Monalisa Pal

Surface Modification of MnFe2O4 Nanoparticles to Impart Intrinsic Multiple Fluorescence and Novel Photocatalytic Properties

The MnFe2O4 nanoparticle has been among the most frequently chosen systems due to its diverse applications in the fields ranging from medical diagnostics to magnetic hyperthermia and site-specific drug delivery. Although numerous efforts have been directed in the synthesis of monodisperse MnFe2O4 nanocrystals, unfortunately, however, studies regarding the tuning of surface property of the synthesized nanocrystals through functionalization are sparse in the existing literature. Herein, we demonstrate the emergence of intrinsic multicolor fluorescence in MnFe2O4 nanoparticles from blue, cyan, and green to red, upon functionalization and further surface modification with a small organic ligand, Na-tartrate. Moreover, we have found an unprecedented photocatalytic property of the functionalized MnFe2O4 nanoparticles in the degradation of a model water contaminant. Detailed characterization through XRD, TEM, and FTIR confirms the very small size and functionalization of MnFe2O4 nanoparticles with a biocompatible ligand. Proper investigation through UV-visible absorption, steady-state and time-resolved photoluminescence study reveals that ligand-to-metal charge-transfer transition from the tartrate ligand to the lowest unoccupied energy level of Mn(2+/3+)or Fe(3+) of the NPs and Jahn-Teller distorted d-d transitions centered over Mn(3+) ions in the NPs play the key role behind the generation of multiple fluorescence from the ligand-functionalized MnFe2O4 nanoparticles. VSM measurements indicates that the superparamagnetic nature of MnFe2O4 nanoparticles remains unchanged even after surface modification. We believe that the developed superparamagnetic, multicolor fluorescent MnFe2O4 nanopaticles would open up new opportunities as well as enhance their beneficial activities toward diverse applications.

Tuning of magnetic properties of CoFe2O4 nanoparticles through charge transfer effect

Herein, we report the microscopic origin of surfactant modified magnetic properties of nearly monodispersed CoFe2O4 nanoparticles (NPs). Surface modification is carried out with four surfactants having π-acceptor/π-donor head group along with different chain-length. Upon functionalization, magnetic NPs show a maximum 65.61% increase in coercivity and 78.24% decrease in magnetization as compared to the bare one. Furthermore, π-donor head group surfactant modified CoFe2O4 NPs show higher coercivity and magnetization with respect to π-acceptor head group surfactant modified NPs and with the increase in chain-length of the surfactant, coercivity of NPs enhances slightly. These consequences are explained in context of crystal field splitting energy and steric hindrance offered by the surfactant.

Facile functionalization of Fe2O3 nanoparticles to induce inherent photoluminescence and excellent photocatalytic activity

Herein, we report the emergence of intrinsic multicolor photoluminescence in Fe2O3 nanoparticles (NPs) ranging from blue, cyan, to green, upon facile functionalization and further surface modification with a small organic ligand, Na-tartrate. Moreover, we have found unprecedented photocatalytic property of the functionalized Fe2O3 NPs in the degradation of a model water-contaminant. Meticulous investigation through UV-visible absorption and fluorescence study along with theoretical support from literature unfolds that ligand-to-metal charge-transfer transition from the tartrate ligand to the lowest unoccupied energy level of Fe3+ of the NPs and d−d transitions centered over Fe3+ ions in the NPs play the key role in the emergence of multiple photoluminescence from the ligand functionalized Fe2O3 NPs. Moreover, vibrating sample magnetometry measurements demonstrate that the surface modification changes the magnetic behaviour of Fe2O3 NPs upon functionalization. We believe that the great potential of our ver...

Electrochemical supercapacitor based on double perovskite Y2NiMnO6 nanowires

The present work unveils the electrochemical properties of a newly emerging multiferroic material, double perovskite Y2NiMnO6, as an active material for the positive electrode of electrochemical supercapacitors. We have designed a facile, low temperature hydrothermal route for the fabrication of Y2NiMnO6 nanowires, to achieve the beneficial effects of a large active surface area at the nanoscale on the electrochemical properties of the material. A comparative study reveals that the Y2NiMnO6 nanowire-based electrode is superior than its bulk counterpart, exhibiting higher specific capacitance (77.76 F g−1 at 30 mA g−1), energy density (0.89 W h kg−1 at 30 mA g−1), power density (19.27 W kg−1 at 150 mA g−1) and cyclability (>1800 cycles), in addition to a good retention of 70.17%.

Surface chemistry modulated introduction of multifunctionality within Co3O4 nanocubes

Co3O4 as a multifunctional nanomaterial, possessing simultaneously, unique optical, magnetic, and catalytic properties is sparse in the existing literature. We have activated intrinsic multicolor fluorescence covering the entire visible region by the functionalization of Co3O4 nanocubes (NCs) with Na-tartrate. The functionalized Co3O4 NCs show excellent catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, which opens up a way for the possible application of the NCs toward therapeutic and wastewater treatment. Systematic investigations using UV-visible absorption, steady state, and time-resolved photoluminescence studies reveal the mechanistic origin behind the generation of multicolor fluorescence from the ligand-functionalized Co3O4 NCs. Moreover, from the magnetic study we have found that the room temperature antiferromagnetic nature of Co3O4 NCs turns to ferromagnetic after ligand functionalization due to the surface modification of the NCs. We believe that the developed multifunctional Co3O4 NCs could open up a new horizon toward their diverse applications in the present era of multitasking.

