Using evanescent wave (EW)–based optical detection methods coupled with video microscopy, we investigated in situ trajectories, diffusion, and interaction energies of ∼140 nm ceria particles near a glass surface at pH 3, 5, and 7. Trajectories of a single ceria particle in a 2D (x–y) plane were obtained by linking its time-sequenced positions. Diffusion coefficients of several single ceria particles were calculated from their respective mean-square displacement (MSD) versus time curves, and the results were interpreted based on the interaction potential energy curves obtained from Boltzmann statistics of the EW scattering intensity fluctuations of the particles. The types and characteristics of particle motions were determined by analyzing the MSD curves. Whereas both confined or subdiffusive and Brownian motions of the particles were observed at pH 7, only confined motion was seen at pH 3 and 5, and their corresponding diffusion coefficients are similar to those reported by several authors.

We report a facile method to fabricate CuNi nano-octahedra and nanocubes using a colloidal synthesis approach. The CuNi nanocrystals terminated with exclusive crystallographic facets were controlled and achieved by a group of synergetic capping ligands in a hot solution system. Specifically, the growth of {111}-bounded CuNi nano-octahedra is derived by a thermodynamic control, whereas the generation of {100}-terminated CuNi nanocubes is steered by a kinetic capping of chloride. Using a reduction of 4-nitrophenol with sodium borohydride as a model reaction, CuNi nano-octahedra and nanocubes demonstrated a strong facet-dependence due to their different surface energies although both exhibited remarkable catalytic activity with the high rate constant over mass (k/m). A kinetic study indicated that this is a pseudo first-order reaction with an excess of sodium borohydride. CuNi nanocubes as the catalysts showed better catalytic performance (k/m = 385 s-1•g-1) than the CuNi nano-octahedra (k/m = 120 s-1•g-1), indicating that 4-nitrophenol and hydrogen were adsorbed on the {100} facets with their molecules parallel to the surface much easier than those on {111} facets.

Enzymes can be a renewable source of catalytic agents and thus be interesting for sustainable approaches to create and modify functional materials. Here, thin hydrogel layers were prepared as thin coatings on hard substrates by immobilized horseradish peroxidase. Hydrophilic 4-arm star shaped telechelics from oligo(ethylene glycol) bearing on average 55% end groups derived from aromatic amino acids served as monomers and enzymatic substrates. Shifts of the contact angle from 84° to 62° for the wetting process and of zeta potential towards the neutral range illustrated an alteration of physicochemical properties of the model surfaces by a hydrophilic shielding. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), quartz crystal microbalance and atomic force microscopy (AFM) experiments enabled the qualitative and quantitative proof of hydrogel deposition at the interface with thicknesses in the medium nanometer size range. Conceptually, as the immobilized enzyme becomes entrapped in the hydrogel and the crosslinking mechanism bases on a radical reaction after enzymatic activation of the monomers with a limited diffusivity and lifetime, the formed network material can be assumed to be inhomogeneous on the molecular level. On the macroscale, however, relative homogeneity of the coating was observed via ToF-SIMS and AFM mapping. As an exemplary functional evaluation in view of bioanalytical applications, the thrombogenicity of the coating was studied in static tests with human blood from several donors. In the future, this “coating-from” approach may be explored for cell culture substrate coatings, for protein/biofilm repellence in technical applications, or in bioanalytical devices.

Amorphous carbon, germanium oxide, and 2-dimensional transition metal dichalcogenides grown by atomic layer deposition (ALD) are considered as promising materials for advanced nanoscale device fabrication processes and electronic devices, owing to their extraordinary characteristics. Deposition of these materials using ALD can overcome the limitations of current deposition techniques, including poor step coverage and wafer-scale uniformity, and uncontrollable stoichiometry. Despite these advantages, there has been a lack of research into these materials due to the absence of suitable precursors or optimized processes. In this review, we focus on these nonconventional materials, which have rarely been studied using ALD. The latest research progress and future outlook on these materials grown by ALD will be highlighted, with a particular focus on the applications of future nanoscale device fabrication processes and new concepts in device fabrication which could lead to a paradigm shift in electronics.

Nanoporous copper (NP-Cu), as a sacrificial support, was used for the synthesis of bimodal nanoporous palladium–copper (BNP-PdCu) for oxygen reduction reaction (ORR) electrodes in fuel cells. The catalytic performance of BNP-PdCu in ORR per electrochemical surface area was enhanced by the dissolution and removal of supporting NP-Cu, which indicates that the intrinsic catalytic properties of palladium are improved by the proposed synthesis strategy including galvanic replacement of copper with palladium, following copper dissolution. Cu remained on Pd surfaces even after dissolution of Cu. Additionally, significant local lattice contraction was observed at the ligament surface. First-principles calculations on the adsorbing oxygen species on Pd show that both lattice contraction and alloying with copper increase the binding energies of oxygen species to the Pd surface. The high ORR activity of the present BNP-PdCu is suggested to be mainly due to the Cu-ligand effect.

