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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 is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
advantages of NAA
Sai Reply
how I can reaction of mercury?
Sham Reply

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Source:  OpenStax, Physical methods in chemistry and nano science. OpenStax CNX. May 05, 2015 Download for free at http://legacy.cnx.org/content/col10699/1.21
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