Template Substrate Research Articles

An efficient and regioselective biocatalytic synthesis of aromatic N-oxides by using a soluble di-iron monooxygenase PmlABCDEF produced in the Pseudomonas species.

SummaryHere, we present an improved whole‐cell biocatalysis system for the synthesis of heteroaromatic N‐oxides based on the production of a soluble di‐iron monooxygenase PmlABCDEF in Pseudomonas sp. MIL9 and Pseudomonas putida KT2440. The presented biocatalysis system performs under environmentally benign conditions, features a straightforward and inexpensive procedure and possesses a high substrate conversion and product yield. The capacity of gram‐scale production was reached in the simple shake‐flask cultivation. The template substrates (pyridine, pyrazine, 2‐aminopyrimidine) have been converted into pyridine‐1‐oxide, pyrazine‐1‐oxide and 2‐aminopyrimidine‐1‐oxide in product titres of 18.0, 19.1 and 18.3 g l‐1, respectively. To our knowledge, this is the highest reported productivity of aromatic N‐oxides using biocatalysis methods. Moreover, comparing to the chemical method of aromatic N‐oxides synthesis based on meta‐chloroperoxybenzoic acid, the developed approach is applicable for a regioselective oxidation that is an additional advantageous option in the preparation of the anticipated N‐oxides.

Effect of substrate preparation on the growth of lead-free piezoelectric (K0.5Na0.5)NbO3 on Pt(111)

Lead-free piezoceramics aiming at replacing the market-dominant Pb(ZrxTi1−x)O3 have been extensively researched for more than a decade worldwide due to the toxicity of lead. In this context, (K0.5Na0.5)NbO3 (KNN) triggered the attention of the scientific community thanks to its bulk record piezoelectric coefficient combined with high critical temperature, which make it a good candidate for applications. In this paper, (001)-oriented KNN thin films grown by pulsed laser deposition on Pt(111)/TiO2/SiO2/Si substrates are investigated. We highlight the relevance of the template substrate in determining the structure of the film. Developing a suitable treatment for the Pt substrate is of great importance to film morphologic and topographic quality and to electric, ferroelectric, and piezoelectric properties. From local characterization of piezoelectric properties, we find a piezoelectric coefficient d33 of about 80 pm/V, comparable to the highest values reported for state-of-the-art undoped KNN thin films. Finally, electrical characterization of fabricated micro-capacitors allows the investigation of dielectric performance and shows remanent ferroelectric polarization over microscopic areas, thus paving the way to the integration of these KNN films in microfabricated actuator devices.

Effects of low temperature buffer layer on all-sputtered epitaxial GaN/AlN film on Si (111) substrate

The effect of an Al buffer layer on the growth of AlN on a Si (111) substrate was investigated to develop an all-sputtered GaN film on a Si (111) template substrate. The X-ray diffraction method revealed an obvious improvement in the crystallinity of an AlN layer on the initial layer. At the interface structure, AlN film without the Al buffer layer exhibited surface nitridation of the Si surface, which degraded the AlN crystal growth. After investigating various growth conditions such as substrate temperature and layer thickness, we achieved the all-sputtered epitaxial growth of a GaN/AlN/Si substrate. The substrate temperature was below 650 °C, and the total thickness was less than 200 nm, which is beneficial as regards the cost efficiency of the template substrate for nitride semiconductors.

Temperature Dependence of Stress and Optical Properties in AlN Films Grown by MOCVD.

