Bulk Molecules Research Articles

Modulating Coarse-Grained Dynamics by Perturbing Free Energy Landscapes.

We introduce an approach to describe the long-time dynamics of multiatomic molecules by modulating the free energy landscape (FEL) to capture dominant features of the energy-barrier crossing dynamics of the all-atom (AA) system. Notably, we establish that the self-diffusion coefficient of coarse-grained (CG) systems can be accurately delineated by enhancing conservative force fields with high-frequency perturbations. Using theoretical arguments, we show that these perturbations do not alter the lower-order distribution functions, thereby preserving the structure of the AA system after coarse-graining. We demonstrate the utility of this approach using molecular dynamics simulations of simple molecules in bulk with distinct dynamical characteristics with and without time scale separations as well as for inhomogeneous systems where a fluid is confined in a slit-like nanochannel. Additionally, we also apply our approach to more powerful many-body potentials optimized by using machine learning (ML).

Tailoring of the Properties of Amorphous Mesoporous Titanosilicates Active in Acetone Condensation.

Amorphous mesoporous materials are promising as catalysts for processes involving or forming bulk molecules. In a reaction such as acetone condensation to form mesitylene, an effective catalyst should not only have a developed porous structure but also have active centers of acidic and basic types. The sol-gel approach allows one to obtain titanosilicates with such characteristics. This work demonstrates the possibility of controlling their properties by varying the conditions for the synthesis of titanosilicate gels. It has been established that controlling hydrolysis allows one to increase the activity of amorphous mesoporous titanosilicates by 10 times: from acetone conversion of 6% to 60%. It has been shown that the use of titanium acetylacetonate complexes in the synthesis of gels leads to an increase in the content of tetracoordinated Ti in the structure and contributes to an increase in the acidity of titanosilicates. During the condensation of acetone on the obtained mesoporous titanosilicates, high acetone conversion (60-79%) and mesitylene selectivity of up to 83% were achieved.

Progress on clay swelling inhibitors: a comprehensive review

Relevance. It is known that swelling of a well wall due to the presence of water negatively affects drilling operations, causing a significant increase in their material costs. The use of various inhibitors prevents this effect and the drilling mud reacting on wellbore narrowing. In this sense, the problems of developing polymer, amino-, ionic liquid and shale inhibitors of surfactants considered in the article are very relevant and of practical interest to oil engineers in terms of the prospects for fundamental and applied researches of these issues. Aim. To study the possibilities of existing approaches and methods that determine the characteristics of the main clay swelling inhibitors, the regularities of changes in the properties of traditional and non-traditional clay materials, as well as the mechanisms of clay swelling with the identification of the most characteristic group of these inhibitors. Object. Processes of minimizing the effect of wall narrowing as a result of exposure to inhibitors. Methods. Systematic, critical and comprehensive analysis of modern data on clay swelling inhibition in the field of drilling muds. Results. The authors have carried out the detailed analysis of clay swelling. The paper discusses the characteristics of inhibitors required to prevent swelling, in the structure of which nitrogen and ionic liquids are contained. It is noted that a high-quality clay swelling inhibitor should include in its base a water-soluble bulk molecule with a distinct hydrophobic and hydrophilic structure; have characteristics, which allow replacing the hydrated cations of the intermediate layer with some hydrophobic cations, such as ammonium ions instead of sodium ions; differ in the ability to disperse multiple cations well. It was found that functional groups that support inhibitor binding to the siloxane groups of the clay are able to significantly expand clay swelling.

