Flight Secondary Ion Mass Spectrometry Research Articles

The effect of calcium hypochlorite on the adsorption of diethyldithiocarbamate (DDTC) on the surface of molybdenite and bismuthinite

In this paper, the effect mechanism of calcium hypochlorite on the adsorption of the collector DDTC on the surface of molybdenite and bismuthinite was explored. The single mineral flotation test showed that calcium hypochlorite had significant inhibition on the flotation behavior of bismuthinite, but had no similar effect on that of molybdenite. The results of FT-IR spectra and contact angle measurement indicated that the collector DDTC was not able to adhere to the bismuthinite surface treated with calcium hypochlorite, but could adhere to the molybdenite surface treated with the same way. Synthesizing the results of electrochemical test, thermodynamic analysis, Raman spectra, and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) test, it could be confirmed that calcium hypochlorite could react on the surface of bismuthinite and molybdenite, and the reaction on the bismuthinite surface first produced Bi3+ and Cl-, which continued to react in solution and finally formed BiOCl precipitation, while the reaction on the molybdenite surface formed soluble components, which dissolved into the solution. Therefore, the hydrophilic BiOCl precipitation covered the bismuthinite surface, hindering the adsorption of DDTC, while the soluble components produced on the molybdenite surface entered the solution without affecting its surface wettability and collector adsorption, which maybe was the root cause of the selective depression of calcium hypochlorite.

Investigation of Effects of Sulfuric Acid in Single Wafer Cleaning Process Using Isopropyl Alcohol

Isopropyl alcohol (IPA) was used in the drying process to remove the contamination after the wet cleaning process. Regardless of the types of chemical solutions, the IPA is more strictly controlled because it is used. However, when the IPA was exposed to low acid concentration, the IPA polymers were generated to the di-isopropyl ether, isopropyl acetate, and di-isopropoxy methane. And the pH of IPA rapidly changed by about 1.99 in ppm level concentration. Generated IPA polymers were adsorbed on the wafer surface. These polymers can occur defects, and the probability increases as the concentration increases. Scanning mobility particle sizer (SMPS) measurement system can be measured the impurity in IPA solution. The total impurity concentration was increased by the concentration of H2SO4 with the same results in both gas chromatography mass spectrometry (GCMS) and time of flight secondary ion mass spectrometry (ToF-SIMS). SMPS results can be correlated with the concentration of impurities. In this paper, IPA polymers were defined by acid contamination, and these polymers have affected the Si wafer surface. In addition, the SMPS measurement system was introduced for the detection of impurities in IPA solutions.

Effect of regulating dissolved oxygen concentration in pulp with aerated gas on pyrite flotation

Moderate oxidation is beneficial to the flotation of sulfide ores, but the exact dissolved oxygen (DO) concentration suitable for flotation is still unclear. In this work, a self–made vacuum aeration flotation equipment was designed and assembled to accurately control the DO concentration in pulp by adjusting the relative proportion of O2/N2 during aeration, and the effect of DO concentration on the floatability and surface properties of pyrite as well as the interaction between pyrite and xanthate was studied. Microflotation experiments, contact angle, time–of–flight secondary ion mass spectrometry, X–ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, electrochemical and localized electrochemical impedance spectroscopy measurements were conducted in this investigation. The results showed that the flotation recovery of pyrite could be remarkably affected by DO concentration in pulp; it increased first and then decreased with the increase of DO concentration; an optimal DO concentration (DO = 3.3 mg/L) was helpful for pyrite flotation recovery; both the formation of dixanthogen and the avoidance of excessive iron oxide/hydroxide formed on pyrite surface were the key to improve the pyrite recovery. This research is expected to be applied in optimizing the flotation separation by DO-pH combined detection and regulation, strengthening the green flotation of sulfide ore with low collectors, and the design and manufacture of new closed and efficient sulfide ore flotation equipment.

