Dr. Gerardo Gamez

Principal Research Interests

• Chemical Imaging
• Optical Spectroscopy
• Mass Spectrometry

The main focus of the Gamez group is to develop novel techniques to overcome challenges encountered in the analysis of relevant materials and biological systems. One area in which we are interested is chemical imaging: the ability to obtain spatially resolved chemical landscapes is critical for understanding the mechanisms in biological systems and guiding the development of novel materials. One of the challenges faced in chemical imaging is obtaining elemental maps of large areas in a fast manner such that it becomes practical for routine analysis. We are overcoming this challenge by developing a glow discharge optical emission spectroscopy technique (i). Another challenge in chemical imaging is that typical analysis techniques that provide high spatial resolution do not give chemically-rich information, and vice versa. We are overcoming this challenge by coupling near-field spectroscopies with scanning force microscopy (ii). Another area in which we are interested is mass spectrometry: the ability to obtain elemental, structural, molecular, and isotopic information is also critical for many relevant samples. One of the challenges in mass spectrometry is the sample preparation that allows the introduction of solid samples into the mass spectrometer and is typically the bottleneck in the analysis. We are overcoming this challenge by developing ambient ionization techniques (iii).

1. Glow discharge optical emission spectroscopy (GDOES) is a cathodic sputtering technique that has gained wide interest because it allows quantitative elemental depth profiling from surfaces (with nm resolution) with high sample throughput. However, the lateral resolution in GDOES is typically limited by the sputtered area (mm). Very recent developments showed the possibility to obtain laterally resolved information from within the sputtered area by operating the GD in pulsed power mode, which opened the possibility to map large areas (100 cm2) simultaneously in a matter of seconds. This research avenue will serve to enable fast chemical imaging and improve the understanding of glow discharge mechanisms.
2.  Areas of research where nanoscales are encountered require analysis techniques to aid in their development. The problem is that typically techniques with high spatial resolution do not give rich chemical information, and vice versa. In this research avenue near-field laser sampling will be coupled to optical and mass spectrometries to develop techniques that yields rich chemical information with nanoscale spatial resolution. Also, an improved understanding of laser-material interactions will be obtained.
3.  Ambient ionization mass spectrometry has gone through a spectacular growth in a short amount of time because they enable desorption, extraction, ionization with little to no sample preparation. There has been a multitude of techniques developed along with a myriad of proof-of-principle applications. Although application development is still growing, there is a need to further understand the fundamental processes and overcome quantitation problems. This research avenue will focus on studying the mechanisms and matrix effects encountered in ambient ionization while developing new applications, such as monitoring medication metabolites.

Members in the group get experience in several disciplines outside of chemistry, including biology and materials science. The multi-component character of the research projects allows the early-stage and experienced researchers to obtain and hone skills in instrument development (from design to implementation), method development, and fundamental experiment design.

Representative Publications

• "Geometric super-resolution on push-broom hyperspectral imaging system for plasma optical emission spectroscopy". Shi, S.; Gong, X.; Mu, Y.; Finch, K.; Gamez, G. J. Anal. Atom. Spectrom., 2018, 33 (1745-1752).
• "Real-Time Quantitative Analysis of Valproic Acid in Exhaled Breath by Low Temperature Plasma Ionization Mass Spectrometry." Gong, X.; Shi, S.; Gamez, G. J. Am. Soc. Mass Spectrom., 2017, 28 (678-687).
• "Compressed Sensing Spectral Imaging for Plasma Optical Emission Spectroscopy." Usala, J.; Maag, A.; Nelis, T.; Gamez, G. J. Anal. Atom. Spectrom., 2016, 31 (2198-2206).
• "Compressed Sensing in Spectroscopy for Chemical Analysis" Gamez, G. J. Anal. Atom. Spectrom., 2016, 31 (2165-2174).
• "Glow Discharge Elemental Mapping with Restrictive Anode Array Masks". Kroschk, M.; Usala, J.; Addesso, T.; Gamez, G., J. Anal. Atom. Spectrom., 2016, 31 (163-170).
• "Ultrafast Elemental Mapping of Materials Combinatorial Libraries and High-throughput Screening Samples via Pulsed Glow Discharge Optical Emission Spectroscopy"., Gamez, G.; Mohanty, G.; Michler, J., J. Anal. Atom. Spectrom., 2013, accepted.
• "Push-broom Hyperspectral Imaging for Elemental Mapping with Glow Discharge Optical Emission Spectrometry"., Gamez, G; Frey, D.; Michler, J.; J. Anal. Atom. Spectrom., 2012, 27 (50-55).
• "Glow Discharge Techniques in the Chemical Analysis of Photovoltaic Materials"., Schmitt, S.W.; Venzago, C.; Hoffmann, B.; Sivakov, V.; Hofmann, T.; Christiansen, S.H.; Michler, J.; Gamez, G.Prog. Photovoltaics.Res. Appl., 2012, DOI: 10.1002/pip.2264.
• "Real-time, In Vivo Monitoring and Pharmacokinetics of Valproic Acid via a Novel Biomarker in Exhaled Breath"., Gamez, G.; Zhu, L.; Disko, A.; Chen, H.; Azov, V.; Chingin, K.; Krämer, G.; Zenobi, R. Chem. Comm., 2011, 47 (4884-4886).
• "Material Ejection and Redeposition Following Atmospheric Pressure Near-Field Laser Ablation on Molecular Solids"., Zhu, L.; Gamez, G.; Schmitz, T. A.; Krumeich, F.; Zenobi, R. Anal. Bioanal. Chem., 2010, 396 (163-172).
• "What Can We Learn From Ambient Ionization Techniques?", Chen, H.; Gamez, G.; Zenobi, R. J. Am. Soc. Mass. Spectr., 2009, 20 (1947-1963).
• "Rapid Detection of Melamine in Untreated Milk and Wheat Gluten by Ultrasound-assisted Extractive Electrospray Mass Spectrometry (EESI-MS)"., Zhu, L.; Gamez, G.; Chen, H.; Chingin, K.; Zenobi, R. Chem. Commun., 2009, 5 (559-561).
• "Towards Nanoscale Molecular Analysis at Atmospheric Pressure by a Near-Field Laser Ablation Ion Trap/Time-of-Flight Mass Spectrometer"., Schmitz, T.; Gamez, G.; Setz, P. D.; Zhu, L.; Zenobi, R. Anal. Chem., 2008, 80 (6537-6544).
• "Photoelectron Emission as an Alternative Electron Impact Ionization Source for Ion Trap Mass Spectrometry"., Gamez, G.; Zhu, L.; Schmitz, T.; Zenobi, R. Anal. Chem., 2008, 80 (6791-6795).
• "Atmospheric-Pressure Chemical Ionization Source. Part I: Ionization of Compounds in the Gas Phase"., Andrade, F. J.; Shelley, J.; Wetzel, W. C.; Webb, M. R.; Gamez, G.; Ray, S. J.; Hieftje, G. M. Anal. Chem., 2008, 80 (2646-2653).