This article focuses on the acoustic-wave enhancement of chemisorption and surface reactions. Acoustic waves generated by a piezoelectric phenomenon on ferroelectric crystals by the application of radio frequency electric power produce periodic lattice distortions at the surface. The effects of surface acoustic waves (SAWs) and the resonance oscillation (RO) of bulk acoustic waves on thin films of metals or metal oxides are described herein. Both SAWs and RO can modify the work functions of thin Ag, Au, or Pd films, and this effect is highly dependent on the surface structures. These changes in the work function can, in turn, affect the adsorptive characteristics of the metals as well as surface reactions and properties such as catalysis. The importance of periodic lattice displacement vertical to the surface is examined in this article, and the acoustic-wave enhancement of metal and metal oxide surfaces as a means of tuning electronic states and chemical properties is discussed.

In the past years, numerous alternative cations to replace Pb2+ in perovskite solar cells have been investigated. In terms of toxicity and chemical stability, methylammonium bismuth iodide [(CH3NH3)3Bi2I9 or MBI] containing the Bi3+ cation has been considered as a promising material. However, fabrication of coherent MBI films remains challenging. Recently, significant progress has been achieved by using vapor deposition processes. Compared with solution-processed ones, vapor-deposited MBI solar cells show higher fill factors and efficiencies. In this work, chemical vapor deposition (CVD) of MBI is investigated. Employing nitrogen as carrier gas, the precursors bismuth iodide (BiI3) and methylammonium iodide (MAI) are deposited sequentially over several cycles and form MBI during the process. In order to form dense and coherent layers, the lengths of the deposition cycles as well as the substrate temperature have been optimized. Scanning electron microscopy reveals the strong influence of both parameters on growth and crystal properties. Optimized films of MBI integrated into solar cells show that CVD of MBI is a promising method for fabricating large-area solar cells.

Hexagonal boron nitride (hBN), a two dimensional (2D) material, has emerged as an important substrate and dielectric for electronic, optoelectronic, and photonic devices based on graphene and other atomically thin two dimensional materials. Here we report on the initial oxidation of (0001) hBN single crystals in ambient air as functions of temperature and time, as determined by atomic force microscopy (AFM) and scanning electron microscope with energy dispersive X-ray spectroscopy (SEM/EDS). For oxidation times of 20 minutes, the first evidence of oxidation appears at 900°C, with the formation of shallow, hexagonal-, and irregular-shaped pits that are less than 100 nm across and several nanometer deep. Oxidation at 1100°C for 20 minutes produced 1.0-2.0-micron size pits with flat and pointed bottoms that were approximately hexagonal-shaped, but with rough and irregular edges, and multiple interior steps. Oxidation was not uniform on the surface of hBN, but starts where dislocations in the crystal intersected the surfaces. Pit depth increased linearly with temperature and oxidation times. In addition to the surface pits, small particles formed on the surface. Elemental analysis of the thermally oxidized hBN crystals by SEM/EDS revealed the major elements of these particles were boron and oxygen.

In this study, 3 types of zwitterionic phospholipid biosurfactants LDP(S), CDP(S) and CTDP(S) were prepared from 3 different raw materials such as rapeseed oil, coconut oil and cottonseed oil respectively. The structure of the resulting phospholipid biosurfactants was elucidated by FT-IR, 1H NMR and 13C NMR spectroscopies and their interfacial properties have been examined such as CMC, static surface tension, wetting property, solution stability, and foam property. Interfacial property measurement and prescription test in cosmetic formulation prepared with the newly synthesized biosurfactants revealed that CDP(S) biosurfactant possesses excellent mildness and superior interfacial properties, indicating the potential applicability in cosmetic product formulations.

Atomic layer deposition (ALD) of air stable cobalt and nickel complexes based on tridentate enaminones N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylethyldiamine (Htfb-dmeda) and N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylpropyldiamine (Htfb-dmpda) successfully produced metallic cobalt and nickel thin films. Detailed X-ray photoelectron spectroscopy (XPS) studies on the binding interaction of the first precursor monolayer with the surface functional groups elucidated the chemisorption behavior of the new precursor systems. A reactive remote hydrogen plasma was used as the co-reactant to activate the precursor decomposition yielding metal hydroxide intermediates. Subsequent hydrogen plasma etching of as-deposited films resulted in phase-pure metallic films through a recrystallization process, verified by surface and sub-surface XPS. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed pinhole-free films, with low surface roughness (0.2 ± 0.06 nm root mean square, RMS) for both, cobalt and nickel thin films. Herein, the competitive role of hydrogen as etchant and reactant was demonstrated as prolonged plasma exposure time periods resulted in the formation of metal hydrides. This is mostly due to the catalytic dissociation of molecular hydrogen on transition metal surfaces, which already occurs upon low energy input.

