# Tag Info

13

I am sorry to say, but your question contains several false assumptions, most importantly: Nanotubes are good conductors: No, not all of them. Certain types have metallic/semi-metallic conductance, others are semiconductors. Single wall carbon nanotubes are generally indexed with a so-called chirality index (m,n) that tells you how the carbon sheet is ...

11

First, let's look at gold's properties. Gold is the most malleable of all metals. This malleability alone is very useful in aiding scientists to create such small gold nanoparticles. Gold also reflects infrared radiation very well and is an excellent conductor of heat and electricity. Generally, gold is not easily affected by oxygen and is generally ...

10

Coagulation is a process which involves coming together of colloidal particles so as to change into large sized particles which ultimately settle as a precipitate or float on the surface. Coagulation is generally brought about by the addition of electrolytes. When an electrolyte is added to a colloidal solution, the particles of the sol take up the ions ...

9

In short, graphite is several graphene sheets piled one above another. Graphene is made up of one single sheet of carbon atoms arranged in hexagonal pattern (like a honeycomb), and graphite are several such sheets, each sheet linked to another by weak intermolecular forces, which gives the graphite its lubricative properties. EDIT: Similarly, graphene ...

9

If the thiolate bounds to the Au nanoparticle, both the electronic, as well as the mechanical properties of the thiolate and the Au nanoparticle change. So you are going to monitor these changes with a spectroscopy susceptible to this, comparing the spectra of the pure starting materials with the one(s) of the decorated NP. One of the easier available ...

8

I don't know about the IR spectra of metals. Certainly metals will have vibrational spectra, but I'm sure where to find it (if NIST does not have). I can tell you how to get x/y data from NIST, if they have the spectrum. For example, for benzoic acid. At the bottom of the page, there is a link to download the sepctrum in JCAMP-DX format. The .JDX file ...

8

I don't know why everyone missed this point. At nanoscale materials tends to have some novel physical and chemical properties comparing to its macro scale. One such phenomenon which is seen especially in metal nanoparticles is Surface plasmon resonance (SPR) Wikipedia: "Surface plasmon resonance (SPR) is the resonant oscillation of conduction electrons ...

7

Density Functional Theory is worth investigating if you're looking for a fairly efficient way of investigating these interactions at an electronic level. The term 'nanoparticle' is wonderfully vague as it encompasses two to three orders of size magnitude - the size of the nanoparticle will inform the specific choice of method: Small (as in, only a couple of ...

7

FWIW, here are some Hückel calculations on the 5775 PAH. I'm showing the first 7 energy levels. Each molecular graph presents the contribution of each atom to the electron density ($\mathrm{Abs}[c_i]^2$). This is not normalized. I do not use wavefunctions, only the coefficients multiplying them, assuming $$\Psi_{\mathrm{mol}} = \sum_i^n c_i\psi_i$$ In ...

7

All three carbon modifications indeed contain covalently bond carbon atoms. The $sp^2$-hybridized C atoms are connected by $\sigma$ and delocalized $\pi$ bonds in all cases. It is the geometric arrangement of the atoms that differentiates the modifications: Stacked planes in graphite, fullerenes: ball-shaped molecules (hence the name buckyball), and for ...

6

I've done a little simulation as a senior year elective, though not in Matlab. Can you be a little more specific about how/what you're trying to model with nanoparticle growth? Perhaps direct us to an abstract or two. The first Monte Carlo simulation you should attempt is the drunken sailor problem. The basic idea is that you have a drunken sailor who has ...

6

I'm hardly an authority on graphene structures (only been reading the literature for about a year), but let me try to contribute. Unfortunately it seems that research into graphene and its derivatives is progressing at such a pace that it can be hard to standardize notation. I have actually previously had a small discussion on the internet regarding the ...

6

Graphite does not contain CNTs, a simple extraction therefore is not possible. Graphite seemingly can be converted to CNTs by a "simple" oxidative method published by DW Lee and JW Seo on arxiv.org in 2010. The authors claim to have used commercially available graphite powder (45 µm, Aldrich) of high purity (>99.995%), but did not provide any information on ...

6

There is known, but poorly understood $\pi-\pi$ stacking. While weak compared to covalent, dipole or ionic interactions, it still beats usual van-der-vaals interactions. Carbon nanotubes are, essentially, polycondensed aromatical systems, so they can and would interact with each other as aromatic systems via $\pi-\pi$ stacking

6

Disclaimer: I am not an expert on this Gold nanoparticles interaction with light is strongly dictated by their environment, size and physical dimensions. Small (~30nm) monodisperse gold nanoparticles absorb light in the blue-green portion of the spectrum (~450 nm) while red light (~700 nm) is reflected, yielding a rich red color. This absorption is due ...