AlN epilayers were grown on a 2-inch [0001] conventional flat sapphire substrate (CSS) and a nano-patterned sapphire substrate (NPSS) by metalorganic chemical vapor deposition. In this work, the effect of the substrate template and temperature on stress and optical properties of AlN films has been studied by using Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible spectrophotometer and spectroscopic ellipsometry (SE). The AlN on NPSS exhibits lower compressive stress and strain values. The biaxial stress decreases from 1.59 to 0.60 GPa for AlN on CSS and from 0.90 to 0.38 GPa for AlN on NPSS sample in the temperature range 80–300 K, which shows compressive stress. According to the TEM data, the stress varies from tensile on the interface to compressive on the surface. It can be deduced that the nano-holes provide more channels for stress relaxation. Nano-patterning leads to a lower degree of disorder and stress/strain relaxes by the formation of the nano-hole structure between the interface of AlN epilayers and the substrate. The low crystal disorder and defects in the AlN on NPSS is confirmed by the small Urbach energy values. The variation in bandgap (Eg) and optical constants (n, k) with temperature are discussed in detail. Nano-patterning leads to poor light transmission due to light scattering, coupling, and trapping in nano-holes.

Abnormal increase of 2DEG density in AlGaN/GaN HEMT grown on free-standing GaN substrate

In this study, AlGaN/GaN high-electron-mobility transistors (HEMTs) were grown on a GaN template and GaN substrate under the same growth conditions. It was observed that, in the HEMT structure grown on the GaN substrate, mobility decreased because of an increase in the two-dimensional electron-gas (2DEG) density; the origin of these redundant electrons was studied. The 2DEG density decreased with decreasing temperature, this phenomenon closely related to unintentionally induced shallow donors with ionization energy calculated to be around 67.8 meV. After Ⅴ/Ⅲ ratio regulation, the 2DEG density returned to a normal level; this combined with photoluminescence, confirmed for the first time that the abnormal increase of 2DEG density in HEMT structure grown on the GaN substrate is associated with nitrogen vacancies. Therefore, increasing the Ⅴ/Ⅲ ratio is beneficial for obtaining higher mobility by returning the 2DEG density to a normal level.

Polymer Coating Effects: Study of Material Properties and Architectural Application Characteristics of Aluminum Template

In construction process, the formwork must be in contact with concrete to help the concrete solidify and fix the shape. Coating the formwork with a polymer can prolong its service life by reducing the amount of concrete sticking to the mold. Herein, an aluminum template substrate was coated with polyvinylidene difluoride (PVDF) or polyurethane (PU). Aluminum template material analysis was conducted, polymer film thickness was measured, and weather, moisture, pollution, salt spray, abrasion, impact, and acid and alkali resistance tests were conducted, as were tensile, bending, adhesion, hardness, and salt water resistance tests. Cement adhesion resistance was repeatedly tested. The experimental results indicated that the PVDF-coated template was superior. The novel PVDF Aluminum template exhibited high corrosion resistance and can be used in building materials, for example, in ceilings, partition walls, curtain walls, roof panels, and roof trusses. For reference, it can also be applied to ship structures and seaside and wind power generation projects.

Nanostructure of a deep eutectic solvent at solid interfaces

HypothesisDeep eutectic solvents (DESs) are an attractive class of tunable solvents. However, their uptake for relevant applications has been limited due to a lack of detailed information on their structure-property relationships, both in the bulk and at interfaces. The lateral nanostructure of the DES-solid interfaces is likely to be more complex than previously reported and requires detailed, high-resolution investigation. ExperimentsWe employ a combination of high-resolution amplitude-modulated atomic force microscopy and molecular dynamics simulations to elucidate the lateral nanostructure of a DES at the solid-liquid interface. Specifically, the lateral and near-surface nanostructure of the DES choline chloride:glycerol is probed at the mica and highly-ordered pyrolytic graphite interfaces. FindingsThe lateral nanostructure of the DES-solid interface is heterogeneous and well-ordered in both systems. At the mica interface, the DES is strongly ordered via polar interactions. The adsorbed layer has a distinct rhomboidal symmetry with a repeat spacing of ~0.9 nm comprising all DES species. At the highly ordered pyrolytic graphite interface, the adsorbed layer appears distinctly different, forming an apolor-driven row-like structure with a repeat spacing of ~0.6 nm, which largely excludes the chloride ion. The interfacial nanostructure results from a delicate balance of substrate templating, liquid-liquid interactions, species surface affinity, and packing constraints of cations, anions, and molecular components within the DES. For both systems, distinct near-surface nanostructural layering is observed, which becomes more pronounced close to the substrate. The surface nanostructures elucidated here significantly expand our understanding of DES interfacial behavior and will enhance the optimization of DES systems for surface-based applications.

