Surface Enrichment Research Articles

Biomass-derived graphene-like carbon nanoflakes for advanced supercapacitor and hydrogen evolution reaction

It is valuable that graphene-like carbon materials are prepared from the biomass resources due to their unique two-dimensional structure, heteroatom enriched, and high specific surface area. Herein, we use egg white and graphene oxides as precursor and employ post-hydrothermal carbonization approach, freeze-drying technique, carbonization, and activation methods by KOH to prepare the graphite carbon nanoflakes with Fe7C3 @graphite carbon nanoflakes hybrid materials. Morphology tests imply that the formation of graphite carbon nanoflakes are mainly depended by activation step, it implies that carbon flakes are exfoliated via introducing K+ into carbon layers and further destroying the van der Waals force (VDWF). As a result, this hybrid materials exhibit an attractive capacitance (528 mF·cm−2 @1 mA·cm−2) and durability (91 @10 mA·cm−2, 4000 cycles). For hydrogen evolution reaction (HER), the as-collected samples also deliver a low overpotential and remarkable stability. We believe that the as-obtained hybrid materials have a greatly application value in energy storage devices.

An efficient nanodiamond-based monolithic foam catalyst prepared by a facile thermal impregnation strategy for direct dehydrogenation of ethylbenzene to styrene

Nanodiamond (ND) has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation (DDH). However, the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process. In this work, we report a facile hexamethylenetetramine nitrate (HN)-assisted thermal impregnation (HNTI) strategy for fabricating a novel nanodiamond-based monolithic foam (ND/CNT-SiC-ms-HN) catalyst through a two-step approach: One is to soak the carbon nanotube-modified SiC foam (CNT-SiC) with the slurry composed of HN, KCl, LiCl, and dispersed ND, and the other is to heat the slurry-soaked CNT-SiC (ND-HN-KCl-LiCl/CNT-SiC) in N2 atmosphere at 750 °C. The as-synthesized ND/CNT–SiC-ms-HN monolithic foam features the enriched surface kenotic CO by promoted ND dispersion and O-doping, abundant stuctural defects, and improved nucleophilicity by N-doping, originating from the promoted ND dispersion by thermal impregnation (TI) in KCl-LiCl molten salt (MS) and the presence of HN in the annealing process. As a result, the ND/CNT–SiC-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate (5.49 mmol g−1 h−1) associated with 98.4% of styrene selectivity compared to the ND-based monolithic foam catalyst (ND/CNT-SiC). Moreover, the ND/CNT–SiC-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene. This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.

Nanoarchitectonics of CuNi bimetallic nanoparticles in ionic liquids for LED-assisted synergistic CO2 photoreduction

An efficient and robust photocatalysts have been developed by combining bimetallic CuNi nanoparticles and TiO2. Simple co-reduction of CuCl2.2H2O and NiCl2.6H2O in 1-n-butyl-methylimidazolium tetrafluoroborate (BMIm.BF4) ionic liquid affords small sized (4–5 nm) bimetallic CuNi NPs. Low-Energy Ion Scattering (LEIS) and magnetic measurements analyses reveals that the NPs are alloyed nanostructure-having Ni enriched surface. CuNi NPs decorated on P25-TiO2 remarkably promote the generation of CH3OH and syngas as compared to their monometallic counter-parts using 1200 mW LEDs of 450 nm (visible) light irradiations in an optofluidic microreactor. The system continuously produces CH3OH with a rate of 102.1 μm.g−1.h−1 (AQY 0.90%) and syngas (H2 118.8 and CO 24.6 μmol.g−1.h−1), represents a high yield and quantum efficiency. Where as, its counter-part, Ni/TiO2, generate CH3OH with a rate of 37.0 μm.g−1.h−1, H2 200.0 μmol.g−1.h−1 and CO 15.1 μmol.g−1.h−1 having 0.33, 0.59 and 0.1% AQY, respectively. The presence of Cu in CuNi NPs significantly boosts the catalytic performance via metal dilution and synergistic effect, causes the red shift and increases the conductivity, while Ni increases the band gap, thereby achieving a record high CH3OH rate generation.

