2.3 Graphene Oxide
Graphene Oxide is single sheets containing defect sites arising from partial oxidation of the edge and basal plane and graphene is an atomically flat single layer of C-atoms with outstanding electrical, mechanical and photonic properties. Figure 1 below shows the structure of graphene oxide.
Figure 1: Structure of Graphene Oxide (Gao et al., 2009)
Graphene oxide is an amorphous with an sp2 hybridised carbon (graphene) base littered with oxygen groups a C/O ratio of between 1.6 and 4 and a sheet thickness of 1 nm (from AFM) (Dreyer et al., 2010). The oxygen groups disrupt the sp2 base and then forming sp3 sites distorting graphene oxide in a corrugated fashion with a surface roughness of approximately 0.6nm (Dreyer et
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By using strong oxidizing agent, oxygenated functionalities are introduced in the graphite structure which not only expand the layer separation, but also makes the material hydrophilic. Hydrophilic mean that they can be dispersed in water. This properties has enable graphite oxide to be exfoliated in water by using sonification, ultimately producing single and few layer of graphene that has been known as graphene oxide. The properties of graphene oxide is its easy dispersability in water and other organic solvents, as well as in the different matrixes due to the presence of the oxygen functionality (Jesus de La Fuente., 2011).
Karthikeyan Krishnamoorthy et al., 2011 has proven that graphene oxide can act as a photocatalytic material because of their photocatalytic properties based on their past research. The photocatalytic characteristics of graphene oxide were investigated by measuring reduction rate of resazurin into resorufin as a function of UV irradiation time. Change in color from blue resazurin into pink resorufin followed by absorption spectra were observe in order to know its progress of photocatalytic reaction.
2.4 Band gap of graphene oxide
Band-gap is the difference in the energy levels between these two states of valance band (VB) and conduction band (CB). When photons of energy E≥Eb are incident on a bandgap material, a photo-generated electron is excited to the conduction band
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At i) the photoelectron can recombine directly with its hole pair of positive where the arrow shows the electron (negative) goes directly to the hole pairs. Next, the second part ii) represent the photoelectron can recombine at a trap as it stop at the middle of the band gap and for final part, iii) states that a photoelectron can transfer to an absorbed species either to encourage a particular (redox) reaction or which is considered a contaminant (Gao et al., 2009).
Figure 2B: FTIR Spectrum of Graphene Oxide
Based on figure 2B, the past research that has been made by Karthikeyan Krishnamoorthy et al., 2011, the FTIR spectrum of graphene oxide shows that the presence of C=O.1728 cm-1, C–OH.1413 cm -1, C–O–C.1250 cm-1, and C–O (1050 cm-1). The peak at 1600 cm-1 arises due to the C–C vibrations from the graphitic domains. The relatively broad peak is at 3260 cm-1 is due to the adsorbed water content in the surface of graphene oxide. All these functional groups present in the graphene oxide makes them hydrophilic nature while the graphite and graphene are hydrophobic in nature.
Figure 2C: UV-vis Spectra of Graphene Oxide
During the light reactions is when the sun’s energy is converted into ATP and NADPH, which is chemical energy (Campbell, 1996). This process occurs in the chloroplasts of plant cells. Within the chloroplasts are multiple photosynthetic pigments that absorb light from the sun (Campbell, 1996). Photosynthetic pigments work by absorbing different wavelengths of light and reflecting others. These pigments are divided into two categories: primary (chlorophyll) and accessory (carotenoids) pigments.
To start with, the first separation technique we performed on the heterogeneous mixture was filtration. According to our observations of the residue, we believed graphite was one of the substances in the mixture. Graphite, a known ingredient used in pencils, is black or dark grey in color, like the dark spots on the filter paper (Figure 1B), and has the ability to leave marks on paper and other objects. Of the potential components given to us, only graphite possessed the ability to make a mark on other surfaces. This was supported by the smudges left behind on our finger and filter paper (Figure 1A, bottom filter paper) when we touched the residue.
