Wednesday, May 31, 2017

Agilent Cary 100 Ultraviolet-Visible (UV-Vis) Spectrometer

Agilent Cary 100 Ultraviolet-Visible (UV-Vis) Spectrometer


Below are some links that helped our understanding of the Agilent Cary 100 Ultraviolet-Visible (UV-Vis) Spectrometer:

http://www.agilent.com/en-us/products/uv-vis-uv-vis-nir/uv-vis-uv-vis-nir-systems/cary-100-uv-vis/ordering-details

https://www.qui.ufmg.br/wp-content/uploads/2013/10/Cary_100_Specifications.pdf


In order to learn more about this instrument one of our research students Brendan Waffle gave some experts a call to ask them some questions.

Thursday, May 25, 2017

SEM Grids And Software

New software that could be used with the SEM;

SmartSEM - https://www.zeiss.com/microscopy/us/products/microscope-software/smartsem.html
Gwyddion - http://gwyddion.net/
Scope Plus Image Processing Software Package - http://www.2spi.com/item/09353-ab/

Grids that can be physically placed in the SEM;

https://www.tedpella.com/sem_html/SEM-grids.htm
http://www.2spi.com/category/grids-sem/grids/

SEM for Physics Laboratory; Article Overview

The post is with regards to the paper by Randolph S. Peterson, Karl Berggren and Mark Mondol on using the Scanning electron microscope as an accelerator for Physics Laboratory.

The paper primarily exploits the use of the SEM as an accelerator in a physics lab. Access to a traditional accelerator is limited to a few number of universities and comparatively, SEMs can be found more commonly. A SEM can be used as a low scaled single-ended accelerator with accelerating potentials ranging from 50kV - 3MV (30kV most common).

The idea of using the SEM as an accelerator is that a beam electrons/particles are accelerated through beam-shaping magnets to hit a beam-target. A Faraday cup can be used to measure the current that the beam receives. 

[Faraday Cup: a metal (conductive) cup designed to catch charged particles in vacuum to determine the number of ions or electrons hitting the cup.
https://en.wikipedia.org/wiki/Faraday_cup]



Condenser Lens 1/Condenser Lens 2 - Field/Condenser Magnets
Condenser Lens 3 - Objective Lens


Certain controls of the SEM can be relabelled to help physics students to relate a SEM to an accelerator system. Such as,

          SEM                    ------------>     Accelerator

Contrast & Brightness                        Detector Range & Gain
Magnification (MAG)                          Scanning Magnet Control
FOCUS                                              Objective Magnet Control
SPOT SIZE                                        Condenser Magnet Control

The magnetic focusing has an observable effect that is the change in direction (angle of rotation) due to the changing magnetic field. The image of the SEM can be seen to rotate from the expected position (spiral motion) that can be predicted from -ev X B of the objective lens (lens 3)

A suitable application that the SEM can be used for in physics lab is to measure the deBroglie wavelength from the diffraction aperture in the SEM. The experimental physics work that can be done using SEM is accelerator physics, atomic physics, and electron-solid interactions. 




Wednesday, May 24, 2017

Quantum Dots

What are Quantum Dots?

Image result for quantum dots

Quantum Dots are very small semiconductor particles, so small that their optical and electronic properties differ from those of larger particles. They are the most prominent aspect in nanotechnology. Many types of quantum dots will emit light of specific frequencies if electricity or light is applied to them. These frequencies can be precisely tuned by changing the dots' size, shape and material, giving rise to many applications.

