Specific Surface Structures Research Articles

Impact of Pt(hkl) Electrode Surface Structure on the Electrical Double Layer Capacitance.

The classical theory of the electrical double layer (EDL) does not consider the effects of the electrode surface structure on the EDL properties. Moreover, the best agreement between the traditional EDL theory and experiments has been achieved so far only for a very limited number of ideal systems, such as liquid metal mercury electrodes, for which it is challenging to operate with specific surface structures. In the case of solid electrodes, the predictive power of classical theory is often not acceptable for electrochemical energy applications, e.g., in supercapacitors, due to the effects of surface structure, electrode composition, and complex electrolyte contributions. In this work, we combine ab initio molecular dynamics (AIMD) simulations and electrochemical experiments to elucidate the relationship between the structure of Pt(hkl) surfaces and the double-layer capacitance as a key property of the EDL. Flat, stepped, and kinked Pt single crystal facets in contact with acidic HClO4 media are selected as our model systems. We demonstrate that introducing specific defects, such as steps, can substantially reduce the EDL capacitances close to the potential of zero charge (PZC). Our AIMD simulations reveal that different Pt facets are characterized by different net orientations of the water dipole moment at the interface. That allows us to rationalize the experimentally measured (inverse) volcano-shaped capacitance as a function of the surface step density.

Escherichia coli Adhesion and Biofilm Formation on Polymeric Nanostructured Surfaces.

Biofilm formation is a multistep process that requires initial contact between a bacterial cell and a surface substrate. Recent work has shown that nanoscale topologies impact bacterial cell viability; however, less is understood about how nanoscale surface properties impact other aspects of bacterial behavior. In this study, we examine the adhesive, viability, morphology, and colonization behavior of the bacterium Escherichia coli on 21 plasma-etched polymeric surfaces. Although we predicted that specific nanoscale surface structures of the surface would control specific aspects of bacterial behavior, we observed no correlation between any bacterial response or surface structures/properties. Instead, it appears that the surface composition of the polymer plays the most significant role in controlling and determining a bacterial response to a substrate, although changes to a polymeric surface via plasma etching alter initial bacteria colonization and morphology.

CO and Propane Combustion on La0.8Sr0.2CoxFe1−xO3−δ Perovskites: Effect of Fe-to-Co Ratio on Catalytic Activity

Perovskites are promising alternative catalysts for oxidation reactions due to their lower cost compared to noble metals, and their greater thermal stability. The catalytic oxidation of CO is essential in order to control CO emissions in a series of applications whereas the catalytic combustion of propane is considered an economical and environmentally acceptable solution for energy production and gaseous pollutant management, since propane is among the organic compounds involved in photochemical reactions. This work concerns the effect of the Co/Fe ratio in the B-sites of a series of eight La0.8Sr0.2CoxFe1−xO3−δ perovskites, with x ranging from 0 to 1, on the catalytic activity towards CO and C3H8 oxidation. The perovskite oxides were synthesized using the combustion synthesis method and characterized with respect to their specific surface areas, structures, and reduction properties. Increasing the Co/Fe ratio resulted in an increase in CO and propane conversion under both oxidative and stoichiometric conditions. The increase in Co content is considered to facilitate the formation of oxygen vacancies due to the lower redox stability of the cobalt cations compared to iron cations, favoring oxygen ion mobility and oxygen exchange between the gas phase and the oxide surface, thus enhancing the catalytic performance.

Controlled porous structures of soybean straw-based carbon via green liquefication and N/S in-situ doping facilitate supercapacitor performance at large current density

It is important to maintain supercapacitor performance at high current density by regulating the micropore/mesopore balance and surface functional groups of biomass carbons. Here, the biomass porous carbon was successfully prepared from agroforestry waste of soybean straw by green activation was introduced on the basis of in-situ doping. Effective liquefaction and doping environment for non-metal N/S doping was achieved via green liquefaction using polyethylene glycol 400 (PEG400). The micropore/mesopore ratio, hydrophilic properties, and active sites of the carbon materials were regulated and enhanced by combing N in-situ doping and green activation with potassium citrate. The obtained soybean straw-based carbon with N doping (SSL-N1) showed higher surface area (1698.9 m2 g−1) and mesopore ratio (78.15%). The mesopore/micropore ratio shortened the ion adsorption distance and increased the ion surface accessibility. The specific capacitance of materials could reach 276.8 F g−1 at a current density of 0.5 A g−1. As the current density expand by 20 times, the specific capacitance could be preserved at 216 F g−1, the capacity retention rate is 78.0%. Notably, the SSL-N1//SSL-N1 symmetrical supercapacitor could generated an energy density of 10.14 W h kg−1. The specific porous and surface structures of carbon composite materials could effectively alleviate the capacity attenuation in supercapacitors at high current density.