Ligand-Induced Evolution of Intrinsic Fluorescence and Catalytic Activity from Cobalt Ferrite Nanoparticles

To develop CoFe(2)O(4) as magneto-fluorescent nanoparticles (NPs) for biomedical applications, it would be advantageous to identify any intrinsic fluorescence of this important magnetic material by simply adjusting the surface chemistry of the NPs themselves. Herein, we demonstrate that intrinsic multicolor fluorescence, covering the whole visible region, can be induced by facile functionalization of CoFe(2)O(4) NPs with Na-tartrate. Moreover, the functionalized CoFe(2)O(4) NPs also show unprecedented catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, pioneering the potential application of these NPs in therapeutics and wastewater treatment. Detailed investigation through various spectroscopic tools unveils the story behind the emergence of this unique optical property of CoFe(2)O(4) NPs upon functionalization with tartrate ligands. We believe our developed multifunctional CoFe(2)O(4) NPs hold great promise for advanced biomedical and technological applications.

Research Update: Facile synthesis of CoFe2O4 nano-hollow spheres for efficient bilirubin adsorption

Herein, we report an unprecedented bilirubin (BR) adsorption efficiency of CoFe2O4 (CFO) nanostructures in contrast to the commercially available activated carbon and resin which are generally used for haemoperfusion and haemodialysis. We have synthesized CFO nanoparticles of diameter 100 nm and a series of nano-hollow spheres of diameter 100, 160, 250, and 350 nm using a simple template free solvothermal technique through proper variation of reaction time and capping agent, oleylamine (OLA), respectively, and carried out SiO2 coating by employing Stober method. The comparative BR adsorption study of CFO and SiO2 coated CFO nanostructures indicates that apart from porosity and hollow configuration of nanostructures, the electrostatic affinity between anionic carboxyl group of BR and cationic amine group of OLA plays a significant role in adsorbing BR. Finally, we demonstrate that the BR adsorption capacity of the nanostructures can be tailored by varying the morphology as well as size of the nanostructures. We believe that our developed magnetic nanostructures could be considered as a potential material towards therapeutic applications against hyperbilirubinemia.

Acoustic vibration induced high electromagnetic responses of Fe3O4 nano-hollow spheres in the THz regime

Herein, we investigate the origin of enhanced absorption and complex conductivity of magnetite (Fe3O4) nano-hollow spheres (NHSs) in contrast to its nanoparticles (NPs) configuration in the frequency range 0.4–2.0 THz. The maximum absorption for NHSs and NPs of the same average diameter (~100 nm) are found to be 246.27 and 48.35 cm−1 at 1.8 THz, respectively. A detailed study suggests that the multiple resonance peaks in the absorption spectra are due to low frequency acoustic vibrational phonon modes of Fe3O4 nanostructures. Moreover, we demonstrate that the magnitude of total absorption can be tailored by varying the shell thickness of NHSs. It is found to increase with increasing shell thickness, and attain a maximum value of 498.5 cm−1 for the NHSs of average diameter 350 nm at 1.8 THz. The invariance of frequency dependent magnetic permeability points out that the absorption is basically due to dielectric loss instead of magnetic loss. The enhanced THz conductivity of Fe3O4 NHSs, as compared to NPs is described in light of thermally activated polaronic hopping which is found to increase with increasing THz absorption. Finally, the size dependent THz conductivity of NHSs confirms its sole dependence on the magnitude of THz absorptivity.

Evaluation of SiO2@CoFe2O4 nano-hollow spheres through THz pulses

We have synthesized cobalt ferrite (CFO) nanoparticles (NPs) of diameter 100 nm and nano-hollow spheres (NHSs) of diameter 100, 160, 250, and 350 nm by a facile one step template free solvothermal technique and carried out SiO2 coating on their surface following Stober method. The phase and morphology of the nanostructures were confirmed by X-ray diffraction and transmission electron microscope. The magnetic measurements were carried out by vibrating sample magnetometer in order to study the influence of SiO2 coating on the magnetic properties of bare CFO nanostructures. Furthermore, we have applied THz time domain spectroscopy to investigate the THz absorption property of these nanostructures in the frequency range 1.0–2.5 THz. Detailed morphology and size dependent THz absorption study unfolds that the absorption property of these nanostructures sensitively carries the unique signature of its dielectric property.

Terahertz conductivity study of magnetite nanostructures

Herein, we report the complex conductivity study of a series of semi-metallic Fe3O4 nano hollow spheres (NHSs) of increasing diameter and its solid configuration in the frequency range of 0.4-3.2 terahertz (THz) through THz Time Domain Spectroscopy. Meticulous analysis of these spectra suggests that they follow Plasmon Model instead of classical Drude Model due to strong plasmon confinement within the nanostructure. Furthermore, we demonstrate the sensitive dependence of THz conductivity on the morphology of the nanostructure which is explained in the context of the strength of localized surface plasmon resonance upon THz excitation. Finally, the size dependent study of NHSs reveals that the magnitude of conductivity increases with increasing average crystallite size of the nanostructure.