Below are some links I found to help better my understanding of Quantum Dots:

https://en.wikipedia.org/wiki/Quantum_dot

http://www.trustedreviews.com/opinions/quantum-dots-explained-what-they-are-and-why-they-re-awesome

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660652/

http://onlinelibrary.wiley.com/doi/10.1002/rcm.4273/abstract

http://www.physics.buffalo.edu/faculty/APetrou/QD_Intro.pdf

Below is an article I found regarding studying quantum dots through spectroscopy:
https://ww3.haverford.edu/physics/Amador/links/documents/SpectroscopyQuantumDotsLab.pdf

Photoelectric Effect:
Image result for photoelectric effect

E=hv

Tuesday, May 23, 2017

Summary- x-ray spectra and Moseley's law using SEM

This experiment is based on the use of the Scanning Electronic Microscope (SEM) in the Saints Center. The Bohr-Rutherford shell model of atomic structure can be used to understand how the SEM performs an elemental analysis using x-rays. The students can measure the K-alpha and K-Beta x-ray  spectra from various metals. These metals can range from atomic numbers between 12 and 41. This can be used to verify Moseley's Law. Moseley's law is an empirical law concerning the characteristic x-rays that are emitted by atoms. (For more on Moseley's Law).

In performing this experiment the students would be taking several photographs/snapshots from the SEM. After taking the photographs the students will be taking measurements of the x-ray spectra of different types of elements in order to analyze the variation of the x-ray spectra with the atomic number. The students will need to be first trained on the SEM of course and then taking the photographs and spectra for a number of elements (approximately 15, taking roughly an hour). The student scan present their data as a function of atomic weight or atomic number, Z. Once this is done a Moseley Plot can be made by taking the square root of x-ray energy vs. Z, using Moseley's Law shown below. This plot should show a linear relationship between the measured quantity, square root of E, and atomic number, Z.

The energies of the x-ray spectra can be fit using this function, which is referred to as Moseley's law.
E=hv=B(Z-sigma)^2
Where B and sigma depend on the family of x-ray lines. B involves Rydberg energy and sigma is like a type of screening parameter.

Another useful equation is the Bohr equation for hydrogenic transition energies, E, that predicts the hydrogenic energy levels of a single electron orbiting a nucleus with a positive charge.
E=R(1/(nf^2)-1/(ni^2))*Z^2
Where nf is the principal quantum number of the final state and ni is of the initial state. R is the Rydberg constant and Z is the effective nuclear charge (Z-sigma).



X-Ray Fluorescence on Microelectronics

http://pubs.acs.org/doi/abs/10.1021/ac00295a809?journalCode=ancham

Possible SEM Labs

https://www.bowdoin.edu/faculty/rbeane/pdf/BeaneSEM2004.pdf
http://www.azonano.com/article.aspx?ArticleID=4118
http://www.imaging-git.com/science/electron-and-ion-microscopy/morphology-nanoparticles


http://www.rrp.infim.ro/2013_65_2/art23Dinescu.pdf

Mass Spectroscopy

The two types of Mass Spectrometers that we have access to in the SAInT Center are:

Bruker Autoflex Speed MALDI TOF-TOF Mass Spectrometer 

Matrix-assisted laser desorption ionization (MALDI) is a mass spectrometry technique used to determine the identity of a large range of molecules including DNA chains, proteins, large organic molecules, and fragile polymers that would be destroyed by other mass spectrometry techniques.  MALDI analysis is especially important for biological applications since it can analyze very low concentrations and is the main instrument used in proteomics and polymer material analysis.

Bruker Maxis Impact HD Q-TOF Mass Spectrometer

Liquid Chromatography High-resolution Mass Spectrometry (LC-HRMS) is a tandem technique that combines chromatography to separate chemical mixtures and mass spectrometry to identify and quantify chemical compounds. This form of analysis has wide applicability to chemistry and biochemistry and is routinely employed in pharmaceutical industry, food and environmental analysis, and for proteomic and metabolomic applications.  The high-resolution mass spectrometer (HRMS) component of this instrument aids in identifying chemical compounds by providing accurate mass data that is used to elucidate the identity and quantity of elements present in a molecule.

So how does a Mass Spectrometer work?