Impact of etching process on Al2O3/GaN interface for MOSc-HEMT devices combining ToF-SIMS, HAXPES and AFM

In this work we present the effect of inductively coupled plasma reactive ion etching (ICP-RIE) combined with atomic layer etching (ALE) on the Al2O3/GaN interface for MOSc-HEMT devices. Time of flight secondary ion mass spectrometry (ToF-SIMS) and hard x-ray photoelectron spectroscopy (HAXPES) highlight an increase of the N/Ga ratio near the interface after etching. ToF-SIMS profiles also show the presence of impurities (H, C, B) at this interface. Atomic force microscopy (AFM) also illustrates a change of the GaN surface morphology for the etched sample.

Covalent and Non-covalent In-Flow Biofunctionalization for Capture Assays on Silicon Chips: White Light Reflectance Spectroscopy Immunosensor Combined with TOF-SIMS Resolves Immobilization Stability and Binding Stoichiometry.

Immunosensors that combine planar transducers with microfluidics to achieve in-flow biofunctionalization and assay were analyzed here regarding surface binding capacity, immobilization stability, binding stoichiometry, and amount and orientation of surface-bound IgG antibodies. Two IgG immobilization schemes, by physical adsorption [3-aminopropyltriethoxysilane (APTES)] and glutaraldehyde covalent coupling (APTES/GA), followed by blocking with bovine serum albumin (BSA) and streptavidin (STR) capture, are monitored with white light reflectance spectroscopy (WLRS) sensors as thickness dΓ of the adlayer formed on top of aminosilanized silicon chips. Multi-protein surface composition (IgG, BSA, and STR) is determined by time of flight secondary ion mass spectrometry (TOF-SIMS) combined with principal component analysis (applying barycentric coordinates to the score plot). In-flow immobilization shows at least 1.7 times higher surface binding capacity than static adsorption. In contrast to physical immobilization, which is unstable during blocking with BSA, chemisorbed antibodies desorb (reducing dΓ) only when the bilayer is formed. Also, TOF-SIMS data show that IgG molecules are partially exchanged with BSA on APTES but not on APTES/GA modified chips. This is confirmed by the WLRS data that show different binding stoichiometry between the two immobilization schemes for the direct binding IgG/anti-IgG assay. The identical binding stoichiometry for STR capture results from partial replacement with BSA of vertically aligned antibodies on APTES, with fraction of exposed Fab domains higher than on APTES/GA.

Novel application of depressant sodium mercaptoacetate in flotation separation of chalcopyrite and pyrite

The development of flotation reagents with high selectivity and strong depression ability is of great significance in the efficient enrichment of copper sulfide ores. In this work, a new depressant, sodium mercaptoacetate (SMA) has been explored for the flotation separation of chalcopyrite and pyrite, and the depression mechanism of SMA was studied by Fourier Transform Infrared spectrometer (FTIR), adsorption tests, local electrochemical impedance spectroscopy test (LEIS), Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). Micro-flotation tests showed that SMA strongly depresses pyrite in the pH range of 6–10. When the dosage of SMA is 2.5 × 10−5 mol/L, the dosage of SBX is 1 × 10−5 mol/L, and pH = 6.5, the concentrate with a Cu grade of 31.93% and chalcopyrite recovery of 85.97% can be obtained, in which the pyrite recovery was only 4.18%, respectively. The strong chemical adsorption between SMA and Fe atomic sites exposed on the surface of pyrite reduces the hydrophobicity of pyrite and hinders the adsorption of SBX. In comparison, SMA has less adsorption on the surface of chalcopyrite and hardly affects the further adsorption of SBX. It was shown that SMA could be used as an effective depressant for pyrite in the flotation separation of chalcopyrite and pyrite.

The effect of elastic and plastic strain on surface and intergranular oxidation of alloy 600 in simulated PWR primary water

The effects of deformation and stress on the surface and grain boundary oxidation of Alloy 600, exposed to primary water of Pressurized Water Reactors (PWRs), were investigated by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Scanning Electron Microscopy (SEM). It was found that tensile straining prior to oxidation does not modify the surface oxide thickness while the intergranular oxide depth increases when the strain reaches a critical value of 15%. The oxide growth rates at surface and grain boundaries are enhanced under stress. The effect of stress is more significant when the specimen is under elastic strain than plastically deformed.

