TY - JOUR
T1 - Curcumin in reverse micelle
T2 - An example to control excited-state intramolecular proton transfer (ESIPT) in confined media
AU - Banerjee, Chiranjib
AU - Ghatak, Chiranjib
AU - Mandal, Sarthak
AU - Ghosh, Surajit
AU - Kuchlyan, Jagannath
AU - Sarkar, Nilmoni
PY - 2013/6/13
Y1 - 2013/6/13
N2 - In this Article, we focused on the modulation of the photophysical properties of curcumin, an anti-cancer drug, in aqueous and nonaqueous reverse micelles of AOT in n-heptane using steady-state and time-resolved fluorescence spectroscopy. The instability of curcumin is a common problem which restricts its numerous applications like Alzheimer disease, HIV infections, cystic fibrosis, etc. Our study reveals that curcumin shows comparatively higher stability after encapsulation into the interfacial region of the reverse micelle. To get a vivid description of the microenvironment, we added hydrogen-bond-donor (HBD) as well as non-hydrogen-bond-donor (NBD) core solvents. For experimental purposes, we used water, ethylene glycol (EG), glycerol (GY) as HBD solvents and N,N-dimethyl formamide (DMF) as a NBD solvent. With increasing amount of core solvents, irrespective of HBD or NBD, the fluorescence intensity and lifetime of curcumin increase with remarkable red-shift inside the reverse micelle. This is attributed to the modulation of the nonradiative rates associated with the excited-state intermolecular hydrogen bonding between the pigment and the polar solvents. We obtained a high partition constant at W0 = 0 (W0 = [core solvent]/[AOT]) which is certainly due to the hydrogen bonding between the negatively charged sulfonate group of AOT and hydroxyl groups of curcumin. Steady-state anisotropy and time-resolved results give an idea about the microenvironment sensed by the curcumin molecules. The red-shift of emission spectra, increase in the value of ET(30), as well as the increase in the fluorescence lifetime were interpreted as being caused by the partition of the probe between the micellar interface and the polar core solvent. Indeed, we show here that it is possible to control the excited state intramolecular proton transfer (ESIPT) process of curcumin by simply changing the properties of the AOT reverse micelle interfaces by choosing the appropriate polar solvents to make the reverse micelle media.
AB - In this Article, we focused on the modulation of the photophysical properties of curcumin, an anti-cancer drug, in aqueous and nonaqueous reverse micelles of AOT in n-heptane using steady-state and time-resolved fluorescence spectroscopy. The instability of curcumin is a common problem which restricts its numerous applications like Alzheimer disease, HIV infections, cystic fibrosis, etc. Our study reveals that curcumin shows comparatively higher stability after encapsulation into the interfacial region of the reverse micelle. To get a vivid description of the microenvironment, we added hydrogen-bond-donor (HBD) as well as non-hydrogen-bond-donor (NBD) core solvents. For experimental purposes, we used water, ethylene glycol (EG), glycerol (GY) as HBD solvents and N,N-dimethyl formamide (DMF) as a NBD solvent. With increasing amount of core solvents, irrespective of HBD or NBD, the fluorescence intensity and lifetime of curcumin increase with remarkable red-shift inside the reverse micelle. This is attributed to the modulation of the nonradiative rates associated with the excited-state intermolecular hydrogen bonding between the pigment and the polar solvents. We obtained a high partition constant at W0 = 0 (W0 = [core solvent]/[AOT]) which is certainly due to the hydrogen bonding between the negatively charged sulfonate group of AOT and hydroxyl groups of curcumin. Steady-state anisotropy and time-resolved results give an idea about the microenvironment sensed by the curcumin molecules. The red-shift of emission spectra, increase in the value of ET(30), as well as the increase in the fluorescence lifetime were interpreted as being caused by the partition of the probe between the micellar interface and the polar core solvent. Indeed, we show here that it is possible to control the excited state intramolecular proton transfer (ESIPT) process of curcumin by simply changing the properties of the AOT reverse micelle interfaces by choosing the appropriate polar solvents to make the reverse micelle media.
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U2 - 10.1021/jp401840z
DO - 10.1021/jp401840z
M3 - Article
C2 - 23687942
AN - SCOPUS:84879039531
SN - 1520-6106
VL - 117
SP - 6906
EP - 6916
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 23
ER -