The large electronic bandgap (around 5.5eV) is well suited for stable high temperature applications. This is because as the temperature of the system increases the bandgap decreases, so because of the large starting value of diamond the band gap will still be wider than that of silicon and other such substances at high temperatures. This bandgap can be linked into the a corresponding wavelength of 225nm which means that diamonds can only absorb the far end of ultraviolet and vacuum ultraviolet (VUV) radiation. This leads to DLC films being considered as solar insensitive which allows them to absorb high VUV intensities while remaining reliable throughout. This allows them to be used in laser power monitors, for UV detection in the next generation of photolithography .
that The Speckled Band is a product of its time as there is a lot of
As we begin to look at how diamonds are formed it’s important to understand a little about the composition. Graphite which is used for pencil lead and a lubricant is pure carbon just like a diamond. So the hardest mineral and one of the softest share the same composition. The difference is in the bonding. Diamonds have covalent bonds that form a three dimensional structure. Graphite also has covalent bonds that form together in sheets with much weaker electrostatic bonds. These bonds also known as van der Waals bonds are what makes graphite so soft (Charles C Plummer).
Answer: It is the difference between interfacial conduction band edge (Ec) and the Fermi level (Ef). From the figure below we get a better idea of the barrier height which is given by ΦB(PhiB).
Graphene has received great mass media coverage since Geim and Novoselov published their foundlings about monocrystalline graphitic films in 2004, which won them the Nobel Prize in Physics in 2010. (Novoselov et al, 2004) It has been described as the wonder substance or super material by the mass media, not only because it is the thinnest material ever known and the strongest ever measured, but also due to its excellent electrical, thermal, mechanical, electronic, and optical properties. It has high specific surface area, high chemical stability, high optical transmittance, high elasticity, high porosity, tunable band gap, and ease of chemical functionalization which helps in tuning its properties (Geim et al, 2007) Moreover, graphene has a multitude of amazing properties such as half-integer room-temperature quantum Hall effect (Novoselov et al, 2007), long-range ballistic transport with almost ten times greater electron mobility than that of silicon, and availability of charge carriers that behave as massless relativistic quasi particle, known as Dirac fermions. (Geim et al, 2007) The outstanding electrical conductivity and the transparency and flexibility of graphene-based material have led to research and development of some future technologies, such as flexible and wearable electronics. In addition, graphene can also be used for efficient energy storage materials, polymer composites, and transparent electrodes. (Geim et al, 2007) This paper presents a
The sequence of bands might be considered similar to the image of layers of electrons around the nucleus of an atom.
Individual atoms can emit and absorb radiation only at particular wavelengths equal to the changes between the energy levels in the atom. The spectrum of a given atom therefore consists of a series of emission or absorption lines. Inner atomic electrons g... ... middle of paper ... ... a sensitive multielement inorganic analyses.
The main purpose of green nanotechnology has been to develop clean technologies that would minimize potential human and environmental health risk. Also, to encourage replacement of existing products with the clean technologies that is more environmentally friendly. There are many benefits of using green nanotechnologies as the new solution for energy in both their current availability and their current development. Over the new few decades, the highest growth opportunities will come from application of nanomaterials for making better use of existing resources. Nanotechnologies will help reduce weight of carbon emission in transportation utilizing nanocomposite materials that quickly diffuses across the automotive and aerospace industries. Applications of nanotechnologies will result in a global annual savings of 8000 tons of carbon dioxide, which will rise even further to over millions tons by 2020. But, let’s focus on the positive effects of Green Nanotechnology in Solar.
The output phosphor, made of zinc cadmium sulfide, is where the electrons produced through photoemission will interact and produce light. It is extremely important that the path of the electrons from the photocathode to the output phosphor be precise.
Grundmann, Marius. Physics of Semiconductors: An Introduction Including Devices and Nanophysics. New York: Springer, 2006. Print.
A Diamond is one of the two natural minerals that are produced from carbon. The other mineral is Graphite. Even though both of these minerals are produced from the same element ,carbon, they have totally different characteristics. One of the most obvious difference is that Diamond is hard and Graphite is soft. The Diamond is considered to be the most hardest substance found in nature. It scores a perfect ten in hardness. Because of its hardness a tiny Diamond is used as a cutting and drilling tool in industry. Even the Greeks called the Diamond “adamas” which means unconquerable. Diamonds also conducts heat better than any other mineral .
The photovoltaic effect, electricity can be created directly from sunlight. Some semi-conductor materials that are exposed to sunlight can create electron-hole pairs, which can be collected to produce electricity. This occurs when photons have energy above a certain threshold. These photons have shorter wavelengths. In silicon, the threshold for electron-hole production is in the infrared region of the electromagnetic spectrum.