Controllable Water-Triggered Degradation of PCL Solution-Blown Nanofibrous Webs Made Possible by Lipase Enzyme Entrapment

Polymers in nanofibrous forms offer new opportunities for achieving triggered polymer degradation, which is important for functional and environmental reasons. The polycaprolactone (PCL) nanofibrous nonwoven polymer webs developed in this work by solution blow spinning with entrapped enzymes were completely, rapidly and controllably degraded when triggered by exposure to water. Lipase (CALB) from Candida antarctica was successfully entrapped in the PCL webs via an enzyme-compatible water-in-oil emulsion in the PCL–chloroform spinning solution with added surfactant. Protein (enzyme) in the nanofibrous webs was detected by Fourier Transform Infrared Spectroscopy (FTIR), while time of flight-secondary ion mass spectroscopy (ToF-SIMS) and laser confocal microscopy indicated that enzymes were immobilized within solid fibers as well as within microbead structures distributed throughout the webs. Degradation studies of CALB-enzyme functionalized solution-blown nonwoven (EFSBN)-PCL webs at 40 °C or ambient temperature showed that EFSBN-PCL webs degraded rapidly when exposed to aqueous pH 8 buffer. Scanning electron microscopy (SEM) images of partially degraded webs showed that thinner fibers disappeared first, thus, controlling fiber dimensions could control degradation rates. Rapid degradation was attributed to the combination of nanofibrous web structure and the distribution of enzymes throughout the webs. CALB immobilized in the solid dry webs exhibited long storage stability at room temperature or when refrigerated, with around 60% catalytic activity being retained after 120 days compared to the initial activity. Dry storage stability at ambient conditions and rapid degradation upon exposure to water demonstrated that EFSBN-PCL could be used as fibers or binders in degradable textile or paper products, as components in packaging, for tissue engineering and for controlled-release drug or controlled-release industrial and consumer product applications.

High‐Voltage Stability of Small‐Size Single Crystal Ni‐Rich Layered Cathode for Sulfide‐Based All‐Solid‐State Lithium Battery at 4.5 V

AbstractMechanical damage of NCM811 (LiNi0.8Co0.1Mn0.1O2), severe interfacial side reactions, and physical contact failure of cathode and solid electrolyte (SE) are the main obstacles for it to achieve high‐voltage stability in all‐solid‐state batteries (ASSLBs). The cathode morphology effects on the structural integrity are directly related to the electrochemical performance of ASSLBs. In this work, small‐size single crystal NCM811 (S‐SC) is synthesized for sulfide‐based ASSLBs to solve mechanical damage and contact failure issues. In addition, the interfacial stability is improved by a Li2O pre‐lithiation strategy. Cross section polisher‐scanning electron microscopy (CP‐SEM) is applied to reveal the mechanical structure evolution behavior of NCM811 cathodes with different morphology. Electrochemical impedance spectroscopy (EIS), time of flight secondary ion mass spectrometry (TOF‐SIMS), and X‐ray photoelectron spectroscopy (XPS) technologies are applied to characterize the interfacial stability among cycling. As a result, with a high mass loading of 35.67 mg cm−2 and high current density of 7.13 mA cm−2, the Li2O pre‐lithiated S‐SC (S‐SC‐PL) cathode delivers extraordinarily high‐voltage stability of 100% after 500 cycles at 2.72–4.4 V and 100% after 200 cycles at 2.72–4.5 V in ASSLBs. This work provides an effective cathode morphological design strategy to improve high‐voltage stability of Ni‐rich layered cathodes for sulfide‐based ASSLBs.

