Ultrathin and nanostructured ZnO-based films for fluorescence biosensing applications

The fluorescence-based sensing capability of ultrathin ZnO-SiO(2) nanoplatforms, deposited by an integrated approach of colloidal lithography and metal organic chemical vapor deposition, has been investigated upon adsorption of fluorescein-labeled albumin, used as model analyte biomolecule. The protein immobilization process after spontaneous adsorption/desorption significantly enhances the green emission of the different ZnO-based films, as evidenced by scanning confocal microscopy, corresponding to a comparable protein coverage detected by X-ray photoelectron spectroscopy. Moreover, experiments of fluorescence recovery after photobleaching evidence that the protein lateral diffusion at the biointerface is affected by the chemical and/or topographical patterning of hybrid ZnO-SiO(2) surfaces. The used approach is very promising for biomolecular detection applications of these ZnO-SiO(2) nanoplatforms, by simple sizing of the 2D vs. 3D patterning design, which in turn is accomplished by the fine tuning of the integrated colloidal lithography-chemical vapor deposition processes. (C) 2011 Elsevier Inc. All rights reserved

Recent advances in upscalable wet methods and ink formulations for printed electronics

This review deals with the use of solution processing approaches for organic electronics with a focus on material ink formulations as well as on their applicability. The solution processing techniques include methods like gravure printing, screen printing and ink-jet printing. Basic principles of each approach are understood and fundamental correlations between material (metals, semiconductors, and dielectrics) ink properties and final device performances can be drawn. Nevertheless, solution processing methods have the potential to evolve as the most promising tools in organic device fabrication techniques and have already been applied successfully in the fields of organic thin film transistors, solar cells and biosensing devices

Integration of Metal Organic Chemical Vapour Deposition and Wet Chemical Techniques to Obtain Highly Ordered Porous ZnO Nanoplatforms

Large-area, highly ordered ZnO micropores-arrays consisting of ZnO nanotubes delimited by ZnO nanorods have been successfully fabricated and tested for protein sensing applications. ZnO seed layers have been deposited by Metal Organic Chemical Vapour Deposition and readily patterned by Colloidal Lithography to attain ZnO nanorods growth at selective sites by Chemical Bath Deposition. The used synthetic approach has been proven effective for the easy assembly of ZnO nanoplatforms into high-density arrays. Both patterned and unpatterned ZnO nanorods have been morphologically and compositionally characterised and, thus, tested for model studies of protein mobility at the interface. The patterned layers, having a higher contribution of surface polar moieties than the corresponding unpatterned surfaces, exhibit a reduced lateral diffusion of the adsorbed protein. This evidence is related to the intrinsic porous nature of the ZnO hemispherical arrays characterised by a nanotube-nanorod hybrid networks. The present study gives a great impetus to the fabrication of tunable ZnO nanoplatforms having multiple morphologies and exceptionally high surface areas suitable for application in sensing devices

Effects of Metal-Organic Chemical Vapour Deposition grown seed layer on the fabrication of well aligned ZnO nanorods by Chemical Bath Deposition

Well aligned, long and uniform ZnO nanorods have been reproducibly fabricated adopting a two-steps Metal-Organic Chemical Vapour Deposition (MOCVD) and Chemical Bath Deposition (CBD) fabrication approaches. Thin (<100 nm) ZnO buffer layers have been seeded on silicon substrates by MOCVD and ZnO layers have been subsequently grown, in form of well textured nanorods, using CBD. It has been found that the structure and thickness of the seed layer strongly influence the final morphology and the crystal texturing of ZnO nanorods as well as the CBD growth rate. There is, in addition, a strong correlation between morphologies of CBD grown ZnO nanorods and those of the seed layer underneath. Thus, nanorods deposited over low temperature MOCVD buffer layers are less homogeneous in lateral dimensions and poorly vertically oriented. On the contrary, higher temperature nano-dimensional ZnO seeds favour the CBD growth of almost mono-dimensional homologue nanorods, with an adequate control of the lateral transport of matter. The nanorod aspect ratio values decrease upon increasing the deposition temperatures of the seed layers. Moreover, the nanorods length can be tailored either by adjusting the CBD growth time or by changing concentration of the N,N,N',N'-tetramethylethylenediamine ligand used in the CBD process. In particular, at high concentrations, the CBD process is faster with a greater global aspect ratio in agreement with a preferential one-dimensional growth of the ZnO nanostructures. Finally, these ZnO nanorod arrays possess good optical quality in accordance to the photoluminescence properties

ZnO nanorod arrays fabrication via chemical bath deposition: Ligand concentration effect study

A new ligand, N, N, N', N'-tetramethylethylenediamine, has been used to grow ZnO nanorods on silicon substrates via a two steps approach. A preliminary seeding on silicon substrates has been combined with chemical bath deposition using a Zinc acetate - N, N, N', N'-tetramethylethylenediamine aqueous solution. The used diamino ligand has been selected as Zn(2+) complexing agent and the related hydrolysis generates the reacting ions (Zn(2-) and OH(-)) responsible for the ZnO growth. The seed layer has been annealed at low temperature (<200 degrees C) and the ZnO nanorods have been grown on this ZnO amorphous layer. There is experimental evidence that the ligand concentration (ranging from 5 to 50 mM) strongly affects the alignment of ZnO nanorods on the substrate, their lateral dimension and the related surface density. Length and diameter of ZnO nanorods increase upon increasing the ligand concentration, while the nanorod density decreases. Even more important, it has been demonstrated, as proof of concept, that chemical bath deposition can be usefully combined with colloidal lithography for selective ZnO nanorod deposition Thus, by patterning the ZnO seeded substrate with polystyrene microsphere colloidal lithography, regular Si hole arrays, spatially defined by hexagonal ZnO nanorods, have been successfully obtained. (C) 2010 Elsevier Ltd. All rights reserved

