Mediator-free interaction of glucose oxidase, as model enzyme for immobilization, with Al-doped and undoped ZnO thin films laser-deposited on polycarbonate supports

Al doped and undoped ZnO thin films were deposited by pulsed-laser deposition on polycarbonate sheets. The films were characterized by optical transmission, Hall effect measurement, XRD and SEM. Optical transmission and surface reflectometry studies showed good transparency with thicknesses ∼100 nm and surface roughness of 10 nm. Hall effect measurements showed that the sheet carrier concentration was −1.44 × 1015 cm−2 for AZO and −6 × 1014 cm−2 for ZnO. The films were then modified by drop-casting glucose oxidase (GOx) without the use of any mediators. Higher protein concentration was observed on ZnO as compared to AZO with higher specific activity for ZnO (0.042 U mg−1) compared to AZO (0.032 U mg−1), and was in agreement with cyclic voltemmetry (CV). X-ray photoelectron spectroscopy (XPS) suggested that the protein was bound by dipole interactions between AZO lattice oxygen and the amino group of the enzyme. Chronoamperometry showed sensitivity of 5.5 μA mM−1 cm−2 towards glucose for GOx/AZO and 2.2 μA mM−1 cm−2 for GOx/ZnO. The limit of detection (LoD) was 167 μM of glucose for GOx/AZO, as compared to 360 μM for GOx/ZnO. The linearity was 0.28–28 mM for GOx/AZO whereas it was 0.6–28 mM for GOx/ZnO with a response time of 10s. Possibly due to higher enzyme loading, the decrease of impedance in presence of glucose was larger for GOx/ZnO as compared to GOx/AZO in electrochemical impedance spectroscopy (EIS). Analyses with clinical blood serum samples showed that the systems had good reproducibility and accuracy. The characteristics of novel ZnO and AZO thin films with GOx as a model enzyme, should prove useful for the future fabrication of inexpensive, highly sensitive, disposable electrochemical biosensors for high throughput diagnostics

Highly transparent and reproducible nanocrystalline ZnO and AZO thin films grown by room temperature pulsed-laser deposition on flexible zeonor plastic substrates

Zeonor plastics are highly versatile due to exceptional optical and mechanical properties which make them the choice material in many novel applications. For potential use in flexible transparent optoelectronic applications, we have investigated Zeonor plastics as flexible substrates for the deposition of highly transparent ZnO and AZO thin films. Films were prepared by pulsed laser deposition at room temperature in oxygen ambient pressures of 75, 150 and 300 mTorr. The growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of as grown films with thicknesses∼65–420 nm were recorded for the three oxygen pressures. The growth rates were found to be highly linear both as a function of film thickness and oxygen pressure, indicating high reproducibility. All the films were optically smooth, hydrophobic and nanostructured with lateral grain shapes of∼150 nm wide. This was found compatible with the deposition of condensed nanoclusters, formed in the ablation plume, on a cold and amorphous substrate. Films were nanocrystalline (wurtzite structure), c-axis oriented, with average crystallite size∼22 nm for ZnO and∼16 nm for AZO. In-plane compressive stress values of 2–3 GPa for ZnO films and 0.5 GPa forAZO films were found. Films also displayed high transmission greater than 95% in some cases, in the 400–800 nmwavelength range. The low temperature photoluminescence spectra of all the ZnO and AZO films showed intense near band edge emission. A considerable spread from semi-insulating to n-type conductive was observed for the films, with resistivity∼103 Ω cm and Hall mobility in 4–14 cm2 V−1 s−1 range, showing marked dependences on film thickness and oxygen pressure. Applications in the fields of microfluidic devices and flexible electronics for these ZnO and AZO films are suggested

Pulsed laser deposition and characterisation of ZnO and aluminium-doped ZnO nanostructures on silicon and flexible plastic substrates