The Gaseous Hydrogen Transport Capacity in Nanopores Coupling Bulk Flow Mechanisms and Surface Diffusion: Integration of Profession and Innovation

Due to its unique chemical structure, hydrogen energy inherently has a high calorific value without reinforcing global warming, so it is expected to be a promising alternative energy source in the future. In this work, we focus on nanoconfined hydrogen flow performance, a critical issue in terms of geological hydrogen storage. For nanopores where the pore scale is comparable to hydrogen’s molecular size, the impact on hydrogen molecules exerted by the pore surface cannot be neglected, leading to the molecules near the surface gaining mobility and slipping on the surface. Furthermore, hydrogen adsorption takes place in the nanopores, and the way the adsorption molecules move is completely different from the bulk molecules. Hence, the frequently applied Navier–Stokes equation, based on the no-slip boundary condition and overlooking the contribution of the adsorption molecules, fails to precisely predict the hydrogen flow capacity in nanopores. In this paper, hydrogen molecules are classified as bulk molecules and adsorption molecules, and then models for the bulk hydrogen and the adsorption hydrogen are developed separately. In detail, the bulk hydrogen model considers the slip boundary and rarefaction effect characterized by the Knudsen number, while the flow of the adsorption hydrogen is driven by a chemical potential gradient, which is a function of pressure and the essential adsorption capacity. Subsequently, a general model for the hydrogen flow in nanopores is established through weight superposition of the bulk hydrogen flow as well as the adsorption hydrogen, and the key weight coefficients are determined according to the volume proportion of the identified area. The results indicate that (a) the surface diffusion of the adsorption molecules dominates the hydrogen flow capacity inside nanopores with a pore size of less than 5 nm; (b) improving the pressure benefits the bulk hydrogen flow and plays a detrimental role in reducing surface diffusion at a relatively large pressure range; (c) the nanoconfined hydrogen flow conductance with a strong adsorption capacity (PL = 2 MPa) could reach a value ten times greater than that with a weak adsorption capacity (PL = 10 MPa). This research provides a profound framework for exploring hydrogen flow behavior in ultra-tight strata related to adsorption phenomena.

Smoothed grain boundary grooves, passivated defects and released compressive stresses via bulk molecule doping for efficient perovskite solar cells

In preparing efficient and stable perovskite solar cells (PSCs), it is challenging to simultaneously overcome the inherent problems of grain boundary grooves (GBGs), residual stress, defect states in perovskite film. Herein, a small organic molecule additive, pyridinium 1,4-zwitterionic thiolates (PZT), is synthesized to prepare high-quality PZT-doped perovskite active layer through bulk molecule doping method. The PZT promotes the crystallization of perovskite, optimizes the crystal orientation, and smooths the GBGs of perovskite films. Meanwhile, PZT releases compressive stress and passivates the perovskite defects at the surface/interface as well as internal grain boundaries in the perovskite film, which inhibits the charge recombination and promotes the charge separation and transport efficiency in the bulk perovskite films through the atomic interaction at the perovskite/PZT interface. In addition, the PZT also inhibits ion migration in perovskite film and increases film hydrophobicity. Benefiting from the above benefits, the PSCs based on perovskite:PZT layer achieved a maximum power conversion efficiency of 23.45%, much higher than that (21.79%) of control device. They also show significantly improved long-term stability under different aging test conditions. Our work provides a guide for improving the performance of PSCs by designing suitable multifunctional molecules.

Molecular dimer junctions forming: Role of disulfide bonds and electrode‐compression‐time

AbstractThanks to their excellent bond strength, phenyl‐based molecules with thiol anchoring groups are extensively employed to form stable single‐molecule junctions. However, two critical questions are still not answered which seriously hinder high‐yield establishing reliable molecular functional devices: (1) Whether molecular dimer junctions will be formed, and if this is the case, whether the dimerization is caused by intermolecular disulfide bonds or π–π stacking of phenyl rings; (2) Upon a mechanical‐compression force, is it possible that both anchoring groups of the molecule bond to the same electrode instead of bridging two opposite electrodes, which would drastically reduce the yield of the molecular junctions. Here, combining UV‐Vis/Raman spectroscopy of bulk molecules and conductance/flicker‐noise measurements of single molecules, we give compelling evidence that molecular dimers naturally form under ambient conditions, primarily via disulfide bonds rather than by π–π stacking. We further proposed a technique, named electrode‐compression‐hold‐on (ECHO), and reveal that the two thiol groups of phenyl‐backboned molecules will bond to the same electrode upon a compression force with a prolongated ECHO time. In contrast, the compression‐time‐dependent phenomenon is not observed for alkyl‐backboned molecules. The underlying mechanism for these unprecedented observations is elucidated, shedding light on the yield of molecular junctions.

