Christu Rajan - Academia.edu (original) (raw)

Papers by Christu Rajan

Accumulation of aluminum in human has been reported to be associated with dementia, Parkinson’s d... more Accumulation of aluminum in human has been reported to be associated with dementia, Parkinson’s disease, and
Alzheimer’s disease. The objectives of this study were to evaluate an edible biopolymer poly(γ-glutamic acid) (γ-PGA) for
aluminum removal efficiency under in vitro conditions as affected by pH, contact time, aluminum concentration, temperature,
ionic strength, and essential metals in both aqueous aluminum solution and simulated gastrointestinal fluid (GIF). A low
aluminum adsorption occurred at pH 1.5−2.5, followed by a maximum adsorption at pH 3.0−4.0 and precipitating thereafter as
aluminum hydroxide at pH > 4. Adsorption was extremely fast with 81−96% of total adsorption being attained within 1 min,
reaching equilibrium in 5−10 min. Kinetic data at low (10 mg/L) and high (50 mg/L) concentrations were well described by
pseudo-first-order and pseudo-second-order models, respectively. Equilibrium adsorption isotherms at different temperatures
were precisely fitted by both Langmuir and Redlich−Peterson models with the maximum adsorption capacities at 25, 37, and 50
°C being 35.85, 38.68, and 44.23 mg/g, respectively. Thermodynamic calculations suggested endothermic and spontaneous
nature of aluminum adsorption by γ-PGA with increased randomness at the solid/solution interface. Variation in ionic strengths
did not alter the adsorption capacity, however, the incorporation of essential metals significantly reduced the aluminum
adsorption by following the order copper > iron > zinc > calcium > potassium. Compared to aqueous solution, the aluminum
adsorption from simulated GIF was high at all studied pH (1−4) with Langmuir monolayer adsorption capacity being 49.43 mg/
g at 37 °C and pH 4. The outcome of this study suggests that γ-PGA could be used as a safe detoxifying agent for aluminum.

Photodynamic therapy (PDT) is a light-induced chemical reaction that produces localized tissue da... more Photodynamic therapy (PDT) is a light-induced chemical reaction that produces
localized tissue damage for the treatment of cancers and various nonmalignant
conditions. In the clinic, patients treated with PDT should be kept away from direct
sunlight or strong indoor lighting to avoid skin phototoxicity. In a previous study, it
was demonstrated that the skin phototoxicity of meta - tetra (hydroxyphenyl)chlorin
(m-THPC), a photosensitizer used in the clinic, can be signifi cantly reduced after
micellar encapsulation; however, no improvement in antitumor effi cacy was observed.
In this work, a folate-conjugated polymeric m-THPC delivery system is developed
for improving tumor targeting of the photosensitizer, preventing photodamage to
the healthy tissue, and increasing the effectiveness of the photosensitizers. The results
demonstrate that folate-conjugated m-THPC-loaded micelles with particle sizes around
100 nm are taken up and accumulated by folate receptor-overexpressed KB cells in
vitro and in vivo, and their PDT has no signifi cant adverse effects on the body weight
of mice. After an extended delivery time, a single dose of folate-conjugated m-THPCloaded
micelles has higher antitumor effects (tumor growth inhibition = 92%) through
inhibition of cell proliferation and reduction of vessel density than free m-THPC or
m-THPC-loaded micelles at an equivalent m-THPC concentration of 0.3 mg kg − 1
after irradiation. Furthermore, folate-conjugated m-THPC-loaded micelles at only
0.2 mg kg − 1 m-THPC have a similar antitumor effi cacy to m-THPC or m-THPCloaded
micelles with the m-THPC concentration at 0.3 mg kg − 1 , which indicates that the
folate conjugation on the micellar photosensitizer apparently reduces the requirement
of m-THPC for PDT. Thus, folate-conjugated m-THPC-loaded micelles with improved
selectivity via folate–folate receptor interactions have the potential to reduce, not only
the skin photosensitivity, but also the drug dose requirement for clinical PDT.

Two novel hydrogen-bonded (H-bonded) triads consisting of triazine derivatives complexed with a p... more Two novel hydrogen-bonded (H-bonded) triads consisting of triazine derivatives complexed with
a perylene bisimide core were synthesized and characterized. NMR, UV/vis, and fluorescence spectra of
these supramolecular triads confirmed the formation of strong multiple H-bonding, which were also
proven to be nano-sized H-aggregates by X-ray diffraction (XRD) measurements.

