2002 CdS, ZnS
by
CdS CdS, ZnS
CdS CdS, ZnS
52 36 15 14 14 10 10 10 3 3
(a) (b) (c) (d) (e) (f) (g) (h)
ev, nm 1240 nm
TiO 2 =3.2eV (= 390nm)
(a) (b) (c)pt
1 Fe 2 O 3 2.2 TiO 2 (rutile) 3.0 Cu 2 O 2.2 TiO 2 (anatase) 3.2 In 2 O 3 2.5 SrTiO 3 3.2 WO 3 2.7 ZnO <3.3 Fe 2 TiO 3 <2.8 BaTiO 3 3.3 PbO 2.8 CaTiO 3 3.4 V 2 O 5 2.8 KTaO 3 3.5 FeTiO 3 2.8 SnO 2 3.6 Bi 2 O 3 2.8 ZrO 2 5.0 Nb 2 O 3 3.0
2 Si 1.1 GaAs 1.4 CdSe, n 1.7 GaP 2.25 CdS, n 2.4 ZnS, n 3.5
P-1. P-2. P-3. P-4. * * P-5. N P-6. P-7.
P-8. P-9. TiO2 P-10. TiO2 P-11. V4+ * * * P-12. * ** ** *** **** * ********** * ** *** **** KAST***** P-13. * * P-14. Ti TiOxNy
TiO 2 O S R.Asahi, T.Morikawa, T.Ohwaki, K.Aoki,, and Y. Taga, Science, 293, 269 (2001).
Umebayashi (TiS 2 ) 500 600 T.Umebayashi T.Yamaki, S.Tanaka,, and K.Asai,, Chem. Lett., 32, 330 (2003).
Ohno
400 700 UV 500 600nm X 700 S T.Ohno, F.Tanigawa, K.Fujihara, S.Izumi,, and M.Matsumura,, J. Photochem. Photobiol., A:127, 107 (1999). T.Ohno, Y.Masaki, S.Hirayama,, and M.Matsumura,, J. Catal., 204, 163 (2001). T.Ohno, T.Mitsui,, and M.Matsumura,, Chem. Lett., 32, 364 (2003).
TiO 2
TiO 2 - ST01 ST01 20nm
TiO 2 TiO 2
TiO 2 (ST01, ) 110 TiO 2 TiO 2 900 Ti(OH) 4
TG Sample (100 Evacuation N 2 refilling CS 2 /N 2 gas flow (5/50 ml/min) Heating (1 ºC/ min) TG curve Telescope Quartz spring Thermal shield Gas inlet Water-cooled cap Sample in Electrical Quartz basket furnace Height meter Gas outlet Schematic drawing of thermobalance
TG curves of sulfurization of TiO 2 powders with CS 2 45 Weight change(%) 30 15 0 Heating rate: 1 C/min Gas flow rate: CS 2 : 5 ml/min N 2 : 50 ml/min Sample: a. ST01 b. Dried ST01 c. Anatase d. Rutile e. Ti(OH) 4 TiS 2 Ti 1.08 S 2 Ti 3 S 4 a b e c d -15 0 250 500 750 1000 Temperature (ºC )
XRD patterns of sulfurized TiO 2 powders Rutile Ti 3 S 4 Ti 1.08 S 2 e. Ti(OH) 4 Intensity (a.u.) d. Rutile c. Anatase b. Dried ST01 a. ST01 10 20 30 40 50 60 2Θ ( degrees)
Reactions Sulfurization TiO 2 +CS 2 TiS 2 + CO 2 Decomposition TiS 2 Ti 1.08 S 2 Ti 3 S 4 Dehydration Ti(OH) 4 TiO 2 + 2H 2 O
TiO 2 -ST01 TiO 2 -ST01 TG T>450 T<
TiO 2 XRD j. 500 C i. 450 C h. 400 C Intensity (a.u.) g. 350 C f. 300 C e. 250 C d. 200 C c. 150 C b. 100 C a. ST01 TiS 2 TiO 2 10 20 30 40 50 60 2Θ (º) 450 TiS 2
TiO 2 100 ST01 80 150 C 200 C 250 C 60 100 C 300 C %R 40 350 C 20 400 C 500 450 C 0 200 300 400 500 600 700 Wave length, nm
TiO 2 (a) TiO 2 (a) 100 TiO 2 (a) 150 TiO 2 (a) 200 TiO 2 (a) 250 TiO 2 (a) 300 TiO 2 (a) 350 TiO 2 (a) 400 450 TiO 2 (a) TiS 2 500 TiO 2 (a) TiS 2 505 4.0 745 780 743 833 637 516 595 93 109 8.4 6.8 8.8 9.5 8.5 4.3 0.0 0.0 0.0
TiO 2 ST01 500
SrTiO 3 n
Introduction SrTiO 3 Band gap energy = 3.3 ev Active for photodecomposition of the water by UV light irradiation Sr 1.15 TiS 3 Band gap energy = 0.3 ev Absorb the visible light Dissolve in water by irradiation of light Partially sulfurized SrTiO 3 : It could be chemically stable and enhance the photocatalytic activity of SrTiO 3.
