Rajib Nandi | Banaras Hindu University, Varanasi (original) (raw)
Papers by Rajib Nandi
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021
Abstract Homeotropic alignment of liquid crystals (LCs) at the aqueous interface and their fundam... more Abstract Homeotropic alignment of liquid crystals (LCs) at the aqueous interface and their fundamental understanding is still limited known, which is a prerequisite for the development of new kinds of LC-based sensors for the detection of biomolecules in the aqueous phase. Herein, we have investigated the orientational ordering of nematic LC at LC-aqueous interface in contact with the different hydrogen bonding strength of para-substituted phenol derivatives (X; functional group attached to phenol at para position = -NO2, -CN, -Cl, -F, -CHO, -H) intending to understand how the intermolecular hydrogen bonding interactions at LC-aqueous interface amplified into supramolecular ordering in LCs. The hydrogen bonding interactions between -CN group of 5CB and -OH group of phenol derivatives lead to a change in tilt angle from planar to homeotropic ordering of 5CB molecules at LC-aqueous interface. Raman measurement of different mixtures between 5CB and para-substituted phenol derivatives have been recorded to correlate the experimental observations at the LC-aqueous interface as well as direct evidence of hydrogen bonding at the LC-aqueous interface. Density functional theory (DFT) has been used to calculate hydrogen bonding strength and charge transfer mechanism between 5CB and phenol derivatives. The orientation of LC at the aqueous interface depends on the strength of the interfacial hydrogen bonding between phenol derivatives and LC, which varies on substitution of phenol and concentration of the phenol molecules.
Advanced Materials Technologies, 2021
Human muscles, including skeletal, smooth, and cardiac muscles, are able to perform diverse defor... more Human muscles, including skeletal, smooth, and cardiac muscles, are able to perform diverse deformations and execute complex biofunctions stimulated by nerve signals. Similarly, liquid crystal elastomer (LCE), which can respond to external stimuli with large and reversible deformations, demonstrates superior advantages to mimic nature muscles to fabricate artificial muscles. Till now, LCE has been utilized to simulate deformations and related functions of skeletal and smooth muscles. However, limited by the existing fabrication strategy, employing LCE to mimic the motion of cardiac muscles and further realizing the structure‐determined pumping functions, is still an open challenge. Learning from the specific spatial arrangements and synergistic actuation of cardiac muscle fibers within human heart, a simple and general strategy to construct artificial cardiac muscles with LCE fibers is proposed. In this work, LCE fibers with similar modulus and actuation behavior to muscle fibers are fabricated and spatially arranged in biological architectures as cardiac muscle fibers. As a result, artificial cardiac muscles are constructed and are able to perform simultaneous contraction and torsion motions, realizing heart‐pumping functions. This general strategy should be also applicable for other smart materials to conduct challenging tasks.
RSC Adv., 2016
N-(4-(Tetradecyloxy)-2-hydroxybenzylidene)-4′((4′′(hexadecyloxy)benzyl)oxy)benzohydrazide exhibit... more N-(4-(Tetradecyloxy)-2-hydroxybenzylidene)-4′((4′′(hexadecyloxy)benzyl)oxy)benzohydrazide exhibits a de Vries reduction factor comparable to, or even lower than that reported heretofore.
Langmuir, 2019
We report a new method for label-free, sensitive, and facile detection of lead(II) ions (Pb 2+) b... more We report a new method for label-free, sensitive, and facile detection of lead(II) ions (Pb 2+) based on an aptamer−target binding event, which is recognized by orientations of liquid crystals (LCs) at aqueous interfaces. The LC film suspended in the aqueous phase demonstrated a homeotropic orientation in contact with a cationic surfactant cetyltrimethylammonium bromide (CTAB) due to selfassembly of CTAB molecules at the aqueous−LC interface. The ordering of LC subsequently changed to planar in the presence of the spinach RNA aptamer (SRNA) due to interactions between CTAB and SRNA. In the presence of the Pb 2+ ion, the ordering of LC changed to homeotropic caused by reorganization of CTAB at the LC−aqueous interface. This is due to formation of more stable quadruplex structures of SRNA with Pb 2+ ions in comparison to the CTAB-SRNA complex. The sensor exhibited a detection limit of 3 nM, which is well below the permissible limit of Pb 2+ in drinking water. Our experiments establish that addition of Pb 2+ leads to (i) the formation of Pb 2+-SRNA complexes and (ii) a decrease in density of SRNA on the LC interface, but additional studies are required to determine which of these processes underlie the response of the LCs to the Pb 2+. We have also demonstrated the potential application of the LC sensor for detection of Pb 2+ in tap water. Unlike current laboratory-based heavy-metal-ion assays, this method is comparatively simple in terms of instrumentation, operation, and optical readout.