Atomically precise noble metal clusters (Ag10, Au10, Pd10 and Pt10) on alumina support: A comprehensive DFT study for oxidative catalysis

A comprehensive study of electronic and geometrical properties of alumina supported M10 (M = Ag, Au, Pd, Pt) clusters has been reported with a focus to unravel chemical reactivity towards oxidative catalysis. Au10, Ag10 and Pd10 clusters on alumina surface, adopt zigzag style hexagonal pseudo-planar structure aligning to substrate template, contrary Pt10@Al2O3 does not follow surface template and forms a bilayer structure due to higher PtPt bond strength. Pd10 and Pt10 cluster bind with alumina surface stronger than Ag10 and Au10 and accordingly receives more charge from surface. The d-band centre of finite size M10@Al2O3 cluster follows the trends of extended M(111) surface and Pt10@Al2O3 shows close matching for d-band centre position values with Pt(111). On interaction with O2 molecule, all four M10@Al2O3 clusters energetically prefer surface assisted molecular adsorption (O2 bridging cluster-surface) over atop molecular adsorption demonstrating pivotal role of substrate. In contrast, dissociative adsorption prefers atop mode configurations. During oxidation, whilst Ag10@Al2O3, Au10@Al2O3 and Pd10@Al2O3 show increase in MM bond-lengths and move away from substrate, Pt10@Al2O3 displays robust behaviour by moving near to surface. Due to minimum overlap between 4d and 5s state (large difference in energy) the O2 interaction energetics of Ag10@Al2O3 as well as Ag(111) depart from usual d-band model.

First-principles study on growth mechanism of TiN on MgO (1 0 0) and (1 1 0) surfaces

Substrate nucleation is one of the important modes of heterogeneous nucleation. The substrate nucleation occurs with the absorbed atoms transforming atomic layers phase of the nucleated phase on the substrate in the actual production process. For example, TiN grows layer by layer on MgO substrate during solidification of steel, which is an important way for MgO inclusions to play the role of oxide metallurgy to induce inclusions or precipitated phase. In this work, the first-principles calculation is employed to study the growth mechanism of TiN on MgO (100) and (110) surfaces. Study on atomic binding energy and charge density difference have shown that the effecting of MgO substrate template effect can be divided into two parts: coherent epitaxial layer and transition layer. For MgO(100)/TiN(100) and MgO(110)/TiN(110) systems, the critical size includes four and five atomic layers(TiN), respectively. The interfacial energy and work of adhesion of MgO(100)/TiN(100) system are both smaller than those of MgO(110)/TiN(110) system in the evolution process of TiN nucleation layer by layer on MgO substrate. The interfacial and surface properties of MgO/TiN systems are both related to MgO substrate, especially at the beginning of nucleation. The relation between electron work function or outermost atoms adsorption energy and charge distribution is also discussed simply.

From starphenes to non-benzenoid linear conjugated polymers by substrate templating.

Combining on-surface synthetic methods with the power of scanning tunneling microscopy to characterize novel materials at the single molecule level, we show how to steer the reactivity of one anthracene-based precursor towards different product nanostructures. Whereas using a Au(111) surface with three-fold symmetry results in the dominant formation of a starphene derivative, the two-fold symmetry of a reconstructed Au(110) surface allows the selective growth of non-benzenoid linear conjugated polymers. We further assess the electronic properties of each of the observed product structures via tunneling spectroscopy and DFT calculations, altogether advancing the synthesis and characterization of molecular structures of notable scientific interest that have been only scarcely investigated to date, as applies both to starphenes and to non-benzenoid conjugated polymers.

