Research interests

Single Nanoparticle/Nanoprobe Photophysics

Using a combination of single molecule spectroscopic and imaging techniques we characterize and quantify the underlying photophysics of a range of new nanoprobes which exhibit potential as fluorescent single molecule reporters for applications in the biological and materials sciences.

Nanoprobe Design and Optimization for Biological/Materials Applications

Passive and reactive molecular and quantum dot (metallic and semiconductor) nanoprobes, generally referred to as fluors, have shown great promise as localized reporters in a range of in vitro biochemical and materials systems. The individual fluor represents the highest possible spatial resolution for chemical processes within a sample. However, in order to achieve sufficient signal-to-noise for single fluor imaging/spectroscopy in complicated materials and biological systems, where the main source of signal is often from background radiation, nanoprobes must be specifically designed taking into account their intrinsic photophysics as well as any potential influences of the system of interest. A broad range of techniques are being employed with the eventual goal of controlling photophysical processes of fluors such as photo-stability, excited state dynamics (i.e. lifetime and triplet dynamics), conformational fluctuations in absorption and emission properties, and environmental (chemical) sensitivity and specificity.

Time-resolved Single–molecule Imaging Spectroscopy

In all high resolution imaging techniques there is a continuing drive to increase the amount of signal, and therefore information, obtained. In general, these techniques fall into one of two categories: High quantum efficiency time-resolved single photon counting, or much lower efficiency spectroscopies using dispersion type monochrometers/spectrometers. In fact, some combination of these techniques represents the potential for the greatest information density: the temporal behavior, energy, and in a scanning format, the point of origin within a 3-dimensional sample of each photon. Recently, this effort has been advanced using single-photon counting techniques coupled with high efficiency optics providing

Publications

• Kennard, R; DeSisto, W; Giririjan, TP; Mason, MD. “Intrinsic property measurement of surfactant-templated mesoporous silica films using time-resolved single-molecule imaging”. Journal of Chemical Physics, 128 (13), 2008.
• King, MD; Khadka, S; Craig, G; Mason, MD. “The effect of local heating on the SERS efficiency of single optically trapped prismatic nanoparticles” J. Phys. Chem. C. 112 (31), 11751, 2008.
• Khalil, A., Mason, M., Dickey, I., Zhang, R., Aponte, C., Davisson, T., Engelman, D., Hawkins, M. “Pattern of Soft Tissue In-Growth into Porous Implants Based on Novel Imaging Tools”, Transactions of the Orthopaedic Research Society, Vol. 33, 1877, 2008.
• Sirbuly, DJ; Gargas, DJ; Mason, MD; Carson, PJ; Buratto, SK. “Optical anisotropy in individual porous silicon nanoparticles containing multiple chromophores”, ACS Nano 2(6), 1131-1136, 2008.
• Gargas, DJ; Sirbuly, DJ; Mason, MD; Carson, PJ; Buratto, SK. “Investigation of polarization anisotropy in individual porous silicon nanoparticles” Microelectronics J., 39(9), 1144-1148, 2008.
• Wise SS; Thompson, WD; Aboueissa, A-M; Mason, MD; Wise, JP. “Particulate Depleted Uranium Is Cytotoxic and Clastogenic to Human Lung Cells” Journal of Chemical Research in Toxicology 20 (5): 815-820 May 2007.
• Hess, ST; Girirajan, TPK; Mason, MD. “Ultra-High Resolution Imaging by Fluorescence Photoactivation Localization Microscopy (FPALM)”. Biophysical Journal 91: 4258-4272, 2006.
• Mason, M.D., Ray, K., Grober, R.D., Pohlers, G., Cameron, J.F. “Single molecule acid-base kinetics and thermodynamics”. Physical Review Letters. 93 (7), 073004(1-4), 2004.
• Ray, K; Mason, MD; Yang, C; Li Z; Grober, RD. “Single-molecule signal enhancement using a high-impedance ground plane substrate” Applied Physics Letters, 85 (23): 5520-5522, 2004.
• Ray, K; Mason, MD; Grober, RD; Pohlers, G; Staford, C; Cameron, JF. “Quantum yields of photoacid generation in 193-nm chemically amplified resists by fluorescence imaging spectroscopy” Chemistry of Materials, 16 (26): 5726-5730, 2004.
• Eck, W; Craig, G; Sigdel, A; Allen, P; Brenner, M; Mason MD. “Pegylated gold nanoparticles conjugated to monoclonal F19 antibodies as targeted labeling agents for human pancreatic carcinoma tissue.” ACS Nano, In press. 2008.

Grants

• 2005 to 2006 — 27136.00 — Paper Based Amplification for Bio-Detection from UMaine PSSP
• 2005 to 2006 — 52794.00 — Gold nanoparticle bioconjugates for the detection, imaging, and treatment to pancreatic adenocarcenoma from Memorial Sloan Kettering Cancer Center
• 2006 to 2007 — 155844.00 — Artificial Bone Implant Research from Stryker Orthopaedics
• 2007 to 2008 — 30000.00 — Paper-based Field Biosensors for Biomolecular Detection from UMaine PSSP
• 2007 to 2008 — 53710.00 — Artificial Bone Implant Research from Stryker Orthopaedics
• 2007 to 2008 — 63564.00 — Cancer Detection using Engineered Metallic Nanoparticle Conjugates from Memorial Sloan Kettering Cancer Center
• 2007 to 2010 — 728102.00 — MRI: Development of a Hybrid Scanning Fluorescence and Sum-Frequency Spectroscopy Imaging Microscope from NSF
• 2008 to 2010 — 75000.00 — MRI: High School and Undergraduate Outreach from UMaine OSRP
• 2008 to 2009 — 9750.00 — RET Supplemental to MRI from NSF
• 2008 to 2009 — 39180.00 — Nanoparticle Bioconjugates for Cancer Detection based on an A33-gold construct from Memorial Sloan Kettering Cancer Center