title: Organic thin film transistors as selective sensing platforms for Hg²⁺ ions and the amino acid cysteine.
abstract: In this short communication we report a sensor for divalent mercuric (Hg²⁺) ions that we constructed from a perylene bisimide (PBI)-based organic thin film transistor. We improved the performance of the n-channel device by positioning N,N'-dioctyl-3,4,9,10-perylenedicarboximide between the dielectric and the active layer (PBI), increasing the electron mobility (μ) from 0.002 to 0.25±0.04 cm² V⁻¹ s⁻¹ and enhancing the on/off ratio (I(on)/I(off)) by two orders of magnitude (from 10² to 10⁴). Based on a "thymine-Hg²⁺-thymine" mechanism and monitoring the shift in the threshold voltage (V(th)), we used this transistor to discriminate Hg²⁺ ions from mixed ion solutions and it extended to different concentration Hg²⁺ solutions (from 50 to 350 μM). By monitoring the shifts in drain current (I(DS)) and V(th), we also used this bilayer device as a sensor for cysteine, a thiol-containing amino acid; the selective detection of cysteine was accompanied by a red shift in the fluorescence maximum of PBI, from 532 to 537 nm.
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan, ROC.
authors.forename: Mohan
authors.initials: M
authors.lastname: Ramesh
authors.forename: Hong-Cheu
authors.initials: HC
authors.lastname: Lin
authors.forename: Chih-Wei
authors.initials: CW
authors.lastname: Chu
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D015374:Biosensing Techniques; D003545:Cysteine / Q000737:chemistry / Q000302:isolation & purification*; D004563:Electrochemistry; D007094:Imides / Q000737:chemistry*; D007477:Ions / Q000737:chemistry / Q000302:isolation & purification*; D008628:Mercury / Q000737:chemistry / Q000302:isolation & purification*; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry; D012996:Solutions / Q000737:chemistry
chemical_list: D000596:Amino Acids; D007094:Imides; D007477:Ions; D012996:Solutions; C510697:perylene bisimide; D010569:Perylene; D008628:Mercury; D003545:Cysteine