Effects of Group-I Elements on Output Voltage Generation of ZnO Nanowires Based Nanogenerator; Degradation of Screening Effects by Oxidation of Nanowires.

Here, we report the successful incorporation of group I elements (K, Na, Li) to ZnO nanowires. Three distinct (2, 4, and 6 wt.%) doping concentrations of group I elements have been used to generate high piezoelectric voltage by employing a vertically integrated nanowire generator (VING) structure. X-ray photoelectron spectra (XPS) indicated the seepage of dopants in ZnO nanowires by substitution of Zn. Shallow acceptor levels (LiZn, NaZn, KZn) worked as electron trapping centers for intrinsically n-type ZnO nanowires. Free moving electrons caused a leakage current through the nanowires and depleted their piezoelectric potential. Reverse leakage current is a negative factor for piezoelectric nanogenerators. A reduction in reverse leakage current signifies the rise in output voltage. A gradual rise in output voltage has been witnessed which was in accordance with various doping concentrations. K-doped ZnO nanowires have generated voltages of 0.85 V, 1.48 V, and 1.95 V. For Na-doped ZnO nanowires, the voltages were 1.23 V, 1.73 V, and 2.34 V and the voltages yeilded for Li-doped ZnO nanowires were 1.87 V, 2.63 V, and 3.54 V, respectively. Maximum voltage range has been further enhanced by the surface enrichment (oxidized with O2 molecules) of ZnO nanowires. Technique has been opted to mitigate the screening effect during an external stress. After 5 h of oxidation in a sealed chamber at 100 ppm, maximum voltage peaks were pronounced to 2.48 V, 3.19 V, and 4.57 V for K, Na, and Li, respectively. A low-cost, high performance mechanical transducer is proposed for self-powered devices.

Fabrication of PVDF/EVOH blend hollow fiber membranes with hydrophilic property via thermally induced phase process

In this study, thermally induced phase separation (TIPS) technology was used to fabricate the PVDF/EVOH blend hollow fiber membranes using water-soluble mixed diluents. An interconnected bulk structure was formed by L-L phase separation for both the pristine membrane and blend membrane. The surface enrichment for EVOH during the cooling process enhanced the hydrophilicity of prepared hollow fiber membranes. It was found that the tensile strength of the blend membrane significantly increased from 2.6 MPa to 8.8 MPa. The variation of the membrane structure made the water permeability increase from 60 L m−2 h−1 bar−1 to 287 L m−2 h−1 bar−1 for the optimized blend membrane. Compared with the pristine membrane, EVOH blend membrane exhibited higher antifouling properties for BSA, HA, and oil-in-water emulsion filtrations.

Gradually Fe-Doped Co3O4 Nanoparticles in 2-Propanol and Water Oxidation Catalysis with Single Laser Pulse Resolution

