After working for two weeks in Professor Crowther’s lab, I have learned a number of skills and techniques. Before joining Professor Crowther’s lab, I had taken two years of Barnard College chemistry classes including general, organic, and quantitative analytical chemistry. Although these classes have shaped me into the chemist I am today, Professor Crowther’s research is in the subfield of physical chemistry and materials chemistry based in part on quantum chemistry - a class I will take in Fall 2017. Beginning research without this course was very intimidating, especially during the first few days. A lot of the information seemed to go over my head. However, Professor Crowther patiently and calmly explained the theory behind the research, and my understanding of the work has increased significantly.
My project in Professor Crowther’s lab involves investigating how chemical reactions affect the electronic properties of graphene. Graphene is a two-dimensional carbon material, making it the thinnest material that exists. It is made up of carbons connected in a honeycomb lattice. Despite being over a million times thinner than hair, graphene is also stiffer than steel. I will be investigating graphene’s potential as an electronic material by performing reactions on graphene samples and observing how these reactions change its electronic properties.
The first few weeks are memorable due to the amount of knowledge I have gained. I have learned a lot of the theory behind my project and many experimental techniques I will use. I learned how to make graphene samples using graphite flakes and Scotch tape. The fact that the material I will be conducting experiments on can be made with Scotch tape is incredible. After preparing these samples, I analyze them under an optical microscope to identify graphene that I will be able to conduct experiments on. This part is rather frustrating because I still have difficulty finding one-layer graphene in the microscope due to its faint purple color. In order for a sample to be useful, the piece of graphene must be not only single-layer, but also must be large enough for subsequent experiments and stand alone as opposed to being near a graphite flake or a piece of graphene that is two or more layers. According to Professor Crowther, obtaining single-layer graphene is 67% skill and 33% luck. Despite making a plethora of samples, only one piece of one-layer graphene was found so far. Most of the graphene that I found was bilayer, which is useful for some experiments, but my work will focus mainly on one-layer graphene. After finding a piece of graphene, I obtain its Raman spectrum.
Raman spectroscopy, unlike IR absorption spectroscopy, is a scattering process. A laser strikes a sample and the scattered light is measured by a detector. The instrument is complex because the laser cannot hit the sample directly, but must first go through several optics, irises, and mirrors. As a result, the process of aligning the laser to take the measurements has many steps. I have spent the last two weeks being trained by Professor Crowther to use the equipment. I must first find the piece of graphene on the sample using a different microscope. Then, I must check the power of the laser before focusing the laser beam on the sample to ensure it strikes in the right position. When that is done, the alignment of the laser must be checked on the pinhole, so it enters the spectrometer slit. After checking all of the alignment, I can then begin measuring the spectra. Although, at first trying to remember all the steps was overwhelming, a few days ago I was able to successfully take Raman spectra of seven different samples. I am excited because I am now able to take these spectra faster and more confidently. Every time I align the Raman spectrometer and measure a spectrum, I go to Professor Crowther with fewer and fewer questions.
Although I have definitely learned a lot these last few weeks, I am also aware that I am nowhere near done with the training and learning necessary concepts and experimental techniques. I feel confident about operating the Raman spectrometer at this point, but next week Professor Crowther will teach me how to take spatial maps of the graphene samples. The laser hits the sample at one specific location so I can generate a Raman map of a graphene sample by taking spectra across the surface of the entire sample. This data will be particular useful for determining the homogeneity of graphene reactants.
In order to successfully obtain the data I need, I must first prepare more graphene samples. As previously mentioned, most of the samples I made had bilayer graphene which is not particular useful for the experiments I will be performing. Therefore, I hope to increase my sample library in the next few days. After doing so, I will take the initial Raman spectrum of each sample. I will also measure an initial Raman map of the graphene sample. After doing so, I will perform chemical reactions on the graphene. I will then measure a second Raman spectrum and map to observe the results of my experiments. Since it is still early in the summer, my goal for the next few weeks is to make many more samples to guarantee that I have a large number of one-layer graphene samples and start running some graphene reactions.
Additionally, I hope to further my knowledge of quantum chemistry. Every day I learn something new, including the theory behind spectroscopy or potential energy diagrams. These concepts prepare me for the class I will take in the fall and allows me to understand my work more completely. When I measure a Raman spectrum, I am aware of how the instrument works by scattering the light as it interacts with the sample. Understanding this interacting, makes me a better scientist.
Overall, I am satisfied with what I have achieved so far. While the lack of one-layer graphene samples is rather frustrating, the fact that I feel confident using the Raman spectrometer is gratifying. Before joining Professor Crowther’s lab, I had never seen a Raman spectrometer. The first time I used it, I was nervous that I would break something because I did not have a clear sense of what I was doing, but with more practice, I became more comfortable with it. Taking seven spectra without needing to go ask Professor Crowther many questions shows a huge improvement. I am excited to measure more spectra in the next few days and become more comfortable with the Raman spectrometer to the point where I can operate it independently.
In terms of STEM education, the information I have gathered from these last two weeks has definitely helped my understanding of science and technology due to different computer programs used to calibrate and analyze the Raman spectra. By understanding the theory behind the research, I will be able to explain and teach the material to someone else. Although I feel good about what I have learned so far, I recognize that I still have a long way to go!