Carbon allotropic forms

For strong Pt fixation on CNM surface it is necessary to introduce functional groups, preferable from ones are -COOH, -OH and quinoid. The diversity of carbon allotropic forms and types of bonds between carbon atoms causes the different approaches to inculcation of a functional groups on CNM surface. 

The combination of sp , sp and sp hybridized atoms can give rise to a large number of carbon allotropic forms and phases, but only carbon solids based on all sp (diamond) and sp (graphite, fullerene) hybridization are well known and characterized [1]. In addition there are innumerable transitional forms of carbon where sp and sp hybridization bonds co-exist in the same... 

The existence of a form of solid carbon where carbynoid species can coexist with sp hybridization has important implications for the achievement of a deeper understanding of the processes leading to the formation of carbon clusters [46], for the synthesis of novel carbon allotropic forms and nanomaterials [1], and for the chemistry of the interstellar medium [12]. 

Carbon is found free in nature in three allotropic forms amorphous, graphite, and diamond. A fourth form, known as "white" carbon, is now thought to exist. Ceraphite is one of the softest known materials while diamond is one of the hardest. 

Sulfur is pale yellow, odorless, brittle solid, which is insoluble in water but soluble in carbon disulfide. In every state, whether gas, liquid or solid, elemental sulfur occurs in more than one allotropic form or modification these present a confusing multitude of forms whose relations are not yet fully understood. 

If you re a sports fan, you ve almost certainly seen this structure before. It is that of a soccer ball with a carbon atom at each vertex. Smalley and his colleagues could have named this allotropic form of carbon "carbosoccer" or "soc-cerene," but they didn t. Instead they called it "buckminster fullerene" after the architect R. Buckminster Fuller, whose geodesic domes vaguely resembled truncated soccer balls. 

Buckminsterfullerene is an allotrope of carbon in which the carbon atoms form spheres of 60 atoms each (see Section 14.16). In the pure compound the spheres pack in a cubic close-packed array, (a) The length of a side of the face-centered cubic cell formed by buckminsterfullerene is 142 pm. Use this information to calculate the radius of the buckminsterfullerene molecule treated as a hard sphere, (b) The compound K3C60 is a superconductor at low temperatures. In this compound the K+ ions lie in holes in the C60 face-centered cubic lattice. Considering the radius of the K+ ion and assuming that the radius of Q,0 is the same as for the Cft0 molecule, predict in what type of holes the K ions lie (tetrahedral, octahedral, or both) and indicate what percentage of those holes are filled. 

We can understand the differences in properties between the carbon allotropes by comparing their structures. Graphite consists of planar sheets of sp2 hybridized carbon atoms in a hexagonal network (Fig. 14.29). Electrons are free to move from one carbon atom to another through a delocalized Tr-network formed by the overlap of unhybridized p-orbitals on each carbon atom. This network spreads across the entire plane. Because of the electron delocalization, graphite is a black, lustrous, electrically conducting solid indeed, graphite is used as an electrical conductor in industry and as electrodes in electrochemical cells and batteries. Its... 

There are more than a million known carbon compounds, of which thousands are vital to life processes. The carbon atom s unique and characteristic ability to form long stable chains makes carbon-based life possible. Elemental carbon is found free in nature in three allotropic forms amorphous carbon, graphite, and diamond. Graphite is a very soft material, whereas diamond is well known for its hardness. Curiosities in nature, the amounts of elemental carbon on Earth are insignificant in a treatment of the... 

The state of research on the two classes of acetylenic compounds described in this article, the cyclo[ ]carbons and tetraethynylethene derivatives, differs drastically. The synthesis of bulk quantities of a cyclocarbon remains a fascinating challenge in view of the expected instability of these compounds. These compounds would represent a fourth allotropic form of carbon, in addition to diamond, graphite, and the fullerenes. The full spectral characterization of macroscopic quantities of cyclo-C should provide a unique experimental calibration for the power of theoretical predictions dealing with the electronic and structural properties of conjugated n-chromophores of substantial size and number of heavy atoms. We believe that access to bulk cyclocarbon quantities will eventually be accomplished by controlled thermal or photochemical cycloreversion reactions of structurally defined, stable precursor molecules similar to those described in this review. 