We have developed recipes for the catalyst-free growth of upstanding/vertically aligned ZnO nanorods featuring core/shell or interconnected core/shell architectures on ZnO-seeded Si (100) substrates using the pulsed laser deposition (PLD) technique. The structural, morphological and luminescent properties of these ZnO nanorod samples were established. A ZnO emission band at 3.331 eV was observed in the core/shell and interconnected core/shell nanorod architectures and its origin linked to the defects observed at the crystalline/amorphous interface of the core/shell structure. This particular defect PL emission appears to be a new observation for ZnO. We have grown vertically aligned ZnO nanorods on PLD prepared ZnO-seeded Si substrates by catalyst-free vapour phase transport (VPT). The nanorods featured excellent optical properties and a coverage density higher than previously published data. The structural, morphological and luminescent properties of the seed layers and nanorods were inter-compared. Importantly, we also compared the near band edge emission of such VPT-and PLD-deposits, with a focus on the identification of the origin of the emission feature at 3.331 eV. We have researched the room temperature PLD growth of highly transparent and conductive ZnO and Al-doped ZnO (AZO) nanocrystalline thin films on flexible Zeonor plastic substrates. The trends for the growth rate, surface morphology, hydrophobicity and the structural, optical and electrical properties of 65 nm - 420 nm thick ZnO/AZO films grown on Zeonor substrates were analysed as a function of oxygen growth pressure (1-300 mTorr). The as-grown films showed highly reproducible deposition behaviour, and featured high transmittance, low-electrical resistance, optical smoothness, low residual stress, and hydrophobicity. The results presented in this thesis are discussed in the context of prospectiv

Crystalline ZnO/amorphous ZnO core/shell nanorods: self-organized growth, structure, and novel luminescence

We have used pulsed-laser deposition, following a specific sequence of heating and cooling phases, to grow ZnO nanorods on ZnO buffer/Si (100) substrates, in a 600 mT oxygen ambient, without catalyst. In these conditions, the nanorods preferentially self-organize in the form of vertically aligned, core/shell structures. X-ray diffraction analyses, obtained from 2θ-ω and pole figure scans, shows a crystalline (wurtzite) ZnO deposit with uniform c-axis orientation normal to the substrate. Field emission SEM, TEM, HR-TEM and selective area electron diffraction (SAED) studies revealed that the nanorods have a crystalline core and an amorphous shell. The low-temperature (13 K) photoluminescence featured a strong I6 (3.36 eV) line emission, structured green band emission and a hitherto unreported broad emission at 3.331 eV. Further studies on the 3.331 eV band showed the involvement of deeply-bound excitonic constituents in a single electron-hole recombination. The body of structural data suggests that the 3.331 eV emission can be linked to the range of defects associated with the unique crystalline ZnO/amorphous ZnO core/shell structure of the nanorods. The relevance of the work is discussed in the context of the current production methods of core/shell nanorods and their domains of application

Al-based MOF derived self-assembled carbon nanosheets as innovative anodes for Li-and Na-ion batteries

Functional modification and structural design of carbon electrode materials are considered as a cost-effective method to improve their electrochemical performance. In this study, a solvothermal method is applied to realize self-assembly of the metal-organic framework. After simple carbonization and acid treatment, carbon nanosheets with 2D adjustable defective sub-units are successfully prepared for the first time. It is found that carbonization temperature has a significant effect on the carbon skeleton structure. The optimal nanostructures with large specific surface area and appropriate pore size distribution make self-assembled carbon nanosheets having excellent Li/Na- ion storage properties. In addition, the adjustable carbon skeleton structure can effectively avoid irreversible damage when charge-discharge cycles. For Li-ion batteries, a specific capacity of 825 mAh g−1 is achieved after 100 cycles at 0.1 C, while for Na-ion batteries a specific capacity of 193 mAh g−1 is observed after 100 cycles at 0.5 C. Moreover, for Na-ion batteries, even at a high rate of 5 C the material delivers a specific capacity of 109.5 mAh g−1 after 3500 cycles

Al-based metal organic framework derived self-assembled carbon nanosheets as innovative anodes for Li- and Na-ion batteries

Functional modification and structural design of carbon electrode materials are considered as a cost-effective method to improve their electrochemical performance. In this study, a solvothermal method is applied to realize self-assembly of the metal-organic framework. After simple carbonization and acid treatment, carbon nanosheets with 2D adjustable defective sub-units are successfully prepared for the first time. It is found that carbonization temperature has a significant effect on the carbon skeleton structure. The optimal nanostructures with large specific surface area and appropriate pore size distribution make self-assembled carbon nanosheets having excellent Li/Na-ion storage properties. In addition, the adjustable carbon skeleton structure can effectively avoid irreversible damage when charge–discharge cycles. For Li-ion batteries, a specific capacity of 825 mAh g−1 is achieved after 100 cycles at 100 mA g–1, while for Na-ion batteries a specific capacity of 193 mAh g−1 is observed after 100 cycles at 100 mA g–1. Moreover, for Na-ion batteries, even at a high rate of 1000 mA g–1 the material delivers a specific capacity of 109.5 mAh g−1 after 3500 cycles