The changes in hydrodesulfurization activity, selectivity, dispersion, sulfidation, and extent of promotion of Co(Ni)Mo catalysts were investigated when the alumina support surface is modified by grafting 4 wt% silica. Adding SiO2 eliminates the most reactive hydroxyl groups on the alumina surface (IR band at 3775 cm−1) decreasing the possibility of generating tetrahedral Mo species difficult to sulfide in favor of octahedral ones capable of contributing to the sulfided active phase. The catalysts were evaluated in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. Incorporating SiO2 to alumina increases the hydrogenation rate constant and therefore the global hydrodesulfurization rate of 4,6-dimethyldibenzothiophene and enhances the promotion of Mo by Co (or Ni). The global sulfidation of Ni is not affected by the addition of silica but the sulfidation of cobalt is significantly improved. The extent of promotion of the NiMo/Al2O3 and NiMo/SiO2/Al2O3 catalysts was greater than the one achieved in their Co-promoted counterparts.

Human dental pulp stem cells (DPSCs) can differentiate, showing potential for regenerative medicine. Designing artificial surfaces with properties appropriate for the initiation of extracellular matrix (ECM) adsorption and organization is a critical step in tissue engineering and can greatly impact protein adhesion. Sulfonated polystyrene (SPS), used as a scaffold for tissue development, stimulates protein adsorption due to the increased negative charge of sulfonate.

Graphene and graphene oxide (GO) sheets enhance stem cell growth and differentiation because they are soft membranes with “high in-plane” stiffness and have the potential to be transferable and implantable platforms. This project functionalized GO and reduced GO (RGO) with gold or silver nanoparticles, mixing with SPS to investigate their combined impact on DPSC differentiation and protein adsorption, hypothesizing that this combination supplies more charges to better absorb the proteins to the surface and stimulate differentiation.

Results indicate that proteins of cells plated on the gold-RGO/SPS surfaces were the most highly adsorbed and most densely packed. Additionally, the cell moduli data indicated that the metal-RGO solutions substantially induced a change in modulus even more than Dexamethasone, a glucocortoid known to enhance this process in DPSCs. This suggests that the metal-RGO solutions may be instrumental in osteogenic induction.

The use of ceria abrasives in the chemical mechanical polishing (CMP) of glass allows us to prepare extremely smooth surfaces because it aides both the chemical and mechanical aspects of the polishing process. The mechanism of CMP has remained vague, but the redox of Ce4+/Ce3+ would play a major role for the formation of hydration layer by the chemical factors of CMP. This redox accompanies the process of the charge transfer at glass/slurry interface. Electron charge carrier would be important role in chemical polishing if the redox reaction occurs during polishing. We then prepared the polishing model that it is possible to estimate slurry resistivity and the interfacial area specific resistance (ASR). The effects of abrasive compositions and slurry solution on chemical factor of CMP were investigated to clarify CMP mechanism. The hydration layer forms as a result of the shear stress during polishing but is independent of polishing loads. The amount of hydration layer as well as removal rate was increasing with increasing lanthanum concentration dissolved in ceria lattice. Small amount addition of NH4NO3 increase electron charge carrier density in slurry and improves removal rate, but excess addition inhibited hydration reaction by steric hindrance.

This study investigates the use of ‘simple’ glasses, comprising six components, to represent the structure of complex LAW glasses proposed for Immobilized Low Activity Wastes from the Hanford site in the USA. The 18 elements present in ILAW glasses LAW A44, ORP LB2, and LAW A23 were represented by Al2O3, B2O3, CaO, Na2O, SiO2, and ZrO2 according to their coordination chemistry and their roles as network formers and modifiers. The dissolution behavior of each ‘simple’ glass was compared to its corresponding candidate “complex” LAW glass through PCT-B tests. Significant differences were observed; the durability of complex glasses was concluded to be LAW A44 > ORP LB2 ≥ LAW A23 whereas in their simplified versions the order was LAW A44 > LAW A23 > ORP LB2. These results are discussed in relation to compositional differences and highlight the importance of minor glass components in controlling glass durability. The implications of these results for the use of simplified glass compositions are discussed.