Controlling the surface composition of colloidal nanoparticles is still a challenging yet mandatory prerequisite in catalytic studies to investigate composition-activity trends, active sites, and reaction mechanisms without superposition of particle size or morphology effects. Laser post-processing of colloidal nanoparticles has been employed previously to create defects in oxide nanoparticles, while the possibility of laser-based cation doping of colloidal nanoparticles without affecting their size remains mostly unaccounted for. Consequently, at the example of doping iron into colloidal Co3O4 spinel nanoparticles, we developed a pulse-by-pulse laser cation doping method to provide a catalyst series with a gradually modified surface composition but maintained extrinsic properties such as phase, size, and surface area for catalytic studies. Laser pulse number-resolved doping series were prepared at a laser intensity chosen to selectively heat the Co3O4-NPs to roughly 1000 K and enable cation diffusion of surface-adsorbed Fe3+ into the Co3O4 lattice. The combination of bulk-sensitive X-ray fluorescence and surface-sensitive X-ray photoelectron spectroscopy was used to confirm the surface enrichment of the Fe-dopant. X-ray diffraction, magnetometry, and Mössbauer spectroscopy revealed an increasing interaction between Fe and the antiferromagnetic Co3O4 with arising number of applied laser pulses, in line with a herein proposed laser-induced surface doping of the colloidal Co3O4 nanoparticles with Fe. Using Fick’s second law, the thermal diffusion-related doping depth was estimated to be roughly 2 nm after 4 laser pulses. At the example of gas-phase 2-propanol oxidation and liquid-phase oxygen evolution reaction, the activity of the laser-doped catalysts is in good agreement with previous activity observations on binary iron-cobalt oxides. The catalytic activity was found to linearly increase with the calculated doping depth in both reactions, while only catalysts processed with at least one laser pulse were catalytically stable, highlighting the presented method in providing comparable, active, and stable gradual catalyst doping series for future catalytic studies.

MIL-68 (In)-derived In2O3@TiO2 S-scheme heterojunction with hierarchical hollow structure for selective photoconversion of CO2 to hydrocarbon fuels

The hierarchical hollow structured photocatalysts of TiO2 nanosheet arrays-decorated In2O3 hexagonal nanotubes (core–shell structural In2O3@TiO2) were successfully fabricated by the in-situ hydrothermal method. Hierarchical hollow structure of In2O3@TiO2 photocatalysts with large specific surface area can improve the light harvesting efficiency and the adsorption capability for CO2 and H2O reactants. The internal electric field in In2O3@TiO2 photocatalysts provides the strong driving force for S-scheme electron transfer from conduction band of TiO2 to valence band of In2O3. The In2O3@TiO2 catalysts exhibited super performance for selectively photocatalytic CO2 conversion with H2O into hydrocarbon fuel (CH4) without sacrificial agent. Among the catalysts, In2O3@TiO2-10 catalyst has the largest yield (11.1 μmol g−1h−1) and selectivity (88.1 %) of CH4 product. Based on results of the characterizations, the mechanism of selective CO2 photoreduction is proposed: the surface enrichment of photogenerated electron induced by the S-scheme In2O3-TiO2 heterojunction is key-step for selective CO2 photoreduction into CH4. This work provides new ideas for the design and construction of high-efficient S-scheme photocatalysts.

Mechanism of solid state diffusion on the performance evolution of iron-based oxygen carrier at different operating conditions for chemical looping process

In the oxidation half cycle of chemical looping, the outward diffusion of Fe cations occurred for Fe-based oxygen carriers. The focus of this study is to investigate into the influence of operating conditions on Fe segregation, and then reveal the role of operating conditions in performance evolution of Fe2O3/Al2O3 in the presence of solid state diffusion. The chemical looping cycles were performed at different operating conditions (temperature, oxygen concentration, reduction degree of oxygen carrier). This work evaluated the performance evolution of Fe2O3/Al2O3 in redox cycles and indicated that the generally accepted theory of particle sintering deactivation in gas–solid reactions was incomplete, which ignored the solid state diffusion in oxygen carrier particles. Contrary to the traditional view, the effect of reaction temperature on the performance evolution of oxygen carrier is conditional, depending on the dominating mechanism of solid state diffusion in redox cycles. The results of the experiment confirmed that the surface enrichment of active components enabled more active components to participate in gas–solid reactions on the surface of material particles, which leaded to a higher deactivation rate at low temperature: 700 °C (68.33 %) > 800 °C (54.41 %) > 900 °C (29.73 %). Reducing the oxygen concentration in oxidation half cycle and reduction degree can effectively inhibit the solid state diffusion of Fe2O3/Al2O3. When the oxygen concentration is reduced to 1 %, the Fe2O3/Al2O3 has the lowest deactivation rate, which is only 9.92 %. This study provided more experimental and theoretical results for better understanding the performance evolution of iron-based oxygen carriers.