Cobalt doped JUC-160 derived functional carbon superstructures with synergetic catalyst effect for Li-SeS2 batteries

The carbon nanostructures with polar metal/heteroatom co-doping are considered as an effective strategy to improve their electrochemical performances. In this context, the crystal-shape engineering is carried out. Based on a new ‘‘one for six’’ strategy, the JUC-160 having a two-dimensional (2D) zeolitic imidazolate framework is transformed into six different carbon materials. These materials do not need a carbon activation process or template removal process. Instead, after a simple carbonization, a series of metal/heteroatom co-doped carbon materials with novel structures are formed. To be highlighted, this work is the first report of using self-assembled carbon nanostructures/SeS2 composites as cathode materials in the field of Li-SeS2. Moreover, those carbon nanostructures can be effectively tailored by adjusting the method of cobalt doping and the amount of cobalt dopant. Because of the benefits from the novel structures and cobalt/nitrogen co-doping, the dissolution of poly-sulfides/selenides is reduced and a high content of SeS2 (73 wt%) is achieved. The optimized cathode displays an extraordinary cycle performance with a reversible capacity of 820.87 mA h g−1 after 100 cycles, and with reversible charge-discharge efficiency is close to 100

2D ultrathin carbon nanosheets derived from interconnected Al-MOF as excellent hosts to anchor selenium for Li-Se battery

Alleviating volume expansion of the electrodes and improving utilization of the active materials have become key problems restricting a successful commercialization of lithium-selenium batteries. In this paper, a 2D ultrathin carbon nanosheets derived from interconnected MOF is designed for the first time. Such carbon nanosheets are composed by parallel stacked 2D sub-units, and this unique hierarchical porous architecture is beneficial for buffering the volume expansion and for improving the utilization rate of the active materials. Therefore, the cathode displays an excellent cycling stability with a reversible capacity of 347.3 mAh g−1 at 2 C after 240 cycles

Automatic Extraction of Component Models from Fault Knowledge: The Diagnostic Remodeler (DR) Algorithm

This paper argues that automated knowledge acquisition for diagnosis has had limited success in both failure-driven diagnosis and model-based diagnosis. The paper describes fault-based and model-based reasoning for diagnosis and surveys some of the approaches to knowledge acquisition in both areas. The Diagnostic Remodeler (DR) algorithm has been implemented for the automated generation of behavioural component models with function from fault-based knowledge. The use of function in this paper is based on the perspective that function complements behaviour where the derived function is more abstract than the behaviour derived by DR [Kumar 94]. DR uses as its first application example the fault-based knowledge base of the Jet Engine Troubleshooting Assistant (JETA). DR is used to extract the model of the Main Fuel System using the knowledge base and two types of background knowledge as input: device dependent and device independent knowledge. This paper is the first presentation of preliminary results of the implemented DR algorithm.Cet article avance que l'acquisition automatis\ue9e de connaissances \ue0 des fins de diagnostic a eu des succ\ue8s limit\ue9s aussi bien dans le diagnostic guid\ue9 par \ue9checs que dans le diagnostic bas\ue9 sur un mod\ue8le. Il d\ue9crit le raisonnement bas\ue9 sur des fautes et le raisonnement bas\ue9 sur un mod\ue8le pour le diagnostic et examine certaines des m\ue9thodes d'acquisition de connaissances dans les deux domaines. L'algorithme Diagnostic Remodeler (DR) a \ue9t\ue9 impl\ue9ment\ue9 pour assurer la g\ue9n\ue9ration automatis\ue9e de mod\ue8les comportementaux constitutifs, avec repr\ue9sentation de la fonction, \ue0 partir de connaissance bas\ue9es sur des fautes. Dans cet article, l'utilisation de la fonction est bas\ue9e sur le point de vue selon lequel la fonction compl\ue8te le comportement, quand la fonction d\ue9riv\ue9e est plus abstraite que le comportement d\ue9riv\ue9 par DR [Kumar 94]. Comme premier exemple d'application, DR utilise la base de connaissances bas\ue9es sur des fautes du syst\ue8me Jet Engine Troubleshooting Assistant (JETA). DR extrait le mod\ue8le du circuit de carburant en utilisant comme intrants la base de connaissances et deux types de connaissances contextuelles, soit des connaissances d\ue9pendantes et ind\ue9pendantes du dispositif. Cet article est la premi\ue8re pr\ue9sentation des r\ue9sultats pr\ue9liminaires de l'algorithme DR.NRC publication: Ye