X-ray absorption spectroscopy (XAS) is a widely used characterization technique to explore the local geometric and electronic structures of materials with element specificity. XAS measurements are performed at synchrotron radiation sources that provide brilliant, tunable, and monochromatic energy photons. The advantages of XAS include good elemental, chemical, and orbital sensitivities, which all stem from inherent electron excitation and transition processes. XAS is categorized into soft (<2000 eV) and hard (>5000 eV) x-ray regimes, based on the incident photon energy. Soft x-rays can probe the K-edges of low-Z (atomic number) elements, including Li, C, N, O, and F, and the L-edges of 3d transition metals, whose K-edge is within the hard x-ray regime. All of these elements are essential components of energy materials. This article introduces the principle of XAS and reviews some recent applications in energy storage and energy conversion, illustrating the capabilities of XAS to investigate the fundamental properties of materials from the points of view of atomic and electronic structures, which play crucial roles in understanding the reaction mechanisms in high-performance devices.

Quantum dots have been applied in sensing with success, but their use in environmental applications has been questioned due to their heavy metal content. Carbon dots are fluorescent nanoparticles that offer a promising alternative to quantum dots for sensing, due to their low cost, benign fabrication process and negligible environmental impact. Fluorescence sensors are specially suited for detection of nitroaromatic compounds such as 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT), since they can quench the emission of excited species. When combined to Molecularly Imprinted Polymers (MIPs), the sensors become specific to the imprinted target molecules. Amino-functionalized carbon dots (CDs) with high photoluminescence were fabricated. The CDs were characterized with respect to their surface charge, surface chemistry, particle size distribution, and photoluminescence properties (PL). A molecularly imprinted polymer with template of DNT was combined with fluorescent carbon dots via a simple covalent reaction. The ability of aqueous DNT to quench amino CDs fluorescence was tested for concentrations in the range of 1mM to 50 mM. It can be concluded that the amino carbon dots can be used in fluorescent-labeled MIP systems and that they provide a feasible method for the detection of DNT, and potentially other nitroaromatic compounds, in environmental water samples.

A series of recent instrumental advances have facilitated the application of atom probe tomography (APT) to the characterization of an increasingly wide range of materials and devices. Whereas APT was previously mostly limited to the analysis of alloys, advances in areas such as laser pulsing and detectors have enabled characterization of semiconductors and brittle materials. Most recently, ultraviolet laser pulsing has facilitated the analysis of materials previously considered not viable for the atom probe, such as minerals and large bandgap insulator materials. The development of in situ gas reaction cells fully integrated in atom probe instruments has enabled the characterization of surface reactions of materials exposed to highly controlled environments. Finally, current work toward an integrated cryo-transfer system is anticipated to create new directions for APT research.

Activated carbon materials are integrated into functionalization of graphene nano-sheets to serve as a high-power lithium cathode. The electrochemical performance shows that the composite displays the highest reversible capacity (c. 170 mAh g-1) comparing with functionalized graphene and activated carbon. Also, approximately 92% of its capacity can be retained after 4,000 cycles at a current of 1 A g-1. Moreover, the composite exhibits an excellent rate performance, a reversible capacity of 90 mAh g-1 even at 6 A g-1, which corresponds to the power density of 15.2 kW kg-1 and energy density of 227 Wh kg-1, respectively. The high performance of this composite can be attributed to the fact that the activated carbon particles not only reduce the graphene sheet stacking thus making it easier for ions to diffuse, but also act as an ion storage buffer against accelerating electron transfer.

The Polymer Electrolyte Membrane Fuel Cells (PEMFCs) platinum catalyst’s susceptibility to poisoning by carbon monoxide (CO) reduces its output power. In an effort to diminish poisoning, gold and platinum nanoparticles were incorporated onto partially reduced graphene oxide (Au/Pt-prGO) sheets to reduce both nanoparticle aggregation and the amount of precious metal needed. Applying this material onto the electrodes and Nafion membrane of a PEMFC was hypothesized to increase CO tolerance as well as power output.

Aliquots of graphene oxide (GO) were functionalized with platinum and/or gold nanoparticles using a simple desktop synthesis at room temperature. Partial reduction with NaBH4 maintained hydrophilic solubility. Test solutions applied to electrodes and to electrodes + Nafion membrane were first tested in a PEM fuel cell with a pure H2 gas feed and then repeated with a H2 gas feed containing 1000 ppm of CO. Test arrangements averaged doubling the output power of the poisoned control, with the most effective yielding an output power ∼250% that of the poisoned control. Additionally, each system’s poisoned output power (PP) was compared to its highest possible output power (PM), with the most effective setup showing no reduction in output power, even with a H2 gas feed containing 1000 ppm of CO. Thus, this offers promise of a simple, cost-effective method of both improving PEMFC power output while reducing or even eliminating CO poisoning at room temperature.