1 octanethiol

Oleylamine (OAm, 70%), oleic acid (OA, 99%), 1-octadecene (ODE, 90%), cadmium oxide (CdO, ≥99.99%), selenium (Se, 99.99%), Trioctylphosphine oxide (TOPO, 99%), 1-octanethiol (≥98.5%), pentaerythritol-tetrakis(3-mercapto-propionate) (95%), ammonia aqueous (28.5%), tetrahydrofuran (THF, ≥99.9%), N-methylformamide (NMF, 99%), toluene (99.8%), hydrofluoric acid (HF, 48%), polyvinylpyrrolidone (PVP, 10k), ethanol (99%), tetraethyl orthosilicate (TEOS, 98%), hexane (95%) and (3-Mercaptopropyl) trimethoxysilane (MPTMS, 95%) were obtained from Sigma Aldrich. Trioctylphosphine (TOP, 97%) was purchased from Strem Chemicals. Octadecylphosphonic acid (ODPA, >99% was purchased from PCI synthesis. All the reagents were used as received without further purification.

Nanohole array sensor chip surfaces were cleaned in the order of isopropanol, acetone and deionized water, and dried at room temperature with nitrogen gas prior to chemical modifications. An amine-reactive self-assembly monolayer (SAM) was formed by incubating the sensor chips in ethanolic solution of 0.4 mM of 10-carboxy-1-decanethiol (Dojindo Laboratories, Japan) and 1.6 mM of 1-octanethiol (Sigma-Aldrich, MO, USA) for 12 h at room temperature, then washed thoroughly with pure ethanol and dried in room temperature. Subsequently, the sensor was incubated in a mixture of 75 mM of sulfo-N-hydroxysuccinimide (sulfo-NHS) and 15 mM of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) (Bio-Rad, Hercules, CA, USA), to activate the carboxylic group of the SAM for 15 min. Next, 50 μl of 200 μg/ml anti-troponin antibody 560 (Hytest, Finland) solution (acetate buffer, pH 4.5) was spotted on the sensor surface and incubated for 30 min. Finally, the sensor chip was immersed in 1 M of ethanolamine-HCl solution (Bio-Rad, Hercules, CA, USA) for 15 min to deactivate the unreacted esters, followed by a rinse with deionized water and dried with nitrogen gas at room temperature.

Cadmium oxide (CdO, 99.99%, trace metals), trioctylphosphine (TOP, 90% technical grade), sulfur (S, 99.98%), 1-octadecene (ODE, 90%, technical grade), iso-Octane (99.7%, HPLC grade), 1-Octanethiol (> 98.5%), trimethylammonium chloride (TMACl, > 98%), potassium hydroxide (KOH, 99.99%), dimethyl sulfoxide (DMSO, > 99.9%) magnesium acetate tetrahydrate (99%), zinc acetate dihydrate (> 98%), lithium acetate (99.95%) and 1-butanol (anhydrous, 99.8%) were purchased from Sigma-Aldrich. Zinc acetate anhydrous (+ 99.9%) and ethyl acetate (> 99.5%, ACS certified) were purchased from Thermoscientific. Selenium (Se, 99.999%, metals basis) and oleic acid (90%, technical grade) were purchased from Alfa-Aesar. Octane (+ 99%, extra pure) was purchased from Acros Organics. All the reagents were used as received. Poly(ethylene dioxythiophene): polystyrene sulfonate (PEDOT: PSS) was purchased from Ossila. Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4’-(N-(p-butylphenyl)) diphenylamine)] (TFB) was purchased from American Dye Source. Polyvinylpyrrolidone (PVP10) with an average molecular weight of 10,000 was purchased from Sigma-Aldrich. Patterned ITO-glass substrates with 15 Ω resistance and 25.4 mm × 25.4 mm × 0.7 mm were purchased from Luminescence Technology Corp.