Modified plastic optical fiber with CNT and graphene oxide nanostructured coatings for ethanol liquid sensing.

A high sensitivity and simple ethanol sensor based on an un-cladded multimode plastic optical fiber (UCPOF) coated with carbon nanotubes (CNTs) for the detection of different concentrations of ethanol in de-ionized water is developed and demonstrated. The UCPOF probe is fabricated by chemically removing the fiber cladding and integrated with CNT as a sensing layer. The effect of surface morphology on the sensor performance is investigated by characterizing another UCPOF coated with GO nanomaterial. The developed fibers are coated with CNTs and GO using drop casting technique. Energy dispersive X-ray spectroscopy (EDX), atomic-force microscopy (AFM) and scanning electron microscope (SEM) are used to investigate the element and morphology of the synthesized nanomaterials. The experimental results indicated that the absorbance spectrum of the CNT-based UCPOF sensor increases linearly with a higher sensitivity of 0.68/vol% and magnitude change of 95.4% as compared to 0.19/vol% and 56.3%, respectively, for the GO-based sensor. The UCPOF coated with CNT exhibits faster response and recovery than that of GO. The sensor shows high selectivity to ethanol amongst a range of diluted organic VOCs. The superior sensing performance of the developed fiber sensor indicates its high efficiency for ethanol detection in various industrial applications.

Mixed ligand complexes involving sulphur containing ligands--Part II. Ternary complexes of Zn(II) involving L-cysteine/D-penicillamine/L-cysteic acid and imidazoles.

The chemical equilibria involved in nine mixed ligand systems Zn(II)-L-cysteine (Cys)/D-penicillamine(Pen)/L-cysteic acid(Cya)(A)-imidazole(Him), histamine(Hist) and L-histidine(His)(B) have been investigated in aqueous perchlorate medium by pH titrimetry at 37 degrees and ionic strength, I = 0.15M (NaClO(4)). The mixed ligand complex species of the types ZnABH(2), ZnABH, ZnAB or ZnAB(2) have been detected in addition to various binary species due to ligands A and B. The results obtained for the ZnABH type of species indicate that the site of protonation is the amino group of Cys/Pen ligands in the Zn(II)-Cys/Pen(A)-Him, Hist and His(B) systems, and the amino group of Hist/His secondary ligands in the Zn(II)-Cya(A)-Hist and His(B) systems. In the ZnABH(2) type of species, one proton is attached with the primary ligand (A) and the other with the secondary ligand(B). In both ZnAB and ZnAB(2) type ternary species in all the systems, the primary ligand binds the metal in a bidentate manner and the secondary ligands Him, Hist and His bind the metal, respectively in a uni, bi and terdentate manner.