Molecular Systems Design & Engineering, 2018
An extensive study on the effect of terminal halogens on the structure–property relationship of p... more An extensive study on the effect of terminal halogens on the structure–property relationship of polar L-shaped mesogens has been elucidated.
The Journal of Physical Chemistry B, 2019
Herein, we report a new type of azobenzene based unsymmetrical bent-core molecules exhibiting pho... more Herein, we report a new type of azobenzene based unsymmetrical bent-core molecules exhibiting photoswitchability in liquid crystalline state, solid state, solution state and in mixture upon UV irradiation and intense visible light. The compounds exhibited solid state photochromism upon exposure of UV light whereas in liquid
The Analyst, Jan 26, 2018
Liquid crystal (LC) based optical sensors have been found to be very promising for detecting aque... more Liquid crystal (LC) based optical sensors have been found to be very promising for detecting aqueous biological samples due to the ease of optical detection, their cost effectiveness and the removal of the need for labelling biological species with fluorescent dyes. To date, all LC based sensors are studied in laboratories using conventional polarizing optical microscopy (POM), and no attention has been paid towards the fabrication of portable LC sensing devices for use in commercial purposes. Here, we designed and fabricated a 3D printed portable, lightweight, and inexpensive sensing device using a smartphone to detect the optical signal of LC based sensors. The accuracy of the optical signal using the fabricated sensing device is similar to that obtained using conventional POM. The fabricated sensing device, using a smartphone, gives a novel and new platform to LC based sensors for practical applications in the industrial world and people's daily lives.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017
The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature depen... more The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature dependent Raman spectroscopic technique. Pyrazinamide is a very useful drug used for the treatment of tuberculosis (TB) and plays a significant role in destroying the dormant tubercle bacilli which are not destroyed by other common TB drugs. Temperature dependent Raman spectra suggest polymorphic phase change from α → γ form of pyrazinamide between 145-146 °C. In situ Raman spectra of pyrazinamide between 145-146 °C show the conversion of α → γ form by the shift in C=O stretching vibration accompanied by several other changes. The phase change is characterized by the breaking of two linear N-H•••O type hydrogen bonds associated with C=O stretching vibration in α dimer and formation of one linear N-H•••N type hydrogen bond along with a weak intramolecular C-H•••O type hydrogen bond in the γ dimer.
Journal of Raman Spectroscopy, 2016
Temperature dependent Raman and X-ray diffraction studies of a calamitic ester substituted aryolh... more Temperature dependent Raman and X-ray diffraction studies of a calamitic ester substituted aryolhydrazone liquid crystal (LC) system; N-[4-(4ʹ-decyloxy)benzoyloxy benzylidene]-Nʹ-[4ʹ-decyloxybenzoyl]hydrazine (DB2H) have been performed to investigate the molecular arrangement and intermolecular interaction environment in LC phase. X-ray diffraction study with the help of density functional theoretical study gives the information of molecular tilt angle in SmC layer. Prominent Raman signatures of crystal I crystal II, crystal II SmC and SmC Isotropic phase transitions were identified in terms of changes in peak position and linewidth as well as Raman intensity. Analysis of Raman marker bands gives evidence of residual intermolecular hydrogen bonds between amide groups responsible for tilting arrangement in SmC phase. Copyright © 2016 John Wiley & Sons, Ltd.
Sensors and Actuators B: Chemical, 2016
We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg... more We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg 2+) in water using liquid crystals (LCs). In this system, newly synthesized amphiphilic potassium N-methyl-N-dodecyldithiocarbamate (MeDTC) was doped in 4-cyano-4-pentyl biphenyl (5CB) LC, which align LC molecules at aqueous interface and polar head group of the amphiphile acts as mecuric ion specific chelating ligand. When this sensor system was incubated in the aqueous solution containing Hg 2+ ions, a dark to bright transition of the image of LCs was observed. This was caused due to rapid and stable complex formation between dithiocarbamate chelating group of MeDTC with Hg 2+ ions at aqueous interface, which disrupted the orientation of LCs giving bright texture. The limit of detection of the system for aqueous Hg 2+ ion is 0.5 M. This sensor did not respond to other metal ions like Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , Na + , Mg 2+ and Ca 2+ , which are common environmental interference in water. We also demonstrated that this sensor is capable of detecting Hg 2+ ions in real water samples (tap water). The very simple and effective procedure reported here should facilitate the development of real time, portable and reliable LC based sensor for mercury pollution control.
