scispace - formally typeset
Search or ask a question

Showing papers by "Rajib Chakraborty published in 2019"


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional triangular/hexagonal lattice silicon photonic crystal (Si) arrangement with hexagonal unit cells and two micromachined silicon cantilever tips is proposed for optical sensing of pressure.

13 citations


Journal ArticleDOI
TL;DR: In this paper, chlorophyll functionalised carbon nanostructures are co-deposited from aqueous media along with in-situ formed hydroxyapatite-calcium orthophosphate phases to develop a biocompatible coating, which eventually can increase the overall coating strength as reinforcement.

13 citations


Journal ArticleDOI
TL;DR: A large number of people from at least 25 countries are suffering from fluorosis, and the number of cases is likely to increase as more countries become aware of the risks to human health.
Abstract: Consumption of excess fluorides through drinking water and its adverse effects on human health is of global concern. Given that people from at least 25 countries are suffering from fluorosis, globa...

13 citations


Journal ArticleDOI
TL;DR: In this paper, the authors have developed a composite of polypyrrole-calcium orthophosphate-hydroxyapatite functional composite coating, which is synthesized over the metallic implant surfaces through pulsed electrochemical deposition.
Abstract: Polypyrrole-calcium orthophosphate-hydroxyapatite functional composite coating is synthesized over the metallic implant surfaces through pulsed electrochemical deposition. Polypyrrole particles are photo-functionalized with the help of chlorophyll during polymerization for their dispersion in the aqueous electrolyte bath. In-situ formation of calcium phosphate phases along with co-deposition of chlorophyll functionalized-polypyrrole particles lead to formation of a ceramic-polymer composite coating. Concentration of chlorophyll molecule in the solution greatly affects the polymerization reaction and subsequent incorporation of functionalized polymer in final coating. Thus, various types of composites structures are developed based on differential amount of polypyrrole presence through varying concentration of chlorophyll, for a detailed comparative study. The polymer chain length and formation bond energy significantly influence the in-situ formation mechanism along with crystal growth direction and rate of formation of various calcium phosphate phases. At low concentration, polymer reinforced hydroxyapatite flakes are formed. High concentration of chlorophyll lead to formation of both the individual polymer phase along with polymer reinforced calcium phosphate phase. While at very high concentration, a polymer layer is formed reinforced with nanocrystalline hydroxyapatite particles. Reinforced coating exhibits three fold higher electrochemical corrosion resistances as compared to bare hydroxyapatite coating. All the coating surfaces display superior osteoconduction capabilities through the formation of stoichiometric hydroxyapatite spherical particles within 7 to 14 days of contact. During osteoconduction, a unique nano porous honeycomb structure over the formed apatite surface enriched with sodium and magnesium ions are formed which would help to ensure higher protein absorption along with a better bonding of cells over the coating surface. Thus, this ceramic-polymer composite developed for the first time through chlorophyll functionalization, can act as one of the potential materials for improvement of both bio-functionalities and corrosion resistance of metallic implant surfaces.

9 citations


Journal ArticleDOI
TL;DR: In this article, the zinc substituted and zinc reinforced calcium phosphate composites were prepared by electro chemical deposition from aqueous electrolyte bath to understand the relation between in-situ formation mechanism of various phases with varying reaction kinematics and kinetics.

4 citations


Journal ArticleDOI
TL;DR: In this paper, a segmented silicon based multimode to dual port slot structure on silicon-on-insulator platform is proposed which can be used as a refractive index sensing device.
Abstract: A segmented silicon based multimode to dual port slot structure on silicon-on-insulator platform is proposed which can be used as a refractive-index sensing device. The introduction of segmentation leads to tuning the effective index of the device which results in increasing compactness of the sensing device. Although the structure supporting TM mode is more compact than TE mode, but TE mode is considered here as vertical slots in the output section enhances optical signal in the slots for TE mode only. By considering dual output, the device length is reduced further as dual self-imaging length is less compared to single self-imaging distance for symmetrical multimode section input. The surface sensitivity of the structure has a typical value of∼2249 nm/RIU. Relative sensitivity can be calculated from the ratio of field amplitudes of the arms of the dual output. Matrix method and 2D FDTD is used for the entire analysis.⁠

2 citations


Journal ArticleDOI
TL;DR: Electrolytes like sodium, potassium, magnesium, calcium etc. are essential for maintaining the fluid balance and homeostasis in the human body.
Abstract: Electrolytes like sodium, potassium, magnesium, calcium etc. are essential for maintaining the fluid balance and homeostasis in the human body. They are also useful biomarkers in understanding the pathophysiology of a host of diseases. The major aim of this study is to develop a strategy for fast, reliable and simultaneous assessment of sodium (Na+), lithium (Li+) and potassium (K+) in human samples. The device is developed utilizing the basic principle of optical emission spectroscopy (OES). The atomic emission spectra of the ions during their transition are acquired and analysed for the simultaneous detection of the specific electrolytes. Our self-developed software is used to acquire the optical signals and to calculate the electrolyte concentration. The device shows a satisfactory adjusted R2 value for the three electrolytes (0.954, 0.932 and 0.984 for Na+, Li+ and K+, respectively) with respect to the standard ISE method. The device utilizes a very small amount (∼100 μL) of serum and provides a good correlation with commercially available costly devices like blood gas analysers and ion selective electrodes for blood electrolyte analysis. Our self-developed low-cost device has the ability to offer a simultaneous assessment of the essential electrolytes. To our understanding, this device would be ideal for the point of care management of constantly recurring physiological disorders including Chronic Kidney Diseases (CKD) and bipolar disorder in economically challenged countries.

2 citations


Journal ArticleDOI
TL;DR: In this article, a symmetric multi cavity resonator for flat-top transmission is reported which is simple and compact than the similar conventional structures and the study of the output spectra is carried out in terms of layer thickness and change in angle of incidence.
Abstract: Antisymmetric multi cavity resonator useful for flat top transmission is reported which is simple and compact than the similar conventional structures. The study of the output spectra is carried out in terms of layer thickness and change in angle of incidence. Electro-optic property of the EO polymer is utilized to convert flat-top output with full width half maximum (FWHM) bandwidth of 10 nm into narrowband output of 0.64 nm (FWHM bandwidth) by applying a maximum voltage of 500 V across the structure. It was shown here that by controlling the low index layer widths, angle of incidence of the light and applying a voltage of 300 V results in a flattop spectrum of FWHM bandwidth of 2.5 nm with tuning sensitivity 0.033 nm/V. The tuning sensitivity and bandwidth of the reported hybrid filter can also be customized comparatively at lower applied voltage than the previously reported electro-optically tunable filters.