<< Chapter < Page Chapter >> Page >

Filter the sample solution by using a Pasteur pipette stuffed with a piece of cotton wool at the neck. Any suspended material like dust can cause changes in the spectrum. When working with dilute aqueous solutions, sweat itself can have a major effect and so gloves are recommended at all times.

Sweat contains mainly water, minerals (sodium 0.9 g/L, potassium 0.2 g/L, calcium 0.015 g/L, magnesium 0.0013 g/L and other trace elements like iron, nickel, zinc, copper, lead and chromium), as well as lactate and urea. In presence of a dilute solution of the sample, the proton-containing substances in sweat (e.g., lactate and urea) can result in a large signal that can mask the signal of the sample.

The NMR probe is the most critical piece of equipment as it contains the apparatus that must detect the small NMR signals from the sample without adding a lot of noise. The size of the probe is given by the diameter of the NMR tube it can accommodate with common sizes 5, 10 and 15 mm. A larger size probe can be used in the case of less sensitive samples in order to get as much solute into the active zone as possible. When the sample is available in less quantity, use a smaller size tube to get an intrinsically higher sensitivity.

Nmr analysis

A result sheet of T 2 ­ relaxation has the plot of magnetization versus time, which will be linear in a semi-log plot as shown in [link] . Fitting it to the equation, we can find T­ 2 and thus one can prepare a calibration plot of 1/T 2 versus S/V of known samples.

Example of T 2 relaxation with magnetization versus time on a semi-log plot.

Limitations of the t 2 Technique

The following are a few of the limitations of the T 2 technique:

  • One can’t always guarantee no magnetic field gradients, in which case the T 1 relaxation technique is to be used. However this takes much longer to perform than the T 2 relaxation.
  • There is the requirement of the odd number of nucleons in the sample or solvent.
  • The solid suspension should not have any para- or ferromagnetic substance (for instance, organics like hexane tend to have dissolved O 2 which is paramagnetic).
  • The need to prepare a calibration chart of the material with known specific surface area.

Example of usage

A study of colloidal silica dispersed in water provides a useful example. [link] shows a representation of an individual silica particle.

A representation of the silica particle with a thin water film surrounding it.

A series of dispersion in DI water at different concentrations was made and surface area calculated. The T 2 relaxation technique was performed on all of them with a typical T 2 plot shown in [link] and T 2 was recorded at 2117 milliseconds for this sample.

T 2 measurement for 2.3 wt% silica in DI water.

A calibration plot was prepared with 1/T 2 – 1/T 2,bulk as ordinate (the y -axis coordinate) and S/V as abscissa (the x -axis coordinate). This is called the surface relaxivity plot and is illustrated in [link] .

Calibration plot of (1/T 2 – 1/T 2,Bulk ) versus specific surface area for silica in DI water.

Accordingly for the colloidal dispersion of silica in DI water, the best fit resulted in [link] , from which one can see that the value of surface relaxivity, 2.3 x 10 -8 , is in close accordance with values reported in literature.

1 T 2 1 T 2, bulk = 2 . 3 x 1 0 8 ( S V ) 0 . 0051 size 12{ { {1} over {T rSub { size 8{2} } } } ` - `` { {1} over {T rSub { size 8{2, ital "bulk"} } } } =2 "." 3`x`1`0 rSup { size 8{ - 8} } \( { {S} over {V} } \) ` - `0 "." "0051"} {}

The T 2 technique has been used to find the pore-size distribution of water-wet rocks. Information of the pore size distribution helps petroleum engineers model the permeability of rocks from the same area and hence determine the extractable content of fluid within the rocks.

Usage of NMR for surface area determination has begun to take shape with a company, Xigo nanotools, having developed an instrument called the Acorn Area TM to get surface area of a suspension of aluminum oxide. The results obtained from the instrument match closely with results reported by other techniques in literature. Thus the T 2 NMR technique has been presented as a strong case to obtain specific surface areas of nanoparticle suspensions.

Bibliography

  • G. R Coates, L. Xiao, and M.G. Prammer, NMR Logging: Principles&Applications , Halliburton Energy Services, Houston (2001).
  • B. Cowan, Nuclear magnetic resonance and relaxation , Cambridge University Press, Cambridge UK (2001).
  • W. E. Kenyon, The Log Analyst , 1997, 6 , 2.
  • A. E. Derome, Modern NMR Techniques for Chemistry Research , Vol 6, Pergamon Press, Oxford (1988).

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied

Get the best Nanomaterials and nano... course in your pocket!





Source:  OpenStax, Nanomaterials and nanotechnology. OpenStax CNX. May 07, 2014 Download for free at http://legacy.cnx.org/content/col10700/1.13
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Nanomaterials and nanotechnology' conversation and receive update notifications?

Ask