Suppressing non-radiative relaxation in a NIR single photon emitter: the impact of deuteration and temperature.

The fluorescence quantum yield of organic NIR-emitters is typically limited by internal conversion (IC), restricting their applications in imaging and quantum technology. Here, we study the impact of deuteration and temperature on the emission properties of dibenzoterrylene (DBT) by bulk and single molecule spectroscopy. Based on simple photophysical modelling, we first clarify how IC affects the single molecule emission rate. Next, we show that deuteration of DBT leads to a concomitant increase in the fluorescence lifetime and quantum yield by up to 60%. This clear deuterium isotope effect indicates a significant contribution of C-H-vibrations in the IC process. The solvent-dependent changes in the IC rate of hydrogenated and deuterated compounds were found to follow the predictions of the energy gap law in the weak coupling limit. This view is supported by the very weak temperature dependence of the IC rate between 5 and 300 K. Our results not only shed light on the non-radiative relaxation of a topical polycyclic aromatic hydrocarbon, but also pave the way for single molecule quantum emitters with high emission yields in the NIR.

Biological evaluation, molecular modeling and dynamic simulation of IDQ bulk and IDQNPs: Organo nano-bio interface in the medical field

The study aimed to synthesize 7,7-dimethyl-10-aryl,-7,8-dihydro-5H-indeno-[1,2-b]-quinoline-9,11(6H,10H)‑dione nanoparticles (IDQNPs) and to explore their biological activities i.e. anticancer, antioxidant and antibacterial. For this purpose, we prepared IDQNPs in a single non-solvent i.e. water by simple reprecipitation method. These nanoparticles were highly fluorescent organic nanoparticles (FONPs). The DLS measurements detected that 114 nm size of synthesized IDQNPs. A microphotograph taken using field emission scanning electron microscope (FE-SEM) of air-dried nanoparticle film showed nanoflakes with a feathery shape. Moreover, absorption and emission spectroscopy measurements displayed discrete peak of IDQNPs from their bulk molecule. The highly fluorescent IDQNPs ultimately give higher quantum yield compared to parental IDQ. Fluorescent organic nanoflakes are additionally utilized in vitro for anticancer and antimicrobial activity and antioxidant properties. Cytotoxicity of IDQ and IDQNPs were determined on the basis of measurement of in vitro growth inhibition of breast cancer cell lines in 96 well plates by using 5-fluoro uracil as a standard. The in vitro cytotoxicity of the IDQNPs assayed against MCF-7 cell lines showed higher cytotoxicity with the lower IC50 value i.e. 3.94 than IDQ parent indicating their efficiency in killing the cancer cells even at low concentrations. Furthermore, antioxidant and antibacterial activities were done by DPPH 96 well method and well plate diffusion method respectively. IDQNPs showed significant antioxidant property against DPPH radical. The IDQ parent compound and IDQNPs suspension at concentration 5 mg, 10 mg, and 100 µL, 200 µL respectively does not show activity against E. coli and Stap. Aureus. The molecular docking and dynamic simulation study were as done for IDQ bulk material. The finding of our study recommend that IDQNPs is a suitable candidate for preclinical cancer and antioxidant studies. This report may open a new avenue in the medical field and life science.

