Water-Induced Tuning of the Emission of Polyaniline LEDs within the NIR to Vis Range

Abstract

Tuning of the emission within the near-infrared to visible range is observed in p -toluenesulfonic acid-doped polyaniline light emitting diodes (PANI/PTSA), when water molecules are absorbed by the active material (wet PANI/PTSA). This is a hybrid material that combines a conjugated π-electron system and a proton system, both strongly interacting in close contact with each other. The proton system successfully competes with the electron system in excitation energy consumption (when electrically powered), thanks to the inductive resonance energy transfer from electrons to protons in wet PANI/PTSA at the energy levels of combination of vibrations and overtones in water, with subsequent light emission. Wet PANI/PTSA, in which electrons and protons can be excited parallelly owing to fast energy transfer, may emit light in different ranges (on a competitive basis). This results in intense light emission with a maximum at 750 nm (and the spectrum very similar to that of an excited protonic system in water), which is blue-shifted compared to the initial one at ∼850 nm that is generated by the PANI/PTSA dry sample, when electrically powered.

Direct evidence for the key role of protons in the protonic p-n junction using L-band EPR and polyaniline as a proton-sensitive spin probe

“…The dark-blue emeraldine base (PANIEB) was dried under ambient conditions (yield 1.8 g) and characterized (FTIR, EPR) getting results similar to the values measured for materials previously prepared in our laboratory [15][16][17][18] Chemicals and solvents: Hydrochloric acid (HCl) (Stanlab, pure p.a.) -600 mL of 1 M solution prepared from concentrated hydrochloric acid (36%) -50 mL of 36% HCl dissolved in 550 mL of H 2 O.…”

“…Ion exchangers Dowex 50W and Dowex 1-4 are the same as used in previous experiments 9 Polyaniline Emeraldine Base, PANI EB is prepared in our laboratory according to the procedure described previously [15][16][17][18] : Aniline hydrochloride (6.9 g) was dissolved in 300 mL of 1 M hydrochloric acid. At the same time, 11.4 g of ammonium persulfate was dissolved in 200 mL of 1 M hydrochloric acid (separately).…”

Proton density monitoring at the interface of proton-donor and proton-acceptor regions in a protonic p–n junction with bias voltage

“…The dark-blue emeraldine base (PANI EB) was dried under ambient conditions (yield 1.8 g) and characterized (FTIR, EPR), getting results similar to the values measured for materials previously prepared in our laboratory. 15–18…”

“…Ion exchangers Dowex 50 W and Dowex 1-4 are the same as used in previous experiments. 8 Polyaniline Emeraldine Base, PANI EB is prepared in our laboratory according to the procedure described previously: [15][16][17][18] aniline hydrochloride (6.9 g) was dissolved in 300 mL of 1 M hydrochloric acid. At the same time, 11.4 g of ammonium persulfate was dissolved in 200 mL of 1 M hydrochloric acid (separately).…”

“…The dark-blue emeraldine base (PANI EB) was dried under ambient conditions (yield 1.8 g) and characterized (FTIR, EPR), getting results similar to the values measured for materials previously prepared in our laboratory. [15][16][17][18] Elemental analysis: Chemicals and solvents: Hydrochloric acid (HCl) (Stanlab, pure p.a.) -600 mL of 1 M solution prepared from concentrated hydrochloric acid (36%) -50 mL of 36% HCl dissolved in 550 mL of H 2 O.…”