Enhanced Cycling Stability of 4.6 V LiCoO2 Cathodes by Inhibiting Catalytic Activity of its Interface Via MXene Modification

AbstractLiCoO2 plays a key role in energy storage devices due to its high energy density. And the volumetric energy density of LiCoO2 cathode can be significantly improved by increasing the charging cut‐off voltage to 4.6 V. However, the increase in resistance at the LiCoO2 interface, and the damage to the LiCoO2 from the outside to the inside by the HF generated that caused by the decomposition of the organic electrolyte and LiPF6 under 4.6 V conditions are not conducive to structural stability during cycling. Here, it is shown that the decomposition of electrolyte and LiPF6 is effectively mitigated by inhibiting the interfacial catalytic activity of LiCoO2 using an atomically thin layer of MXenes as a interlayer. Density functional theory results suggest that the decomposition energy of LiPF6 is 1.13 and 3.21 eV at the interface of LiCoO2 and MXenes, respectively. Time of Flight Secondary Ion Mass Spectrometry results further indicate that the decomposition products of the organic electrolyte and LiPF6 have a thinner thickness at the interface of MXenes (5 nm) than LiCoO2 (10 nm). This study provides a new and universal strategy for stabilizing the cathode interface to support the development of high energy density lithium‐ion batteries.

Optimized emitter-base interface cleaning for advanced Heterojunction Bipolar Transistors

Heterojunction Bipolar Transistors needed for high-frequency applications require precise dopant control. In-situ doped epitaxies used during device fabrication rely on surface preparation to obtain an optimized doping profile. Defects due to imperfect cleaning relates to high emitter resistance and low-frequency noise.Base epitaxy is followed by the fabrication of thin L-shaped oxide spacers and in-situ arsenic-doped emitter epitaxy by Low Pressure Chemical Vapor Deposition. A cleaning step between spacers formation and emitter epitaxy is mandatory to remove residual contamination. Hydrofluoric acid (HF) wet cleaning, in-situ remote plasma cleaning (SiconiTM) and thermal treatments have been tested. A minimum etching budget is sought for limiting spacer consumption while adequately cleaning the interface.Time Of Flight-Secondary Ion Mass Spectroscopy (TOF-SIMS) and High-Resolution Transmission Electron Microscopy (HR-TEM) are used to characterize the interface and measure levels of arsenic, oxygen, fluorine and carbon. Emitter resistance and base-emitter breakdown voltage measurements are used to show the impact on electrical figures of merit. Siconi targeting 10 Å of thermal oxide removal followed by a thermal treatment (800 °C, 60 s) in the deposition chamber results the best process among the tested ones.

Oxyanion Engineering Suppressed Iron Segregation in Nickel-Iron Catalysts Toward Stable Water Oxidation.

Nickel-iron catalysts represent an appealing platform for electrocatalytic oxygen evolution reaction (OER) in alkaline media because of their high adjustability in components and activity. However, their long-term stabilities under high current density still remain unsatisfactory due to undesirable Fe segregation. Herein, a nitrate ion (NO3 - ) tailored strategy is developed to mitigate Fe segregation, and thereby improve the OER stability of nickel-iron catalyst. X-ray absorption spectroscopy combined with theoretical calculations indicate that introducing Ni3 (NO3 )2 (OH)4 with stable NO3 - in the lattice is conducive to constructing the stable interface of FeOOH/Ni3 (NO3 )2 (OH)4 via the strong interaction between Fe and incorporated NO3 - . Time of flight secondary ion mass spectrometry and wavelet transformation analysis demonstrate that the NO3 - tailored nickel-iron catalyst greatly alleviates Fe segregation, exhibiting a considerably enhanced long-term stability with a six-fold improvement over FeOOH/Ni(OH)2 without NO3 - modification. This work represents a momentous step toward regulating Fe segregation for stabilizing the catalytic performances of nickel-iron catalysts.

