Invented by Keir Cajal Neuman, Ganesh Shenoy, Chandrasekhar Mushti, Rolf E. Swenson, US Department of Health and Human Services
The Market For Method to Functionalize Carbon Nanoparticles Or Compositions
The market for Methods to Functionalize Carbon Nanoparticles or Compositions is growing rapidly. This is because nanoparticles are finding applications in energy storage, electronics, catalysts and biomaterials.
However, there are still some limitations to their potential applications. For instance, they can be difficult to graft and contain high levels of impurities which could affect the final products’ quality.
Chemical Reactions
Chemical reactions are processes that create new substances by combining two or more substances, typically producing different products from their component parts. Chemical equations symbolically depict the starting materials, end products and sometimes intermediate products as well as reaction conditions.
Stoichiometry, or the ratio of reactants to products, is based on conservation of matter principles. One mole of an element or compound contains exactly the same number of atoms as another element or compound; this can be used to calculate concentrations within solutions or solids.
Chemical reactions are an integral part of everyday life and can be observed in a variety of activities. Examples include the combustion of fuels (like coal or gas), formation of water from molecules of hydrogen and oxygen, as well as formation of metal oxides such as calcium oxide.
Some reactions result in temperature changes, while others do not. Some of these modifications are easily visible, such as when metals react with oxygen to form a distinctive flame; other changes are more subdued, like when baking soda reacts with acid to form carbon dioxide.
Students must comprehend the concept of chemical reaction and its relevance to their daily lives. Through this inquiry, they will be encouraged to consider how chemical change plays a role in producing everyday items like food and recognize that it plays an integral role in maintaining our natural world.
To reinforce this concept, the activity uses a Carolina Chemonstrations(r): Reaction Types Kit. This set comes complete with materials for performing several experiments to demonstrate chemical reactions as well as instructions and safety glasses or goggles.
The reaction types kit provides students with the opportunity to investigate several reactions, such as the oxidation of a steel nail and plastics production. These experiments will test out the usefulness of the chemical reaction model and help solidify student concepts about what constitutes a chemical reaction. They can compare products with their starting materials and discuss them in class.
Molecular Recognition
Molecular recognition is the process by which molecules bind to each other through noncovalent interactions such as hydrogen bonding, metal coordination, hydrophobic forces and van der Waals forces. It plays an integral role in many biochemical reactions such as immune reactions, enzyme catalysis, DNA binding and protein-protein interactions.
Molecular recognition is a critical topic in medicinal chemistry, as it determines whether a compound will exhibit desired biological activity or not. Therefore, an understanding of molecular recognition and how it operates is necessary to create compounds with improved clinical properties.
One of the most crucial applications of recognition in molecular biology is protein folding. In this process, proteins recognize their target proteins through molecular recognition features (MoRFs), regions of residue disorder that take on a more rigid three-dimensional shape when interacting with another molecule.
Molecular recognition features can range from a single amino acid residue, peptide or small molecule. Synthesis of these bio-inspired materials is often complex due to their intricate structures and various chemical affinity levels with biological analytes.
Synthetic approaches are employed to produce recognitive polymers. Free radical polymerization is the most popular, as it allows the use of a wide range of commercially available monomers. Other polymerization mechanisms such as sequential click reactions and template directed assembly have also been utilized for creating highly ordered polymers with excellent specificity for molecular recognition.
Even with these methods, creating these materials remains a difficult challenge. To guarantee they bind the target analyte securely and remain stable, polymers must be designed that are compatible with the analyte while simultaneously providing an unbreakable interface for recognition elements to attach to.
Though there are challenges associated with the production of these materials, the future holds promise for functional, highly-ordered cognitive systems. By maintaining our focus on fundamental chemistry, sensitive characterization methods and physiologically relevant experiments, we can sustainably advance this field.
Catalysts
Catalysts are essential elements in many chemical reactions, controlling their reactivity and increasing efficiency. Unfortunately, catalysts are expensive and difficult to make, so scientists are searching for more cost-effective alternatives. One promising approach involves using carbon molecules instead of metals like platinum which could save costs while also helping reduce environmental pollution.
