Literature Presentation14th Jan 2015

By Saurav Chandra Sarma

Characterizations

XRD

SEM

EDS

HRTEM

UV-Vis-DRS

PL

Schematic illustration of the synthesis process

XRD patterns ofa) Pure TiO2 nanobeltb) Scaly Sn3O4 nanoflakesc) Sn3O4/TiO2

•Molar ratio Sn/Ti=2/1•TiO2 is in anatase phase•Sn3O4 has triclinic phase

SEM images

SEM images of scaly Sn3O4/TiO2 (molar ratio Sn/Ti=2/1) heterostructure obtained atdifferent synthetic stages of (a) 1 h; (b) 4 h; (c) 12 h.

SEM images

a) TiO2 nanobeltsb) Sn3O4 nanoflakesc,d) Sn3O4/TiO2

nanobelts

Sn3O4 nanoflakes are assembled perpendicular to the surface of TiO2 nanobelts.

HRTEM images

a) (101) layered structure of triclinic Sn3O4

b) The distance between the lattice fringes agree well with the triclinic Sn3O4 phase.

c) Individual scaly nanobeltheterostructure.

d) Sn3O4 and TiO2 at the interface level.

e-h) EDS elemental mapping analysis.

UV-Vis Diffuse Reflectance Spectrum

Indirect band gap using Kubelka-Munk method

a) Sn3O4 (475 nm)

b) Sn3O4/TiO2 (479 nm)

c) TiO2 (380 nm)

Photocatalytic Dye degradation

• Dye: Methyl Orange

• Irradiated with UV and

simulated solar lights

• After regular interval

aliquot collected,

centrifuged and studied

with UV-vis

spectrophotometer.

Photocatalytic Dye degradation

Photocatalytic Hydrogen Evolution

Schematic diagram of electron transfer in Sn3O4/TiO2

heterostructure

Comparison of the phtocatalytichydrogen evolution activities of different samples

Photocatalytic Hydrogen Evolution

PL spectra of (a) TiO2 nanobelts, (b) (b) Sn3O4/TiO2 (molar ratioSn/Ti= 2:1) heterostructure,(c) Sn3O4 nanoflakes.

Photoelectrochemical measurements

Mott-Schottky plots of (a) scaly Sn3O4 and (b) TiO2 nanobelt atdifferent frequencies in a 0.1 M Na2SO4 solution (0.1 M; pH= 6.8)electrolyte.

Conclusions

The hydrothermal growth of Sn3O4 resulted incrystallographic connection of (1-11) plane of Sn3O4 and (101)plane of TiO2.

Sn3O4/TiO2 nanobelts can absorb both in the UV and visiblerange.

The heterostructure exhibits superior photocatalyticpollutant degradation and hydrogen evolution under either UVor visible light irradiation.

Partial cation exchange synthesis

Scheme of the synthesis of pristine Cu2S NCs and their exchange reactions to CIS and CIZS NCs

Sequence exchange

Combined Exchange

TEM images of Cu2S and CIS

a) Parent Cu2S NCs, b)Exchanged CIS NCs, c,d) HRTEM image,FT analysis of e) Cu2S, f) NCs with axial projection

Cu2S (7.9 nm)

CIS (5.7 nm)

Slight etching by TOP

PXRD pattern

TEM images of CIZS

X-ray Photoelectron Spectroscopy (XPS)

Absorption Spectrum

Cyclic Voltammogram

Conclusions

Sequentially synthesized CIZS form core/shell like structure whereas combining

two precursors in one pot forms homogeneously alloyed CIZS NCs.

Sequential exchange with Zn2+ leads to a sufficient increase of the PL

efficiency.

PL peak can be tuned from 850 nm to 1030 nm by carefully controlling the

Cu:In:Zn ratio in the NCs.

Combination of optical characterization with cyclic voltammetry results

provides a further insight into the electronic structure of the NCs.