mediated agonism (Δ expansion). co-planar PCB metabolite exposure (Lext · H-1: 1.95–3.91) results in activation of AhR (Erα/β)/Nrf2, Rev-Erbβ, Errα, Dio3 (Dio2) and Trα limbs with a Δ Cmicro contraction of 0.89 and Δ Cmicro expansion of 1.05 as compared to p-dioxin. co-, ortho-planar PCB metabolite exposure results in activation of Car/PxR, Pparα (Srebf1,—Lxrβ), Arnt (AhR-Erβ), AR, Dio1 (Dio2) and Trβ limbs with a Δ Cmicro contraction of 0.73 and Δ Cmicro expansion of 1.18 (as compared to p-dioxin). Bisphenol A exposure (Lext struct ∙ H-1: 1.08–1.12, BPA–BPE, Errγ; BPAF, Lext struct ∙ H-1: 1.23, CM Erα, β) results in increased duration at Peff for Timm8b (Peff 0.247) transcription and in indirect activation of the AhR/Nrf-2 hybrid pathway with decreased duration at Peff 0.200 (Nrf1) and increased duration at Peff 0.257 (Dffa). The Bpa/Bpaf convergent pathway Cmicro contraction-expansion response increase in the lower Peff interval is 0.040; in comparison, small molecule hormone Δ Cmicro contraction-expansion response increases in the lower Peff intervals for gene expression ≤ 0.168 (Dex· GR) ≥ 0.156 (Dht · AR), with grade of duration at Peff (min·count) of 1.33x105 (Dex/Cort) and 1.8–2.53x105 (Dht/R1881) as compared to the (-) coupled (+) Δ Cmicro Peff to 0.136 (Wnt5a, Esr2) with applied DES (1.86x106). The subtype of trans-differentiated cell as a result of an applied toxin or toxicant is predictable by delta-Cmicro determined by Peff mapping. Study findings offer additional perspective on the basis for pressure regulated gene transcription by alterations in cell micro-compliance (Δ contraction-expansion, Cmicro), and are applicable for the further predictive modeling of gene to gene transcription interactions, and small molecule modulation of cell effective pressure (Peff) and its potential.

Enhancing the pervaporation performance of PEBA/PVDF membrane by incorporating MAF-6 for the separation of phenol from its aqueous solution

Phenol is highly toxic and carcinogenic even at low concentrations. This study focused on preparing high-performance mixed matrix membranes (MMMs) for the pervaporation separation of phenol from its aqueous solution. A highly-efficient zeolitic metal azolate framework, RHO-[Zn(Heim)2] (MAF-6, Heim = 2-ethylimidazole) was incorporated into the polyether block amide (PEBA-2533) supported on the polyvinylidene fluoride (PVDF) ultrafiltration membrane. The MAF-6 was chosen as the filler due to its inherent hydrophobic surfaces and aperture size (7.6 Å), which is larger than the molecular kinetic diameter of phenol (6.6 Å). Effects of the casting solution concentration, active layer thickness, MAF-6 loading, operating temperature, and phenol concentration were systematically investigated. With the increase of the MAF-6 loading ratio X from 0 to 7, the phenol flux of the membrane was gradually enhanced, but the water flux was reduced. For 1000 ppm phenol aqueous solution at 80 °C, MAF-6–7@MMM displayed the optimal separation factor of 25.9 with a phenol flux of 89.2 g∙m−2∙h−1. The pervaporation separation index (PSI) of the MAF-6–7@MMM was 1317.7 kg∙µm∙m−2∙h−1 at 80 °C, which was much higher than the PEBA/PVDF membrane (787 kg∙µm∙m−2∙h−1). Impressively, an increasing feed temperature enhanced the phenol flux more prominently than water, owing to the hydrophobicity and porosity of MAF-6. Consequently, the resultant MAF-6-X@MMMs broke the trade-off limitation between phenol permeability and selectivity. The as-prepared membrane also exhibited exceptional long-term stability, suggesting its prospect of industrial application.

How does the shape and surface energy of pores affect the adsorption of nanoconfined fluids?

AbstractWe report a systematic molecular simulation study of the behavior of Lennard–Jones fluids inside nanopores of diverse shapes, focusing on the effect that the pore geometry and the local energetic environment have on the adsorption isotherms. Infinitely long pores with polygon (triangle, square, pentagon, hexagon, octagon, decagon, and circle) cross sections are considered. Three different pore sizes commensurate with the molecular diameters along with three different values of fluid–solid energy interactions are chosen to perform Grand Canonical Monte Carlo simulations at a subcritical temperature. Overall, the effect of nanoconfinement on the adsorption of fluids is seen to be a delicate balance between the geometric packing restrictions imposed by the hard cores of the molecules and the surfaces, the excess adsorption induced by the presence (or absence) of energetically favored “hot spots” and the overall ratio of surface/bulk fluid volume present in the pore.