300 MPa grade highly ductile biodegradable Zn-2Cu-(0.2-0.8)Li alloys with novel ternary phases

Although a few high-strength biodegradable Zn alloys with yield strengths (YSs) over 300 MPa in rolled state have been developed, their elongations (ELs) are generally less than 30%. This study developed rolled Zn-2Cu-xLi (x = 0.2 wt.%, 0.5 wt.%, 0.8 wt.%) alloys with YSs of 316–335 MPa and ELs of 44%–61%. Three-dimensional atom probe (3DAP) and time of flight secondary ion mass spectrometry (TOF-SIMS) were employed to characterize Li distribution. Three kinds of Zn-Cu-Li ternary phases are identified, which are blocky ε′-(Cu0.5, Li0.5)Zn4, blocky β′-(Li0.9, Cu0.1)Zn4, and small round γ particles with high Li content in the annealed state. Other identified phases are Zn, β-LiZn4, and ε-CuZn4 phases. With the increase of Li content in the alloys, ε′ phase with 6.50 at.% Cu transforms into β′ phase with 2.12 at.% Cu, i.e., the average level in the alloys. Within ε′ phase, there exist nano-scale Li clusters and ε phase, resulting in ε′/ε structure. Dense Zn laths precipitate from β′ phase, resulting in β′/Zn lamellar structure. The lamellar structure is the matrix of Zn-2Cu-0.8Li and leads to near-isotropic plasticity. Electrochemistry tests show that degradation rates fall in the range of 153–196 μm/year, which decrease with Li content. All the alloys exert positive effects on the growth of MC3T3-E1 cells with 10% extract. This research reveals how microstructure evolves in Zn-2Cu-xLi alloys, which lays the foundation for their future applications.

Area-selective atomic layer deposition of Al2O3 using inkjet-printed inhibition patterns and lift-off process

Area-selective atomic layer deposition (AS-ALD) has been studied as an alternative method for metal oxide ALD film patterning in the microelectronics industry. To perform AS-ALD, area-deactivation or -activation processes should be implemented in advance using selective surface modification through a photography-based lift-off process and printing techniques. This study introduces a novel approach for Al2O3 AS-ALD using inkjet-printed inhibition patterns. ALD-inhibition patterns with two-layer structures of fluorocarbon (FC) thin film and photoresist (PR) were patterned by inkjet printing. Low surface energy FC thin films were used to block the Al2O3 nucleation and growth during the ALD process, and PR was patterned to easily remove ALD-inhibition patterns using a lift-off process. To demonstrate AS-ALD, an Al2O3 thin film approximately 10 nm thick was deposited via an in-house built system with a multiple-slit gas source. The proposed AS-ALD method was evaluated for topological analysis using atomic force microscopy and surface composition analysis using a time of flight secondary ion mass spectrometry after Al2O3 deposition and a lift-off process. Finally, a 6 nm thick Al2O3 film was selectively patterned by the lift-off process using an inkjet-printed 1.28 μm thick FC-covered PR inhibition pattern.

Feldspar Pb isotope evidence of cryptic impact-driven hydrothermal alteration in the Paleoproterozoic

Hypervelocity impacts throughout Earth's history have profoundly affected the evolution of the continental crust. Accessory minerals like zircon are typically used to date impact events and rock-forming minerals like quartz are routinely used as shock barometers. However, feldspar group minerals – a major constituent of most crustal rocks – are generally underutilized in the documentation of impact-induced deformation and alteration. Alkali feldspar contains appreciable amounts of Pb and analysis of Pb isotopes in feldspar may offer the opportunity to identify impact-related isotopic modifications of shocked crustal target rocks and estimate their timing. Here, we apply a combination of laser ablation inductively coupled plasma (LA-ICP) and thermal ionization mass spectrometry (TIMS) Pb isotope analysis with imaging techniques, including electron backscatter diffraction (EBSD), cathodoluminescence (CL), and time of flight secondary ion mass spectrometry (ToF-SIMS), to shocked alkali feldspar from monzogranite in the oldest confirmed terrestrial impact structure (2229 ± 5 Ma) at Yarrabubba, Western Australia. Alkali feldspar preserves microstructures such as sub-planar and irregular fractures, sets of planar deformation bands that accommodate misorientations of up to ∼20°, sets of damage lamellae, and broad domains of lattice damage that can be linked to impact-related deformation. The Pb isotope compositions in alkali feldspar correlate with variations in electron diffraction band contrast – a proxy for crystallinity – and also the degree of misorientation and CL response. Less damaged alkali feldspar yields Pb model ages similar to the igneous zircon U–Pb crystallization age of the host monzogranite (∼2650 Ma), whereas younger Pb model ages correspond to zones of damage (high relative misorientation, low crystallinity, weak CL response). The observed Pb isotope behaviour implies radiogenic ingrowth of Pb, from decay of U and Th within damaged alkali feldspar, and therefore mixing with a grain-scale Pb reservoir that formed at the time of impact. The U and Th zonation in some shock-deformed alkali feldspar is broadly similar and follows the orientation of sub-planar fractures and damage lamellae. Detailed imaging reveals the zones of U and Th enrichment are associated with trains of monazite micro-inclusions, in conjunction with magnetite and/or hematite in places, which are inferred to have precipitated during impact-induced hydrothermal circulation. Hence, the Pb isotopic data record grain-scale hydrothermal alteration in superficially weakly altered monzogranite target rocks.