The Nobel prize in Chemistry for the year 1996 was awarded for the discovery of the fullerenes, the third allotropic form of carbon, with Cgo and C70 as the two most prominent representatives. While the fullerenes of course are the epitome of carbon-rich molecular compounds, it is an irony that their synthesis is more of a physical phase transition, taking place under drastic conditions [1]. 

Potassium violently reacts with carbon in most of its allotropic forms. Thus the action of molten metal on graphite results in the formation of some kind of a carbide ... 

When a test confirms the presence of a substance without determining the amount of substance present, the process is called qualitative analysis. In this activity, you will detect the presence of potassium in coffee by the characteristic yellow color that appears when potassium ions react with sodium hexanitrocobaltate. To make it easier to detect the yellow color, the coffee solution will be decolorized with charcoal, an allotropic form of solid carbon. 

There are other allotropic forms of carbon, including graphite, Wurzite carbon... 

Fullerenes, the third allotropic form of carbon along with graphite and diamond, are a novel class of spheroidally shaped molecules made exclusively of carbon atoms. They have generated much enthusiasm and numerous research efforts during the past few years.206 Hence, the chemical and physical features of C6o, also named... 

Many elements including sulphur, carbon and oxygen can exist in two or more forms with different physical, and often chemical, properties such elements are said to exhibit allotropy and the different forms are known as allotropes or allotropic forms. 

Carbon atoms have the ability to bond to themselves to a greater extent than those of any other element. Known as catenation, this ability gives rise to the several allotropic forms of the element. The most common form of elemental carbon is graphite, which has the layered structure shown in Figure 13.11. 

In 1985, another allotropic form of carbon, fullerenes, were discovered. Two important fullerenes are C60 and C70. 

V.I. Sokolov, I.V. Stankevich. Fullerenes - new allotropic forms of carbon structure, electron structure and chemical properties. // Success in chemistry, 1993, v.62, N°5, p.455-473. 

The toxicity of this third allotropic form of carbon is an aspect related to application in medicine and biology, while the concern about the environmental impact is due to the industrial production of fullerenes. Many studies are dedicated to both aspects and, so far, it is not possible to have a definitive answer although the current findings allow some optimistic vision. 

Once upon a time there were three brilliant researchers who isolated and identified the third allotropic form of carbon. C60 fulleiene is the most common compound of this family and, since its discovery it has attracted glances and attentions from the scientific community for its biological potentialities (Fig. 1.5). 

The emerging field of nanotechnology is affirming its increasing importance day by day. In this context fullerenes and carbon nano tubes (CNTs) play an important role. These new allotropic forms of carbon have been discovered in the last two decades, and, since then, they have stimulated the curiosity and interest of physicists and chemists. 

Carbon nanotubes (CNTs) constitute a nanostructured carbon material that consists of rolled up layers of sp2 hybridized carbon atoms forming a honeycomb lattice. After diamond, graphite and fullerenes, the one-dimensional tubular structure of CNTs is considered the 4th allotrope of carbon (graphene is the 5th). 

The field of carbon nanostructure research is vast and novel, and it experienced a major breakthrough after the discovery of fullerenes in 1985 [1], and their subsequent bulk synthesis in 1990 [2]. This event opened the minds of various scientists towards discovering novel carbon allotropes. Promptly, yet another allotrop of carbon was observed by Iijima [3], although it had previously been produced by M. Endo et al. in the 1970s by chemical vapor deposition (CVD) [4]. The most recent important advance in the quest for novel forms of carbon constitutes the isolation of graphene layers [5], which exhibit unique and exceptional electrical properties [6]. In addition, graphene nanoribbons have recently been synthesized and produced using diverse methods [7]. 

Carbon is unique among chemical elements since it exists in different forms and microtextures transforming it into a very attractive material that is widely used in a broad range of electrochemical applications. Carbon exists in various allotropic forms due to its valency, with the most well-known being carbon black, diamond, fullerenes, graphene and carbon nanotubes. This review is divided into four sections. In the first two sections the structure, electronic and electrochemical properties of carbon are presented along with their applications. The last two sections deal with the use of carbon in polymer electrolyte fuel cells (PEFCs) as catalyst support and oxygen reduction reaction (ORR) electrocatalyst. 

Figure 4.19 shows four allotropic forms of carbon. Allotropes are different crystalline or molecular forms of the same element that differ in physical and chemical properties. 

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