RSC Adv., 2015
Lamellar smectic A to columnar mesophase crossover is observed in p-substituted aroylhydrazones b... more Lamellar smectic A to columnar mesophase crossover is observed in p-substituted aroylhydrazones by variation of the alkoxy chain density at peripherals.
Vibrational Spectroscopy, 2013
ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy... more ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of C trans cis
Chemical Physics Letters, 2014
A novel liquid crystal (LC) based sensor to detect trace level amount of hydrazine vapour has bee... more A novel liquid crystal (LC) based sensor to detect trace level amount of hydrazine vapour has been developed. The LC 4-pentyl-4-biphenylcarbonitrile (5CB) doped with 0.5 wt% 4-decyloxy benzaldehyde (DBA) shows dark to bright optical texture upon exposure of hydrazine vapours as revealed by polarizing optical microscopy under crossed polarizers. The hydrazine interacts with the doped DBA and form diimine compound which disrupt the orientation of aligned 5CB. The interaction between DBA and hydrazine has been also studied by Raman spectroscopy.
Liquid Crystals, 2015
ABSTRACT The present study is focused on the development of green microwave process for the synth... more ABSTRACT The present study is focused on the development of green microwave process for the synthesis of mesogenic substituted aroylhydrazones and their nickel(II) and copper(II) complexes. The compounds have been synthesised by microwave-assisted as well as thermal methods for comparison purpose. The compounds were structurally characterised by using suitable spectroscopic techniques. The mesomorphic properties were studied by differential scanning calorimetric analysis and polarising optical microscopy. The stable molecular structures of the mesogenic methylidenehydrazinato-nickel(II) complex have been obtained by density functional theoretical method to understand the structural origin responsible for the mesomorphic property.
Molecular Crystals and Liquid Crystals, 2013
A novel homologous series of α-4-(4-n-alkoxy cinnamoyloxy) phenyl β-2-nitro, 3-4 di methoxy benzo... more A novel homologous series of α-4-(4-n-alkoxy cinnamoyloxy) phenyl β-2-nitro, 3-4 di methoxy benzoyl ethylenes, H 2n+1 CnO-C 6 H 4-CH=CH-COO-C 6 H 4-CO-CH=CH-C 6 H 2 (NO 2) (OCH 3) 2 (n = 1-8, 10, 12, 14, 16, 18) has been synthesized. All these compounds have been characterized by suitable spectroscopic techniques. C 1 homologue is nonmesogenic, while C 2 homologue shows enantiotropic nematogenic property and the rest of the homologous (C 3-C 18) displayed enantiotropically smectogenic plus nematogenic phase. Phase transition temperatures and textures of the LC phase were determined by an optical polarizing microscopy (POM) equipped with a heating stage. The mesomorphic properties of these compounds were confirmed by differential scanning calorimetry (DSC) analysis.
Biosensors
In this work, we have combined the advantages of sequence programmability of DNA nanotechnology a... more In this work, we have combined the advantages of sequence programmability of DNA nanotechnology and optical birefringence of liquid crystals (LCs). Herein, DNA amphiphiles were adsorbed onto LC droplets. A unique phenomenon of LC droplet aggregation was demonstrated, using DNA-modified LC droplets, through complementary DNA hybridization. Further functionalization of DNA-modified LC droplets with a desired DNA sequence was used to detect a wide range of chemicals and biomolecules, such as Hg2+, thrombin, and enzymes, through LC droplet aggregation and vice versa, which can be seen through the naked eye. These DNA-modified LC droplets can be printed onto a desired patterned surface with temperature-induced responsiveness and reversibility. Overall, our work is the first to report DNA-modified LC droplet, which provides a general detection platform based on the development of DNA aptamers. Additionally, this work inspires the exploration of surface information visualization combined w...