SURFACE “CLICK” REACTION BETWEEN ACETYLENE-DECORATED POLYMERIC PLATFORM AND AZIDE-DECORATED COMPOUNDS

A proof on concept study was conducted in the quest for dual-functional surfaces that provide both biopassivity and bioactivity. It presents the development of a biopassive platform that readily binds to bioactive molecules via copper-catalyzed acetylene-azide cycloaddition reaction. Acetylene-decorated poly(2-methyl-2-oxazoline) (PMOXA) brushes were grafted on an Nb2O5 surface. This biopassive brush platform was then exposed to various azide-decorated compounds of different sizes (molecular weight) and chemical structure, i.e. benzyl, mannose, and antimicrobial peptide (AMP), to react through the cycloaddition reaction. The different nature of the compounds “clicked” to the brushes requires different strategies of characterization. Time of flight-secondary ion mass spectroscopy (ToF-SIMS) results showed that benzyl-triazole-characteristic fragments were successfully bound to the surface. Fluorescence spectroscopy results indicated that mannose-azide molecules tagged with dye-carrying Concanavalin A (Con-A) could bind to the PMOXA-acetylene brush via specific and, to some extent, nonspecific interactions. Similarly, optical waveguide light-mode spectroscopy (OWLS) and quartz crystal microbalance-dissipation (QCM-D) analysis showed a successful reaction between AMP-azide and the PMOXA-acetylene brush platform. Together, these results validated the original approach of generating dual-functional surfaces using a “click” reaction between oxazoline brushes and a variety of ligands relevant to a range of applications.

Surface and subsurface alterations in freshly fractured and corroded soda‐lime float glass

AbstractWe have investigated the corrosion behavior of the soda‐lime silicate float glass on freshly created active surfaces. The process of ion diffusion and ion exchange during surface corrosion is explained at the initial stages. We have reported a unique subsurface activity in the glass, which achieves equilibrium. This varies at the subsurface depth level of ≈ 10–30 nm and is visible as a broad peak in the elemental depth profile. The prolonged corrosion and heating process assists surface relaxation of the glass samples. We have observed the formation of active nucleation sites for the corrosion process on the surface. In this study, we report that the sodium ions and its corrosion compounds are decoupled from other metal ions present in the glass during diffusion relaxation and ion exchange. A combination of time of flight secondary ion mass spectrometry (TOF‐SIMS) and energy dispersive X‐ray (EDX) microanalysis help to explain the evolution and quantify the changes at the initial stages in the freshly formed glass surface.

The role of ion solvation in lithium mediated nitrogen reduction.

