(1) Chemical modification
When a diamond is treated with an oxidizing acid solution (such as nitric acid, chromic acid, Fenton reagent, etc.), impurities (graphite and metal) on the surface of the diamond are removed, and C-O surface functional groups are formed on the surface of the diamond. Carbonyl and ether functional groups are formed on the surface of the diamond (100), and hydroxyl groups are formed on the surface of the diamond (111). Energy group. Carboxylic acidified nano-synthetic diamond can be obtained by using hydrogen peroxide and piranha solution (a mixture of sulfuric acid and hydrogen peroxide). Chlorine substitutes for hydrogen on the surface of the diamond film at 250-400 C. The active point on the surface of diamond film is formed. It is easy to react with nucleophilic reagents (such as hydrogen peroxide, NH3, CHF).
(2) Photochemical modification
There are two typical photochemical modification techniques:
1) under ultraviolet light, olefins react with the diamond surface to form carbon-carbon bonds;
2) various types of organic peroxides are used to initiate free radical reactions. The photochemical method can make the surface of diamond connect alkyl chain, carboxylic acid or primary amine group. YANG et al. used the second method to connect DNA strands to the diamond surface, and the stability of DNA strands was very good. Ultraviolet illumination can also be used to activate free radical reactions, such as MILLER, which chlorinates the surface of the diamond, realizes amination or mercaptan on the surface of the diamond, SMENTKOWSKI and other photochemical modifications form very stable C-F terminals on the surface of diamond films.
(3) electrochemical modification
The electrochemical modification methods include:
(1) anodic polarization in acid or alkali solution;
(2) adding aromatic diazo salts to electrolyte solution and introducing aromatic groups on the diamond surface. Compared with chemical modification oxidation, electrochemical modification can achieve rapid oxidation in a wide range; compared with plasma oxidation, the oxidation process is the easiest to achieve because it does not involve high energy and can avoid thermal damage to diamond surface. By electrochemical oxidation, the C=O bond is formed on the surface of the diamond, and the diamond film electrode is prepared, which can improve the detection accuracy and selectivity. Diamond film electrodes have been used in electroanalysis and electrochemical degradation of organic pollutants.
(4) Modification of Metals and Metal Oxides
Metal particles (such as gold, copper, silver, nickel, platinum, ruthenium and palladium) can be deposited on the diamond surface by thermal deposition or potentiostatic electrodeposition. Nano-electronic devices can be prepared and applied in the catalytic reaction, disease diagnosis and treatment, biological sensing and other fields. For example, diamond/platinum composite electrodes not only have good catalytic activity but also have excellent corrosion resistance and stability. They can be used in electrochemical energy conversion devices (such as fuel cells); thin film electrodes are prepared by electrodeposition of nano-gold onto the diamond surface, which can catalyze the reduction of oxygen in acidic solution. The catalytic efficiency is 20 times higher than that of the diamond electrode under the same conditions; the electrocatalytic activity of glucose is enhanced by the deposition of copper and nickel on the surface of nano-diamond; the reduction yield of carbon dioxide to carbon monoxide can be increased by the deposition of ruthenium dioxide or cobalt oxide hydrate on the surface of diamond. In this way, it can not only reduce carbon dioxide emissions but also provide technical support for the use of carbon dioxide as raw material for chemical synthesis.
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