The Department of Energy’s Office of Science Basic Energy Sciences program actively encourages research on catalysis. Their goal is to develop new concepts for catalysis and create catalysts that can efficiently and sustainably convert fossil and renewable raw materials into fuels and chemicals.
Researchers have recently discovered a way to make catalysts from vegetable oils by controlling combustion and collecting carbon soot on ceramic plates. This environmentally friendly process produces highly pure and high-quality carbon nanoparticles with superior catalytic properties.
Another technique uses chemical crosslinking and dry mixing to functionalize carbon nanoparticles or compositions without the need for a solvent. The method works by providing the nanoparticles with an aryl diazonium salt that can be readily created in the lab from various precursors. Once mixed, ball mill or stir until particles are evenly distributed.
Alternatively, carbon nanoparticles can be mixed with a polymer for in situ functionalization. The polymer used can be any chemical, biological or natural polymer that is compatible with the carbon nanoparticles. In certain embodiments, this mixture is combined with either an inert catalyst support that is inert or activated during the reaction.
Catalysts can be supported on a range of supports, such as granular, powdered, colloidal, coprecipitated, extruded, pelleted, spherical, wires, honeycombs or skeletal ones. The shape of the support has an immense effect on catalyst properties like distribution and stability as well as catalytic reactivity.
Catalysts with various combinations of supports have been developed for various applications, such as oxidative dehydrogenation of ethanol to acetaldehyde, carbon adsorption onto silicon and other semiconductor surfaces, direct methanol fuel cell electrocatalysis, and the fabrication of novel metal catalysts from metallized multi-walled carbon nanotubes. These catalysts have demonstrated excellent performances with up to 54-percent conversion rate and 84 percent acetaldehyde selectivity.
Electrochemistry
Electrochemistry is the study of oxidation-reduction reactions that either create or consume electrical energy. This includes batteries used in modern devices like cars and airplanes for propulsion.
These batteries consist of electrodes (conductors through which electrons enter or leave the cell) and an electrolyte solution. When an electron moves from electrode to electrode, it takes on a negative charge and travels to anode where it is lost and transformed into neutral elements or molecules.
Electrochemistry, commonly referred to as “electrolysis,” involves the passage of ions through an electrolyte between two electrodes that create an electric current with a potential. This potential is known as the “cell potential” for an electrochemical cell.
An electrochemical cell can be created using any pair of metals with differing tendencies to lose or gain electrons. Zinc, for instance, loses more electrons than copper does. Combining zinc and copper in solutions of their salts causes electrons to flow from zinc to copper as illustrated in the figure below.
The electrical current created can be utilized for various functions, such as charging batteries, coating metals with less reactive metals or isolating metals like aluminum from ores. Furthermore, this electrical current produces an ionic flow which helps make other electrochemical processes work effectively.
Electrochemical cells can also be employed to create a metallic silver coating on metal objects, known as electroplating. This treatment increases corrosion resistance and enhances an object’s strength or aesthetic qualities.
This technique is highly sought-after, especially for precious metals like gold and silver. Unfortunately, it requires a great deal of electricity and silver-plated objects can corrode rapidly when exposed to it.
Thus, it is essential to comprehend how an electrochemical cell operates and its potential applications. Doing so will enable you to decide the most advantageous use for it in your laboratory setting.
Electrochemical techniques have applications in chemistry, physics, biology and even archaeology. They provide an efficient means of observing and measuring changes to the physical environment. Furthermore, they can be employed to make things like lamps more energy-efficient or clean archaeological artifacts from rust and other contaminants.
The US Department of Health and Human Services invention works as follows
A method for increasing the density of carboxylic acid on a surface carbon nanoparticles is disclosed. This method involves contacting an oxygen-containing functional groups on a carbon nanoparticle’s surface with a reducer to give a hydroxyl. Then, react the hydroxyl with a diazoacetate ester in the presence of transition metal catalyst to give an ester. The diazoacetate ester has the structure wherein R, C1-8 hydrocarbyl. Finally, cleaving it to create a carboxylic acid. Surface-functionalized carbon nanoparticles made by the method are also disclosed.
