A new fluorescent and electrochemical Zn2+ ion sensor based on Schiff base derived from benzil and L-tryptophan.
Single molecule acting as both fluorescent and electrochemical sensor for Zn(2+) ion is rare. The product (L) obtained on condensation between benzil and L-tryptophan has been characterized by H NMR, ESI-MS and FT-IR spectroscopy. L in 1:1 (v/v) CH3OH:H2O solution shows fluorescence emission in the range 300 nm to 600 nm with λmax at 350 nm when is excited with 295 nm photon. Zn(2+) ion could induce a 10-fold enhancement in fluorescent intensity of L. Fluorescence and UV/Visible spectral data analysis shows that the binding ratio between Zn(2+) ion and L is 1:1 with log β=4.55. Binding of Zn(2+) ion disrupts the photoinduced electron transfer (PET) process in L and causes the fluorescence intensity enhancement. When cyclic voltammogram is recorded for L in 1:1 (v/v) CH3OH:H2O using glassy carbon (GC) electrode, two quasi reversible redox couples at redox potential values -0.630±0.005 V and -1.007±0.005 V are obtained (Ag-AgCl as reference, scan rate 0.1 V s(-1)). Interaction with Zn(2+) ion makes the first redox couple irreversible while the second couple undergoes a 0.089 V positive shift in redox potential. Metal ions - Cd(2+), Cu(2+), Co(2+), Hg(2+), Ag(+), Ni(2+), Fe(2+), Mn(2+), Mg(2+), Ca(2+)and Pb(2+), individually or all together, has no effect on the fluorescent as well as electrochemical property of L. DFT calculations showed that Zn(2+) ion binds to L to form a stable complex. The detection limit for both fluorescence as well as electrochemical detection was 10(-6) M.
Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India.
Kaku
K
Dutta
Department of Chemical Science, Tezpur University, Napaam, Tezpur 784 028, Assam, India.
Ramesh C
RC
Deka
Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India. Electronic address: digantakdas@gmail.com.
Diganta Kumar
DK
Das
D055664:Electrochemical Techniques / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008958:Models, Molecular; D010658:Phenylglyoxal / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory; D012015:Reference Standards; D012545:Schiff Bases / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014364:Tryptophan / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
D007477:Ions; D012545:Schiff Bases; D012996:Solutions; D014364:Tryptophan; D015032:Zinc; D010658:Phenylglyoxal; C006697:benzil
Cyclic voltammetry; Fluorescence; L-Tryptophan; Photoinduced electron transfer; Sensor; Zn(2+)