Some of the following sites prove useful in understanding how this machine works, and how we plan on using it for our research: https://www.bruker.com/products/mass-spectrometry-and-separations/maldi-toftof/autoflex/overview.html

https://www.physics.uci.edu/~advanlab/massspec.pdf







The following websites were provided by Dr. McColgan regarding using the MALDI instrument to study hair samples for corn:





https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4613234/


(m/z) = (2eU/L^2)*t^2

Where
m = Mass
z = Charge
e = Elementary Charge
U = Acceleration Voltage
L = Path Length
t = Time

List of SAInT Center Instruments at:
https://www.siena.edu/centers-institutes/saint-center/instrumentation-of-the-saint-center/#sthash.NQBMuMPv.dpuf

Monday, May 22, 2017

Hair Samples in the SEM

An interesting phenomena that has fascinated Dr. Rose Finn and scientists around the world is this idea that we are made of corn. Now, I know what you might be thinking, "No way we are made of corn!" Obviously humans aren't literally made of corn, but corn is in almost every processed food. High Fructose Corn Syrup is the least expensive sweetener available and used in almost every manufactured food product that uses a sweetener. Therefore, our bodies are made up of a good percentage of corn/maize. Using the Scanning Electron Microscope, we plan on studying a number of hair samples where we can see the chemical composition of our hair. Hopefully, we will discover a direct correlation to our hair and corn. 

CORN!!!
Image result for CORN
Below is a link to a lab write-up of hair analysis on the SEM:
https://www.jstor.org/stable/1142283?seq=1#page_scan_tab_contents

A brief summary of the article above is as follows. Hair identification under the Scanning Electron Microscope (SEM) has played a significant role in the field of forensic investigation. No two strands of hair are completely identical, so looking at hair samples under the SEM can be the difference in solving crimes and catching criminals. All types of hair can be examined under the SEM from all types of mammals that naturally grow hair. This includes head hair, pubic hair, and body hair. Some mammals grow hair in wave patterns, while others grow hair continuously. Mammals such as sheep and humans fall under this category of mammals that grow hair continuously. Of the 18 orders of mammals, all grow differently structured hair.
To study a hair sample there is a specific way to prepare a sample.Hair samples are mounted on metal stubs with either double-stick cellophane tape or conductive paint on the ends. The hairs are then metal vaporized with a thin-layer of aluminium, coating the sample with a featureless metal at a thickness of less than 200A, which is under the resolution of the SEM. The variability of human hair in each race is greater than the variability of hairs on a single individual's head. The dividing line between large and small hairs is about 95u. In this article there are Figures 1-7 that depict what different types of hairs look under the SEM. Overall, SEM research used in investigative crime studies is very important and would be really interesting to study in our own SAInT Center using our own SEM. First we would just need approval to study human hair samples.

Below is a link that tells us the essential elements in a piece of corn.
http://www.farmwest.com/node/941

Below are other useful links that are related to this topic:
https://www.washingtonpost.com/news/wonk/wp/2015/07/14/how-corn-made-its-way-into-just-about-everything-we-eat/?utm_term=.d9b31f5cc5ed

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4989398/

(We will post data collections of what we find once we get into the SAInT Center and take data)

Isn't that A(maize)ing! :)

What we will be using is a Hitachi SU1510 Scanning Electron Microscope (SEM).

Things to do:
Test dog hair/ hair from Dr. McColgan's hair dresser (Cannot test Human Hair yet)

Summer 2017 Literature and Data Links


An undergraduate experiment on x-ray spectra and Moseley's law using a scanning electron microscope:https://physlab.lums.edu.pk/images/7/73/An_udergraduate_experiment_Ref4.pdf

The scanning electron microscope as an accelerator for the undergraduate advanced physics lab:
http://www.rle.mit.edu/qnn/documents/Peterson-2010-78.pdf

Advanced Physics Laboratory Manual - Edited by J.W. Hammer

https://www.physics.utoronto.ca/~phy326/xrf/

https://www.physics.utoronto.ca/~phy326/xrf/APPENDIX%20A.pdf