Vibrational Spectroscopy, 2013
ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy... more ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of C trans cis
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2021
Abstract Homeotropic alignment of liquid crystals (LCs) at the aqueous interface and their fundam... more Abstract Homeotropic alignment of liquid crystals (LCs) at the aqueous interface and their fundamental understanding is still limited known, which is a prerequisite for the development of new kinds of LC-based sensors for the detection of biomolecules in the aqueous phase. Herein, we have investigated the orientational ordering of nematic LC at LC-aqueous interface in contact with the different hydrogen bonding strength of para-substituted phenol derivatives (X; functional group attached to phenol at para position = -NO2, -CN, -Cl, -F, -CHO, -H) intending to understand how the intermolecular hydrogen bonding interactions at LC-aqueous interface amplified into supramolecular ordering in LCs. The hydrogen bonding interactions between -CN group of 5CB and -OH group of phenol derivatives lead to a change in tilt angle from planar to homeotropic ordering of 5CB molecules at LC-aqueous interface. Raman measurement of different mixtures between 5CB and para-substituted phenol derivatives have been recorded to correlate the experimental observations at the LC-aqueous interface as well as direct evidence of hydrogen bonding at the LC-aqueous interface. Density functional theory (DFT) has been used to calculate hydrogen bonding strength and charge transfer mechanism between 5CB and phenol derivatives. The orientation of LC at the aqueous interface depends on the strength of the interfacial hydrogen bonding between phenol derivatives and LC, which varies on substitution of phenol and concentration of the phenol molecules.
Advanced Materials Technologies, 2021
Human muscles, including skeletal, smooth, and cardiac muscles, are able to perform diverse defor... more Human muscles, including skeletal, smooth, and cardiac muscles, are able to perform diverse deformations and execute complex biofunctions stimulated by nerve signals. Similarly, liquid crystal elastomer (LCE), which can respond to external stimuli with large and reversible deformations, demonstrates superior advantages to mimic nature muscles to fabricate artificial muscles. Till now, LCE has been utilized to simulate deformations and related functions of skeletal and smooth muscles. However, limited by the existing fabrication strategy, employing LCE to mimic the motion of cardiac muscles and further realizing the structure‐determined pumping functions, is still an open challenge. Learning from the specific spatial arrangements and synergistic actuation of cardiac muscle fibers within human heart, a simple and general strategy to construct artificial cardiac muscles with LCE fibers is proposed. In this work, LCE fibers with similar modulus and actuation behavior to muscle fibers are fabricated and spatially arranged in biological architectures as cardiac muscle fibers. As a result, artificial cardiac muscles are constructed and are able to perform simultaneous contraction and torsion motions, realizing heart‐pumping functions. This general strategy should be also applicable for other smart materials to conduct challenging tasks.
RSC Adv., 2016
N-(4-(Tetradecyloxy)-2-hydroxybenzylidene)-4′((4′′(hexadecyloxy)benzyl)oxy)benzohydrazide exhibit... more N-(4-(Tetradecyloxy)-2-hydroxybenzylidene)-4′((4′′(hexadecyloxy)benzyl)oxy)benzohydrazide exhibits a de Vries reduction factor comparable to, or even lower than that reported heretofore.
Langmuir, 2019
We report a new method for label-free, sensitive, and facile detection of lead(II) ions (Pb 2+) b... more We report a new method for label-free, sensitive, and facile detection of lead(II) ions (Pb 2+) based on an aptamer−target binding event, which is recognized by orientations of liquid crystals (LCs) at aqueous interfaces. The LC film suspended in the aqueous phase demonstrated a homeotropic orientation in contact with a cationic surfactant cetyltrimethylammonium bromide (CTAB) due to selfassembly of CTAB molecules at the aqueous−LC interface. The ordering of LC subsequently changed to planar in the presence of the spinach RNA aptamer (SRNA) due to interactions between CTAB and SRNA. In the presence of the Pb 2+ ion, the ordering of LC changed to homeotropic caused by reorganization of CTAB at the LC−aqueous interface. This is due to formation of more stable quadruplex structures of SRNA with Pb 2+ ions in comparison to the CTAB-SRNA complex. The sensor exhibited a detection limit of 3 nM, which is well below the permissible limit of Pb 2+ in drinking water. Our experiments establish that addition of Pb 2+ leads to (i) the formation of Pb 2+-SRNA complexes and (ii) a decrease in density of SRNA on the LC interface, but additional studies are required to determine which of these processes underlie the response of the LCs to the Pb 2+. We have also demonstrated the potential application of the LC sensor for detection of Pb 2+ in tap water. Unlike current laboratory-based heavy-metal-ion assays, this method is comparatively simple in terms of instrumentation, operation, and optical readout.