Background for Method to functionalize carbon nanoparticles or compositions
Carboxylic acid is one of the most widely used functional groups for covalent surfaces conjugation of nanoparticles. Carboxylic acids are a useful functional group for biomedical and biological applications. They can be used to coupling with biologically relevant molecules like antibodies or other peptides.
The most popular way to create carboxylic acid on carbon nanoparticle surface is by treating it with an oxidizing mixture such as nitric acid or sulfuric acid. Carbon nanoparticles are exposed to oxidizing environments that result in the formation many oxygen-containing functional group on the surface. These functional groups include epoxides and ketones, aldehydes and carboxylic acid, as well as lactones. See Mochalin (V. N.); Shenderova O.; Ho D.; Gogotsi Y., Nanodiamonds: Properties and Applications. Nature Nanotechnology 2012 7 (1), 11-23 Huang, J., Deming, C. P., Song, Y., Kang, X., Zhou, Z.Y. Chen, S. Chemical Analysis of Surface Oxygenated Moites of Fluorescent Carbon Nanoparticles. Nanoscale 2012, 4 (3), 1010-1015.) This acid treatment method is not able to produce select carboxylic acids. Unintended reactions and poor characterisation can lead to a product with multiple functional groups that is less likely for therapeutic purposes. The nanoparticle’s surface has a higher total oxygen content, which results in lower carboxylic acid levels and consequently lower loading of molecules that are later coupled to these carboxylic acids.
During the ongoing development of fluorescent nanodiamonds as molecular imaging probes for molecular imaging, the inventors encountered the problem with low carboxylic acids content. This prevents the functionalization necessary for most FNDs. Researchers and manufacturers of diamonds reported low yields when using carboxylic acid-based coupling methods for FNDs. Low levels of carboxylic acid group presence on FNDs are a major barrier to biologically compatible functionalization and, more generally, functionalization of carbon nanoparticles.
There is therefore a need to improve methods for increasing the density carboxylic acid on a carbon nanoparticle’s surface.
Methods for increasing the density carboxylic acids on the surface of carbon nanoparticles are disclosed herein. This method involves contacting an oxygen-containing functional groups on a surface carbon nanoparticles with a reducer to give a hydroxyl; reacting the diazoacetate ester with a transition metal catalyst in order to give an ester and then cleaving it to produce a carboxylic acid.
A surface-functionalized carbon nanoparticle including carboxylic acid groups is also disclosed.
These and other benefits, as well as additional inventive elements, will be evident from the following Drawings.
Carbon nanomaterials like fluorescent nanodiamonds and graphene can have important biological applications in near future. Because they can be used to combine biologically relevant molecules such as antibodies or other peptides, carboxylic acids are one the most valuable functional groups in biological Chemistry. The most common method of producing carboxylic acid on carbon nanoparticle surface is to use an oxidizing mixture (typically nitric or sulfuric acid). The oxidizing acid mixture can produce a variety of oxygen-containing functional group on carbon nanoparticle surfaces, including epoxides. The carbon nanoparticle’s total oxygen content is distributed among various functionalities, which can lead to undesirable side products in further functionalization.
Methods to generate carboxylic acids selectively from the wide variety of oxygen-containing functional groups present on a carbon nanoparticle surface after oxidation, in particular acid oxidation, and the surface-functionalized carbon nanoparticles made by the methods are disclosed herein. These methods produce carbon nanoparticles with a significantly higher number of surface carboxylic acids groups than the ones obtained from non-specific oxidation. The carboxylic acid-functionalized carbon particles obtained using the methods can be easily derivatized with functional groups such as carbodiimide conjugation with higher efficiency and yield.
In one aspect, a method for increasing the density carboxylic acids on the surface of a carbon-nanoparticle is disclosed. This involves contacting an oxygen-containing functional groups on a surface carbon nanoparticles with a reducer to give a hydroxyl; reacting the diazoacetate ester with a transition metal catalyst in order to produce an ester.