Sr2TiO4 Prepared Using Mechanochemical Activation: Influence of the Initial Compounds’ Nature on Formation, Structural and Catalytic Properties in Oxidative Coupling of Methane

Methane oxidative coupling (OCM) is considered a potential direct route to produce C2 hydrocarbons. Layered perovskite-like Sr2TiO4 is a promising OCM catalyst. Mechanochemical activation (MA) is known to be an environmentally friendly method for perovskite synthesis. Sr2TiO4 were synthesized using MA of the mixtures containing SrCO3 or SrO and TiO2 or TiO(OH)2 and annealing at 900 and 1100 °C. XRD and FT-IRS showed that MA leads to the starting component disordering and formation of SrTiO3 only for SrO being pronounced when using TiO(OH)2. After annealing at 900 °C, Sr2TiO4 was mainly produced from the mixtures of SrCO3 or SrO and TiO(OH)2. The single-phase Sr2TiO4 was only obtained from MA products containing SrCO3 after calcination at 1100 °C. The surface enrichment with Sr was observed by XPS for all samples annealed at 1100 °C depending on the MA product composition. The OCM activity of the samples correlated with the surface Sr concentration and the ratio of the surface oxygen amount in SrO and perovskite (Oo/Op). The maximal CH4 conversion and C2 yield (25.6 and 15.5% at 900 °C, respectively), and the high long-term stability were observed for the sample obtained from (SrCO3 + TiO2), showing the specific surface morphology and optimal values of the surface Sr concentration and Oo/Op ratio.

Surface Enrichment of Polymer-Grafted Nanoparticles in a Miscible Polymer Nanocomposite

Surface Enrichment of Polymer-Grafted Nanoparticles in a Miscible Polymer Nanocomposite

Kinetics of Surface Enrichment of a Polymer in a Glass-Forming Molecular Liquid

X-ray photoelectron spectroscopy has been used to measure the surface concentration and the surface enrichment kinetics of a polymer in a glass-forming molecular liquid. As a model, the bulk-miscible system of maltitol-polyvinylpyrrolidone (PVP) was studied. The PVP concentration is significantly higher at the liquid/vapor interface than in the bulk by up to a factor of 170, and the effect increases with its molecular weight. At a freshly created liquid/vapor interface, the concentration of PVP gradually increases from the bulk value at a rate controlled by bulk diffusion. The polymer diffusion coefficient obtained from the kinetics of surface enrichment agrees with that calculated from viscosity and the Stokes-Einstein equation. Our finding allows prediction of the rate at which the surface composition equilibrates in an amorphous material after milling, fracture, and a change in ambient temperature.

Boosting the activity of PdAg2/Al2O3 supported catalysts towards the selective acetylene hydrogenation by means of CO-induced segregation: A combined NAP XPS and mass-spectrometry study

Selective hydrogenation (or semi-hydrogenation) of acetylene into ethylene is an important industrial process. The aim of the present work is thus to learn regularities governing the CO-induced segregation and elaborate practical procedures for tuning the surface structure of Pd-Ag nanoparticles to improve their catalytic performance towards the selective hydrogenation of acetylene to ethylene. Utilizing NAP XPS the CO adsorption-induced Pd atoms segregation in supported PdAg2/Al2O3 catalysts already at room temperature has been shown. The surface enrichment with Pd further increases if the treatment temperature is increased up to 250 °C. This specific configuration with a redistributed Pd/Ag surface atomic ratio is appreciably stable and self-sustained even at the absence of CO at moderately elevated temperatures. Nevertheless, a reductive treatment in hydrogen at 450 °C reverts the nanoparticle surface structure to the pristine state. Catalytic properties of this peculiar CO-induced configuration of PdAg2/Al2O3 towards the selective acetylene hydrogenation was investigated using a combination of NAP XPS and MS techniques. The PdAg2/Al2O3 catalyst with the surface enriched with Pd due to the CO-induced segregation manifests improved activity with 100 % selectivity under the conditions used. The results obtained clearly demonstrate that CO adsorption-induced segregation is a powerful tool that can be used to optimize the surface composition and catalytic performance of bimetallic nanoparticles.

