ADVISOR

Professor Robert J. Levis

rjlevis@temple.edu

CV

 

FACULTY

 

Dr. Dmitri Romanov

Dmitri Romanov, PhD

Research Interests:

  • Strong-field control of molecular transformations.
  • Optical nonlinearities in atoms, molecules, and ions.
  • Control of femtosecond laser filamentation and evolution of laser filament channels in gases.
  • Dimensionality reduction in ultra-high-dimensional control and detection spaces.
  • Quantum mechanics of particles with nonparabolic dispersion.
  • Electronic and optical properties of nanostructures based on novel materials.
  • Light scattering in turbid media as applied to noninvasive blood characterization.

 

Johanan Odhner

Johanan Odhner, PhD

The applications of femtosecond laser filament-based standoff/remote spectroscopy and control of atmospheric chemistry motivate my studies of the fundamental process of laser filamentation in order to better understand how to control and direct the process. Particularly interesting for spectroscopy is the pulse shortening that occurs during filamentation, which results in excitation of all Raman-active modes present in the propagation medium, leading to the generation of molecule-specific signatures. Continuum generation by filamentation also acts as a source of intrinsically short pulses that cover the entire visible range, making it a good source for time-resolved spectroscopy.

 

 

POSTDOCTORAL FELLOWS

 

 

GRADUATE STUDENTS

 

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Jieutonne Archer

My research focuses on validating various methods employing laser electrospray mass spectrometry (LEMS) for the quantitative study of non-covalent protein-ligand interactions. LEMS has proven to be effective in the analysis of native protein samples. Its ability to analyze unprepared solid and liquid samples makes it ideal for biologically sensitive analytes. The use of a temperature-controlled stage to simulate natural environmental temperatures or even to assess temperature related stresses on biological systems also adds to the versatility of LEMS. I believe that my research can help to further prove that LEMS is an ideal tool that can be used to study biologically relevant molecular phenomena within the realm of mass spectrometry.

 

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Colin Fitzpatrick

Ultrafast lasers present a unique manner of exerting control over chemical reactions. The focus of this research is to modify or create novel materials using femtosecond pulses. The photo-isomerization of azobenzene has previously been used to induce motion on the nanometer and Angstrom scale, using the rotation from trans to cis or cis to trans. However, most applications have only utilized a single species of azobenzene and are therefore limited to simple binary functions. By modifying azobenzene with different side-groups and tailoring laser pulses to selectively excite different derivatives we can induce complex motions and build intricate and versatile molecular machines. We are also exploring controlled surface chemistry of carbon. Graphitic carbon is normally not highly reactive, unless under extreme conditions like high heat or with strong acids. The aim is to use high-energy pulses to control surface the functionalization by adding more reactive moieties. These chemically active groups would then allow the unique mechanical properties of macroscopic carbon structures to be incorporated into a diversified range of materials in less extreme conditions.

 

JueHuan Liu

Juehuan Liu

Juehuan is working on shaping the filamentation, a broadband ultrafast laser pulse that is induced by the laser ionized air. As the front of a near IR laser pulse is for creating ionized air and the back of the pulse is for creating broadband white light, optimizing the shape of the incoming pulse is critical. After obtained a controllable filament with close loop process, it will be used for analyzing.

 

Rachel Parise

My research focuses on designing experiments to optimize the femtosecond laser ablation process for laser electrospray mass spectrometry and develop a more sophistocated understanding of the nonresonant multiphoton excitation mechanism. Determining the influence of specific parameters on the detection sensitivity will reveal the capabilities and mechanistic properties of the LEMS system in order to improve the resolution for laser electrospray mass spectrometry imaging (LEMS-MSI) applications.

 

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Habib Sistani

My research focuses on sample preparation for laser electrospray mass spectrometry (LEMS) in order to improve the reproducibility of LEMS analyses. The idea is to use electrospray deposition (ESD) technique to make a homogeneous film of analytes. Electrospray deposition is accomplished by using a home built apparatus, which consists of a high voltage power supply, a syringe pump, a needle and a sample substrate. The needle is mounted in a holder and it is biased to a high voltage of approximately +5 kV while the sample substrate is maintained at ground. A spray is formed between the tip of the needle and the substrate. Electrospray deposition results in a homogeneous circular film of sample. The higher sample homogeneity from ESD samples decreases both the within-film of sample and between-films of sample (film-to-film) variability, resulting in a decrease in the relative standard deviation (RSD) for LEMS experiments.

 

Jacob Shusterman

My current research interests are in biomarker discovery and quantitative mass spectral imaging (Q-MSI). Tissue and serum contain a plethora of biomolecules. The range of concentration of these biomolecules can be quite large depending on the sample being examined. Thus, mass spectral signal from less concentrated biomolecules can be masked by the more highly concentrated ones. I’m interested in exploring various front-end separation techniques in hopes of revealing less concentrated biomolecules. Some of which could be potential biomarkers for various physiological states. Additionally, quantitative mass spectral imaging has been gaining attention as it offers several advantages over current quantitative tissue studies such as whole body autoradiography (WBA). One advantage of Q-MSI is the ability to differentiate between administered drugs and their metabolites/degradation products. While efforts have been made to standardize Q-MSI, there remains significant work to be done in improving current methodology and sample variation. Major challenges include analyte recovery from the tissue, variation in ionization efficiencies, peak interference, ionization matrix affects, and the choice of effective and reproducible standards. Laser electrospray mass spectrometry (LEMS) may offer certain advantages for exploring the limitations of Q-MSI, as no matrix is required. This may eliminate some of the ionization matrix effects which can interfere with quantification and reduce sample preparation, allowing analysis of a more native sample state. I would like to explore the limitations of LEMS and examine its applicability to Q-MSI.

 

Yu Wang

Metal nanomaterials have attracted extensive attention and scientific interest due to their unique optical properties and potential applications in technology and medicine. My research uses femtosecond laser pulses to synthesize novel metal nanoparticles. By changing the experimental parameters including irradiation time and laser intensity, we can actually exert control over the size and shape of the nanoparticles we made. Also by studying the mechanism behind it, we can get a new perspective of how molecules behave in strong laser field.

 

UNDERGRADUATE STUDENTS

Candice Bizzaro

Evan Haley

Benjamin Hawkins

Alumni

 

 

Levis Group, Department of Chemistry, Temple University, Beury Hall 244, 1901 N. 13th Street, Philadelphia, PA 19122    Tel: 215-204-5241     Fax: 215-204-6179
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