I thought I should discuss surface plasmons a bit because they are a part of our research and just plain cool. So get pumped, it’s time for surface plasmons! Let’s start with the basics. We know surface plasmon resonance is an effect that has to do with light but what exactly is light?

Light is a wave (don’t forget there’s some particle duality too, but I won’t focus on that) that consists of oscillating electric and magnetic fields. So what happens when visible light hits things? Like glass and water and squids? Well, many of these phenomena we see every day: the light can be transmitted through, refracted (Yay Snell!), reflected (which we observe as colors), and lots more. But what happens when we shine light onto something really small, I mean nanoscale small, and what if that something happens to be gold? Say a gold nanoparticle?

Well if the size of the gold nanoparticle is within a certain range compared to the wavelength of the light, those oscillating electric fields can induce a dipole (separation of charge) across the gold nanoparticle, like so:

The Go-To Image for explaining surface plasmon resonance in nanoparticles. Look at those electrons ride that sick wave!

This creates collective oscillations of free electrons in the metal. These oscillations are in resonance with the frequency of the light, hence why this is called surface plasmon resonance. Surface plasmon resonance occurs in other metals as well, just at different frequencies. Silver and copper nanostructures have surface plasmon frequencies within the visible light spectrum as well, while other metals will have plasmon frequencies at longer or shorter wavelengths. The frequency can also be tuned by the size and shape of the nanostructures (they don’t have to be spherical like in the picture above). As the structures become larger, longer wavelengths (like infrared) must be used to excite surface plasmons. Conversely, as smaller structures are used, shorter wavelengths must be used (like ultraviolet). However, at a certain point the structures are too small and quantum effects start to dominate, so surface plasmon resonance ceases. At this point, I have to just throw my hands up in the air, take some quantum physics classes, and let you know that “I’ll get back to you on how that works.”

These oscillating electrons now have some additional energy. We can use these energetic electrons for various purposes, including solar water splitting devices (what first attracted me to the Moskovits group), photovoltaics, and photocatalysis. I’ll save that for a future blog post but let’s bring this back into everyday life. I said that changing the size of the nanoparticles alters the plasmon frequency, so what if we place nanoparticles of different size in different solutions? Well, the nanoparticles will absorb at different frequencies because of the different plasmon frequencies, so that means the reflected visible light will differ for each solution:

Beautiful. Science.

Finally, my mentor, Jose, has been in China for the last couple of weeks (so proud of him by the way, what a boss) and today was my first day back in the lab for a while. I just wanted to add how I really missed everything at the lab the last few weeks or so, not just the research, the surface plasmons, and the frustrating field effect transistors but the people who I get to work with and around. Though I may not always understand the many accomplishments of the Moskovits group, I feel privileged to be a part of the group and contributing to the research. I can’t say enough how amazing our group is, and I’m happy to have been able to learn so much from them and work with such great people!

Look at these beautiful and talented people!

Another quarter, another full work load.

This quarter I am taking a variety of physics and biology classes, mixed in with a couple exercise classes (if you work hard, you’ve got to play hard!). With all these classes I have learned a lot, and I’m pleased to be able to share it with all of you. So, if you’ve always wanted to take quantum but couldn’t find the time, no worries, I’ll give you the main idea behind it all. Or maybe you’ve always wanted to be a gymnast but never had the opportunity to pursue that dream. Well, with my beginner’s experience, I can give you a few pointers.* Here is a glimpse of what I’ve learned this winter quarter:

1) Quantum Mechanics: A physicist’s first method of attack for solving a differential equation is using something called separation of variables (now you can solve the Schrodinger Equation!**)

2) Advanced Mechanics: Almost all of those physics problems you solved in an introductory physics class (remember the classic block sliding down an incline plane, or those lovely masses attached to a string on a pulley?) can be solved in an arguably easier and more beautiful way, without directly using Newton’s Laws. You can thank a couple guys named Lagrange and Hamilton for what’s called Lagrangian and Hamiltonian mechanics (no disrespect, Sir Isaac Newton).

3) Complex Variables: A lot of those ugly integrals you thought you couldn’t do without  Wolfram Alpha*** can be solved relatively easily by hand using something called contour integration in the complex plane.

4) Thermodynamics/Statistical Mechanics: I will never forget that the Boltzmann Probability is proportional to exp(-βE_i )  (where β is a constant based on temperature and E_i  is the energy of the i-th state of a particle in a system of particles). This probably has no meaning to you, but if you ever take stat. mech. almost everything comes down to this.

5) Biochemistry: DO NOT cut out carbs completely from your diet, contrary to whatever any of the latest fad diets say.