Positron emission tomography in oncology

Positron emission tomography (PET) is ahighly sensitive imaging tool that noninvasively characterizes metabolic processes and molecular targets. PET has become an integral part of oncological diagnostics and an increasingly important tool for oncological therapy management. PET assessment, for example, directly influences treatment escalation or de-escalation in context of Hodgkin lymphomas or is, in case of lung cancer, able to reduce unnecessary surgeries. Hence, molecular PET imaging represents an indispensable tool in the development of personalized treatments. Furthermore, the development of new radiotracers for specific cell surface structures offers apromising potential for diagnostics and-combined with therapeutic nuclides-also for therapies. One recent example are radioligands targeting prostate-specific membrane antigen, which are relevant in prostate cancer.

Novel electrochemiluminescence resonance energy transfer platform involving PTCA@Fe(III)-MIL-88B-NH2@Au as a double-amplified emitter for the detection of cystatin C

A luminescent reagent, 3,4,9,10-perylenetetracarboxylic acid (PTCA), was linked to a metal–organic framework (MOF) Fe(III)-MIL-88B-NH2 through an amide reaction to form a PTCA@Fe(III)-MIL-88B-NH2 complex, and then gold nanoparticles (AuNPs) were grown in situ. Thus, the PTCA@Fe(III)-MIL-88B-NH2@Au electrochemiluminescence (ECL) probe was obtained. The MOF of 2-aminoterephthalic acid with large specific surface area, pore sizes, and structures, which served both as the carrier and a co-reaction promoter, promoted the conversion of more S2O82- into SO4•-, further enhancing the ECL signal of PTCA. An electrochemiluminescence resonance energy transfer (ECL-RET) platform was designed for the ultrasensitive and highly selective detection of cystatin C (CysC). The developed ECL-RET biosensor presented a linear range from 0.01 pg/mL to 100 ng/mL and a detection limit of 2.2 fg/mL (S/N = 3). Moreover, all the results showed that the developed ECL-RET biosensor broadened the application in the fields of biosensing and medical diagnosis.

A Universal Synthesis Strategy for Tunable Metal-Organic Framework Nanohybrids.

Metal-organic frameworks (MOFs) with encapsulated nanoparticles (NPs) enjoy a vastly expanded application potential in catalysis, filtration, and sensing. The selection of particular modified core-NPs has yielded partial successes in overcoming lattice mismatch. However, restrictions on the choice of NPs not only limit the diversity, but also affect the properties of the hybrid materials. Here, we show a versatile synthesis strategy using a representative set of seven MOF-shells and six NP-cores that are fine-tuned to incorporate from single to hundreds of cores in mono-, bi-, tri- and quaternary composites. This method does not require the presence of any specific surface structures or functionalities on the pre-formed cores. Our key point is to regulate the diffusion rate of alkaline vapors that deprotonate organic linkers and trigger the controlled MOF-growth and encapsulation of NPs. This strategy is expected to pave the way for the exploration of more sophisticated MOF-nanohybrids.