The Development of the School of Spatial Analysis of W.Isard on the Basis of Economic and Supply Chain Management Models of the Petrochemical and Chemical Production Cluster

Abstract- In the first post-war decade, studies of the problems of the regional economy were developed in many countries based on the supply chain management. Prerequisites were created for the unification of regional scientists and a new attempt to synthesize theories of spatial and regional economics. At this stage, the avant-garde role was played by an American scientist, W. Isard.Hi is first major monograph, “The Placement and Economics of Space,†was published in which he posed the problem of eliminating the deep discrepancies that exist for more than 100 years between classical theories; accommodation and leading schools of general economic theory.W. Isard rightly criticizes all classical and neoclassical economic theories for the fact that they limited themselves to studying "a country of miracles devoid of any spatial characteristics." This was partly due to the classical placement theories, which were expounded in outdated language and with excessive simplifications of "partial equilibrium", constant coefficients, cost minimization, constant demand curves, etc. Overcoming the stereotypes of these theories, W. Isard will clothe the theory of locating production in a more general economic form. He deduced the following law: profit maximizing firms will be located; so that the marginal rates of replacement of transportation costs of goods from two different points (regions) are equal to the reciprocal of their transportation tariffs. From this condition of the first order of maximizing profit, one can derive all particular allocation theories (Tyunen, Launhardt, Weber, etc.). Further, W. Aizard links, where it is possible, the theory of location with the known theories of production, pricing, trade, etc

Digital Modeling of Economic Processes and Supply Chain Management in the Formation of Cooperative Relations in the Petrochemical Cluster of the Region

Abstract- A study of the state of the theory of fuzzy sets shows that until recently in Russia there were almost no studies in the chemical sector of the economy and finance using fuzzy analysis and forecasting, although by that time all necessary prerequisites for modeling financial systems had been created. The current situation in Russia is characterized by a high degree of science lagging behind the requests of state and commercial supply chain management.Fuzzy sets have not been used to date for financial analysis and planning of chemical corporations, evaluating the investment attractiveness of securities, optimizing the stock portfolio, forecasting stock indices and macroeconomic indices. You can also talk about the lack of software based on fuzzy models, although abroad, such software products and information technologies that solve economic problems using fuzzy-plural and related descriptions already exist.In the 80's, software solutions and information technologies began to emerge, solving economic problems using fuzzy-plural and related descriptions. Thus, under the leadership of C. Zopounidis at the Technical University on the island of Crete, an expert system was developed for detailed financial analysis of corporations. A little earlier in Germany, a group led by H. Zimmerman developed a strategic planning system, in which the positioning of the corporation's business is based on fuzzy descriptions of the competitiveness and attractiveness of the business.As an example of such software, you can use expensive complex systems, which include fuzzy logic, which bankers and financiers use to solve the most complicated problems of forecasting financial indicators. The beginning of this process was laid by the Japanese financial corporation. Having set out to automate the game on the securities market, this company attracted about 30 specialists in artificial intelligence

Spectroscopic and Theoretical Study of the Grafting Modes of Phosphonic Acids on ZnO Nanorods

Metal oxides are versatile substrates for the design of a wide range of SAM-based organic-inorganic materials among which ZnO nanostructures modified with phosphonic SAM are promising semiconducting systems for applications in technological fields such as biosensing, photonics, and field-effect transistors (FET). Despite previous studies reported on various successful grafting approaches, issues regarding preferred anchoring modes of phosphonic acids and the role of a second reactive group (i.e., a carboxylic group) are still a matter of controversial interpretations. This paper reports on an experimental and theoretical study on the functionalization of ZnO nanorods with monofunctional alkylphosphonic and bifunctional carboxyalkylphosphonic acids. X-ray photoelectron and infrared spectroscopies have been combined with DFT modeling to explain and understand the interactions that drive the surface anchoring of phosphonic acids on ZnO surface. It was found that both monofunctional and bifunctional acids anchor on ZnO through a multidentate bonding which involves both P=O and P-O moieties of the phosphonic group. Moreover, anchored bifunctional acids bend to the surface, promoting a further interaction between surface hydroxyl groups and carboxylic terminations. This secondary interaction can be limited by increasing the surface density of the anchored molecules

Colloidal lithography and Metal-Organic Chemical Vapor Deposition process integration to fabricate ZnO nanohole arrays

A complete set up of optimal process conditions for an effective colloidal lithography/catalyst assisted MOCVD process integration is presented. It mainly focuses on the determination of the deposition temperature threshold for ZnO Metal-Organic Chemical Vapour Deposition (MOCVD) as well as the concentration of metal-organic silver (Ag) catalyst. Indeed, the optimization of such process parameters allows to tailor the ZnO film morphology in order to make the colloidal lithography/catalyst assisted MOCVD approach a valuable bottom up method to fabricate bi-dimensional ordered ZnO nanohole arrays. (C) 2010 Elsevier B.V. All rights reserved