Hydrogen-terminated preparation

In 1993, Linford firstly reported a quite useful method to prepare monolayers of alkyl chains by thermal hydros-ilylation of hydrogen-terminated silicon surfaces [25]. Alkyl chains are covalently bound to Si surface by Si-C bonds. This thermal hydrosilylation could be attributed to a free-radical process with 1-alkene. First, a diacyl peroxide initiator was used to produce free radicals. However, at higher temperature, only hydrogen-terminated silicon and a neat solution of 1-alkene or 1-alkyne can form Si-C linkages [26]. Furthermore, lately it is found that such Si-C covalent links can be observed even in dilute solutions of 1-alkenes [27]. In that case, the density of monolayer packing strongly depends on the reaction temperature. 

Wet preparation of metal nanoparticles and their covalent immobilization onto silicon surface has been surveyed in this manuscript. Thiol-metal interaction can be widely used in order to functionalize the surface of metal nanoparticles by SAM formation. Various thiol molecules have been used for this purpose. The obtained functionalized particles can be purified to avoid the effect of unbounded molecules. On the other hand, hydrogen-terminated silicon surface is a good substrate to be covered by Si-C covalently bonded monolayer and can be functionalized readily by this link formation. Nanomaterials, such as biomolecules or nanoparticles, can be immobilized onto silicon surface by applying this monolayer formation system. 

Linford, M. R., Fenter, P., Eisenberger, P. M. and Chidsey, . E. D. Alkyl monolayers on silicon prepared from 1-alkenes and hydrogen-terminated silicon. Journal of the American Chemical Society 117, 3145 (1995). 

Living polymers usually require special reagents to achieve termination. Any electrophilic reagent that reacts with the carbanion active center and also allows preparation of polymers with desired terminal functionalities can be used for this purpose.168,174,181 Hydrogen-terminated polymers can be produced by proton donors, whereas carbon dioxide results in a carboxylate end group. Terminal alcohol functionalities can be formed through reaction with ethylene oxide and carbonyl compounds. 

Linford MR, Fenter P, Eisenberger PM, Chidsey CED (1995) Alkyl Monolayers on Silicon Prepared from 1-Alkenes and Hydrogen-Terminated Silicon, J Am Chem Soc 117 3145—3155... 

Figure 2 Preparation of hydrogen-terminated Ge followed by hydrogermylation...

The procedure for preparing atomically smooth, hydrogen-terminated silicon surfaces involves a number of steps removal of hydrocarbon contamination, formation of a uniform oxide, oxide removal, etching of the silicon surface, and the formation of the passivation layer. The uniformity of the oxide is important in developing a smooth surface at the Si/Si02 interface. 

Figure 5 MA LDI-TOF spectrum of GTP prepared hydroxyl functional PMM A hydrogen terminated...

Thus, unless in a vacuum, the surface of silicon is never clean because of the adsorption by foreign species. As will be seen in the following sections, the type of termination, in terms of chemical nature, thickness, and composition, is a function of how the surface is prepared and cleaned. In particular, the surface cleaned with HF solutions, which are widely used for preparation of silicon surfaces, is known to be hydrogen terminated. On the other hand, in water and non-HF solutions, silicon surfaces tend to be covered with an oxide film. Employing certain treatment processes, the surface of siheon can be terminated by different species—and/or F and/or OH—using different cleaning solutions as shown in Table 2.7. ... 

The filtered polyynes and monocyanopolyynes solution prepared in acetonitrile at —40°C is not stable if stored at room temperature for 5 days in a closed flask. In fact, on standing, the solution becomes deep yellow. HPLC analysis of the aged solution produces the chromatogram shown in Figure 15.3 where it is possible to observe that the ordinary hydrogen-terminated polyynes survived unchanged while the monocyanopolyynes... 

Depending on the method of their preparation, the individual nanodiamond particles do not exist as isolated crystallites, but they form tightly bound agglomerates. Apart from unordered sp - and sp -hybridized carbon, they may also include other impurities. The latter may originate either from synthesis or purification, for example, finely dispersed material from the reactor walls may contaminate the sample (Section 5.3). This is especially true for material produced by the detonation or shock wave method, whereas hydrogen-terminated diamond nanoparticles do not show this effect. 

To extend the hydrogen evolution potential in an aqueous media, a fluorine-terminated diamond surface is prepared in a radio frequency plasma reactor of CF-He [124]. Fluorine-terminated diamond is usually used to study electrode reactions that require high over potential. For covalent attachment of different biomolecules, hydrogen-terminated diamond electrodes are also treated with ammonia plasma to prepare the surface with terminal amine groups [125]. 

Hamers and coworkers have shown that the hydrogen-terminated, electrically insulating diamond surface can be chemically modified with functionalized alkenes (e.g., perfluorodecene) [154]. They also showed that it is possible to prepare diamond surfaces terminated with organic molecules containing primary amine and carboxylic acid functional groups. In their approach, chemical functionalization is accomplished with the aid of UV irradiation. The diamond surface, in an enclosed vessel, is exposed to a small volume of the particular organic compound. The solution environ-... 

Fig. 1 Comparison of the magnetization curves of bare n silicon (full line), as-etched porous silicon prepared from the same wafer (dotted line), and aged porous silicon offering a native oxide layer (dashed line). All three samples show a diamagnetic behavior, whereas the estimated susceptibility varies between —1.2 10 (Si), —7.5 10 (as-etched), and —2.6 10 (aged). The measurements have been performed at T = 4.2 K. The diamagnetic behavior of porous silicon decreases if the sample is oxidized (in contrast to hydrogen terminated) which might be caused by the occurrence of dangling bonds...

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