A comparative study between Monte Carlo entropic sampling method and local mean field investigations of thermal properties of spin-crossover nanoparticles based on Ising-like model

The thermally induced transitions between low-spin (LS) and high-spin (HS) configurations of spin-crossover (SCO) nanoparticles are simulated, focusing on the effects of localized surface and bulk interactions on the average magnetization of 2D square lattices. The thermal behaviors and hysteresis cycles are investigated within the framework of the Ising model Hamiltonian and are conducted following two approaches: local mean field approximation (LMFA) and Monte Carlo entropic sampling (MCES) techniques. The results obtained by these two methods are compared for the two square lattice sizes, 6 $$ \times $$ 6 and 7 $$ \times $$ 7. Thus, when the bulk-surface interaction term is set to zero, the two approaches lead to identical values of the surface and bulk transition temperatures separated by a long intermediate plateau in both cases. Although hysteresis curves exhibit a similar shape, LMFA shows slightly larger widths $$ \Delta T $$ than MCES. On increasing bulk-surface interaction term, the two methods lead to different shifts in equilibrium temperature values for both bulk and surface components, respectively, to lower and higher values by MCES. In general, it is found that LMFA shifts surface equilibrium temperature differently to lower values and enhances the hysteresis effect, particularly for surface molecules. On the other hand, for the 7 $$ \times $$ 7 square lattice, the equilibrium temperatures are slightly higher by 1.5% and 3.2% for bulk and surface molecules, respectively, with a narrower hysteresis width in the surface. Moreover, with the MCES method, an abrupt transition instead of a hysteresis transition is calculated for surface molecules ($$ \Delta T_{surf}^{MCES}=0 $$ K).

Water/organic liquid interface properties with amine, carboxyl, thiol, and methyl terminal groups as seen from MD simulations.

Molecular dynamics simulations were performed to study structural and dynamic properties of polar butanamine/water/butanamine, pentanoic acid/water/pentanoic acid, butanethiol/water/butanethiol, and nonpolar pentane/water/pentane systems. The mass density profiles along the interface normal to the organic liquid/water system, the difference in the local structure of H O molecules in bulk and in the vicinity of interface, as well as the diffusion behavior of water molecules at the interface with above-mentioned organic liquids have been investigated. Our MD simulation has shown that the diffusion of water molecules across the water/organic liquid interface is influenced by the hydrogen bonds between water molecules and the terminal groups of organic liquids. It was found that the loss of the hydrogen bonds in the nonpolar organic liquid leads to a decrease in the value of the normal component of the diffusion coefficient , while the tangential diffusion coefficients, both and , increase.

Evolution, Stability, and Applicability of Surfactant Aggregates in Targeted Delivery.

Self-assembly/self-aggregation of surfactant molecules in bulk and the vicinity of a surface has been a topic of interest for decades because of its utilization in numerous modern technical applications. In this article, the results of molecular dynamics simulations are reported to investigate the self-aggregation of sodium dodecyl sulfate (SDS) at an interface of mica and water. SDS molecules starting from lower to higher surface concentrations tend to create distinct aggregated structures in the vicinity of a mica surface. The structural properties, such as density profiles, radial distribution functions, and thermodynamic properties like excess entropy and second virial coefficient, are calculated to address the bits and pieces of the self-aggregation. The change in the free energy for aggregates of varied sizes approaching the surface from the bulk aqueous solution, along with the change in their shapes during the process in terms of change in the radius of gyration and its components, is reported respectively to model a generic pathway for a surfactant-based targeted delivery system.

Probiotic disruption of quorum sensing reduces virulence and increases cefoxitin sensitivity in methicillin-resistant Staphylococcus aureus

Therapies which target quorum sensing (QS) systems that regulate virulence in methicillin-resistant Staphylococcus aureus (MRSA) are a promising alternative to antibiotics. QS systems play a crucial in the regulation of MRSA antibiotic resistance, exotoxin production, antioxidant protection and immune cell evasion, and are therefore attractive therapeutic targets to reduce the virulence of a pathogen. In the present work the the effects of bioactive peptides isolated from two strains of lactic acid bacteria were tested against antibiotic resistance, carotenoid production, resistance to oxidative killing and biofilm structure in two clinical MRSA isolates. The results obtained from fractional-inhibitory concentration assays with bulk and semi-purified bioactive molecules showed a significant synergistic effect increasing cefoxitin mediated killing of MRSA. This was coupled to a six-fold decrease of the major membrane pigment staphyloxanthin, and a 99% increase in susceptibility to oxidative stress mediated killing. Real-time quantitative PCR analysis of the QS-genes agrA and luxS, showed differential expression between MRSA strains, and a significant downregulation of the hemolysin gene hla. Light microscopy and scanning electron microscopy revealed alteration in biofilm formation and clustering behavior. These results demonstrate that bioactive metabolites may be effectively applied in tandem with beta-lactam antibiotics to sensitize MRSA to cefoxitin. Moreover, these results shown that several key QS-controlled virulence mechanisms are diminished by probiotic metabolites.