Large-Area Graphene Transfer through Synthesis of an Interfacial Release Layer between Epitaxial Cu(Ni)(111) and Al2O3(0001) Template

As the pioneer two-dimensional material with outstanding properties, graphene is still lacking a CMOS compatible handling process, both for growth and transfer. This restriction slows down the application of large-scale-high-quality monolayer graphene (MLG). The synthesis of wafer-scale single-crystal MLG has matured utilizing a single-crystal Cu(111) deposit epitaxially on c-plane sapphire as a growth template[1,2]. However, the non-straightforward intercalation base transfer process [3] becomes a bottleneck. Hence, an interfacial release layer between Cu and sapphire could provide an alternative route for the graphene transfer process.Here, we report on the synthesis of large-area multilayer graphene at the interface of epitaxial Cu(Ni)(111)/ Al2O3(0001) using atmospheric pressure chemical vapor deposition (CVD). The interfacial carbon layer (ICL) was synthesized by introducing CH4 and H2 gases in the CVD chamber at 1050°C, and characterized by micro-Raman spectroscopy, XRD, and AFM. Carbon layers with thickness up to 80nm were observed at the interface between 500nm thick Cu and Al2O3.The effects of the partial pressure of gases - PH2 and PCH4 – and template substrate on the growth dynamics were investigated systematically by optical microscopy and image analysis. The growth rate and deposition area of ICL are positively correlated with PCH4. In the Cu85Ni15(111) system, ICL coverage is significantly lower compared to Cu(111). This is attributed to the faster growth rate of a top surface MLG, which blocks the access of carbon into the interface of Cu(Ni)/Al2O3. A higher PH2 slows down the MLG growth, leading to a denser ICL deposition in both substrates.The growth mechanism of this ICL is also proposed as the result of two competing effects: 1. The high PCH4 environment drives the decomposed carbon species to the interface from the top surface by diffusion through the bulk of the catalytic metal. 2. The blockage of carbon access to the bulk of metal once the top layer MLG is closed.After process optimization, the ICL could be synthesized simultaneously with top layer high-quality CVD MLG. In the future, this process could provide opportunities to enable CMOS compatible large-scale-high-quality MLG transfer. K. Verguts et al., ECS J. Solid State Sci. Technol., 5, Q3060–Q3066 (2016).M. Huang et al., ACS Nano, 12, 6117–6127 (2018).K. Verguts et al., ACS Appl. Mater. Interfaces, 9, 37484–37492 (2017).

Depletion-Mediated Uniform Deposition of Nanorods with Patterned, Multiplexed Assembly.

Device-scale, uniform, and controllable deposition of nanoparticles on various substrates is fundamentally important not only for the fabrication of thin-film devices but also for the large sample statistics of single-particle performances. However, it is challenging to obtain such predefined depositions using a simple and efficient method. Here, we present a novel strategy for obtaining the uniform and particle density/spacing-tunable deposition of nanorods on a linker-free substrate. The deposition is driven by the tailored particle-substrate depletion attraction owing to the size-matched design of the substrate roughness and the nanorod diameter. Both gold nanorods and upconversion nanorods were applied to demonstrate the generality of the method. The high particle density of more than 21 per μm2 and correspondingly the small particle spacing of fewer than 0.3 μm were achieved on a scalable substrate template. On this basis, orientational ordering and pattern-selective deposition of nanorods were realized by controlling the liquid flow rate and employing the substrate with patterned roughness areas, respectively. With the roughness-directed density-tunable depositions of nanorods integrated onto a single platform, multiplexed gold nanorod assembly and programmable surface-enhanced Raman mapping were achieved, with a promising prospect in information encoding by using the Raman signals as the translation units. The thermal stability and related transition temperature of about 160 °C of gold nanorods were also revealed as an application of single-particle statistics. This practical method could be extended to wide ranges of potential applications in plasmonic coupling devices, cryptography, or single-particle performance statistics with the feature of the high-throughput, low-cost, and scalable fabrication.

