Near infrared driven photocatalysis by novel up converting TiO 4 :Yb 3+,Tm 3+ core/shell nano composites

Transcription

1 Near infrared driven photocatalysis by novel up converting TiO 4 :Yb 3+,Tm 3+ core/shell nano composites Pr. Stéphane DANIELE Dr. Shashank MISHRA Ms Ying CHEN Ms Hana AYADI Dr. Gilles LEDOUX Dr. Erwann JEANNEAU

2 UP CONVERTING NaYF 4 Ln 3+ NANOMATERIALS Lower energy photons = Near IR light Upconverting nanomaterials Higher energy photons = UV Visible light Applications: solid-state lasers, temperature sensors, IR quantum counter detectors, bio-probes and imaging NaYF 4 nanoparticles one of the most efficient host matrixes for NIR-to-visible upconversion cubic (α) phase (kinetic product) key word NaYF 4 Hexagonal (β) phase (thermodynamically stable & more efficient) 1/20

3 UP CONVERTING NaYF 4 Ln 3+ NANOMATERIALS Phase and concentrations for best efficiencies in nanoparticles: 8 order of magnitude larger / LnPO 4 Low phonon energy of the fluoride matrix Hexagonal or phase ( ~ 10 x cubic one) Yb 20% + Er 2% Yb 20% + Tm 0.5% 2/20

4 HETEROMETALLIC FLUORIDE NANOMATERIALS Synthesis of NaYF 4 nanocrystals (co-doped with Yb, Er and/or Tm) co-precipitation, hydrothermal or solvothermal route, combustion and flame synthesis Drawbacks post-heat treatment required, specilized reaction vessels required, getting cubic phase alone, particle aggregation, high temperature, etc. uncertain reproducibility Bottom-up synthetic approach remains almost unexplored for these nanomaterials Unavailability of single source precursors for upconverting NaYF 4 - Ln 3+ nanomaterials? Ln(O 2 CCF 3 ) 3 (H 2 O) 3 + NaO 2 CCF 3 capping reagents such as oleic acid 330 C α- and/or β-phase NaYF 4 nanocrystals Mai et al, J. Am. Chem. Soc., 2006, 128, 6426 Boyer et al, Nano Lett., 2007, 7, 847 3/20

5 OUTLINE 1. Upconverting NaYF 4 :Yb 3+, Er 3+ /Tm 3+ nanomaterials a) Novel Na-Ln heterometallic trifluoroacetate complexes with glyme ligands b) Advantages over the homometallic hydrated trifluoroacetate complexes c) Transformation of these single source precursors into Ln 3+ -doped NaMF 4 (M = Y, Gd) NCs d) Upconverting properties of NaMF 4 :Yb 3+, Er 3+ /Tm 3+ NCs (M = Y, Gd) 2. Catalytic applications a) TiO 4 :Yb 3+,Tm 3+ and TiO 2 /NaGdF 4 :Yb 3+,Tm 3+ for near-ir driven photocatalysis 3. Conclusions & perspectives 4/20

6 NOVEL Na Ln SINGLE SOURCE PRECURSORS tetraglyme THF [LnNa 2 (TFA) 5 (tetraglyme)] 1 [Ln = Y, Er, Yb] Ln(TFA) 3 (H 2 O) 3 + NaTFA triglyme THF [Na(triglyme) 2 ][Y 2 (TFA) 7 (THF) 2 ] 1 TFA = O 2 CCF 3 diglyme THF [LnNa(TFA) 4 (diglyme)] 1 [Ln = Y, Tm, Er, Yb ] 5/20

7 NOVEL Ln SINGLE SOURCE PRECURSORS M(TFA) 3 (H 2 O) 3 THF diglyme M = Tm M = Yb [Tm(TFA) 3 (diglyme)] 2 (μ,η 1,η 1 TFA)(η 1 TFA) bonding mode of TFA ligand Diglyme is tridentate to complete the Ln coordinations sphere Square antiprisme geometry [Yb(TFA) 3 (diglyme)] 2 6/20

8 NOVEL Na Ln SINGLE SOURCE PRECURSORS Structural features : a new μ 3 η 1 :η 1 :η 2 (O,F) bonding mode of TFA ligand exceptional F Na interaction ( ) Advantages over homometallic precursor Ln(TFA) 3 (H 2 O) 3 : YNa 2 (TFA) 5 (tetraglyme) [Y 2 (TFA) 7 (THF) 2 ] [Na(triglyme) 2 ] YNa(TFA) 4 (diglyme) formation of anhydrous species lowering of decomposition temperature the glyme ligand present in the complex acts as capping reagent = control of the size Y(TFA) 3 (H 2 O) 3 1/1 ratio of Na/Y in case of diglyme ligand 7/20