Since its verification in 2019, there have been numerous high-profile papers reporting improved efficiency of lithium-mediated electrochemical nitrogen reduction to make ammonia. However, the literature lacks any coherent investigation systematically linking bulk electrolyte properties to electrochemical performance and Solid Electrolyte Interphase (SEI) properties. In this study, we discover that the salt concentration has a remarkable effect on electrolyte stability: at concentrations of 0.6 M LiClO4 and above the electrode potential is stable for at least 12 hours at an applied current density of -2 mA cm-2 at ambient temperature and pressure. Conversely, at the lower concentrations explored in prior studies, the potential required to maintain a given N2 reduction current increased by 8 V within a period of 1 hour under the same conditions. The behaviour is linked more coordination of the salt anion and cation with increasing salt concentration in the electrolyte observed via Raman spectroscopy. Time of flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy reveal a more inorganic, and therefore more stable, SEI layer is formed with increasing salt concentration. A drop in faradaic efficiency for nitrogen reduction is seen at concentrations higher than 0.6 M LiClO4, which is attributed to a combination of a decrease in nitrogen solubility and diffusivity as well as increased SEI conductivity as measured by electrochemical impedance spectroscopy.

Controllable hierarchical self-assembly: systematic study forming metallosupramolecular frameworks on the basis of helical beta-oligoamides.

Self-assembly is a key guiding principle for the design of complex nanostructures. Substituted beta oligoamides offer versatile building blocks that can have inherent folding characteristics, offering geometrically defined functionalities that can specifically bind and assemble with predefined morphological characteristics. In this work hierarchical self-assembly is implemented based on metal coordinating helical beta-oligoamides crosslinked with transition metals selected for their favourable coordination geometries, Fe2+, Cu2+, Ni2+, Co2+, Zn2+, and two metalates, MoO42-, and WO42-. The oligoamide Ac-β3Aβ3Vβ3S-αHαHαH-β3Aβ3Vβ3A (3H) was designed to allow crosslinking via three distinct faces of the helical unit, with a possibility of forming three dimensional framework structures. Atomic force microscopy (AFM) confirmed the formation of specific morphologies that differ characteristically with each metal. X-Ray photoelectron spectroscopy (XPS) results reveal that the metal centres can be reduced in the final structures, confirming strong chemical interaction. Time of flight secondary ion mass spectrometry (ToF-SIMS) confirmed the spatial distribution of metals within the self-assembled networks, also revealing molecular fragments that confirm coordination to histidine and carboxyl moieties. The metalates MoO42- and WO42- were also able to induce the formation of specific superstructure morphologies. It was observed that assembly with either of nickel, copper, and molybdate form thin films, while cobalt, zinc, and tungstate produced specific three dimensional networks of oligoamides. Iron was found to form both a thin film and a complex hierarchical assembly with the 3H simultaneously. The design of the 3H substituted beta oligoamide to readily form metallosupramolecular frameworks was demonstrated with a range of metals and metalates with a degree of control over layer thicknesses as a function of the metal/metalate. The results validate and broaden the metallosupramolecular framework concept and establish a platform technology for the design of functional thin layer materials.

Topochemical Design of Cellulose-Based Carriers for Immobilization of Endoxylanase

Xylooligosaccharides (XOSs) gained much attention for their use in food and animal feed, attributed to their prebiotic function. These short-chained carbohydrates can be enzymatically produced from xylan, one of the most prevalent forms of hemicellulose. In this work, endo-1,4-β-xylanase from Thermotoga maritima was immobilized on cellulose-based beads with the goal of producing xylooligosaccharides with degrees of polymerization (DPs) in the range of 4-6 monomeric units. More specifically, the impact of different spacer arms, tethers connecting the enzyme with the particle, on the expressed enzymatic activity and oligosaccharide yield was investigated. After surface functionalization of the cellulose beads, the presence of amines was confirmed with time of flight secondary ion mass spectrometry (TOF-SIMS), and the influence of different spacer arms on xylanase activity was established. Furthermore, XOSs (DPs 2-6) with up to 58.27 mg/g xylan were obtained, which were greatly enriched in longer oligosaccharides. Approximately 80% of these XOSs displayed DPs between 4 and 6. These findings highlight the importance of topochemical engineering of carriers to influence enzyme activity, and the work puts forward an enzymatic system focusing on the production of longer xylooligosaccharides.