Preparation of underwater superoleophobic porous coating via a co‐deposition method for oil/water mixture separation

AbstractOil contamination is problematic in subaqueous environments. Here, a cationic poly(N,N‐dimethyl‐N‐(ethoxycarbonylmethyl)‐N‐[2′‐(methacryloyloxy)ethyl]‐ ammonium chloride) (PCBMAE) was synthesized, and a one‐step approach of dopamine‐assisted codeposition was used to generate PCBMAE/polydopamine (PDA) superhydrophilic and underwater superoleophobic coatings coated on a stainless steel mesh for oil/water separation. The structures, surface morphologies, and properties of the coatings were analyzed by IR, SEM, TGA, and contact angle measurements. During deposition at a PCBMAE and DA mass ratio of 1:1, PCBMAE/PDA mixture particles uniformly adhered to the skeletons of the mesh, increased the surface roughness, created enriched surface micro/nanostructures, and reduced the surface energy of the coating. This endowed the metal mesh with superhydrophilicity and underwater superoleophobicity (oil contact angle 163°) without blocking the mesh, and the deposition density was 0.26 mg/cm2. The separation efficiency of the coated mesh was 99.6% for the first castor oil/water separation and dropped to 98.0% after 5 cycles. After 25 cycles, the separation efficiency was still higher than 95%. The PCBMAE/PDA codeposited mesh exhibited high oil/water separation efficiency, stable mechanical properties, and weather stability under different harsh environments, making it a promising separation material for future industrial applications.

Negative muons reveal the economic chaos of Rome’s AD 68/9 Civil Wars

During the AD 68/9 Civil Wars, Galba, Otho, Vitellius and then Vespasian fought for — and gained — control of the Roman Empire. Our textual sources suggest that this was a period of serious and sustained disruption. However, existing analyses of gold coinages produced in AD 68/9 show only a minor reduction in the purity of the gold coinage. Using X-ray fluorescence, we identify a number of heavily debased gold coins issued during the AD 68/9 Civil Wars, and many slightly debased coins issued in their immediate aftermath. We then confirm the interior composition of these coins totally non-destructively using muonic X-ray emission spectroscopy, thus eliminating hypothetical problems of ‘surface enrichment’ or compositional differences between ‘surface’ and ‘core’. Here we show that heavily debased Civil War gold coinages were indeed produced; that copper was used to debase Roman gold coins during this time, c. 185 years earlier than first shown; and that slightly debased gold coins were regularly issued in the years immediately after the Civil Wars. The metallurgical evidence from the gold coinage now allows us to show that the AD 68/9 Civil Wars caused significant and sustained disruption to the Roman economic system. More broadly, we have shown that muonic X-ray emission spectroscopy is a powerful tool for generating important archaeological conclusions from high-value cultural heritage objects that simply cannot be destructively analysed, but need to have their interior compositions sampled.

Novel exploration of the flame retardant potential of 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-functionalized metallophthalocyanines in epoxy composites