9 From MOLECULES to MATERIALS [NaLn(TFA) 4 (diglyme)] 1 [Ln = Y, Yb, Er or Tm] 1 Octadecene C (250 C) (280 C) 250 C 315 C NaYF 4 : Yb 3+, Er 3+ NCs in CH 2 Cl 2 (10%wt) (315 C) HRTEM As prepared nanoparticles capped with glyme ligand & hence well dispersed in organic solvents 8/20

10 From MOLECULES to MATERIALS Decomposition of Na Ln heterometallics with non equivalent ratio of the two metals? [Na 2 Ln(TFA) 5 (tetraglyme)] 1-Octadecene C NaLnF 4 NCs + NaF 9/20

11 Upconversion properties of NaYF 4 :Yb 3+,Er 3+ /Tm 3+ Sensitization of Er 3+ by Yb 3+ by Energy Transfer Upconversion (ETU) intensity (normalized) monitored at 550nm NaYF 4 :Er NaYF 4 :Yb,Er ( ) 0.2sensitizer activator Excitation wavelength (nm) Cubic vs hexagonal phase NaYF 4 : Yb 3+,Er 3+ NaYF 4 : Yb 3+,Tm 3+ Narrow absorption for NaYF 4 :Er 3+ ( 4 I 15/2 to- 4 I 11/2 of Er 3+ ) Broad absorption for NaYF 4 :Yb 3+ /Er 3+ ( 2 F 7/2 to- 2 F 5/2 absorption of Yb 3+ transferred to Er 3+ ) upconversion intensity (normalized) Up conversion emission spectra (excited at 970nm) Tm 1 D 2 -> 3 H 6 Tm 1 D 2 -> 3 F 4 Tm 1 G 4 -> 3 H 6 Er 2 H 11/2 -> 4 I 15/2 Er 4 S 3/2 -> 4 I 15/2 NaYF 4 :Yb,Tm NaYF 4 :Yb,Er Er 4 G 11/2 -> 4 I 15/2 Er 2 H 9/2 -> 4 I 15/2 Er 4 F 7/2 -> 4 I 15/2 Tm 3 F 3 -> 3 H 6 Er 4 F ->4 9/2 I 15/2 250 C 400 C 270 C 315 C digital images of NCs taken in CH 2 Cl 2 (1 wt %) Wavelength (nm) UC efficiency better in hexagonal phase 10/20

12 UP CONVERTING NaYF 4 Ln 3+ NANOMATERIALS Surface modifications of the glyme capped nanoparticles : NCs capped by diglyme NCs capped by tetraglyme diglyme NCs capped by PEG 600 diacid PEG 600 diacid Poly Acrylic acid NaYF 4 : Yb 3+, Er 3+ NCs in H 2 O 1 %wt 11/20

13 Upconversion properties of NaYF 4 :Yb 3+,Er 3+ /Tm 3+ Nanopowder vs dispersed in CH 2 Cl 2 /H 2 O Effect of aging of NCs on upconversion kcounts/s hexagonal, 150W/cm² freshly prepared capped by diglyme ligand in CH 2 Cl 2 capped by polyacrylic acid in water capped by PEG-diacid-600 in water after 100 days capped by diglyme ligand in CH 2 Cl 2 capped by polyacrylic acid in water capped by PEG-diacid-600 in water Emission wavelength (nm) Similar spectra but lower intensity in dispersed phase due to grain dispersion, functionalisation Good stability in CH 2 Cl 2, but destruction in water 12/20

14 From MOLECULES to MATERIALS Decomposition of NaLn(TFA) 4 (diglyme) into NaLnF 4 (Ln = Y & Gd): A comparative study [NaLn(TFA) 4 (diglyme)] (Ln = Y, Gd) Ln = Gd 1-Octadecene, 285 C Hexagonal NaGdF 4 (JCPDS ) Ln = Y 1-Octadecene, 285 C Getting hexagonal phase easier for the matrix NaGdF 4 than that for NaYF 4 Smaller energy barrier for higher ionic radii 13/20

15 TiO 4 :Yb 3+,Tm 3+ for near IR driven photocatalysis Extending absorption of TiO 2 in IR region O 2 - e - TiO 2 Near-IR ~ 9 times more IR than UV in the sunlight O 2 H 2 O H +, HO CB VB h + UV Tm 3+ ET NaGdF 4 Yb 3+ Wang et al., Appl. Cat B 2014, 144, 379 Tang et al. ACS Catalysis 2013, 3, 405 Wang et al. Nanoscale 2013, 5, 8930 Xua et al. Appl. Cat B 2013, , 377 Zhang at al. J. Power Sources 2013, 226, 47 Synthesis of core shell TiO 4 :Yb 3+,Tm 3+ ❶ Ti(OnBu) 4 in toluene NaGdF 4 :Yb 3+,Tm 3+ NCs dispersed in toluene 2h H 2 O in butanol (h = 3-6) ❷ Centrifugation TiO 4 :Yb 3+,Tm C 4h 14/20

