Episode 11 – Plant Materials

LASER: Materials Science Podcast

Image of plant wires ( source)

This week on LASER we have a plant materials themed episode where we discuss cellulose nanocrystals for use in composites, using plants as wires for computing, and using green tea to synthesize gold nano-stars for cancer treatments, drug delivery, and photonics.

2:00 Introductions and Emily explains the shiny new lab she is working for!

4:30 we start in on “The Elastic Properties of nano-crystalline cellulose” calculated from first principals. (Article and PAPER)

6:20 the calculations from this paper come from Density Functional Theory, a complicated, but fairly accurate method of simulating material properties.

13:00 one good application for cellulose nanocrystals is in short-fiber composites.

14:00 its not exactly like glass…

19:20 Alex has never listened to an episode of the podcast.

20:20 This paper (published on the arXiv) is called “Towards Plant Wires” from “The Unconventional Computing Centre” of “University of the West of England”

21:20 the only electrical measurements made on plants in the past were impedance measurements on cucumbers to measure their physiological state? This seems strange, let us know if you’ve found anything else. ***We also found http://link.springer.com/article/10.1023/A:1004684310108 Measurement of the activation enthalpies of ionic conduction in apples” ***

22:20 they measured the electrical properties of 3-4 day old lettuce sprouts!

25:00 The resistances measured from these lettuce seedlings is in the Mega-Ohm range (1000000 Ohms), so the measurements suggest the plants are insulators.

26:50 Cameron has some problems with the methods of making contact to the plant.

27:50 we mixed up the units, Distilled water is 0.2 MOhm-meters, while DI water is 15MOhm-cm, so the distilled water is really only 0.002MOhm-cm, much lower than the resistivity measured.

42:15 This paper (also from the arXiv) is titled “Green tea induced gold nanostar synthesis mediated by Ag(I) ions”
43:35 They use Green Tea to reduce Silver Nitrate which then helps the formation of gold nanostarts that nucleate on the Silver ion

47:00 Gold nanostars are useful for photonic applications (LEDs, photovoltaic/solar materials, like Quantum Dots), drug delivery (where we can put drugs on or inside the nanoparticle, then functionalize the material to only attach to certain cells, and then deliver drugs directly where we want to in the body), and cancer imaging (where cancer cells will uptake more nanoparticles and then they are easy to image using Near-Infrared radiation.

52:30 I asked @thecollapsedpsi on twitter, and @murphyslab responded to say that citrate is often used to reduce Au3+, so they think it is likely that green tea could be used. Thanks for the quick answers!

54:20 what were their motivations for even trying green tea? they mention it is a “green” process and “non-toxic” but we don’t really buy the non-toxic argument without more analysis.

58:00 Thanks to Alfonso for leaving us a rating on iTunes and a comment on the website!

Instead of being topically relevant, the music this week are songs we mentioned/sung during the recording.
Intro: Open – Crying (Get Olde)
Intermission – Monty Python’s Holy Grail
Super Rad – The Aquabats!
Outro: Dreams are Maps – The Wild (Dreams are Maps)