This document summarizes a literature presentation on the synthesis and characterization of Sn3O4/TiO2 nanobelt heterostructures and partial cation exchange synthesis of Cu2S, CIS, and CIZS nanocrystals. Various characterization techniques were used including XRD, SEM, HRTEM, EDS, UV-Vis, PL, and photoelectrochemical measurements. The Sn3O4/TiO2 heterostructures showed superior photocatalytic activity under UV and visible light due to efficient charge separation. The sequential and combined cation exchange syntheses of CIZS nanocrystals resulted in different structures and photoluminescence properties that were tunable based on the Cu:In:Zn ratio.

1. Literature Presentation
14th Jan 2015
By Saurav Chandra Sarma

3. Characterizations
XRD
SEM
EDS
HRTEM
UV-Vis-DRS
PL

4. Schematic illustration of the
synthesis process
XRD patterns of
a) Pure TiO2 nanobelt
b) Scaly Sn3O4 nanoflakes
c) Sn3O4/TiO2
•Molar ratio Sn/Ti=2/1
•TiO2 is in anatase phase
•Sn3O4 has triclinic phase

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

6. SEM images
a) TiO2 nanobelts
b) Sn3O4 nanoflakes
c,d) Sn3O4/TiO2
nanobelts
Sn3O4 nanoflakes are
assembled
perpendicular to the
surface of TiO2
nanobelts.

7. 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 nanobelt
heterostructure.
d) Sn3O4 and TiO2 at the
interface level.
e-h) EDS elemental mapping
analysis.

8. 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)

9. 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.

10. Photocatalytic Dye degradation

11. Photocatalytic Hydrogen Evolution
Schematic diagram of electron
transfer in Sn3O4/TiO2
heterostructure
Comparison of the phtocatalytic
hydrogen evolution activities of
different samples

12. Photocatalytic Hydrogen Evolution
PL spectra of
(a) TiO2 nanobelts,
(b) (b) Sn3O4/TiO2 (molar ratio
Sn/Ti= 2:1) heterostructure,
(c) Sn3O4 nanoflakes.

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

14. Conclusions
The hydrothermal growth of Sn3O4 resulted in
crystallographic connection of (1-11) plane of Sn3O4 and (101)
plane of TiO2.
Sn3O4/TiO2 nanobelts can absorb both in the UV and visible
range.
The heterostructure exhibits superior photocatalytic
pollutant degradation and hydrogen evolution under either UV
or visible light irradiation.

16. 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

17. 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

18. PXRD pattern

19. TEM images of CIZS

20. X-ray Photoelectron Spectroscopy
(XPS)

21. Absorption Spectrum

22. Cyclic Voltammogram

23. 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.