16 TiO 4 :Yb 3+,Tm 3+ for near IR driven photocatalysis 100 As prepared 450 C 4h normalized intensity to 1 G 4 3 H E-3 1E-4 I 7/2 8 S 7/2 6 I 6 3 H 6 1 Gd 3+ P 7/2 8 S 7/2 6 I 6 3 F 4 1 D 2 3 H 6 1 D 2 3 F 4 1 G 4 3 H 6 1 D 2 3 H 5 1 G 4 3 F 4 1 D 2 3 H 4 or 3 F 3 3 H 6 1 G 4 3 H 5 or 1 I 6 > 1 G 4 1 H 4 3 H 6 3 NaGdF 4 :Yb,Tm TiO 2 (4%)@NaGdF 4 :Yb,Tm TiO 2 (21%)@NaGdF 4 :Yb,Tm 1E Wavelength (nm) Quenching of the UV transitions by energy transfer or FRET The core shell structure TiO NCs is destroyed due to thermal shrinkage of TiO 2 shell 15/20

17 TiO 4 :Yb 3+,Tm 3+ for near IR driven photocatalysis Degradation of Methylene blue by TiO 2 (21%)@NaGdF 4 :Yb 3+,Tm 3+ i) Different lightsources (7h) Conditions : 2mg of photocatalyst 1 ml MB (15mg.L 1 ) NIR Laser diode: 980 nm / 300mW Activity on a cloudy day lower due to reflection of longer wavelength NIR by clouds 16/20

18 TiO 4 :Yb 3+,Tm 3+ for near IR driven photocatalysis Degradation of Methylene blue by TiO 2 (21%)@NaGdF 4 :Yb 3+,Tm 3+ ii) Comparison of two catalysts (7 hrs) NIR laser irradiation Solar light TiO obtained via calcination of core shell TiO 4 :Yb 3+,Tm 3+ P25 TiO 2 (21%)+UC: physical mixture of commercial P25 TiO 2 and NaGdF 4 :Yb 3+,Tm 3+ NCs TiO better photocatalyst than P25TiO 2 +UC NCs, due to proper intimacy between UC NCs & TiO 2 and thus efficient energy transfer between the two components 17/20

19 CONCLUSIONS and PERSPECTIVES i) First single source precursors (SSP) for upconverting NaY(Ln)F 4 nanomaterials Straightforward synthesis with quantitative yield of sub-20 nanometric particles, which show excellent up-converting properties Multiple advantages over the homometallic Ln(TFA) 3 (H 2 O) 3 Particles dispersible in organic solvents without adding any stabilizer Hydrophobic glyme ligand easily exchangeable with hydrophilic ligands polyacrylic acid and PEG diacid, which renders NCs water dispersibility for potential bio-applications Direct synthesis of hexagonal phase at low temperature (colloidal suspension) Elaborations of NaY(Ln)F 4 thin films on a substrate of desired shape Elaborations of core/shell structures ii) TiO 4 :Yb 3+,Tm 3+ nanocomposites for near-ir driven photocatalysis Preliminary results validates the concept of transferring the NIR into the visible light to activate the anatase TiO 2 for the photocatalysis Chemical transformation? 18/20

20 PERSPECTIVES i) Enhance the overall upconversion due to increased absorptivity and overall broadening of the absorption spectrum Grafting of NIR chromophores (aza-bodipy, cyanine) NIR UC UV-Vis NIR - Zou, W. et al, Nature Phot. 2012, ii) Enhance multiphoton upconversion through energy clustering at sublattice level in KYb 2 F 7 :Er 3+ NCs [NaLn 2 (TFA) 7 (triglyme)] 1-Octadecene NaLn 2 F 7 NCs? - Liu, X. et al, Nature Mater. 2014, 13, /20

21 AKNOWLEDGEMENTS IRCELYON Staff Marlène DANIEL (TEM) Noëlle CRISTIN & Pascale MASCUNAN (Elemental analyses) Françoise BOSSELET & Yoann AIZAC (PXRD) Dr. Prakash N. SWAMY (XPS) Bernadette JOUGUET (TG-DTA) ECUST Collaborator Prof. Jinlong ZHANG Daniele et al., Chem. Comm. 2010, 46, 3756 Dalton Trans. 2012, 41, 1490 Chem. Asian J. 2014, 9, /20