Synthesis, characterization and photocatalytic activity of Au-ZnO heterostructures

Heterostructures of semiconductor metal oxides and metals have been studied extensively due to the synergistic photocatalytic activity they display. Gold-Zinc oxide (Au-ZnO) heterostructured photocatalysts are one of the most widely studied photocatalysts due to the high photocatalytic activity of ZnO and the ability of Au to transfer photoexcited electrons away from ZnO, which leads to enhanced carrier separation and improved catalytic activity. Au heterostructuring is also known to alter the electronic structure of ZnO leading to better photochemical band alignment and a decreased work function which both contribute to enhanced catalytic activity. The use of Au to form heterostructures with ZnO also opens the possibility of using its plasmonic activity for engineering the photophysics of this system through plasmonic heating or optical field enhancement. As such, it is interesting to synthesize a variety Au-ZnO heterostructures and correlate the catalytic activity of these materials with structural details such as nanoparticle morphology, lattice dynamics at the interface, and the general crystallinity of the two materials forming the heterostructure.;In this work, I have synthesized, characterized, and investigated two types of Au-ZnO heterostructured catalysts and evaluated their activity for carbon dioxide (CO2) conversion and waste-water remediation applications. The Au-ZnO catalysts were characterized using Transmission Electron Microscopy, Scanning Electron Microscopy, X-Ray Diffractometry, Raman spectroscopy, UV-Vis absorption spectroscopy and Fourier Transform Infrared spectroscopy. Initial efforts focused on simple heterostructures made by soaking nanocrystalline ZnO in a Au salt with a subsequent heat treatment to reduce the Au to its metallic state. This resulted in ∼20 nm Au particles dispersed on ZnO at ∼5 wt % loading. Plasmonic excitation of the Au nanoparticles also heats the ZnO substrate it is grown on up to ∼600 °C and drives the catalytic conversion of CO2 and hydrogen (H2) to methane (CH4), carbon monoxide (CO), and water (H2O) on the ZnO portion of the heterostructure. In addition, I have also investigated methods to increase the Au-ZnO ratio and to improve the degree of contact between these two materials. For these efforts, ZnO nanopyramids were grown on Au seeds using a wet-chemical method. Electron microscopy was used to characterize an unusual and large lattice expansion for ZnO at the Au interface in these samples. Optical measurements of these samples point to subtle electronic structure changes caused by the Au that improve band alignment for the production of radicals from photoexcited carriers in the ZnO. The improved production of radicals in turn leads to an enhanced photodegradation of organic contaminants in water. In addition to experimental work, computational calculations were performed in order to calculate vibrational modes, phonon spectral density and plasmon relaxation time constants. Two Au clusters (Au20 and Au55) which contain 20 and 55 of Au atoms respectively were used for the calculations

New Methods for Palladium-catalyzed Decarboxylative Benzylation, Arylation and Dearomatization Reactions

Development of novel synthetic methods for the efficient generation of new carbon-carbon bonds is a valuable endeavor in organic synthesis. In this regard, palladium-catalyzed decarboxylative cross-coupling has significant potential as a waste-free reaction manifold with increased functional group tolerance due to the avoidance of preformed organometallics and basic reagents. Since the initial reports by Saegusa and Tsuji on decarboxylative allylation (DcA) of β-ketoesters in 1980, this concept remained relatively unexplored until the independent reports from Tunge and Stoltz in 2004. Since then, couplings of a broad array of nucleophiles, as well as asymmetric variants of the DcA reactions, have been heavily developed. However, due to the inherently low reactivity of benzyl electrophiles, catalytic decarboxylative benzylation reactions are comparatively less developed. Presented herein are the developments of new methods for the catalytic decarboxylative benzylic cross-coupling reactions with weakly-stabilized nucleophiles. In particular, the benzyl alkyne cross-coupling, which was initially limited to extended aryl systems, was further developed to allow couplings of primary benzyl electrophiles without extended π-conjugation. Our efforts were then directed toward developing a highly stereospecific decarboxylative coupling of acetylides and ketone enolates with secondary benzyl electrophiles that possess a 1,1-diarylmethane structure. The coupling of secondary benzyl electrophiles with acetylides proceeded with high stereospecificity to provide enantioenriched 1,1-diarylethynyl methanes, and we are unaware of any other method for the direct synthesis of such motifs. However, racemization was observed in the decarboxylative coupling of enantioenriched benzylic β-ketoesters. In the search for a new method to couple secondary benzyl electrophiles with ketone enolates, we serendipitously discovered the unprecedented catalytic decarboxylative dearomatization and arylation reactions of ketone enolates. Two sets of protocols involving simple variation of ligands were then developed for the selective decarboxylative dearomatization or arylation of enolates. These methods provided alicyclic and mono-α-arylated ketones in a highly regioselective manner and the expected benzylation of ketone enolates was never observed. Additionally, initial results have also shown that the palladium-catalyzed decarboxylative dearomatization of benzyl carbonates is highly stereospecific