Facile flame deposition of carbon coating onto Ni foam and the study of the derived carbon foam with high capacitive performance

Porous carbon foam was directly synthesized in an ethanol vapor flame within only 1 min for the first time. Nickel foam served as both hard template and catalyst substrate for catalyzing deposition of carbon coating on its surface. Carbon foam modified with oxygen-containing organic groups was obtained after etching the metal substrate. The following thermal treatment endowed the carbon foam with corrugated strut surface, decreased thickness of carbon strut layer, and reduced hetero-atom doping level. Moreover, the electrical conductivity of the foam was enhanced by >3 orders of magnitude up to 59.3 S m−1. Additionally, the free-standing thermal-annealed carbon foam electrode exhibited a desirable electric double-layer capacitance of 172 F g−1 at 2 Ag−1 in a three-electrode half-cell configuration, which could be due to its unique porous structure, high electrical conductivity, rich defects and oxygen-doping of the carbon foam.

Effect of Electric and Magnetic States of Substrate on the Deposition of Organic Polymers

The processes of deposition of organic polymers (using lysozyme an example) on substrates with different magnetic and electric states have been studied using a complex of microscopy methods. It is shown that substrates with a well-developed electric relief promote the immobilization of lysozyme. For substrates with a type of freshly cleaved mica, with specific dipole surface structure, the ordering of lysozyme islands in the form of filaments is observed. An effect of lysozyme self-organization with the formation of dendritic structure upon the deposition of cobalt ferrite films on the surface of films is found, which makes such template substrates promising biotropic structures.

Characterization of epitaxial titanium nitride mediated single-crystal nickel oxide grown on MgO-(100) and Si-(100)

Single-crystal nickel oxide (NiO) was grown, using epitaxial titanium nitride (TiN) as a preorienting interlayer, on both the lattice-matching substrate of magnesium oxide in the (100) surface orientation, MgO-(100), and a lattice-mismatched silicon (100) substrate, Si-(100), by high-temperature pulsed-laser deposition. To the best of the authors’ knowledge, this is the first report of its kind in the literature. The high-temperature sputter-deposited TiN interlayer is crucial for forming a bottom contact for the implementation of a device, and as a lattice-matching layer for NiO and MgO. The structural, surface-related, and elemental properties of the as-grown NiO/TiN/MgO(100) and NiO/TiN/Si(100) samples were determined by high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), thin-film x-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy in conjunction with energy-dispersed x-ray spectroscopy. XRD rocking curve data confirmed that the NiO layers were single crystalline on both template substrates, and the structural quality of NiO/TiN on the lattice-matching MgO substrate surpassed that on the Si substrate. XRD φ-scan data confirmed the cube-on-cube stacking of NiO and TiN. An analysis of HRTEM fast Fourier transform (FFT) images further confirmed the single crystallinity of the NiO and TiN layers, while lattice mismatches at the NiO/TiN, TiN/MgO, and TiN/Si interfaces were examined using the FFT line profile measurements of HRTEM. The resulting thin film of single-crystalline NiO can be used as a transparent conducting electrode in group-III oxide and group-III nitride semiconductor devices, and in such electrochemical processes as solar hydrogen generation and nitrogen reduction reactions.

Electronic‐ECM: A Permeable Microporous Elastomer for an Advanced Bio‐Integrated Continuous Sensing Platform

AbstractTissue interfaced electronics have become promising candidates for transcending beyond conventional diagnostic technology, enabling chronic, quantitative health monitoring possibilities; however, these systems have primarily relied on impenetrable materials that contribute to the mechanical and physical mismatch of bioelectronic interfaces. Inspired by the soft mechanics and physical architecture of the epidermal extracellular matrix, this study presents a 3D microporous, fibrous mesh of polydimethylsiloxane for epidermal electronics. The resulting elastic microfiber mat, exhibits a minimal mechanical footprint with analogous viscoelastic behavior, cytocompatibility, and biofluid‐permeable interface capable of small molecule, gas, and transdermal water diffusion. Electrocardiography electrodes heterogeneously integrate within the synthetic electronic‐extracellular matrix (e‐ECM) membrane and achieve chronic high resolution biopotential monitoring during typically debilitating environments (e.g., vigorous sweating) for conventional bioelectronics. The e‐ECM platform provides a substrate template for open‐mesh electronics, enabling advanced implementations in long‐term quantitative analysis monitoring for wearable and implantable devices.