Molecular Systems Design & Engineering, 2018
An extensive study on the effect of terminal halogens on the structure–property relationship of p... more An extensive study on the effect of terminal halogens on the structure–property relationship of polar L-shaped mesogens has been elucidated.
The Journal of Physical Chemistry B, 2019
Herein, we report a new type of azobenzene based unsymmetrical bent-core molecules exhibiting pho... more Herein, we report a new type of azobenzene based unsymmetrical bent-core molecules exhibiting photoswitchability in liquid crystalline state, solid state, solution state and in mixture upon UV irradiation and intense visible light. The compounds exhibited solid state photochromism upon exposure of UV light whereas in liquid
The Analyst, Jan 26, 2018
Liquid crystal (LC) based optical sensors have been found to be very promising for detecting aque... more Liquid crystal (LC) based optical sensors have been found to be very promising for detecting aqueous biological samples due to the ease of optical detection, their cost effectiveness and the removal of the need for labelling biological species with fluorescent dyes. To date, all LC based sensors are studied in laboratories using conventional polarizing optical microscopy (POM), and no attention has been paid towards the fabrication of portable LC sensing devices for use in commercial purposes. Here, we designed and fabricated a 3D printed portable, lightweight, and inexpensive sensing device using a smartphone to detect the optical signal of LC based sensors. The accuracy of the optical signal using the fabricated sensing device is similar to that obtained using conventional POM. The fabricated sensing device, using a smartphone, gives a novel and new platform to LC based sensors for practical applications in the industrial world and people's daily lives.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017
The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature depen... more The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature dependent Raman spectroscopic technique. Pyrazinamide is a very useful drug used for the treatment of tuberculosis (TB) and plays a significant role in destroying the dormant tubercle bacilli which are not destroyed by other common TB drugs. Temperature dependent Raman spectra suggest polymorphic phase change from α → γ form of pyrazinamide between 145-146 °C. In situ Raman spectra of pyrazinamide between 145-146 °C show the conversion of α → γ form by the shift in C=O stretching vibration accompanied by several other changes. The phase change is characterized by the breaking of two linear N-H•••O type hydrogen bonds associated with C=O stretching vibration in α dimer and formation of one linear N-H•••N type hydrogen bond along with a weak intramolecular C-H•••O type hydrogen bond in the γ dimer.
Journal of Raman Spectroscopy, 2016
Temperature dependent Raman and X-ray diffraction studies of a calamitic ester substituted aryolh... more Temperature dependent Raman and X-ray diffraction studies of a calamitic ester substituted aryolhydrazone liquid crystal (LC) system; N-[4-(4ʹ-decyloxy)benzoyloxy benzylidene]-Nʹ-[4ʹ-decyloxybenzoyl]hydrazine (DB2H) have been performed to investigate the molecular arrangement and intermolecular interaction environment in LC phase. X-ray diffraction study with the help of density functional theoretical study gives the information of molecular tilt angle in SmC layer. Prominent Raman signatures of crystal I crystal II, crystal II SmC and SmC Isotropic phase transitions were identified in terms of changes in peak position and linewidth as well as Raman intensity. Analysis of Raman marker bands gives evidence of residual intermolecular hydrogen bonds between amide groups responsible for tilting arrangement in SmC phase. Copyright © 2016 John Wiley & Sons, Ltd.
Sensors and Actuators B: Chemical, 2016
We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg... more We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg 2+) in water using liquid crystals (LCs). In this system, newly synthesized amphiphilic potassium N-methyl-N-dodecyldithiocarbamate (MeDTC) was doped in 4-cyano-4-pentyl biphenyl (5CB) LC, which align LC molecules at aqueous interface and polar head group of the amphiphile acts as mecuric ion specific chelating ligand. When this sensor system was incubated in the aqueous solution containing Hg 2+ ions, a dark to bright transition of the image of LCs was observed. This was caused due to rapid and stable complex formation between dithiocarbamate chelating group of MeDTC with Hg 2+ ions at aqueous interface, which disrupted the orientation of LCs giving bright texture. The limit of detection of the system for aqueous Hg 2+ ion is 0.5 M. This sensor did not respond to other metal ions like Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , Na + , Mg 2+ and Ca 2+ , which are common environmental interference in water. We also demonstrated that this sensor is capable of detecting Hg 2+ ions in real water samples (tap water). The very simple and effective procedure reported here should facilitate the development of real time, portable and reliable LC based sensor for mercury pollution control.