Ultra‐Fast In Situ Reconstructed Nickel (Oxy)Hydroxide Nanoparticle Crosslinked Structure for Super‐Efficient Alkaline Water Electrolysis by Sacrificing Template Strategy

The rapid construction of water electrolysis catalysts by a sacrificing template in an electrochemical environment is rarely a concern. Herein, using a fluorine‐rich (F‐rich) nickel fluoride (NiF2) grown on nickel foam (NF) as a sacrificial template, a highly effective alkaline catalyst is designed. In terms of in situ reassembling, the NiF2 template can be transformed into nickel hydroxide (Ni(OH)2) in hydrogen evolution reaction (HER) and nickel oxyhydroxide (NiOOH) in oxygen evolution reaction (OER), respectively, after only 100 CV cycles, on account of the rapid ion exchange of F− and OH− in an electrochemical environment. Due to the presence of nanocatalytic units, abundant lattice defects, and porous large specific surface structures caused by the reconstruction, it only takes low overpotentials of 57 mV for HER and 228 mV for OER (@10 mA cm−2), with outstanding stability up to 15 d (@100 mA cm−2). Consequently, only a low cell voltage of 1.53 V (@10 mA cm−2) is needed for overall water splitting, superior to commercial noble metal catalysts as benchmarks. Meanwhile, it can output stable current densities of 10, 100, and 500 mA cm−2 approaching 10 d under constant cell voltages of 1.55, 2.0, and 2.5 V, respectively.

Contact Angle on Rough Curved Surfaces and Its Implications in Porous Media

The equilibrium contact angle depends on both the chemistry of the two fluids and solid base and the microstructure on the solid surface. Actual surface of the pore wall in porous media is typically rough and curved, which has not been well-considered in related applications. This work uses a free interfacial energy minimization approach to theoretically derive the equilibrium contact angle on two specific surface structures on flat surfaces and extends the derivation considering the surface curvatures in porous media. Results reveal that the equilibrium contact angle is not dependent on the curvature of spherical surfaces, and we further prove that this conclusion applies to any point along the apparent common line at solid surfaces with any arbitrary curvature. The fundamental physics is the local mechanical balance of a composite contact among three interfacial tensions. Furthermore, the contacting mode can shift from non-wetting to wetting when the pressure difference between two fluids exceeds the entry pressure of the microstructures, which should be considered in relative dynamic scenarios such as rain droplet impact and fluid displacement in porous media. Note that these conclusions are from pure theoretical analysis based on idealistic assumptions, and real circumstances may deviate from these assumptions.

Structure–Activity Relationship between the Superhydrophilic Nanowire Structure and the Oil Dewetting Property

Materials require specific surface structures to achieve the best performance, but achieving an optimal structural design requires a systematic study of how structure affects performance. In this work, we comprehensively and systematically investigated the structure-activity relationship between the nanowire structure and the oil dewetting self-cleaning performance. It is easy for an oil droplet to enter this structure, but it is difficult for it to escape from the gaps between the structures even under the action of water. So, the oil dewetting ability is greatly reduced, showing that this "easy to enter and difficult to exit" mode is very disadvantageous for oil desorption. Moreover, if the structure is dissolved during the test, the oil dewetting ability will be restored. The desorption effect is affected by structural parameters and reaction conditions, which further verifies the negative effect of this structure. In contrast, copper(II) oxide nanowires completely lose their self-cleaning ability due to the enhancement of hydrophobicity and oleophilicity, and the larger-diameter copper(II) oxalate nanorods exhibit a "difficult to enter and difficult to exit" mode, leading to the partial recovery of the oil dewetting performance. This study helps us deeply understand the influence of the surface microstructure on the oil dewetting performance and lay a solid foundation for further appropriate structural design.

Positronenemissionstomographie in der Onkologie

Positron emission tomography (PET) is a highly sensitive imaging tool that noninvasively characterizes metabolic processes and molecular targets. PET has become an integral part of oncological diagnostics and an increasingly important tool for oncological therapy management. PET assessment, for example, directly influences treatment escalation or de-escalation in context of Hodgkin lymphomas or is, in case of lung cancer, able to reduce unnecessary surgeries. Hence, molecular PET imaging represents an indispensable tool in the development of personalized treatments. Furthermore, the development of new radiotracers for specific cell surface structures offers a promising potential for diagnostics and—combined with therapeutic nuclides—also for therapies. One recent example are radioligands targeting prostate-specific membrane antigen, which are relevant in prostate cancer.

Regulation of the Structure of Zirconium-Based Porphyrinic Metal-Organic Framework as Highly Electrochemiluminescence Sensing Platform for Thrombin.

