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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

how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
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
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
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Damian
silver nanoparticles could handle the job?
Damian
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Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply

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Source:  OpenStax, Nanomaterials and nanotechnology. OpenStax CNX. May 07, 2014 Download for free at http://legacy.cnx.org/content/col10700/1.13
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