Shubhra Jyotsna - Publications

1. Investigating the ferrimagnetic behaviour in 3C Fe7S8 nanoparticles - Bulletin of Materials Science · May 27, 2023

The magnetic properties of trigonal 3C Fe7S8 nanoparticles, synthesized via the thermal decomposition method, are investigated using temperature-dependent zero-field cooled (ZFC) and field-cooled (FC) magnetization (M–T) curves. The M–T data, recorded at 100 and 1000 Oe, reveal magnetic ordering with high Curie transition temperature (TC [ 300 K) in the specimen. The magnetization vs. applied magnetic field (M–H) data measured in the temperature range from 7 to 300 K show that the compound exhibits ferrimagnetic ordering. The values of coercivity (HC), saturation magnetization (M60 kOe), and remanent magnetization (MR) appear to increase at lower measuring temperatures. As the result of increasing M60 kOe at lower measuring temperatures, within the temperature range of 7 to 300 K, the maximum energy product (BHmax) has the highest value of 128 kG Oe at 7 K.

2. Luminescence turn-off detection of metal ions and explosives using graphene quantum dots - MRS Communications · Feb 14, 2022

Green luminescent graphene quantum dots (GQDs) obtained from combustion of white printing paper were used for detection of fourteen different metal ions and six different explosives in an aqueous medium. These were obtained using a microwave-assisted synthesis process. After optimizing the experimental conditions (pH 6; quantum yield (QY) ~ 38.2%), a sensitive sensing system was developed to detect explosives and free residual metal ions in the environment based on fluorescence quenching of GQDs. The as-synthesized GQDs, as a sensing system, is most sensitive for Cu2+ ion and 2,4-DNP with a detection limit of 0.62 µM and 0.50 µM, respectively.

3. Designing Multifunctional MOFs Using the Inorganic Motif [Cu3(μ3-OH)(μ-Pyz)] as an SBU and Their Properties - Crystal Growth & Design · Dec 19, 2018

In a continuation of our interest in pyrazole-based multifunctional metal–organic frameworks (MOFs), we report herein the construction of a series of Cu(II) MOFs using pyrazole and various 5-substituted isophthalic acids. The central theme is to generate MOFs using the crystal engineering strategy of spacer and node; however, for the node we have introduced a well-known inorganic motif, a [Cu3(μ3-OH)(μ-Pyz)3] unit. The appearance of the SBU in five MOFs confirms the robustness and reproducibility of the motif with some interesting structures of various dimensionality ranging from 1D helical and 2D herringbone grid to a complex 3D framework. The deployment of bent acids brings chirality via helicity in the system, as further confirmed by solid-state CD spectra. A detailed investigation of the porous MOFs reveals their importance as zeolite analogues for environment remediation. MOF-1–MOF-5 show some interesting photodegradation of harmful organic dyes. MOF-4 and MOF-5 show impressive selective CO2 gas sorption properties. Furthermore, magnetic properties associated with the trinuclear and hexanuclear SBUs of MOF-1 and MOF-3–MOF-5 have also been investigated.

4. The role of substrates and environment in piezoresponse force microscopy: A case study with regular glass slides - Solid State Communications · Aug 7, 2016

Piezoresponse force microscopy (PFM) is a powerful tool for probing nanometer-scale ferroelectric and piezoelectric properties. Hysteretic switching of the phase and amplitude of the PFM response are believed to be the hallmark of ferroelectric and piezoelectric behavior respectively. However, the application of PFM is limited by the fact that similar hysteretic effects may also arise from mechanisms not related to ferroelectricity or piezoelectricity. In this paper we report our studies on regular glass slides that show ferroelectric-like signal without being ferroelectric and frequently used as a substrate in PFM experiments. We demonstrate how the substrates and other environmental factors like relative humidity and experimental conditions may influence the PFM results on novel materials.

5. High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb - Applied Physics Letter · Jun 15, 2016

Piezoresponse force microscopy (PFM) is a powerful tool for probing nanometer-scale ferroelectric and piezoelectric properties. Hysteretic switching of the phase and amplitude of the PFM response are believed to be the hallmark of ferroelectric and piezoelectric behavior respectively. However, the application of PFM is limited by the fact that similar hysteretic effects may also arise from mechanisms not related to ferroelectricity or piezoelectricity. In this paper we report our studies on regular glass slides that show ferroelectric-like signal without being ferroelectric and frequently used as a substrate in PFM experiments. We demonstrate how the substrates and other environmental factors like relative humidity and experimental conditions may influence the PFM results on novel materials.

6. Ferroelectric-like response from the surface of SrTiO3 crystals at high temperatures - Journal of Applied Physics · Oct 9, 2014

Since SrTiO3 has a high dielectric constant, it is used as a substrate for a large number of complex physical systems for electrical characterization. Since SrTiO3 crystals are known to be non-ferroelectric/non-piezoelectric at room temperature and above, SrTiO3 has been believed to be a good choice as a substrate/base material for PFM (Piezoresponse Force Microscopy) on novel systems at room temperature. In this paper, from PFM-like measurement using an atomic force microscope on bare crystals of (110) SrTiO3 we show that ferroelectric and piezoelectric-like response may originate from bare SrTiO3 at remarkably high temperatures up to 420 K. Electrical domain writing and erasing are also possible using a scanning probe tip on the surface of SrTiO3 crystals. This observation indicates that the role of the electrical response of SrTiO3 needs to be revisited in the systems where the signature of ferroelectricity/piezoelectricity has been previously observed with SrTiO3 as a substrate/base material.