Research

Title of the Project : Graphene & its Related Materials for Energy & Environmental Applications

Funding Agency : Department of Science and Technology (DST)

Year               : 2016-2022

 Role                   : Principle Investigator

The hydrothermal approach was used to produce Dy3+/Eu3+ co-doped LiGd(WO4)2 phosphors (LGdW). The LGdW's tetragonal phase structure was established using

powder X-ray diffraction. The LGdW's microstructure was reported to be irregular, quasi-ellipsoidal, and oval-like using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photoluminescence (PL) spectra revealed emission peaks at roughly 488 (blue) and 575 nm (yellow) for Dy3+ doped LGdW, with x=0.06 being the optimal doping concentration of Dy3+ ions for maximal emission under 354 nm illumination. The PL emissions of Eu3+ and Dy3+ co-doped LGdW phosphors were also studied. Strong emissions were recorded at 488, 575, and 615 nm, corresponding to the 4F9/2 → 6H15/2 - Dy3+, 4F9/2 → 6H13/2 -Dy3+, 5D0 →7F2 -Eu3+ transitions, respectively. Dipole-dipole interactions were identified as the mechanism for energy transmission between Dy3+ and Eu3+ in LGW phosphors. The Dy3+/Eu3+ co-doped LGdW phosphors were tested for warm white-emitting solid-state lighting applications

A Ag3PO4/SnS2 heterojunction composite electrocatalyst was fabricated using combined facile liquid exfoliation and hydrothermal technique by varying the concentration of SnS2 in Ag3PO4. Tin disulfide (SnS2) is a transition metal dichalcogenide that is a promising non-precious catalyst for hydrogen evolution reaction (HER) application. However, the practical application of this material is limited due to its poor electrical conductivity, to overcome this limitation it is made as a composite with Ag3PO4 as a n-type semiconductor which function by absorbing visible light with its suitable bandgap. The HER is evaluated through the three-electrode electrochemical set-up, where the catalyst coated on carbon cloth serves as a working electrode along with Ag/AgCl and platinum wire as reference and counter electrode respectively. The electrocatalyst is considered as best when it has certain criteria including lesser value of overpotential implying low current requirement to produce hydrogen. The catalyst should obey the following criteria like low resistance, high conductive nature, smaller exchange current density and has large surface area to actively participate in the electrochemical reaction. Apparently Ag3PO4/5 wt% of SnS2 is found to be the best performing composite as evidenced from the experimental data. This work may be useful for heterojunction composite catalyst for the practical application in electrochemical water splitting.

A series of Sm3+:LiGd(WO4)2 phosphors with various concentrations of Sm3+ was prepared by the Pechini sol-gel method. The X-ray diffraction pattern of pure and Sm3+:LiGd(WO4)2 samples show the formation of LGW compound with tetragonal phase and a noticeable peaks shift toward lower angle with increasing Sm3+ concentration. The particles were of size 1–2 μm with irregular spherical and rectangular-like mixed morphology were witnessed from the scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) spectrum of the doped sample depicts the presence of all the elements in the Sm3+ doped LiGd(WO4)2 compound. Board band excitation for CTB and the number of sharp excitation peaks for f-f transition were observed in excitation spectra. The emission spectra show sharp peaks at 562, 606, 645 and 701 nm due to transition from sm3+ ions. The optimal dopant concentration of Sm3+ ions and its critical distance in LiGd(WO4)2 matrix was calculated to be x = 0.01 and 3.0 nm for intense emission peak at 645 nm that corresponds to 4G5/2 → 6H9/2 transition of Sm3+ ions. The type of energy transfer interaction among Sm3+ was found as electric dipole-dipole interaction using the Dexter theory. CIE coordinates and color purity (CP) for reddish-orange emission of the Sm3+:LiGd(WO4)2 phosphors was determined to be (0.568, 0.425) and 82.4%, respectively. The observed properties of Sm3+:LiGd(WO4)2 proves its potential application for near UV based light-emitting diodes and optical display devices.

Titanium oxide (TiO2) has received growing attention as a photocatalyst owing to its chemical stability and eco-friendly nature. Among the different phases of TiO2, pure anatase and mixed-phase TiO2 (Degussa P25) have been recognized as superior photocatalysts. Indeed, the mechanism of photocatalysis and the roles of various parameters in the process have been well documented for pure anatase TiO2 and Degussa P25. However, the pure rutile phase remains unexplored in photocatalytic applications. Thus, herein, we report a one-pot method to modify the surface of pure rutile TiO2 and examine the factors that affect its photocatalytic performance. This modification was achieved by treating rutile TiO2 with H2O2 under microwave irradiation. This led to the formation of core-shell rutile TiO2 with a crystalline core and an amorphous shell bearing Ti3+ and Ti–OH species on the surface. The photocatalytic performance of this modified TiO2 species was enhanced threefold compared with that of unmodified rutile TiO2. This basic understanding of improving the photocatalytic performance of rutile phase TiO2 will play a crucial role in enhancing the catalytic performance of other metal oxides.

Application No. : 1020150100444 dated 15-07-2015.

Registration No. : 1017668890000 dated 03-08-2017.  Link: https://goo.gl/WTR9ka 

Applicant: Inha University Research and Business Foundation.

Inventors: Ki-Joon Jeon, K. Vijayarangamuthu, Seungbae Ahn.

Application No. : 1020150100443 dated 2015-07-15.

Registration No. : 1017036380000 dated 01-02-2017.  Link: https:/goo.gl/9z2San

Applicant: Inha University Research and Business Foundation.

Inventors: Ki-Joon Jeon, K. Vijayarangamuthu, Seungbae Ahn.

Application No. : 1020150100445 dated 2015.07.15.

Registration No. : 1016863980000 dated 08-12-2016.   https://goo.gl/yv4xfE

Applicant: Inha University Research and Business Foundation.

Inventors: Ki-Joon Jeon, Seungbae Ahn, K. Vijayarangamuthu.