Mica-Based Multilayer Nanocoating as a Highly Effective Flame Retardant and Smoke Suppressant.

Highly flammable polyurethane foam (PUF) remains a key risk factor associated with bedding and upholstered furniture, contributing to the yearly destruction of property and loss of lives. In an attempt to tackle this issue and develop a more benign flame retardant for PUF, a mica-based nanocomposite was deposited using layer-by-layer assembly. Chitosan (CH) and poly(acrylic acid) (PAA) were used to stabilize high-aspect-ratio mica. Foam treated with eight bilayers of CH- and PAA-stabilized mica preserves the porous foam structure, prevents melt dripping, and self-extinguishes during a 10 s torch test, while uncoated foam is completely consumed. When exposed to 35 kW/m2 heat flux during cone calorimetry, the peak heat release rate is reduced by 54% and less-volatile molecules are released during combustion, resulting in a 76% reduction in the total smoke release. This multilayer coating serves as an environmentally benign template for flame-retarding PUF and various other three-dimensional substrates.

Band alignment at non-polar AlN/MnS interface investigated by hard X-ray photoelectron spectroscopy

The band alignment and interface reaction at the AlN/MnS interface were investigated by hard X-ray photoelectron spectroscopy. The AlN/MnS/Si (100) stack structure is a candidate of a template substrate for the non-polar GaN growth on a Si (100) substrate. For the band alignment of AlN/MnS, the AlN film on MnS buffer layer had a type II band structure. The conduction band offset from AlN to MnS was −0.59 eV. For the interface stability at the AlN/MnS interface, the S 2s spectra showed undistinguishable change regardless of the growth temperature of AlN. The nitrogen and sulfur defects were formed. The Fermi level position did not show the growth temperature dependence, although the depletion layer was formed at the interface of AlN and the Fermi level moved in-gap direction. The growth temperature of AlN did not affect the band offset of AlN/MnS. The AlN/MnS interface was chemically and electrically stable interface.

Long carrier lifetime in faceted PbS quantum dot superlattice fabricated by sedimentation method

We fabricated colloidal quantum dot (QD) superlattice films and investigated their primal optical properties. The films were prepared by depositing faceted PbS QDs on pyramidal-microhole-array template and flat substrate in solution. The red shift in the quantum state emission of QDs was observed in photoluminescence spectra after film formation, which suggested the weakened quantum confinement of carriers in intermediate bands. Emission decay curves at the excited states in the QD superlattice film were double exponential. The longer lifetime was several tens of nanoseconds and attributed to the carrier delocalization in the intermediate bands. The emission lifetime of the QD film prepared on the template was found to be more than twice as long as that on the flat substrate, which suggested that the template helped to form large area QD superlattice.

Water-Stable Flexible Nanocellulose Chiral Nematic Films through Acid Vapor Cross-Linked Glutaraldehyde for Chiral Nematic Templating.

Cellulose nanocrystals (CNCs) have drawn considerable attention for their use in optical and sensor applications due to their appealing properties of chiral nematic photonic structures. However, the flexibility and water instability of neat CNC chiral nematic films are questionable and compromise their outstanding properties. We propose a room-temperature process for fabricating flexible, water-stable chiral nematic CNC films. Aqueous glutaraldehyde (GA) was first mixed with CNCs, and then free-standing films were formed by evaporation-induced self-assembly. The chiral nematic dry films that formed were then exposed to hydrochloric acid vapor for subsequent GA cross-linking with CNCs. The GA cross-linked CNC films had a highly ordered chiral nematic organization. The enhanced water stability of the films was demonstrated by using GA cross-linked CNC films as freestanding template substrates for conducting polymers (polypyrrole) and metal oxides (iron oxide) to form flexible chiral nematic photonic hybrids.