# 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 ...

11

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

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 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

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 ...

7

Is there any existing examples of single-molecule magnets with permeability that can be controlled via altering current flow just like in case of electromagnets? If not, is there an explanation why it is not possible? Short answers: no, and not yet. Longer answer, and a warning that I'm using recent results from my group as references: Yes, single molecule ...

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

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 ...

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 ...

4

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 ...

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 ...

4

According to the authors of Ref. 1 this is a general property. They provide an explanation for the stability of such sheets based on formation of particular buckled geometries: The discovery of a flat two-dimensional crystal known as graphene has contradicted Landau−Peierls−Mermin−Wagner arguments that there is no stable flat form of such crystals. Here, ...

3

You can use hydrated tri-sodium citrate, it's readily soluble in water. As for its chemical reactivity, it's identical to tri-sodium citrate. You should take into consideration the increase in the molecular weight in the hydrated form due to the presence of water molecules.

3

The reason reference electrodes are needed in 3 electrode solution cells is that you're trying to control the interfacial potential of the working electrode (basically from the surface to a point very near the electrode in solution). The wiki's kinda lousy, but the diagram explains essentially what the potentiostat is doing: It's controlling the counter ...

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

As indicated in the comment above, "magic numbers" (i.e., atom counts with much higher stability) have been known in atomic clusters of many types for a long time. Each magic number has a specific geometry. Some are non-spherical, so it's hard to make generalizations about surface area or lattice structure. A very famous non-gold example is ...

3

This nomenclature refers to a core-shell arrangement of nanoparticles. This is where you have a nanoparticle core consisting of one material that has been coated/decorated/wrapped/overlaid with another material. There are a few accepted forms of nomenclature for describing these types of nanoparticles: core@shell In your case, it would be Fe2O3@Au core-...

3

There is a fairly simple explanation of why small-enough particles are different from bulk materials. Once the particle becomes similar in size to the wavelengths of light involved then quantum effects start to matter for how the particle behaves. The actual mechanisms that give specific colour may vary, but the main point is that the size of the particle ...

3

I recall seeing a system that consisted of two planar components (and I am fairly certain those were aromatic) that could couple to form the product. The self-catalysis consisted of a product molecule acting as a template for two component molecules to absorb to, which was claimed to have increased the reaction rate. Edit: I have found the system I was ...

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