RSC Adv., 2015
Lamellar smectic A to columnar mesophase crossover is observed in p-substituted aroylhydrazones b... more Lamellar smectic A to columnar mesophase crossover is observed in p-substituted aroylhydrazones by variation of the alkoxy chain density at peripherals.
Vibrational Spectroscopy, 2013
ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy... more ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of C trans cis
Chemical Physics Letters, 2014
A novel liquid crystal (LC) based sensor to detect trace level amount of hydrazine vapour has bee... more A novel liquid crystal (LC) based sensor to detect trace level amount of hydrazine vapour has been developed. The LC 4-pentyl-4-biphenylcarbonitrile (5CB) doped with 0.5 wt% 4-decyloxy benzaldehyde (DBA) shows dark to bright optical texture upon exposure of hydrazine vapours as revealed by polarizing optical microscopy under crossed polarizers. The hydrazine interacts with the doped DBA and form diimine compound which disrupt the orientation of aligned 5CB. The interaction between DBA and hydrazine has been also studied by Raman spectroscopy.
Liquid Crystals, 2015
ABSTRACT The present study is focused on the development of green microwave process for the synth... more ABSTRACT The present study is focused on the development of green microwave process for the synthesis of mesogenic substituted aroylhydrazones and their nickel(II) and copper(II) complexes. The compounds have been synthesised by microwave-assisted as well as thermal methods for comparison purpose. The compounds were structurally characterised by using suitable spectroscopic techniques. The mesomorphic properties were studied by differential scanning calorimetric analysis and polarising optical microscopy. The stable molecular structures of the mesogenic methylidenehydrazinato-nickel(II) complex have been obtained by density functional theoretical method to understand the structural origin responsible for the mesomorphic property.
Molecular Crystals and Liquid Crystals, 2013
A novel homologous series of α-4-(4-n-alkoxy cinnamoyloxy) phenyl β-2-nitro, 3-4 di methoxy benzo... more A novel homologous series of α-4-(4-n-alkoxy cinnamoyloxy) phenyl β-2-nitro, 3-4 di methoxy benzoyl ethylenes, H 2n+1 CnO-C 6 H 4-CH=CH-COO-C 6 H 4-CO-CH=CH-C 6 H 2 (NO 2) (OCH 3) 2 (n = 1-8, 10, 12, 14, 16, 18) has been synthesized. All these compounds have been characterized by suitable spectroscopic techniques. C 1 homologue is nonmesogenic, while C 2 homologue shows enantiotropic nematogenic property and the rest of the homologous (C 3-C 18) displayed enantiotropically smectogenic plus nematogenic phase. Phase transition temperatures and textures of the LC phase were determined by an optical polarizing microscopy (POM) equipped with a heating stage. The mesomorphic properties of these compounds were confirmed by differential scanning calorimetry (DSC) analysis.
Biosensors
In this work, we have combined the advantages of sequence programmability of DNA nanotechnology a... more In this work, we have combined the advantages of sequence programmability of DNA nanotechnology and optical birefringence of liquid crystals (LCs). Herein, DNA amphiphiles were adsorbed onto LC droplets. A unique phenomenon of LC droplet aggregation was demonstrated, using DNA-modified LC droplets, through complementary DNA hybridization. Further functionalization of DNA-modified LC droplets with a desired DNA sequence was used to detect a wide range of chemicals and biomolecules, such as Hg2+, thrombin, and enzymes, through LC droplet aggregation and vice versa, which can be seen through the naked eye. These DNA-modified LC droplets can be printed onto a desired patterned surface with temperature-induced responsiveness and reversibility. Overall, our work is the first to report DNA-modified LC droplet, which provides a general detection platform based on the development of DNA aptamers. Additionally, this work inspires the exploration of surface information visualization combined w...
Vibrational Spectroscopy, 2013
ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy... more ABSTRACT A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal → smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of C trans cis