Numerical Model for Hydration-Lubricated Contact and Its Friction Behavior at Nanoscale

In this study, we propose a numerical model to investigate the contact and friction behaviours of hydration lubricated contact in an aqueous solution confined in a gap of several molecular diameters. A force–distance curve was obtained under different surface forces, and friction behaviour was determined using the modified Eyring thermal activation model. The results showed that the normal boundary contact pressure and contact gaps were obtained using the proposed numerical model. In addition, friction force increased with the logarithm of sliding velocity. Hence, the Eyring model could predict the friction behaviour of hydration lubrication. Moreover, it could capture the underlying physical principles of the contact and friction behaviours of hydration lubrication.

Noble metal location in porous supports determined by reaction with phosphines

Different phosphines (PR 3 , R = phenyl, 4-methoxyphenyl) are demonstrated to be useful probe molecules for the spatial location and quantification of noble metal (NM) atoms within mesoporous and microporous support materials, such as silica A200, mesoporous SBA-15, and different zeolites Y. For this purpose, the high NMR sensitivity of 31 P nuclei (spin I = ½, abundance of 100%) and the characteristic chemical shifts of phosphine complexes formed with noble metals were utilized. A straightforward method of physically mixing the reduced noble metal-containing catalysts with the solid phosphine powders and heating under well-defined conditions is shown. Complexation of triphenylphosphine (PPh 3 ) and tris(4-methoxyphenyl)phosphine, P(PhOMe) 3 , with Pt, Rh, Pd, and Ru on open surfaces and in mesopores leads to characteristic 31 P MAS NMR signals at δ = 33–41 ppm. Because of the different molecular diameters of PPh 3 (0.72 nm) and P(PhOMe) 3 (0.91 nm), adsorption of these two probe molecules allows to distinguish between noble metal atoms located at the outer surface of zeolite particles and those in secondary mesopores and in supercages of zeolites Y. For the first time this method enables the characterization of noble metals directly using probe molecules and 31 P MAS NMR spectroscopy. • Noble metals on silica, mesoporous SBA-15, and multiple zeolites Y investigated. • Application of new phosphine probes with varied sizes. • Phosphines form complexes with supported noble metals Pt, Pd, Ru, Rh. • Refined, quantitative evaluation of the signal intensity. • New method for determining the location of noble metals within zeolites.

Probing the mechanism of gelation and anion sensing capability of a thiazole based amide gelator: A case study

In priori design of Low Molecular weight Gelators (LMWGs) based on the molecular structure is a challenging task and requires the hierarchy knowledge from single molecule packing to a supramolecular assembly in gelator fibers. A simple strategy to select and probe the packing of a molecule from a crystalline state to a semi solid gel state was undertaken in a Thiazole based amide, undecaneamido thiazole (Thz-9). The novel approach to select the promising molecule with gelation property was made using Small Angle Neutron Scattering (SANS) and Small Angle X-ray Scattering (SAXS) analysis of solid samples. Based on the preliminary examination of SANS/SAXS studies Thz-9 molecule was selected and subjected to study the packing of molecule in crystalline to a gel state. The sol-gel transition and variation of the molecular diameter of the supramolecular assembly of Thz-9 molecules in the various states were established using temperature dependent SANS study. Efforts were also directed to establish the relationship between the packing of molecules in single crystal structure to packing in xerogel (dried gel) using Powder X-ray Diffraction (PXRD). A potential application of Thz-9 as a fluoride ion sensor with good selectivity and sensitivity was established.

Purification of Lumbricus terrestris Mega-Hemoglobin for Diverse Oxygen Therapeutic Applications.

Oxygen therapeutics are being developed for a variety of applications in transfusion medicine. In order to reduce the side-effects (vasoconstriction, systemic hypertension, and oxidative tissue injury) associated with previous generations of oxygen therapeutics, new strategies are focused on increasing the molecular diameter of hemoglobin obtained from mammalian sources via polymerization and encapsulation. Another approach towards oxygen therapeutic design has centered on using naturally occurring large molecular diameter hemoglobins (i.e. erythrocruorins) derived from annelid sources. Therefore, the goal of this study was to purify erythrocruorin from the terrestrial worm Lumbricus terrestris for diverse oxygen therapeutic applications. Tangential flow filtration (TFF) was used as a scalable protein purification platform to obtain a >99% pure LtEc product, which was confirmed by size exclusion high performance liquid chromatography and SDS-PAGE analysis. In vitro characterization concluded that the ultra-pure LtEc product had oxygen equilibrium properties similar to human red blood cells, and a lower rate of auto-oxidation compared to human hemoglobin, both of which should enable efficient oxygen transport under physiological conditions. In vivo evaluation concluded that the ultra-pure product had positive effects on the microcirculation sustaining functional capillary density compared to a less pure product (~86% purity). In summary, we purified an LtEc product with favorable biophysical properties that performed well in an animal model using a reliable and scalable purification platform to eliminate undesirable proteins.