An electrochemiluminescence (ECL) sensor provides a sensitive and convenient method for early diagnosis of diseases; however, it is still a challenge to develop simple and sensitive sensing platforms based on efficient ECL signals and luminophore groups. Porphyrin-based metal-organic frameworks (MOFs) show great potential in ECL sensing; however, the mechanism and structure-activity relationship, as well as application, are rarely reported. Herein, hydrothermal reactions obtained porphyrin Zr-MOFs (PCN-222) with different specific surface areas, pore sizes, structures, and surface charge states by tuning the reaction time were developed, which served both as the ECL luminophore, coreaction promoter for S2O82-, and a connection in the ECL immunoassay. By progressively controlling the condition of the hydrothermal reaction, PCN-222 with large surface area-abundant micropores can be obtained, which has good conductivity and positively charged surfaces, obtaining excellent ECL performance. The ECL performance and the enhancement mechanism were investigated in detail. Using PCN-222-6h with the best ECL intensity as the immobilization matrix for the aptamer, a highly sensitive and selective assay for thrombin was developed. The decrease of the ECL signal was logarithmically linear with the concentration of thrombin in the range from 50 fg mL-1 to 100 pg mL-1 with a low detection limit of 2.48 fg/mL. This proposed strategy provides a brand new approach for tuning of the structures of MOFs as effective ECL signal probes, thus providing wider possibilities for effective ECL immunoassays in the detection of other biomarkers in diagnosis of diseases.

Correlation between slip precursors and topological length scales at the onset of frictional sliding

Understanding the interplay between concurrent length scales is a fundamental issue in many problems involving friction between sliding interfaces, from tribology to the study of earthquakes and seismic faults. On the one hand, a macroscopic sliding event is preceded by slip precursors with a characteristic propagation length scale. On the other hand, the emergent frictional properties can be modified by surface patterning depending on their geometric length scale. This suggests that macroscopic sliding of structured surfaces is governed by the interplay between the length scale of the slip precursors and those characterizing the geometric features. In this paper, we investigate these aspects by means of numerical simulations using a two-dimensional spring-block model. We discuss the influence of the geometric features on the occurrence and localization of slip precursors, extending the study to interfaces characterized by two geometric length scales. We find that different types of detachment sequences are triggered by specific surface structures, depending on their scales and relation to sliding direction, leading to a macroscopically smooth transition to sliding in the case of hierarchical and/or anisotropic features. These concepts could be exploited in devices switching from static to dynamic sliding, and can contribute to an improvement in the understanding and interpretation of seismic data.

Bioinspired Topological Surfaces for Mitigating Water, Thermal and Energy Crises

ConspectusThe remarkable advances in technical and industrial fields have stimulated the world’s economic prosperity and population growth while also exacerbating the global water, thermal, and energy crises. To mitigate these crises, numerous large-scale devices have been constructed to harvest water, dissipate heat, and generate energy, yet they still encounter several bottlenecks, such as bulky size and climatic and/or geographic constraints. In contrast, miniature and portable water-based devices have demonstrated their tremendous potential in water harvesting and thermal/energy management due to the ubiquitous existence, large phase-change latent heat, and abundant kinetic energy of water. Owing to the strong dependence of their performance on the interfacial interactions between water and a surface, designing novel surface topology, in both physical and chemical aspects, is of practical importance to impart them with the ability to control the interfacial interaction/exchange among water, heat, and energy in an efficient, precise, and programmable manner.Developing novel, functional, and topological surfaces can involve learning from nature because many living organisms have evolved functional surface topologies to fundamentally tailor their interactions with liquids to survive in complicated and harsh environments. Although great progress has been made in bioinspired topological surfaces, two major bottlenecks consisting of a fundamental understanding and practical applications remain elusive. From the perspective of a fundamental understanding, the principles by which the surface topology of an organism controls the dynamic behavior of water droplets need to be deciphered comprehensively. From the perspective of practical applications, rationally designing surface topologies to achieve multifunctionality in industrial processes, especially in complex and harsh conditions, is of great importance. In this Account, we systematically review our recent progress in promoting bioinspired topological surfaces toward practical applications. We start with a fundamental investigation of various topological surfaces for rapid droplet bouncing facilitated by specific surface structures or a slippery liquid film. Subsequently, we introduce different surface topology designs for directional liquid transport. On the basis of these fundamental understandings, we further demonstrate their representative practical applications, including water harvesting, thermal management, and energy conversion. Finally, we offer a brief summary and perspectives on the development of novel bioinspired topological surfaces.

