Catalysis In Chemistry

a. O3: The O has an oxidation number of 0, because the oxidation number of an element is always 0 regardless of its subscript.

I. The objective of this laboratory experiment is to be able to identify and precisely classify each reaction as one of the five different types of chemical reactions by comparing the reactants from the product.

Background: In this lab, we will be observing a chemical reaction dealing with enzymes. You may ask, what are enzymes? Enzymes are proteins produced by living cells. For example, you have enzymes in your digestive system to help you break down food. Without enzymes, organisms will not be able to survive. Enzymes act as catalyst in biochemical reactions and catalyst speeds up the reaction by lowering the amount of activation energy. Activation energy is required for reactants to react into products. Although enzymes are essential, substrate plays an crucial role as well. The substrate and enzyme bind together on the active site of the enzyme, like a key to a lock. Each substrate has its own specific shape and structure. The active site of

Recently metal-catalyzed carbon–carbon and carbon–heteroatom cross-coupling reactions have been developed as an important reaction class in chemical synthesis.1 Nowadays, there is a variety of competitive methods for synthesis of aryl-nucleophile bonds with various sources of C-, O-, N-, P-, and S-nucleophiles.1-5 Researchers have extensively applied palladium-based catalysts in cross-coupling reactions in both academic and industrial settings,5, 6 however, our goal is the development of a range of copper-based catalysts for cross-coupling reactions. Copper-assisted Sonogashira-type coupling reactions are valuable transformations for organic synthesis. C-C bond formation between aryl halides and terminal aryl- and alkyl-alkynes affords the corresponding substituted internal alkynes. Alkynes are the building blocks of a wide range of pharmaceuticals, natural products, biologically active molecules, conducting polymers, nonlinear, optical and liquid crystal materials.7-12 The routine reaction method for Sonogashira-type coupling is the use of a palladium-based catalyst and a copper(I) salt as a co-catalyst.13 The role of the copper co-catalyst is to produce a copper-acetylide intermediate that subsequently transmetallates to the palladium center.

In chemistry, there are six types of chemical reactions; synthesis, decomposition, combustion, single replacement and double replacement. There are acid bases as well. Each type of reaction is unique in its own way. The process involves one or more reactant to be rearranged to form a different product. You can prove that a chemical reaction has occurred if there was a change in temperature, color, odor , appearance or the presence of gas bubbles.

Organic chemistry is the complexity of natural compounds. It is applied to the production of mundane objects that include: plastics, polymers, soaps, detergents and drugs. Such compounds of organic chemistry involve the identification, modelling, chemical reactions and synthesis – it initiates the concept of design implemented in organic compounds (Helmenstine A, 2014). An example of an organic compound is the product of organic drugs in which are manipulated behind the chemistry of its design. A particular category of drugs: NSAIDs (Non-steroidal anti-inflammatory drugs) is one the most common types of medication utilised to treat a range of conditions associated with the human body. Aspirin, paracetamol and ibuprofen are among the category of NSAIDs (Deruiter, 2002, p.1). The product formed by the basis of organic chemistry provides the insight that organic compounds can be morphed and designed in a way to produce a particular product. Thus, organic chemistry is the application of organic molecules to form products; it is the chemistry of design.

A Biological Catalyst A Biological catalyst is a catalyst that is produced organically. In other words, a cell makes it. It is usually a protein or steroid molecule that works to catalyse a specific reaction. For example, amylase is a biological catalyst.

The possibilities of employing a nanoscale metal topography that will employ surface plasmon excitation phenomena towards improving the light absorption efficiency of organic solar cells will be investigated. This goal is achievable by analytically designing and producing optically active nanostructures which are used to excite surface plasmons at the wavelengths range dictated by the sun in order to support the confinement of light beyond the diffraction limit, thus leading to high weighted enhancements over a wider range of the solar spectrum. This can be achieved by employing nanostructured materials with unique properties tailored for the materials characteristics of II-VI nanorod systems across the solar spectrum capable of creating significant enhancements while preventing unwanted thermal losses. Also external quantum efficiency measurements on the nanostructured cells will be made, this is expected to demonstrate a substantial photon absorption enhancement across the solar spectrum. Finally, key insights into light absorption and trapping mechanisms in these plasmon enhanced cells through a combination of three-dimensional finite-difference time-domain simulations, optical absorption, and external quantum efficiency measurements will be obtained

As shown in Fig. 1, the bonds about 278 and 335 nm were related to the presence of polyphenolics as the antioxidant for green synthesis of nanoparticles, which assigned to the π → π* transitions [40]. The addition of the Safflower extract to the HAuCl4 solution was resulted in the Au3+ reduction and visual color change from light yellow to reddish brown is meaning the formation of Au-NPs. Therefore, this color change is due to Surface Plasmon Resonance (SPR) excitation the collective oscillation of free conduction electrons induced by an interacting electromagnetic field. The strong SPR band was observed near 520 nm. These bands are centered in the ideal wavelength range reported for Au-NP colloidal solutions [41].