Wherein R is a C1-8 Hydrocarbyl, preferably T-butyl or methyl, ethyl and isopropyl.
The carbon nanoparticle is any carbonaceous material with an average dimension of 100 nanometers (nm), or less. As used herein, ?carbonaceous? A structure that is dominated by carbon-carbon bonds. However, other elements may be present such as trace amounts (e.g. a catalyst residue) and functional groups (e.g. oxygen-containing functional group as discussed below). A carbon nanoparticle could be a carbon nanotube or graphene, graphene, and graphene oxide. It can also be a nanodiamond or combination of both. The carbon nanoparticle can be a nanodiamond or preferably a fluorescent one.
A fullerene” can be any of the well-known hollow cage-like hollow allotropic carbon forms with a polyhedral arrangement. Fullerenes can contain, for example, between 20 and 100 carbon atoms. C60, for example, is a fullerene that’s readily available and has 60 carbon atoms.
Carbon nanotubes can be tubular fullerene structures with open or closed ends. They are entirely or partially made of carbon and can also include metals, metalloids, or ceramics. You can choose from single-walled or multi-walled carbon nanotubes (SWNTs),
Graphene is available in a single or multiple sheets. It can also be layered on several sheets with nano-scale dimensions. Graphene is a two-dimensional plate structure made up of fused hexagonal rings. They are layered and weakly bonded together by pi-pi stacking interaction. You can prepare nanographene by exfoliating nanographite, or by catalytically breaking a series carbon-carbon bonds within a carbon nanotube. This will form a nanographene stripe by unzipping? This is followed by derivatization to make nanographene oxide.
The method involves reducing the various oxygen-containing elements on the nanoparticle surfaces to alcohols by using a reducing agent that converts the oxygen-containing group. The reducing agent, which is strong and non-selective, is capable of converting all or almost all of the oxygen-containing compounds to groups containing a C-OH bond. A metal hydride can be used as the reducing agent. LiBHEt3, LiAlH4, LiAlH4, and AlH3 are all examples of metal hydrides. A strong, non-selective reducer converts most oxygen-containing functional group into alcohols (see Nystrom, R. F. and Brown, W. G. Reduction of Organic Compounds By Lithium Aluminium Hydride). I. Aldehydes and Ketones, Esters Acid Chlorides, Acid Anhydrides. Journal of the American Chemical Society 1947. 69(5): 1197-1199. Nystrom, R. F. and Brown, W. G. Reduction of Organic Compounds By Lithium Aluminum Hydride. II. Carboxylic Acids. Journal of the American Chemical Society 1947. 69 (10). 2548-2549
The temperature can be lowered to room temperature by adding 1 M HCl or another suitable acid or using other techniques known in the art. To remove any metal salts formed from the reduction process, you can wash the nanoparticles one or more times. The reduced particles can be washed with an acid at 1N, a base of 1 N and/or distilled waters. In some cases, the base is NaOH and the acid is HCl.
The reduced nanoparticles are contacted with a diazoacetate ester in the presence of a transition metal catalyst and solvent to provide a surface-functionalized ester attached to the nanoparticle surface via an ether linkage formed with the surface alcohol group (see, Aller, E.; Brown, D. S.; Cox, G. G.; Miller, D. J.; Moody, C. J., Diastereoselectivity in the O?H Insertion Reactions of Rhodium Carbenoids Derived from Phenyldiazoacetates of Chiral Alcohols. Preparation Of .Alpha.-Hydroxy And .Alpha.-Alkoxy Esters. The Journal of Organic Chemistry, 60 (14), 4449-4460. The transition metal catalyst can be Rh2 (OAc), Rh2 (NHAc),4, Rh2 (2NHCOCF3)4, Rh2 (3F7)4, or Cu(OTf). In which Ac is acetate and Tf is triflate, Me, acetylacetate, Et is ethyl, acac are acetylacetate, and Me is methane, Ni is methyl, and Tf is triflate. Preferably, the transition metal catalyst is Rh2(OAc), Rh2(NHAc),4, or a combination thereof.
Click here to view the patent on Google Patents.