Nanosecond laser-induced controllable periodical surface structures on silicon

In this paper, an effective method is proposed to generate specific periodical surface structures. A 532 nm linearly polarized laser is used to irradiate the silicon with pulse duration of 10 ns and repetition frequency of 10 Hz. Laser-induced periodic surface structures (LIPSSs) are observed when the fluence is 121 mJ/cm2 and the number of pulses is 1000. The threshold of fluence for generating LIPSS gradually increases with the decrease of the number of pulses. In addition, the laser incident angle has a notable effect on the period of LIPSS, which varies from 430 nm to 1578 nm, as the incident angle ranges from 10° to 60° correspondingly. Besides, the reflectivity is reduced significantly on silicon with LIPSS.

Direct Etherification Reaction of Glycerol Using Alkali Metal Cation (Li+, Na+ and K+) Containing X-Type Zeolites as Heterogeneous Catalysts: Optimization of the Reaction Conditions

X-type zeolite (XZ-Na) containing Na+ as a cation was synthesized, and XZ-Li and XZ-K were prepared by exchanging the cations of XZ-Na with Li+ and K+, respectively. The specific surface areas, structures, and chemical compositions of the prepared zeolites were analyzed by BET, XRD, and SEM-EDX. The activity of the direct and selective etherifications of glycerol to diglycerol (DG) and triglycerol (TG) were investigated using each zeolite XZ-M (M = Li, Na or K) as a basic heterogeneous catalyst. The etherification reactions of glycerol were carried out at atmospheric pressure while controlling the reaction temperature, reaction time, and the amount of each zeolite. As the amount of each zeolite, reaction time, and reaction temperature increased, the conversion of glycerol also increased, but the selectivities of DG and TG decreased due to the increase in the production of oligomers. When each zeolite was used as a catalyst, the catalytic activity for the conversion of glycerol was observed as XZ-K > XZ-Li > XZ-Na, but the selectivities of DG and TG were observed as XZ-Li > XZ-Na > XZ-K. Especially, 3 wt.% of XZ-Li exhibited the excellent catalytic performance when the etherification of glycerol was optimized and carried out at 280 °C for 2 h: the conversion of glycerol was 89.6% and the yields of DG and TG were 61.2 and 21.2%, respectively.

PHYSICOCHEMICAL AND TEXTURE CHARACTERISTICS OF NATURAL BENTONITE

The study was conducted on the modification of bentonite of Navbahor district of Navoi region of the Republic of Uzbekistan in chloride, sulfuric and nitric acids and their boiling point. Modified samples were analysed by IR-spectroscopic, X-ray phase, elemental and electronmicroscopic analysis methods. Morphology, specific surface structures and spatial composition of bentonite powder found in Navbahor were studied. Mechanical processing was carried out in a planetary mill. The aim of the study is to investigate the mechanical effects and the effects of acidic processing on the structure and composition of bentonite, its structure and physicochemical properties. The following methods of inspection were used: scanning electron microscopy (SEM), X-ray structural analysis, Brunauera - Emmeta - Taylor (BET), method laser beam diffraction and element analysis. It was shown that in the first 60 minutes of mechanical processing, a further grinding of the powder was carried out in a planetary mill, with an increase in the specific surface area of 33m2/g. Subsequent mechanical activation resulted in particle agglomeration and shrinkage of the specific surface area.

Imaging Commensal Microbiota and Pathogenic Bacteria in the Gut.

