With less than two weeks left it has changed into crunch time. Nevertheless, it was nice to take a break from all the lab work and visit the Kay Bailey Hutchinson Desalination Plant in El Paso. We were informed that it is the largest inland desalination plant in the world. It is also amazing to know that representatives from various countries visit El Paso just to tour the desalination plant.
We are finally bearing the fruits of our labor. Our week began a bit shaky but, in the end, we finally have data. The Instrument Gods blessed us with several days of remarkable work.
This week we continued our quest in trying to conceive a method for detecting nano-TiO2 in water. Our foundation is based on finding an organic chelate (molecular magnet) that will latch onto nano-TiO2 and keep it in suspension in order to examine the water sample in a UV-Vis Spectrometer. The chelate and the nano-TiO2 form a coordination complex. The close coordination between the two molecules allows for a charge to transfer back and forth from the chelate to the TiO2 and back when excited by light (electrons). This transfer results in a fluorescence signal that we will use to detect TiO2 in water. This measurement will be key to detecting nano-TiO2 in different types of water samples.
We finally have found promise in one of the 40 chelates we have tested. 2,3-Dimercaptosuccinic acid (DMSA) has proven its weight in Titanium. It has kept nano-TiO2 in suspension. Has produced significant zeta potential numbers.
The zeta potential is the electric charge between the chelate-nanoparticle complex and the solution it is in (for now we are using DI Water). The higher the zeta potential, especially in the range of +/- 30-40mV, then signifies the chelate-nanoparticle complex will remain in suspension. This will then allow us to possibly attain a measurement via the UV-Vis Spectrometer, which will be the center for further studies.
So relieved that we were able to move forward and get a step closer to our final goal. Let’s see what this week has in store!!!! Happy Fourth of July everyone.
We entered the week full of hope and confidence. However, life in the lab is sometimes unpredictable. You live, learn, and move on. Having done all the background research, we had established our plan for the week. This week’s focus was all about refinement. We were destined to move forward with leaps and bounds. Geared with a new instrument, which would allow us to duplicate last year’s work within a few days. This in itself would be a remarkable feat because we could validate our previous data and finally move on testing our samples via fluorescence. However, the lab gods had other plans.
Last year’s design utilized TiO2 solutions which had nanoparticles that averaged about 70nm in diameter. One of the complications was each particle varied in size, thus producing some discrepancies. In order to mitigate the variances, this year we would have two standardized nanoparticles TiO2. One being 18nm rutile and the other 30nm anatase.
We commenced the analysis by creating the two different colloid suspensions using the two different sizes of TiO2. Both solutions had approximately 1.6mg of their respective nanoparticle and 40mL of water, which were dispensed into two separate 50mL centrifuge tubes. The two samples were then placed in a sonicator. A sonicator applies sound energy to agitate the particles throughout the solution. After sonication, the samples were allowed to rest for a day in order to evaluate their suspension. Day one was a success!!!!
Nonetheless, 24hrs later a good percentage of the TiO2 remained in suspension with a small amount of precipitate observed at the base of both test tubes. This was a delightful sign because last year a good amount of the particles did precipitate to the bottom of the tubes, which posed a major challenge when conducting further studies.
The following day came upon us. Both my mentor and I knew this day would be critical. We aspired to measure the zeta potential of both solutions at different pH’s. The zeta potential is the potential difference (measured in mV) between the dispersed particle and the surrounding fluid. The zeta potential measurement is key in determining the stability of a colloid in solution.
Meaning if the solution has an optimal zeta potential then there is an elevated resistance to aggregation (which is what we are looking for). In regards to our nanoparticle solution, which is a small colloid, then a high zeta potential (+ or -) measurement shows an excellent resistance to aggregate. On the other hand, small colloids with a low zeta potential tend to coagulate or precipitate out of solution.
We went ahead and proceeded to assess the zeta potentials of both the 18nm and 30nm TiO2 in water and at different pHs in order to determine our next plan of action.
I carried this task out manually last year, which was time consuming, tedious, and took up most of my time in the lab. This time around we were prepared with a titration instrument, which is linked to a zeta potential analyzer. This instrument would complete 3-4 days worth of work into just several hours. However, this would not be the case.
We attempted 3 trials and did not attain the results we were hoping to observe. We had many difficulties with the titration of the acid and base solutions in order to reach our target pHs. The instrument would not properly adjust the pH as we had set into the parameters.
Yet, this is what the research is all about. A problem arises, you solve the problem, then move on to the next. We spent two days troubleshooting and to no avail. We are hoping this Monday that we can get through our obstruction and continue as planned. Will keep you all posted!!!
The first week is down and not let the fun begin. It just happened that my mentor was out for most of the week. I was tasked to read several articles to get a grasp of what we will do these next few weeks and see how I will apply this to my lesson.
We will be attempting to develop a novel Titanium Dioxide detection protocol. This analytical technique uses organic ligands/chelates, which will associate with Nano-TiO2 in solution to form a molecular chelate complex. The formation of this chelate complex should display a shift or change in absorbance/fluorescence. This change will then be measured by the following instrument. This is a CUV-ALL-UV spectrometer and will be my best friend for the upcoming two weeks.
Once the organic chelate with best suspension stability is found then different manufactured water samples (brackish, freshwater, groundwater, oil and gas water, etc.) will be utilized to test the validity of this novel method.
Additionally, (time permitting of course) we will apply the new method with two different types of TiO2 nanoparticles: 18nm rutile and 30nm anatase. Although the plan for this model is in its early stages it is beginning to display great promise based on last year’s research. However, we all know that things in the lab are unpredictable, so with an open heart and an open mind, I enter our great adventure willing and ready to rock this summer.
K-12 Educators Disseminating Research from Rice University, Arizona State University, and University of Texas-El Paso