Two novel highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N4,N6-dibutyl-1,3,5- triazi... more Two novel highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N4,N6-dibutyl-1,3,5-
triazine-4,6-diamine probe were synthesized via normal synthetic routes. Both dendrimers (TPAD1 and
TPAD2) form H-bonded donor–acceptor–donor (D–A–D) supramolecular triads TPAD1-PBITPAD1
and TPAD2-PBI-TPAD2 with 3,4,9,10-perylene tetra carboxylic diimide derivative (PBI). The
presence of multiple H-bonds in the solution state was elucidated by 1HNMRtitrations and IR spectral
studies. J-aggregations and electron/energy transfers provided by both dendrimers were verified by
UV–Vis and photoluminescence (PL) titrations with PBI and the particle sizes of supramolecular triads
were calculated by X-ray diffraction (XRD) analysis. Similarly, both dendrimers also showed
sensitivities towards Cu2+ in comparison with 19 interfering metal ions, which were evidenced via UV–
Vis and PL titraions in both single and dual metal systems. The maximum detection limit of Cu2+ ions
was determined to be 20 ppm from PL titrations for both dendrimers, and the 1 : 2 stoichiometry of the
complexes formed by both dendrimers (TPAD1-Cu2+ and TPAD2-Cu2+) were calculated by Job plots
based on UV–Vis absorption titrations. More importantly, the binding mechanism of the 1,3,5-triazine-
4,6-diamine probe of both dendrimers was well characterized by 1H and 13C NMR titrations ([D8]
THF : D2O ¼ 2 : 1 in vol.) and supported by the fluorescence reversibility by adding metal ions and
PMDTA sequentiall

New p-extended porphyrin dyes YD26–YD29 with long alkoxyl chains at the ortho positions of the me... more New p-extended porphyrin dyes YD26–YD29 with long alkoxyl chains at the ortho positions of the mesophenyls,
and meta di-tert-butylphenyl-substituted porphyrins YD12–CN, and YD13–CN were synthesized for
dye-sensitized solar cells, and their optical, electrochemical and photovoltaic properties were investigated
and compared with those of YD12 and YD13. The absorption spectra of YD26–YD29 showed a slight red
shift of Soret bands and blue shift of Q bands as compared to the meta-substituted porphyrins due to the
electron-donating effects of dioctyloxy substituents at the ortho-positions of the meso-phenyl rings.
Replacement of the carboxyl with a cyanoacrylic acid as the anchoring group results in significant
broadening and red shifts of the absorptions, which is due to the strong electronic coupling between the
pull unit and the porphyrin ring facilitated by the CRC triple bond. The electrochemical studies and
quantum-chemical calculations (DFT) indicated that the ortho alkoxy-substituted sensitizers exhibit lower
oxidation potential, i.e. a higher HOMO energy level, and their HOMO–LUMO gaps are comparable to the
meta-substituted analogues. The photovoltaic measurements confirmed that the ortho-octyloxy groups in
the two meso-phenyls of YD26 and YD27 play a significant role in preventing dye aggregation thereby
enhancing the corresponding short-circuit current density and open-circuit voltage. The power conversion
efficiency (Z) of YD26 is 8.04%, which is 11% higher than that of YD12, whereas the efficiency of YD27 is
6.03%, which is 135% higher than that of YD13. On the other hand, the poor performance of YD28 and
YD29 is due to the floppy structural nature and limited molecular rigidity of the cyanoacrylic acid anchor.

Cheminform, 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tetrahedron Letters, 2007

Bis-chromanones and their derivatives were prepared via alkylation, saponification and cyclizatio... more Bis-chromanones and their derivatives were prepared via alkylation, saponification and cyclization reactions under conventional conditions. These bis-chromanones displayed bathochromic shifts and also showed potential biological activity against human pathogenic bacteria.

Singlecrystalsofsemicarbazoneofp-hydroxy-3-methoxyacetophenone(SPH3MA)weregrownbya slow evaporati... more Singlecrystalsofsemicarbazoneofp-hydroxy-3-methoxyacetophenone(SPH3MA)weregrownbya
slow evaporationsolutiongrowthtechniqueatroomtemperature.Thisisthefirstreportinthe
literatureonthecrystallizationofSPH3MA.Thecellparametersofthegrowncrystalswereestimated
by singlecrystalX-raydiffractionanalysis.ThevariousplanesofreflectionwereidentifiedfromtheXRD
powderpattern.ThepresenceoffunctionalgroupswasidentifiedfromFTIRand 1H NMR.Theresults
were foundtobeinaccordancewiththestructureofthecrystal.Theformationofchargetransfer
complexwasconfirmedbyUV–vis–NIRspectroscopy.Thethermalstabilityofthegrowncrystalwas
studiedbythermalanalysis.

Organic single crystal of Phthalic Anhydride (PA) was successfully grown by slow evaporation meth... more Organic single crystal of Phthalic Anhydride (PA) was successfully grown by slow evaporation
method. The structure of the grown crystal was confirmed by X-ray diffraction analysis. FT-IR, and
FT-Raman spectral analysis of the crystalline sample reveal that it consists of all functional groups.
The number of protons was identified from H1-NMR spectral analysis. UV-visible and
photoluminescence spectral analyses were carried out for the grown crystals. The thermal behavior
was studied with TGA-DTA analyses. The existence of second harmonic generation (SHG) signal
was observed using Nd:YAG laser with a fundamental wavelength of 1064 nm.