Materials SrTiO 3 nanoparticles (SR-01) were prepared by sol-gel method. Ti(OPri) 4 were mixed with tri-ethanol amine (0.05:0.1) and maintained for 24 hours in argon atmosphere. De-carbonated water were added to complete 100 ml (stock solution). 5,3 g of Sr(OH) 2 8H 2 O were dissolved in 10ml H 2 O and mixed with 10 ml of stock solution. The formed gel was heated in autoclave at 250 for 3hrs. The powders were obtained after rinsing with water ultrasonically and centrifugal separation. The powders were dried at R.T. for 1d. Commercial SrTiO 3 were obtained from Wako Pure Chemical Co. Ltd. (SR-02) and High Purity Chemicals Co. Ltd. (SR-03).
TEM microphotographs of initial materials 50 nm 200 nm 200 nm SR-01 SR-02 SR-03 The particle size of SR-01 is smaller than 40 nm.
A cubic SrTiO 3 phase was founded in initial materials. XRD patterns for initial materials a. SR-01 Intensity/a.u. b. SR-02 c. SR-03 SrTiO 3 (Cub., JCPDS 35-734) 10 20 30 40 50 60 2θ/degree
TG curves of initial materials in Ar atmosphere Weight change/% 0-2 -4-6 -8-10 -3.9 SR-01 SR-02 Samples: SrTiO 3 Heating rate: 5 ºC/min, in argon atmosphere 0 250 500 750 1000 Temperature/ºC SR-03-0.90-6.73 Carbonates SR-01 only contents 3.9 % of adsorbed water and 2.83 % of OH groups.
TG curves of sulfurization in CS 2 30 Gas flow: N2 50 ml/min CS2 5mL/min Heating Rate: 1 C/min Weight change/% 25 20 15 10 5 0-5 SR-01 starts to sulfurize at 280 ºC -1.9 SrTiS 3 Sr 1.05 TiS 3 Sr 1.15 TiS 3 SR-01 SR-03 20.0 SR-02 0 250 500 750 1000 Temperature/ C 17.1 SR-02 and SR-03 start to sulfurize at 550 ºC 19.8 16.5 SR-01 is sulfurized at lower temperatures than SR-02 and SR-03
XRD patterns for Sulfurized SR-02 d. 1000 C Intensity/a.u. c. 750 C b. 650 C a. As-received SR-02 Sr 1.15 TiS 3 (JCPDS 49-1367) SrTiO 3 (Cub., JCPDS 35-734) 10 20 30 40 50 60 2Θ/degree A hexagonal Sr 1.15 TiS 3 phase was founded as final product in SR-02.
XRD patterns for sulfurized SR-03 d. 1000 C Intensity/a.u. c. 750 C b. 650 C a. As-received SR-03 Sr 1.15 TiS 3 (JCPDS 49-1367) SrTiO 3 (Cub., JCPDS 35-734) 10 20 30 40 50 60 2 /degree A hexagonal Sr 1.15 TiS 3 phase was also founded as final product in SR-03.
XRD patterns for Sulfurized SR-01 e. 1000 C d. 750 C Intensity/a.u. c. 650 C b. 550 C a. As-prepared SR-01 Sr 1.15 TiS 3 (Hex., JCPDS 49-1367) SrTiO 3 (Cub., JCPDS 35-734) 10 20 30 40 50 60 2Θ/degree However, a hexagonal Sr 1.15 TiS 3-x phase was founded in SR-01.
Sulfurization SR-02 and SR-03 Between 550 and 950 ºC C the sulfurization of SrTiO 3 is carried on SrTiO 3 Sr 1.15 TiS 3 Sr 1.15 SR-01 At temperature below 180 ºC C is produced the desorption of water. Between 180 and 280ºC, the adsorption of CS 2 on SrTiO 3 surface occurs. Between 280 and 850ºC, SrTiO 3 is sulfurized. At higher temperatures, the decomposition of obtained Sr 1.15 TiS 3 is produced. SrTiO 3 Sr 1.15 TiS 3 Sr 1.15 TiS Sr 1.15 Sr 1.15 TiS 3-x
Conclusions SrTiO 3 nanoparticles was sulfurized at low temperatures in comparison with commercial powders. The sulfurization behavior of SR-01 could be summarized as follows: Evaporation of water, adsorption of CS 2, sulfurization of SrTiO 3 and decomposition of Sr 1.15 TiS 3.