As a newly discovered organ, gut microbiota has been extensively studied in the last two decades, with their highly diverse and fundamental roles in the physiology of many organs and systems of the host being gradually revealed. However, most of the current research heavily relies on DNA sequencing-based methodologies. To truly understand the complex physiological and pathological functions demonstrated by commensal and pathogenic gut bacteria, we need more powerful methods and tools, among which imaging strategies suitable for approaching this ecosystem in different settings are one of the most desirable. Although the phrase gut "dark matter" is often used in referring to the unculturability of many gut bacteria, it is also applicable to describing the formidable difficulties in visualizing these microbes in the intestines. To develop suitable and versatile chemical and biological tools for imaging bacteria in the gut, great efforts have been devoted in the past several years.In this Account, we highlight the recent progress made by our group and other laboratories in the development of visualization strategies for commensal microbiota and pathogenic bacteria in the gut. First, we summarize our efforts toward the development of derivatized antibiotic staining probes that directly bind to specific bacterial surface structures for selective labeling of different groups of gut bacteria. Next, metabolic labeling-based imaging strategies, using unnatural amino acids, unnatural sugars, and stable isotopes, for imaging gut bacteria on various scales and in different settings are discussed in detail. We then introduce nucleic acid staining-based bacterial imaging, using either general nucleic acid-binding reagents or selective-labeling techniques (e.g., fluorescence in situ hybridization) to meet the diverse needs in gut microbiota research. This classical imaging strategy has witnessed a renaissance owing to a series of new technical advancements. Furthermore, despite the notorious difficulties of performing genetic manipulations in many commensal gut bacteria, great effort has been made recently in engineering gut bacteria with reporters like fluorescent proteins and acoustic response proteins.Our perspectives on the current limitations of the chemical tools and strategies and the future directions for improvement are also presented. We hope that this Account can offer valuable references to spark new ideas and invite new efforts to help decipher the complex biological and chemical interactions between commensal microbiota and pathogenic bacteria and the hosts.

Quantitatively Switchable pH-Sensitive Photoluminescence of Carbon Nanodots.

pH sensing plays a key role in the life sciences as well as the environmental, industrial, and agricultural fields. Carbon nanodots (C-dots) with small size, low toxicity, and excellent stability hold great potential in pH sensing as nanoprobes due to their intrinsic pH-sensitive photoluminescence (PL). Nonetheless, the undesirable sensitivity and response range of C-dot PL toward pH cannot meet the requirements of practical applications, and the unclear pH-sensitive PL mechanism makes it difficult to control their pH sensitivity. Herein, the quantitative correlation of pH-sensitive PL with specific surface structures of C-dots is uncovered for the first time, to our best knowledge. The association of carboxylate and H+ increases the ratio of nonradiation to radiation decay of C-dots through excited-state proton transfer, resulting in the decrease of PL intensity. Meanwhile, the dissociation of α-H in β-dicarbonyl forming enolate increases the extent of delocalization of the C-dots conjugated system, which induces the PL broadening to the red region and a decreasing intensity. Based on the understanding of the pH-sensitive PL mechanism, the pH-sensitive PL of C-dots can be switched by quantitative modulation of carboxyl and β-dicarbonyl groups to achieve a desirable pH response range with high sensitivity. This work contributes to a better understanding of the pH-sensitive PL of C-dots and therefore presents an effective strategy for controllably tuning their pH sensitivity, facilitating the rational design of C-dot-based pH sensors.

Self-assembly nuclei with a preferred orientation at the extended hydrophobic surface toward textured growth of ZnO nanorods in aqueous chemical bath deposition

Textured growth of ZnO nanorods with no restriction of the substrate material is beneficial to their applications. The approaches to grow ZnO nanorods with texture are based on preparing suitable surface structure on the growth substrate, e.g. using a crystalline substrate with a specific surface structures or pre-depositing seed layers by high-temperature annealing of precursors. In the aqueous nutrient solution of the chemical bath deposition (CBD) process for ZnO growth, the concentration of Zn2+ ions at the extended hydrophobic surface is sufficiently high for forming self-assembly nuclei with a preferred orientation, resulting in the subsequent textured growth of ZnO nanorods. In this research, the hydrophobic surface is prepared by modifying Si surface with a self-assembly octadecyltrimethoxysilane (OTMS) monolayer. The formation mechanism of the nuclei on this hydrophobic surface for the textured growth of ZnO nanorods is investigated. It is shown that the nuclei form at the beginning of the CBD process and later transform into the Wurtzite structure to seed ZnO growth. An alternative approach to prepare seed layers is therefore involved in the aqueous CBD process, which is applicable to a range of hydrophobic substrates for textured growth of ZnO nanorods.