Detection and spatial mapping of mercury contamination in water samples using a smart-phone.
Detection of environmental contamination such as trace-level toxic heavy metal ions mostly relies on bulky and costly analytical instruments. However, a considerable global need exists for portable, rapid, specific, sensitive, and cost-effective detection techniques that can be used in resource-limited and field settings. Here we introduce a smart-phone-based hand-held platform that allows the quantification of mercury(II) ions in water samples with parts per billion (ppb) level of sensitivity. For this task, we created an integrated opto-mechanical attachment to the built-in camera module of a smart-phone to digitally quantify mercury concentration using a plasmonic gold nanoparticle (Au NP) and aptamer based colorimetric transmission assay that is implemented in disposable test tubes. With this smart-phone attachment that weighs <40 g, we quantified mercury(II) ion concentration in water samples by using a two-color ratiometric method employing light-emitting diodes (LEDs) at 523 and 625 nm, where a custom-developed smart application was utilized to process each acquired transmission image on the same phone to achieve a limit of detection of ∼ 3.5 ppb. Using this smart-phone-based detection platform, we generated a mercury contamination map by measuring water samples at over 50 locations in California (USA), taken from city tap water sources, rivers, lakes, and beaches. With its cost-effective design, field-portability, and wireless data connectivity, this sensitive and specific heavy metal detection platform running on cellphones could be rather useful for distributed sensing, tracking, and sharing of water contamination information as a function of both space and time.
Electrical Engineering Department, ‡Bioengineering Department, §California NanoSystems Institute (CNSI), ∥Department of Physics & Astronomy, and ⊥Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA) , Los Angeles, California 90095, United States.
Qingshan
Q
Wei
Richie
R
Nagi
Kayvon
K
Sadeghi
Steve
S
Feng
Eddie
E
Yan
So Jung
SJ
Ki
Romain
R
Caire
Derek
D
Tseng
Aydogan
A
Ozcan
D002140:California; D040421:Cell Phone; D003124:Colorimetry; D006046:Gold / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D053768:Metal Nanoparticles; D008838:Microcomputers; D014874:Water Pollutants, Chemical / Q000032:analysis*
D014874:Water Pollutants, Chemical; D006046:Gold; D008628:Mercury