Anisotropy and Hybrid Heterosurface-Modulated Two-Dimensional Hydrogen Bond Network of Water

We report the structure and dynamics of layered water structure near a bilayer heterosurface using classical molecular dynamics simulations and network graph theory. The heterosurfaces of our choice are technologically essential and well-studied hexagonal boron nitride (h-BN) and graphitic carbon nitride (g-C3N4). Starting with the water density distribution profile, we have studied different hydrogen bondings (HBs) associated with distance and angle distributions and correlated them with the HB count, followed by the investigations of dynamic properties. We realize the oddity while corresponding to the tetrahedral order parameter (TOP), HB donor/acceptor count, and HB lifetime. A quantitative gap is observed between the TOP and HB counts, and we perceive another structural factor playing a significant role. We observe a 2D sheetlike arrangement of hydrogen-bonded water molecules, namely, 2D-HB, in the interfacial layer instead of 3D tetrahedral arrangements. 2D-HB qualitatively acts as a key descriptor of the hydrophobicity of the interface. The probability of higher TOP among the interfacial layer water molecules is less for h-BN compared to g-C3N4. However, the per-water HBs for both the heterosurfaces remain indistinguishable, implying the existence of another significant physical factor related to HB. Hence, 2D-HB serves as a deciding factor. In the case of h-BN, water molecules in the first layer form extended 2D sheets compared to the second and bulk, which is not a scenario for g-C3N4. Following the network graph theory, we calculated the temporal evolution of the maximum number of water molecules connected in a single network. The layer 1 water molecules have slower orientational dynamics, higher HB lifetime, and consequently slower translational diffusion than layer 2 and bulk water molecules. The experimental studies suggested that the contact angle of water on h-BN can vary from 61.4 to 85.8°, higher than that of g-C3N4, depending on the surface stacking, support material, and exposure to air, which effectively makes h-BN more hydrophobic compared to g-C3N4. The interfacial water molecules have a smaller HB lifetime and a faster diffusion coefficient than g-C3N4. The HB lifetime of water molecules in bulk is less than that in the interface, irrespective of the surface. A slower reorientation lifetime, that is, 2.69 ps, for g-C3N4 interfacial water molecules is observed versus 2.20 ps for h-BN. Our results agree with the experimental observations and can help to understand the hydrophobicity of other relevant materials.

Mechanistic Principles for Engineering Hierarchical Porous Metal–Organic Frameworks

Metal-organic frameworks (MOFs) have generated tremendous research interest in the past two decades, due to their high surface areas, tailorable active sites, and tunable structures. Hierarchical porous MOFs (HP-MOFs) with two or more pore systems are particularly attractive, benefiting from improved active site accessibility and enhanced mass diffusivity in applications involving bulk molecules. This review outlines the mechanistic principles used for the rational design of HP-MOFs, current techniques used to measure their hierarchical porosities, as well as their emerging applications. We then critically summarize the current challenges in this field and provide a contemporary perspective on the technological innovations that would address current synthetic challenges in the field of HP-MOFs. The aim of this review is to provide an in-depth understanding of the formation mechanisms, materials chemistry, and structural and chemical properties of HP-MOFs while exploring ways to enhance the performance of current MOF materials in a range of fields.

The Energy Gap Law at Work: Emission Yield and Rate Fluctuations of Single NIR Emitters.