The advancement in technology has resulted in new and intriguing applications for the materials that in the past were considered inconceivable. This is evidenced in the rapidly emerging nanotechnology field. The distinctive size-dependent characteristics of substances on the scale of nanometer have led to their applications in various disciplines, for instance, solar cells, bio-imaging, drug delivery, wavelength-tunable lesser and catalysis. Nanometer-sized materials are materials that range in size from one to one hundred in nanometre scale. Organic polymers are macromolecules or molecules which are made up of several repeated subunits (monomers). The polymer can either be natural or synthetic. The ‘nanometer-sized polymer materials’ are described as polymer materials with sizes that range from 1 to 100 on a nanometer scale. The majority of the nanometer-sized organic polymers in various applications are formed from the combination of the organic components and the metal at the molecular level. This kind of combination has provided a new class of hybrid nanomaterials referred to as the nanoscale coordination polymers. The nanoscale coordination polymers are synthesized from the polydentate bringing ligand and the metal ion cluster that possesses at least two empty coordination sites. Some examples of coordination polymers are the mixed metal cyanometallates and the Prussian blue. The coordination polymers can be made from different organic building blocks

Currently, interest has taken over in developing an intramolecular carbon-carbon bond that ends up forming reactions catalyzed by transition metals, and research for this focuses on the activation of carbon-hydrogen bonds. There are a number of functional groups that may be capable of certain carbon-hydrogen activation. With this comes developing strategies that involve steroinduction, complexity generating reactions, and carbon-carbon bonding formation processes. However, to efficiently identify possible new processes, parallel screening techniques enable scientists to preform and monitor these reactions. The new discovery and development process can be now be accelerated, which leads to a new optimized transformation faster.

Therefore, various efforts have been focused on the design and synthesis of Cu2O-based nanocomposite materials to achieve high photochemical stability and improve the charge separation ability for high photocatalytic efficiency. In this context, the fabrication of Cu2O materials with noble metal nanoparticles is an efficient approach to improve the photocatalytic efficiency, as the schottky barrier developed at the heterojunction interface inhibits the recombination of photogenerated electrons and holes in photocatalytic reactions. Further, the surface plasmon resonance (SPR) of noble metal nanoparticles also enhances the photocatalytic efficiency by increasing the absorption of photons on the surface of the catalyst. However, the use of stabilizing/capping agents for the synthesis of noble metal-semiconductor nanocomposite materials decreases the catalytically active surface area by aggregating on its surface and cause lower catalyst contact with the reactant molecules. Further, surfactants affect the shape, size, and growth of the deposited metal nanoparticles and prompt the formation of large sized aggregated nanoparticles with low photochemical stability and reduced catalytic efficiency. In this context, graphene oxide (GO) was used as an efficient support for Cu2O-based NCs, because of its large surface area, high electron conductivity, and high optical transparency to achieve enhanced photochemical stability

Recently semiconductor based photo-catalysis as a sort of green technology which has attracted notable attraction among the researchers.

In top-down techniques, clusters are synthesized from larger nanoparticles or bulk metal. Etching of nanoparticles using ligands (as thiols) is one of the most top-down techniques can be used for the synthesis of metal clusters. Removing the surface atoms or break the metal nanoparticles into smaller clusters by using the etching capacity of such ligands will lead to synthesize stable quantum clusters. For example, Habib et al. has used the etching of mercaptosuccinic acid protected gold nanoparticles with excess glutathione to yield small photoluminescent gold clusters either with 8 or 25 gold atoms [16]. Polyethylenimine as multivalent coordinating polymers can also be used to etch preformed colloidal gold nanocrystals producing highly fluorescent nanoclusters [17]. it is well confirmed that small noble metal nanoclusters display excellent catalytic activities such as aerobic oxidation of thiophenol [18], propene epoxidation[19], oxidation of styrene [20], p-nitrophenol reduction with NaBH4 [21] and the reduction of methylene blue with hydrazine [22].

Electron microscopy image in fig.2 implied the conduction (e-) of Au spheroidal aggregation depicts the association of surface plasmin resonance(SPR)[12] with the band shown by a tapered absorption peak around 520nm, following the surface functionalization concentration of Au particles was 61.410-3M owing to have an absorption coefficient of about 3995M-1cm-1 at wavelength 522nm [12]. Absorption spectra displays (Fig.3.) the SPR band rising from Au-NPs in TiO2-Au films as well undoped films is observable in each temperature variant films by solid and dotted line respectively. The upright stippled line indicates an escalated refractive index of sol-gel results in a change to red with the insertion of Au-particles in Titanium dioxide lattice at 522nm. There is no indication of this association with just undoped films with Au-particles. Though, the optical intrusion of hardened sample results in a wide absorption belt around 800nm at 100 C transformed to blue around 375nm at 500C. Doping concentration did not transform SPR peak locus, due to the small volume fraction of Au, since the peak is much affected by the annealing temperatures (refer. Fig.4). Absorption spectra illustrate the linear behaviour of Au volume with absorption peak except the one annealed at 100C