5

In order to explain the Schuze-Hardy rule, you have to take into account that you are working with a colloidal dispersions stabilized electrostatically. The stability of this dispersions is well described by the DLVO theory. According to this theory, the particles interaction potential can be expressed as the sum of two contributions, $$V_T = V_A + V_R$$ ...

5

Yes, this is feasible in practice for a fair definition of "permanent". Monolayers (sheets a single atom thick) of graphene are impermeable to any gas, including helium. To be more precise, the bulk permeability rate for helium through graphene is very low, of the order of $10^{-15}\ mm\ g\ cm^{-2}\ s^{-1}\ bar^{-1}$. For comparison, it means a stack of ...

5

I believe that ethylene glycol in this reaction is used as a solvent and Aniline is used as a reducing agent. Ethylene glycol solution heated with chloroauric acid produces $Au^{3+}$ ions (first 20 min) which is then reduced to $Au^{0}$ (3hr reaction) in the presence of aniline. Because there is no stirring during those 3 hrs (so less agitation of the ...

5

Gold is special: Electrodes: gold electrodes are advantageous because bulk gold is inert, so electrodes are air/water stable (do not oxidise), such that devices are more reliable in the long term. Catalyst: gold nanoparticles can be used as a catalyst (high surface to volume ratio, unlike bulk gold), for filtering purposes for example. Quantum dots: gold ...

4

As Surface Plasmon Resonance phenomenon is mainly seen in metal nanoparticles, I don't know whether this answer will help you? The size dependent optical phenomenon of semiconductor nanoparticles (e.g., $\ce{CdS}$) can be explained using the effective mass approximation model. where r is radius of the particle (the rest details of the above equation can be ...

4

Short answer: "quantum clusters" is not widespread and likely confusing. I'd suggest "small nanoparticles" or perhaps "metal nano clusters." I can't comment on optical shifts, but many of these properties are distinct to the particular material and the onset of quantized energy levels in that material. So I doubt you can simply combine properties of quantum ...

4

One of the authors has recently established a research group at my university, so I spoke to a member of their lab: The corona phase is not exactly a phase in the thermodynamic sense, but rather the portion of the polymer in contact with the nanotube. In the below image (taken from the Nature Nanotechnology paper in question), the blue portion and the parts ...

4

While I can't find specific justification for the surface, the first competition involved both gold and silver "racetracks." Drivers gear up for world’s first nanocar race How to build and race a fast nanocar The competition involves propulsion and imaging using STM so the substrate must be conductive. Gold (and silver to a lesser degree) is particularly ...

4

All metals look black or dark when presented as a sufficiently thin powder. The metals display their color only when the dimension of the grain is greater than the wavelength of the light, namely 400 to 700 nm. This is about 1000 times bigger than the atoms. When prepared from a precipitation reaction, the metal atoms are never arranged neatly in a regular ...

3

Carbon nanotubes are not polar or ionic. Therefore I do not expect any ion or dipole intermolecular interactions. Since carbon has electrons, that only leaves us with dispersion forces (induced-dipole). Therefore carbon nanotubes exhibit dispersion as the only intermolecular force.

3

In part, your vision already exists and uses electrons as "ink". In a process kown as electron capture, a proton "swallows" an electron of sufficient energy and is thus converted to a neutron. $$\ce{^{A}_{Z}X + e- -> ^{A}_{Z-1}Y + \nu_{e}}$$ As a consequence, the atomic mass number A remains the same, but the atomic number Z is decreased by one: ...

3

The absorption spectrum of any material is related to the dielectric constant/refractive index. Since there are no sharp resonance peaks for metals in the infrared, the absorption spectrum is pretty boring. However, there are many sources of data for metals. The most comprehensive set of data is the Handbook of Optical Constants of Solids by Edward D. ...

3

It is caused by the wettability of the surface of the nanoparticles. For naked particles this will be determined by the properties of gold but, as Daniel mentioned, it is likely that there is a capping agent, in which case the wettability will be governed by the properties of the capping agent. From this point on I will just call this the solid. Collecting ...

3

For thermally grown amorphous $\ce{SiO2}$ films, a bandgap of 9.3 eV was measured by Weinberg. Measurements on $\alpha$-quartz by Calabrese give $E_g(\Gamma)$ = 6.3 eV, compared to 9.2 eV calculated by Chelikowsky and Schlüter. Calculations by Ramos on $\beta$-cristobalite with the space groups $Fd3m$ (face-centred cubic, fcc), $I\bar{4}2c$ (body-centred ...

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