Internal conversion (IC) often is the dominating relaxation pathway in NIR emitters, lowering their fluorescence quantum yield. Here, we investigate dibenzoterrylene (DBT) by bulk and single molecule spectroscopy. With increasing solvent polarity, the S1-S0 energy gap decreases leading to a decrease of the fluorescence quantum yield and an increase of the IC rate in full accordance with the energy gap law. Making use of the unexpectedly strong fluorescence solvatochromism of this aromatic hydrocarbon, the validity of the energy gap law could also be demonstrated at the single molecule level. The S1-S0 energy gap not only controls the fluorescence lifetime and quantum yield of single molecules but also dictates how these quantities develop during spectral fluctuations. Our results open new avenues into unexplored single molecule photophysics and appear as a promising tool for nanoscale probing of dynamic heterogeneities.

Hierarchically Porous MOFs Synthesized by Soft-Template Strategies.

The past few decades have been witnessing the rapid research boom of metal-organic frameworks (MOFs), which are assembled from metal nodes and multitopic organic linkers. In virtue of their modular assembly mode, they can be tailored according to desired functions to satisfy numerous potential applications. However, most initially reported MOFs were restricted to the microporous regime, limiting their practical applications with bulk molecules involved. Therefore, the research attention was immediately directed toward enlarging the intrinsic pore size of frameworks by extending the secondary building units or organic ligands. Unfortunately, the synthesis of more extended ligands is frequently tedious, and the most resultant MOFs are not sufficiently stable, restricting their popularization. The soft-template strategy is recognized as a promising avenue to produce hierarchically porous MOFs (HPMOFs), although early attempts generally failed due to the incompatibility between the surfactant self-assembly and guided crystallization process of MOF precursors in the organic phase. Therefore, developing a rational soft-template strategy to achieve the precise control of morphology and porosity of HPMOFs is of great significance.In this Account, we present our recent progress on the development and applications of HPMOFs prepared by soft-template strategies. We highlight the key issues upon using the soft-template strategy to synthesize HPMOFs. To enhance the interaction between the template and MOF precursor, a long-chain monocarboxylic acid strategy is introduced to synthesize HPMOFs with irregular mesopores in the organic phase. Then, to improve the order of mesopores, an aqueous-phase synthesis method using amphoteric surfactants as templates is developed to prepare ordered HPMOFs. To further enlarge the pore size and make the synthesis conditions of MOFs compatible with the self-assembly of surfactants, a salting-in species-induced self-assembly strategy is proposed and coupled with the structure-directing properties of copolymer templates to synthesize a series of HPMOFs with large mesopores and even macropores. This salting-in ion-mediated self-assembly (SIMS) strategy paves the way to modify the pore size, pore structure, morphology, and chemical composition of HPMOFs. The separated but intimately interconnected hierarchical pores in the resultant HPMOFs can not only realize rapid mass transport but also isolate different-size guest molecules so that they are competent for a broad range of applications including protein digestion, cascade catalysis, enzyme-assisted substrate sensing, and DNA cleavage. Finally, the limitations, challenges, and future developments of this rapidly evolving field are described. This Account with a highlight to the soft-template strategies not only provides interesting insights to understand the assembly process between templates and MOFs but also inspires an optimization of the properties of HPMOFs from diverse aspects for desired applications.

Ammonio Methacrylate Copolymer (Type B)-Diltiazem Interactions in Solid Dispersions and Microsponge Drug-Delivery Systems.

This paper presents a complex analytical study on the distribution, solubility, amorphization, and compatibility of diltiazem within the composition of Eudragit RS 100-based particles of microspongeous type. For this purpose, a methodology combining attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX), and in vitro dissolution study is proposed. The correct interpretation of the FTIR and drug-dissolution results was guaranteed by the implementation of two contrasting reference models: physical drug–polymer mixtures and casting-obtained, molecularly dispersed drug–polymer composites (solid dispersions). The spectral behavior of the drug–polymer composites in the carbonyl frequency (νCO) region was used as a quality marker for the degree of their interaction/mutual solubility. A spectral-pattern similarity between the microsponge particles and the solid dispersions indicated the molecular-type dispersion of the former. The comparative drug-desorption study and the qualitative observations over the DSC and SEM-EDX results confirmed the successful synthesis of a homogeneous coamorphous microsponge-type formulation with excellent drug-loading capacity and “controlled” dissolution profile. Among them, the drug-delivery particles with 25% diltiazem content (M-25) were recognized as the most promising, with the highest population of drug molecules in the polymer bulk and the most suitable desorption profile. Furthermore, an economical and effective analytical algorithm was developed for the comprehensive physicochemical characterization of complex delivery systems of this kind.