with special references to furniture factory state timber corporation Ampara

Degree of Bachelor of Science in Information Technology for Management StudiesThe State timber corporation is one of the oldest and a very popular corporation for its value added furniture among its customers in Sri Lanka .The purpose of this study was to examine the relationship between job performance and factors affecting on the employee in State Timber Corporation. Primary and secondary data were use for this study and mainly the questioners were used as a primary data tool. This study was conducted through a field survey by a structured questionnaire comprising various elements of concepts such as motivation, reward, and internal factor to measure job performance. Data was collected through survey from a selected sample of 70 employees from the state timber corporation through simple random sampling method. The study generated 100% response rate. Response from the survey was astatically analyzed using spearman correlation coefficient using the version of SPPS software. Hypotheses were tested. Accordingly motivation, human capital and rewards were highly influencing on job performance, whereas internal factor was also moderately influencing on the job performance of the employees. Key words - Motivation - Human capital - Reward - Internal factor

TOLL HIGHWAYS TO SRI LANKA FOR ECONOMIC DEVELOPMENT

Infrastructure facilities of a country play an important role in economic development. The highway infrastructure is more superior among other facilities and conditions of those facilities affects the economic returns of a nation indirectly. Traffic congestion is a massive problem today and improving road network properly is required to overcome such problems, most of the developing countries like Sri Lanka face lot of difficulties to uplift the road infrastructure because of unstable economic conditions and lack of investment funds. So, a few class A highways are available in the road network in Sri Lanka and no expressways have been completed so far. The concept of toll highway is initiated during last decade in the world and it is a better solution for solving funding problems in expressway constructions of developing countries.  It allows private entities to participate in infrastructure investments and there are several strategies for financing infrastructure projects on this basis. However, the first nations’ toll highway, the Colombo - Katunayake Expressway (CKE) has been held at the construction stage and there are several arguments in this country about the matching of the toll concept to our economy. Therefore, this paper is focused to discuss the concept of toll highway together with various issues relating to financing such projects in Sri Lanka. Keywords: Colombo-Katunayake expressway, Economic development, Private sector participation, Toll highways For full Paper: [email protected]

A Congestion Control Method to Support Coordinated Bandwidth Allocation

In networked data fusion or control applications, a data sink node may require participating source nodes to transmit data according to certain bit-rate allocations, or bit-rate ratios that are determined by the fusion or control task. In a shared network, the coordinated flows of a fusion or control application will need to coexist with the flows of other applications. In this paper, we examine the problem of congestion control of coordinated flows of a fusion or control application along with flows of ordinary data transfer applications. Through a simple modification of a utility function to accommodate the rate coordination, we employ network utility maximization methods to derive window flow control algorithms for both ordinary and coordinated flows. While the congestion control method for the ordinary flows remains unchanged, the coordinated flows require scalar feedback from a sink node to maintain rate coordination. We examine the equilibria, and the impact of the rate coordination algorithm on the ordinary flows, and provide simulation results that demonstrate the efficacy of the new congestion control method

Towards a Framework For Resource Allocation in Networks

Network resources (such as bandwidth on a link) are not unlimited, and must be shared by all networked applications in some manner of fairness. This calls for the development and implementation of effective strategies that enable optimal utilization of these scarce network resources among the various applications that share the network. Although several rate controllers have been proposed in the literature to address the issue of optimal rate allocation, they do not appear to capture other factors that are of critical concern. For example, consider a battlefield data fusion application where a fusion center desires to allocate more bandwidth to incoming flows that are perceived to be more accurate and important. For these applications, network users should consider transmission rates of other users in the process of rate allocation. Hence, a rate controller should consider application specific rate coordination directives given by the underlying application. The work reported herein addresses this issue of how a rate controller may establish and maintain the desired application specific rate coordination directives. We identify three major challenges in meeting this objective. First, the application specific performance measures must be formulated as rate coordination directives. Second, it is necessary to incorporate these rate coordination directives into a rate controller. Of course, the resulting rate controller must co-exist with ordinary rate controllers, such as TCP Reno, in a shared network. Finally, a mechanism for identifying those flows that require the rate allocation directives must be put in place. The first challenge is addressed by means of a utility function which allows the performance of the underlying application to be maximized. The second challenge is addressed by utilizing the Network Utility Maximization (NUM) framework. The standard utility function (i.e. utility function of the standard rate controller) is augmented by inserting the application specific utility function as an additive term. Then the rate allocation problem is formulated as a constrained optimization problem, where the objective is to maximize the aggregate utility of the network. The gradient projection algorithm is used to solve the optimization problem. The resulting solution is formulated and implemented as a window update function. To address the final challenge we resort to a machine learning algorithm. We demonstrate how data features estimated utilizing only a fraction of the flow can be used as evidential input to a series of Bayesian Networks (BNs). We account for the uncertainty introduced by partial flow data through the Dempster-Shafer (DS) evidential reasoning framework