BaTiO 3
Introduction BaTiO 3 is used as Dielectric material. Supported catalyst for CO 2 reforming and partial oxidation of CH 4 at higher temperatures. Catalyst for processing of hazard pollutants by non-thermal plasma reactors. However, BaTiO 3 is unknown photocatalyst due to High band energy of 3.27 ev (378 nm). Photoactivity in UV spectra.
Preparation of BaTiO 3 14.429 g TIPO* 14.949 g TEA* De-carbonated water *TIPO: titanium tetra-iso-propoxide TEA: tri-ethanol-amine Solution Argon atm. Overnight Stock Solution TIPO:TEA 0.05:0.1 10 ml stock solution 6.315 g Ba(OH) 2 10 ml de-carbonated water Stirring 30 min Gel Teflon autoclave Heating: 3 hrs T: 250 C BaTiO 3 Cleaning Centrifugation Drying at r. t. BaTiO 3
Partial sulfurization of BaTiO 3 BaTiO 3 Sulfurization Purification Evacuation N 2 refilling CS 2 /N 2 gas Flow rate: 5/50 ml/min Heating : 3 ºC/min T: 100-500 ºC Toluene 100 ºC Vacuum Partially Sulfurized BaTiO 3 Thermocouple Electric furnace Quartz tube Gas inlet Gas outlet Quartz boat Sample:1 g BaTiO 3 Schematic drawing of reaction tube
Characteristics of ultrafine BaTiO 3 particles 200 nm TEM microphotograph of BaTiO 3 BaTiO 3 particles were obtained by using TIPO and TEA as precursors. Characteristics: Phase: Cubic Particle size: 95 nm Lattice parameter: 4.0061 Å Specific area:12.42 mg/m 2 H 2 O (%): 1.6
Sulfurization behavior of BaTiO 3 25 20 BaTiS 3 Weight change/% 15 10 5 0 Starting temperature of sulfurization 19.2 Gas flow: N 2 50 ml/min CS 2 5mL/min Heating Rate: 1 C/min 18.4-0.6-5 0 100 200 300 400 500 600 700 800 900 1000 Temperature/ C BaTiO 3 reacts slowly with CS 2 at around 400 ºC forming BaTiS 3. Reaction: BaTiO 3 +1.5CS 2 BaTiS 3 +1.5CO 2
XRD patterns for partially sulfurized BaTiO 3 500 C Sulfide Sulfide 400 C Intensity/a.u. 300 C 200 C 100 C Initial Material BaTiO 3 (cub., JCPDS 31-174) BaTiS 3 (hex., JCPDS 15-328) 10 20 30 40 50 60 2Θ/degree Peaks corresponding to BaTiS 3 appears only when BaTiO 3 is sulfurized at 500ºC
Variation of lattice parameter 4.02 Lattice parameter a/ Å 4.015 4.01 4.005 Lattice parameter : 4.031 Å JCPDS 31-174 Cubic BaTiO 3 Formation of hex. BaTiS 3 4 0 100 200 300 400 500 Temperature/ºC Lattice parameter increases with increasing the sulfurization temperature. However, it decreases with formation of sulfide.
XPS of S2p 3/2 for partially sulfurized BaTiO 3 Sulfate Sulfide Intensity/a.u. 500 ºC 400 ºC 300 ºC 200 ºC Sulfite Sulfur 100 ºC 174 172 170 168 166 164 162 160 158 Binding energy/ev From 200 and 500 ºC, a peak assigned to sulfide appears at around 161.4 and 160.8 ev whose intensity increases with the temperature.
UV-Vis Vis spectra for partially sulfurized BaTiO 3 Band gap of BaTiO 3 : 100 BaTiO 3 378 nm 80 100 º C R /% 60 40 200 ºC 300 ºC 400 ºC 20 500 ºC BaTiS 3 0 200 300 400 500 600 700 800 Wave length/nm Increasing the sulfurization temperature, the absorption of visible light increases in sulfurized BaTiO 3 samples.
Conclusions Partially sulfurized BaTiO 3 absorbed higher visible light than initial BaTiO 3 sample. The absorption increased with increasing the temperature of sulfurization. Since sulfide as BaTiS 3 is formed above 400 ºC, it is suggested that absorption of visible light is caused by replacement of sulfur by oxygen in the initial BaTiO 3 structure.