Surface chemistry modifications

Interphase — A spatial region at the interface between two bulk phases in contact, which is different chemically and physically from both phases in contact (also called interfacial region). The plane that ideally marks the boundary between two phases is called the interface. Particles of a condensed phase located near a newly created (free) surface are subject to unbalanced forces and possibly to a unique surface chemistry. Modifications occurring to bring the system to equilibrium or metastability generally extend somewhat into one of the phases, or into both. 

The enormous surface to volume ratio of the nanowires profoundly impacts the nanowire properties, making it imperative to control the surface chemistry. Several chemical routes have been explored for passivating or functionalizing nanowire surfaces. Hanrath and Korgel reported a comprehensive investigation of Ge nanowire surface chemistry modification including oxidation, sulfidation, hydride and chloride termination, and organic monolayer passivation... 

J.Y Park, D. Ahn, YY Choi, C.M. Hwang, S. Takayama, S.H. Lee, S. Lee, Surface chemistry modifications of PDMS elastomers with boiling water improves cellular adhesion. Sens. Actuators B 173 (2012)765-771. 

Surface Chemistry Modification — The most dramatic and widely used effect of plasma is the surface modification of polymers, where the surface layer of a polymer is altered to create chemical groups capable of interacting with adhesives or other materials deposited on the polymer. The inherently low surface-energy of untreated polymers hinders the wetting and interaction with adhesive systems [28-29] or deposited metals. Typically, plasma is used to add polar functional groups which dramatically increase the surface energy of polymers. 

Another example of polymer modification by pulsed laser exposure is the surface chemistry modification [12.13]. For this purpose pulse fluencies of the UV laser should be higher than those used for the periodic ripple formation [10]. By exposing polymer surfaces to pulsed UV lasers, chemical properties of polymer surfaces can be improved to more desirable ones. 

Gases or mixtures of gases used for plasma treatment of polymers include nitrogen, argon, oxygen, nitrous oxide, helium, tetrafluoromethane, water, and ammonia. Each gas produces a unique surface treatment process. It should be noted that surface chemistry modification by plasma treatment can make polymer surfaces totally wettable or nonwettable. Nonwettable plasma treatments generally... 

New fibers are being proposed all the time. During the 1980s, the aramid fibers, including Kevlar and Nomex, along with other nylon derivatives, enjoyed a brief spell of popularity. Eventually their hydroscopic nature and markedly positive Poisson s ratio, along with poor surface chemistry modifications, rendered them less suitable than carbon fiber for aerospace applications. 

In this review, we will specifically discuss the similarities and the differences between the chemistry on surfaces and molecular chemistry. In Sect. 2, we will first describe how to generate well-dispersed monoatomic transition metal systems on oxide supports and understand their reactivity. Then, the chemistry of metal surfaces, their modification and the impact on their reactivity will be discussed in Sect. 3. Finally, in Sect. 4, molecular chemistry and surface organometallic chemistry will be compared. 

The optical properties of semiconductor QDs (Fig. la-c, Tables 1 and 2) are controlled by the particle size, size distribution (dispersity), constituent material, shape, and surface chemistry. Accordingly, their physico-chemical properties depend to a considerable degree on particle synthesis and surface modification. Typical diameters of QDs range between 1 and 6 nm. The most prominent optical features of QDs are an absorption that gradually increases toward shorter... 

In this building-block approach, the components are synthesized separately and then hybridized via linking agents/methods that utilize covalent, noncovalent (van der Waals, n-n interactions, hydrogen bonding), or electrostatic interactions. The attachment of these building blocks often requires the chemical modification of at least one component to overcome the differences in surface chemistry. As a consequence deposition is often limited to the first layer. Excess nanoparticles can be removed by filtration or centrifugation. 

Noncovalent interactions such as van der Waals, hydrogen bonding, n-n stacking and electrostatic interactions have been widely used to hybridize pristine nanocarbons via ex situ approaches. The major advantage of this route is that the nanocarbons do not require modification prior to hybridization and their structure remains undisturbed, an important factor in many electronic applications. The strength of hybridization is weaker compared to covalent interactions but the synthetic process is generally simpler. Noncovalent attachment of small molecules to nanocarbons is often used to change the surface chemistry for subsequent ex situ or in situ hybridization. 

Titanium dioxide differs from silica mainly in two respects (1) the Ti + ions are octahedrally coordinated in all three modifications of TiOji (2) the Ti—0 bond is more pronouncedly ionic than the Si—O bond. Using Pauling s electronegativity values (297), one calculates a 63% ionic character for the Ti—0 single bond versus 50% for Si—O. In SiOj, there is certainly some double bond character involving 3d orbitals of the Si atom, causing lowered ionic character. Therefore, characteristic differences should be expected regarding the surface chemistry. 

Titanium dioxide occurs in three crystalline modifications anatase, rutile, and brookite. In all three forms, each Ti + ion is surrounded by six 0 ions and each ion has three Ti + neighbors. Both anatase and rutile are important white pigments which are produced on a large scale. Even though their surface chemistry is very important for their technological application, astonishingly little has been published in the chemical literature on this subject. However, it is very likely that many investigations have been undertaken in industrial laboratories. 

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