20.109(F09): Mod 3 Day 2 Phage nanowires

Phage nanowires

Introduction

Edited from material originally written by the Belcher lab. Special thanks to Mark Allen, John Burpo.

The materials prepared in this lab have activity as battery electrodes. The redox properties of the material will determine the operating voltage of the electrode, while other properties of the material will improve capacity (how long the battery will last under a given current load) and rate capability (how quickly the battery can be discharged or charged). Capacity and rate capability can be improved by either making materials very small (nanomaterials) or by incorporating conducting metals into the matrix of the material.

Assembly and testing of the phage-based battery will take place over several sessions. Today's lab will focus on material synthesis. The next lab will be analyzing material by TEM. In the final sessions of the module, dried materials will be formed into electrodes, and finally, these materials will be assembled into a coin type battery and tested. In this lab, each group will make both an anode battery cell and a cathode battery cell.

File:Charge Discharge.png

400px

In order to determine the capacity of each battery we will be testing each battery on a Galvanostat. This is a machine that can apply either positive or negative current in order to either charge or discharge a battery with a specific amount of current. As an example, look at your cell phone battery, if you have a typical LiCoO2 lithium ion battery you will notice that it has a voltage (3.7 V) and a capacity (mine is 1100 mAh). We know that LiCoO2 has a theoretical capacity of 130 mAh/g, so in my battery I must have about 8.5 g of active material in my cell phone battery. The way that the capacity and voltage was determined was identical to what you will be doing in this lab, i.e. they hooked up my battery to a Galvanostat and applied a constant current (1100 mA) in order to charge the battery in one hour, and the applied a negative current of 1100 mA to discharge my battery in one hour. Figure 2 is an example of the curve that you will be generating. This is a charge/discharge curve for FePO4.2H2O, the positive slope curve is the charge curve and the negative slope is the discharge curve. The plateau centered around 3 V corresponds to the operating voltage of the battery. In answering the questions in this lab, you will be able to compare the capacity of each of your batteries, you can compare the operating voltage and if there is time you can look at cycling of the battery if you are able to come back and look at how well your battery performs after several cycles.

Protocols

Part 1: Dilute the 8#9 phage stock

Count the number of plaques on your phage titering plates from last time. Calculate the concentration of phage in your undiluted purified phage sample. Be sure to take into account each dilution when you try this calculation. Express the concentration as PFU/ul and determine the volume of phage needed to make 10 ml of 3.5x10^7 PFU/µl.

Part 2: Template the gold and silver on the phage

1. Add 15ml CTAB, 10ml water, 10ml of phage (3.5x107pfu/µl), and 1ml of Au+; rock for two hours.
2. Add 300µl ascorbic acid; 150 µl Ag+; incubate overnight.

Part 3: Research proposal

Writing a research proposal requires that you identify an interesting topic, spend lots of time learning about it, and then design some clever experiments to advance the field. It also requires that you articulate your ideas so any reader is convinced of your expertise, your creativity and the significance of your findings, should you have the opportunity to carry out the experiments you’ve proposed. To begin you must identify your research question. This may be the hardest part and the most fun. Fortunately you started by finding a handful of topics to share with your lab partner. Today you should discuss and evaluate the topics you’ve gathered. Consider them based on:

• your interest in the topic
• the availability of good background information
• your likelihood of successfully advancing current understanding
• the possibility of advancing foundational technologies or finding practical applications
• if your proposal could be carried out in a reasonable amount of time and with non-infinite resources

It might be that not one of the topics you’ve identified is really suitable, in which case you should find some new ideas. It’s also possible that through discussion with your lab partner, you’ve found something new to consider. Both of these outcomes are fine but by the end of today’s lab you should have settled on a general topic or two so you can begin the next step in your proposal writing, namely background reading and critical thinking about the topic.

A few ground rules that are 20.109 specific:

• you should not propose any research question that has been the subject of your UROP or research experience outside of 20.109. This proposal must be original.
• you should keep in mind that this proposal will be presented to the class, so try to limit your scope to an idea that can be convincingly presented in a ten minute oral presentation.

Once you and your partner have decided on a suitable research problem, it’s time to become an expert on the topic. This will mean searching the literature, talking with people, generating some ideas and critically evaluating them. To keep track of your efforts, you should start a wiki catalog on your OpenWetWare user page. How you format the page is up to you but check out the “yeast rebuild” or the “T7.2” wiki pages on OpenWetWare for examples of research ideas in process. As part of your “for next time assignment” you will have to print out your wiki page specifying your topic, your research goal and at least five helpful references that you’ve read and summarized.

DONE!

For next time

Define your research proposal or exhibit ideas by making a wiki page to collect your thoughts and resources (you can do this on one page with your partner or split the effort and each turn in an individual page).
Keep in mind that your presentation to the class will need:

• a brief project overview
• sufficient background information for everyone to understand your proposal
• a statement of the research problem and goals
• project details and methods
• predicted outcomes if everything goes according to plan and if nothing does
• needed resources to complete the work

You can organize your wiki page along these lines or however you feel is most helpful. Print your user page(s) for next time, making sure it defines your topic, your idea and some references you've collected and summarized.

==Reagents list==