Biomass-derived mesoporous and super-hydrophilic carbon manufactured by cycling-pressure-switching air activation process towards ultrahigh adsorption efficiency of tetracycline

Mesoporous and super-hydrophilic carbon materials have been synthesized with sugar cane bagasse via a cycling pressure-switching (CPS) air oxidation process. Facilitated by the pressure-switching process, reactive gas (air) can diffuse into porous channels for activation reaction and create rich mesoporous structure as well as abundant surface functional groups. Compared to conventional atmospheric pressure (AP) method, CPS process simultaneously maximizes the mesopore volume fraction (37%) and enriches the surface functional groups. Such unique carbon materials were systematically characterized by various techniques to reveal the evolution of pore structure and surface property. These materials have been demonstrated very effective for the adsorption of bulk antibiotics such as tetracycline (TC) and the maximum adsorption capacity of 671.14 mg/g was achieved at room temperature with feeding TC concentration of 150–400 mg/L−1. In a word, this work presents an environmental benign approach to manufacture porous carbon with direct air activation, the unique features of the materials with large mesopore volume and superhydrophilic surface enable efficient adsorption of bulk molecules in aqueous solution and show promising application in antibiotics removal from polluted water.

Nanoemulsion-directed growth of MOFs with versatile architectures for the heterogeneous regeneration of coenzymes

As one of the most appealing strategies for the synthesis of nanomaterials with various architectures, emulsion-directed methods have been rarely used to control the structure of metal-organic frameworks (MOFs). Herein, we report a versatile salt-assisted nanoemulsion-guided assembly to achieve continuous architecture transition of hierarchical Zr-based MOFs. The morphology of nanoemulsion can be facilely regulated by tuning the feed ratio of a dual-surfactant and the introduced amount of compatible hydrophobic compounds, which directs the assembly of MOFs with various architectures such as bowl-like mesoporous particle, dendritic nanospheres, walnut-shaped particles, crumpled nanosheets and nanodisks. The developed dendritic nanospheres with highly open and large mesochannels is successfully used as matrix for the co-immobilization of coenzymes and corresponding enzymes to realize the in situ heterogeneous regeneration of NAD+. This strategy is expected to pave a way for exploring sophisticated hierarchical MOFs which can be competent for practical applications with bulk molecules involved.

An Insight into the Role of Reactant Structure Effect in Pd/C Catalysed Aldehyde Hydrogenation.

The different activity of a 1% Pd/carbon catalyst towards aromatic and aliphatic aldehydes hydrogenation has been explored by 13C NMR relaxation. The ratio between T1 relaxation times of adsorbed (ads) and free diffusing (bulk) molecules (T1ads/T1bulk) can be used as an indicator of the relative strength of interaction between the reactant and the catalytic surface, where the lower the T1ads/T1bulk, the higher the adsorption strength. It can be seen that 1% Pd/carbon showed a reverse catalytic behaviour towards benzaldehyde and octanal hydrogenation, which can be explained by analysing the T1 relaxation times related to each substrate in the presence of the catalyst. Comparing and correlating the different T1ads/T1bulk values, we were able to prove that the different catalytic results mainly depend on the contrasting adsorption behaviour of substrates on the catalyst. Moreover, the role of the solvent has been disclosed, as NMR results revealed that the adsorption of the reactants was strongly affected by the choice of solvent, which is revealed to be critical in modulating catalytic activity. As a consequence, T1ads/T1bulk measurements can provide a guide to the selection of appropriate reaction conditions for improving catalytic activity.