Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 112, Issue 46, Pages 17931-17939Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp8065647
Keywords
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Funding
- Robert A. Welch Research Foundation [D-1158]
- U.S. Department of Justice
- National Institute of Justice [2003-IJ-CX-K016]
- University of Texas at Arlington, TX
- NSF
- DHS [CBET-0736172]
- DOD [HDTRA1-08-P-0034]
- DOD Congressionally Directed Medical Research Programs [W81XWH-08-1-0450]
- Division Of Graduate Education
- Direct For Education and Human Resources [0742402] Funding Source: National Science Foundation
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We have studied the luminescence decay and trace biomaterials detection potential of two surface-functionalized nanoparticles, poly(ethylene glycol) bis(carboxymethyl) ether-coated LaF3:Ce,Tb (similar to 20 nm) and thioglycolic acid-coated ZnS/Mn (similar to 5 nm). Upon UV excitation, these nanoparticles emitted fluorescence peaking at 540 and 597 nm, respectively, in solution. Fluorescence imaging revealed that these nanoparticles targeted the trace biomaterials from fingerprints that were deposited on various nonporous solid substrates. Highly ordered, microscopic sweat pores within the friction ridges of the fingerprints were labeled with good spatial resolutions by the nanoparticles on aluminum and polymethylpentene substrates, but not on glass or quartz. In solution, these nanoparticles exhibited multicomponent fluorescence decays of resolved lifetimes ranging from nano-to microseconds and of average lifetimes of similar to 24 and 130 mu s for the coated LaF3:Ce,Tb and ZnS:Mn, respectively. The long microsecond-decay components are associated with the emitters at or near the nanocrystal core surface that are sensitive to the size, surface-functionalization, and solvent exposure of the nanoparticles. When the nanoparticles were bound to the surface of a solid substrate and in the dried state, a decrease in the microsecond decay lifetimes was observed, indicative of a change in the coating environment of the nanocrystal surface upon binding and solvent removal. The average decay lifetimes for the surface-bound ZnS:Mn in the dried state were similar to 60, 30, and 11 mu s on quartz, aluminum, and polymethylpentene, respectively. These values were still 2 orders of magnitude longer than the typical fluorescence decay background of most substrates (e.g., similar to 0.36 mu s for polymethylpentene) in trace forensic evidence detections. We conclude that coated ZnS: Mn nanoparticles hold great promise as a nontoxic labeling agent for ultrasensitive, time-gated, trace evidence detections in nanoforensic applications.
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