6) Beginning Tumbling:  Don’t attempt a gymnastics move if you are afraid, otherwise you’ll chicken-out mid-air and hurt yourself when you try to stick the landing.

7) Weight Training: Feel the burn, be proud of the burn.

With all of these classes you may be wondering whether I’ve had time for my research. The answer is yes – my research is very important to me! I’ve made some very exciting progress on my project, and I’ve begun writing a paper! I’d love to say more, but alas, that is for another blog post!

*Nothing in this blog post should be used in lieu of taking an actual class. What I’ve written is only the tip of the iceberg for each of these classes!

**”Solving” the Schrodinger Equation entails a little more than this.

***I do not condone the use of Wolfram Alpha in place of doing an integral by hand.

Do not click on the link below (addictive website alert).

http://thegradcafe.com/survey/index.php 

I want to know whether I got into graduate school or not already! The feeling is comparable to waiting for a grade after you take a final, except this takes way longer and is much more important than just a grade. As time passes by, I get more and more anxious. Whenever I get a new e-mail, I’m crossing fingers it’s from the admissions committee (I get a fair amount of e-mails per day, so this is painful). Whatever their decision is, I just want to know it already. I know it’s still early, but I don’t like the time uncertainty of the notification. Some students hear back as early as January, while others have to wait until March or even April! I also dislike not knowing for sure what I am going to do after I graduate. If I knew I got in, then I could relax and not worry about anything. If I knew I didn’t get in, then I would start working on applications towards my back-up plans. For back-ups, I’m considering:

• jobs $$$
• research internships at DOE national labs. http://science.energy.gov/wdts/suli/
• Bridge to Doctorate programs. http://www.apsbridgeprogram.org/

I want to elaborate on the Bridge to Doctorate programs because it’s likely you haven’t heard about them. Up until a few months ago I had no idea these programs existed. Bridge to Doctorate programs are one-to-two years long programs designed usually for underrepresented students who plan to pursue a Ph.D. but want/need to strengthen their application. Although it varies from program to program, generally during a Bridge to Doctorate program the student receives a yearly stipend of around 30K/year, works full time in a research lab, can take undergraduate/graduate courses, and gets prepared for the GRE. I almost feel like a Bridge to Doctorate program should be a pre-requisite in order to apply for graduate school. You get to experience what it is to be a full-time researcher for a prolonged period of time, explore and define your research interests, prepare for GREs, and apply to graduate school without having to worry about your classes. And you are still getting a 30K stipend? Definitely worth looking into.

As I wait for graduate admission decisions, I’m trying to figure out what to do if I get a successful response. I only applied to two schools, so statistically wise the odds are against me. Comment if you have any suggestions, I’m open to semi-crazy ideas (i.e. shave my head, jump into the lagoon, ask a professor out for valentine’s in front of class?)

PROGRESS! After months of trying to fix our probing station, it is finally working! Now I can test and characterize devices and work on getting results! Reproducible results! Thanks to Jose (my mentor), our probing station is no longer an issue (take that probing station–except I love you). I was pretty stoked when this happened; it had been awhile since I had truly tested some of our devices. This of course does not mean the next steps will be easy but at least we have conquered that monster of an obstacle.

Working hard in the cleanroom with Jose.

The next step will be looking at the photoeffects on the nanowires covered with gold nanoparticles. This will show us the plasmonic effects on the gold nanoparticles, which we can monitor under different electrical conditions of our device. Though I have already done some testing with this, I would like to do more with our devices before drawing conclusions. There is still a lot of testing to be done in the future. We have also been having some issues with our nanowire growth (why nanowires, why now?). Therefore, we may be changing the design of our devices to have a thin film instead of a nanowire covered with gold nanoparticles. It is all very exciting and I aspire to seeing this work through.

On a completely different note, this quarter I have been able to better appreciate where I am. Last quarter, though very exciting and eventful, was a bit overwhelming at times and I did not have the chance to fully embrace the science around me. This quarter I am trying much harder to take in and relish the amazement. How often do we really get to focus on that warm fuzzy feeling that science and research gives us?

The plot thickens…

My favorite has been chalkboards. I remember when I was younger looking at chalkboards and papers, even in old textbooks, at massively complex equations with symbols and mathematical notation that was another language (but really, since much of these are Greek symbols). Now I can look at much of this same notation and understand it fully. Lately this has been a small but treasured pleasure of mine. It is like a mystery that slowly unfolds as I learn more. This is pretty inspiring to me; it is a sort of reality check: I have made progress, even compared to when I first came to UCSB. 

My point is, sometimes it is nice to savor the science. Sometimes I get wrapped up with the homework and grades, tests and finals, research and organizations, oh my! Though when I really step back and look at it all, would I really choose a different place?

Nope.