A series of novel 1-oxo-4-hydroxymethyl-2,6,7-trioxy-1-phosphabicyclo[2,2,2]octane (PEPA)-functionalized metallophthalocyanines (PEPA-MPcs, M = Al, Co, Ni, Zn, and Ce) have been successfully synthesized and characterized. The obtained PEPA-MPcs were added to epoxy resin (EP) to prepare a variety of flame retardant composites (EPP-MPcs) and their thermal behavior and flame retardancy were investigated using thermogravimetric analysis (TGA), the limiting oxygen index (LOI), and cone calorimetry. The flame-retardant mechanism was systematically analyzed in the gas and condensed phases, respectively. The highest LOI value of EP containing 2 wt.% PEPA-MPcs was increased by 19% to 27.6% when compared to pure EP. The peak of heat release rate (pHRR) and the total heat release (THR) values observed for EPP-AlPc were reduced by 64.3% and 48.6%, respectively. The main flame retardant mechanism of the PEPA-MPcs is the synergistic effect of the P and N atoms, including the dilution of highly non-flammable gases in the gas phase and the formation of an intumescent char layer from the condensed phase. Furthermore, the char residues of the EPP-MPcs were significantly increased via the catalysis and surface enrichment of the metal atoms, which reduced the fire hazards of the EP composites. In addition, the EPP-MPcs exhibit excellent mechanical properties and uniform dispersions. This work provides a new approach to the preparation of metal containing/non–halogen/phosphorus-containing flame retardants.

Structural and Molecular Packing study of Three New Amidophosphoric Acid Esters and Assessment of Their Inhibiting Activity Against SARS-CoV-2 by Molecular Docking.

Three new compounds of amidophosphoric acid esters with a [OCH2C(CH3)2CH2O]P(O)[X] segment (where X=cyclopentylamido (1), 2‐aminopyridinyl (2) and pyrrolidinyl (3)) were synthesized and studied using FT‐IR and 31P/13C/1H NMR spectroscopies and single‐crystal X‐ray diffraction analysis. The compounds crystallize in the triclinic space groups P 1‾ for 1 and 3 and in the orthorhombic space group Pca21 for 2, where the asymmetric unit consists of three symmetrically‐independent molecules for 1 and one molecule for 2 and 3. The intermolecular interactions and supramolecular assemblies are assessed by Hirshfeld surface analysis and enrichment ratios. The results reveal that the substituent effect plays an important role in directing the supramolecular structures. The presence of the aromatic substituent aminopyridine in 2 providing the C−H…π interactions leads to a larger variety in interactions including H…H, H…O/O…H, H…C/C…H and H…N/N…H contacts, whereas the packings of the compounds 1 and 3 bearing aliphatic substituents only include H…H and H…O/O…H contacts. The enrichment ratios affirm the importance of O…H/H…O contacts reflecting the hydrogen bond N−H…O interactions to be the enriched contacts. Compounds 1–3 were also investigated along with five similar reported structures with a [OCH2C(CH3)2CH2O]P(O) segment for their inhibitory behavior against SARS‐CoV‐2. The molecular docking results illustrate that the presence of the aromatic amido substituent versus the aliphatic type provides a more favorable condition for their biological activities.

Effect of nitriding treatment on char reducing nitric oxide at high temperature

To reduce nitric oxide (NO) emissions from coal-fired industrial boilers, char waste could be collected from the tail flue and fed into the furnace to reduce NO, which would also decrease the incomplete combustion loss. Nitriding treatment could be used to enhance the NO reducibility of char waste. In this paper, char with nitriding treatment (nitriding char) was prepared from Shenhua char and urea. The effect of nitriding treatment on char reducing NO at high temperatures (700 °C–900 °C) was studied using a fixed-bed experimental system and various urea masses and pretreatment times. Increasing the urea mass and decreasing the pretreatment time resulted in more urea residue being present in the char, which increased the nitrogen complex which existed in the form of C(N) and caused the surface enrichment of nitrogen element, but blocked the pore structure. In an inert atmosphere, the NO reduction rates of all the nitriding chars were higher than that of the raw char, but there was an optimal limit parameter for the urea mass and pretreatment time. The presence of 2 vol% O2 was not conducive to the NO reduction by nitriding char because of the higher char-nitrogen (char-N) content resulting from the nitriding treatment, which generated more NO and offset the benefit of the nitriding treatment. This paper provides a useful NO control strategy in coal-fired industrial boilers, and the relevant process route has achieved a 20%–35% decrease in NO emissions in engineering applications.