Herein the synthesis and the crystal growth of benzoyl valine (BV), an organic nonlinear optical ... more Herein the synthesis and the crystal growth of benzoyl valine (BV), an organic nonlinear optical
(NLO) material for frequency conversion was grown by slow evaporation solution growth technique at room
temperature has been reported. The compound was prepared by Stockman method of benzoylation. The
solubility curve shows linear nature up to a temperature of 313 K. XRD study reveals that the crystal
belongs to monoclinic system with P21 non-centrosymmetric space group. The fundamental vibrational
frequency of various functional groups (400−4000 cm
−1) in the crystal was determined from FTIR analysis.
1H and 13C NMR spectral studies reveal the presence of proton and carbon network in the grown crystalline
sample. The optical behaviour of the crystal was ascertained by optical UV absorption spectral studies.
The UV cut off region (λmax) lies around 200 nm and the crystal is absolutely transparent from 220–
800 nm suggesting its application as NLO material. The thermal stability of the crystal was determined
by thermogravimetric and differential thermal analyses. Laser damage threshold of BV was found to be
0.34 GW/cm2 and hence BV can be used in frequency doubler system. Photoconductivity study of BV
revealed negative photoconductiviting nature of the sample. The microhardness studies confirm that BV
has a moderate Vickers hardness number (VHN) value in comparison to the other organic NLO crystals.

Journal of Materials Science & Technology, 2011

Single crystals of β-Naphthol (βN), an organic nonlinear optical (NLO) material was successfully ... more Single crystals of β-Naphthol (βN), an organic nonlinear optical (NLO) material was successfully grown by temperature lowering method using chloroform as solvent. The initial compound was purified by repeated recrystallization process. As-grown crystals were characterized by single crystal X-ray diffraction (XRD) studies to ascertain that βN crystal crystallized in the monoclinic system with a noncemtrosymmetric space group. Vibrational frequencies of various functional groups in the crystals were derived from Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (NMR) spectrum. Optical characterization was done using UV-Visible near-infrared (NIR) spectroscopy. The thermal behaviour of the material was studied by thermo gravimetric and differential thermal plots. Scanning electron microscopy (SEM) study was carried out on the surface of the grown crystals to investigate the nature of defects in the crystal surface and the NLO property of the crystal was tested by Nd:YAG laser as a source.

Journal of Thermal Analysis and Calorimetry

The growth of semicarbazone of p-hydroxy benzaldehyde (SPHB) single crystal by slow evaporation s... more The growth of semicarbazone of p-hydroxy benzaldehyde (SPHB) single crystal by slow evaporation solution growth technique is reported in this article. The grown crystal was subjected to powder XRD study to identify the crystalline nature. Single crystal XRD study was done to measure unit cell parameters and to confirm the crystal structure. In the presence of various functional groups of SPHB was identified by FTIR spectrum. Its optical behavior was examined by UV–Vis–NIR spectrum and the crystal was found to have transparency in the region between 245 and 1100 nm. Thermal properties of the crystal were investigated using thermogravimetric and differential thermal analysis (TG-DTA), which indicated that the melting of the material occurred before decomposition. The nonlinear optical (NLO) property was tested by Kurtz–Perry powder technique for second harmonic generations.

Journal of Thermal Analysis and Calorimetry

Semicarbazone of dl-camphor (SdlC) crystals were grown using methanol as a solvent by slow evapor... more Semicarbazone of dl-camphor (SdlC) crystals were grown using methanol as a solvent by slow evaporation solution growth technique at room temperature. Formation of the product and the presence of various functional groups present in the grown crystal have been identified using FTIR spectra. Single crystal XRD study was conducted to obtain the crystal structure and lattice parameters. The grown crystal was subjected to 1HNMR and 13CNMR spectral studies and TG-DTA in order to confirm its structure, purity, and stability, respectively. The optical transparency of the crystal was tested using UV–Vis–NIR spectroscopy. The nonlinear optical (NLO) property of the grown crystal was confirmed from the second harmonic generation (SHG) by Kurtz–Perry powder test.

Journal of Thermal Analysis and Calorimetry

A new organic nonlinear optical material semicarbazone of p-hydroxy acetophenone (SPHA) was synth... more A new organic nonlinear optical material semicarbazone of p-hydroxy acetophenone (SPHA) was synthesized. Good quality single crystal of SPHA was successfully grown by slow evaporation method at room temperature. The crystal system was identified and lattice dimensions were measured from the single crystal X-ray diffraction (XRD) analysis. The various planes of reflection were identified from the powder XRD pattern. The presence of functional groups was qualitatively found by Fourier transform infrared (FTIR) spectral analysis. The proton and carbon nuclear magnetic resonance (1HNMR and 13CNMR) spectral studies confirmed the presence of hydrogen and carbon bonded network in the grown crystal. The UV–Visible absorption spectrum was recorded to study the optical transmittance in the range from 200 to 800 nm. The thermal stability of compound was determined by thermogravimetric and differential thermal analysis (TG-DTA) traces. The existence of second harmonic generation (SHG) signal was observed using Nd:YAG laser with fundamental wavelength of 1064 nm.

Cheminform, 2008

Tetrahedron Letters, 2007

Journal of Materials Science & Technology, 2011

Journal of Thermal Analysis and Calorimetry