Sr Surface Enrichment in Solid Oxide Cells – Approaching the Limits of EDX Analysis by Multivariate Statistical Analysis and Simulations

AbstractIn solid oxide cells, Sr segregation has been correlated with degradation. Yet, the atomistic mechanism remains unknown. Here we begin to localize the origin of Sr surface nucleation by combining force field based simulations, energy dispersive X‐ray spectroscopy (EDX), and multi‐variate statistical analysis. We find increased ion mobility in the complexion between yttria‐stabilized zirconia and strontium‐doped lanthanum manganite. Furthermore, we developed a robust and automated routine to detect localized nucleation seeds of Sr at the complexion surface. This hints at a mechanism originating at the complexion and requires in‐depth studies at the atomistic level, where the developed routine can be beneficial for analyzing large hyperspectral EDX datasets.

Plasma-Assisted Fabrication of Molecularly Imprinted NiAl-LDH Layer on Ni Nanorod Arrays for Glyphosate Detection.

An inorganic-framework molecularly imprinted NiAl layered double hydroxide (MI-NiAl-LDH) with specific template molecule (glyphosate pesticide, Glyp) recognition ability was prepared on Ni nanorod arrays (Ni NRAs) through electrodeposition followed by a low-temperature O2 plasma treatment. The freestanding Ni/MI-NiAl-LDH NRA electrode had highly enhanced sensitivity and selectivity. The electrocatalytic oxidation of Glyp was proposed to occur at Ni3+ centers in MI-NiAl-LDH, and the current response depended linearly on the Glyp concentration from 10.0 nmol/L to 1.0 μmol/L (R2 = 0.9906), with the limit of detection (LOD) being 3.1 nmol/L (S/N = 3). An exceptional discriminating capability with tolerance for other similar organophosphorus compounds was achieved. Molecular imprinting (N and P residues) affected the electronic structure of NiAl-LDH, triggering the formation of highly active NiOOH sites at relatively lower anodic potentials and substantially enhancing the electrocatalytic oxidation ability of the NiAl-LDH interface toward the C-N bonds in Glyp. In combination with the surface enrichment effect of MI-NiAl-LDH toward template molecules, the electrochemical oxidation signal intensity of Glyp increased significantly, with a greater peak separation from interfering molecules. These results challenge the common belief that the excellent performance of inorganic-framework molecularly imprinted interfaces arises from their specific adsorption of template molecules, providing new insight into the development of high-performance organic-pollutant-sensing electrodes.

Surface Mobility of Amorphous Indomethacin Containing Moisture and a Surfactant: A Concentration-Temperature Superposition Principle.

An amorphous material can have vastly higher mobility on the surface than in the bulk and, as a result, shows fast surface crystallization. Most amorphous materials contain multiple components, but the effect of composition on surface dynamics remains poorly understood. In this study, the surface mobility of amorphous indomethacin was measured using the method of surface-grating decay in the presence of moisture and the surfactant Tween 20. It is found that both components significantly enhance the surface mobility, and their effects are well described by the principle of concentration-temperature superposition (CTS); that is, the same surface dynamics is observed at the same Tg-normalized temperature T/Tg, where Tg is the composition-dependent glass transition temperature. For doped indomethacin showing CTS, the mechanism of surface evolution for a 1000 nm wavelength surface grating transitions from viscous flow at high temperatures to surface diffusion at low temperatures at 1.04 Tg. For the surfactant-doped system, the Tg used is the value for the surface layer that reflects the surface enrichment of the surfactant (measured by X-ray photoelectron spectroscopy). At a high surfactant concentration (>10% by weight), the surface-grating decay rate in the surface-diffusion regime is limited by the large, slow-diffusing surfactant molecules; in this case, CTS holds only for the viscous-flow regime. The CTS principle allows the prediction of the surface dynamics of multicomponent amorphous materials.