Synthesis of metallic Ag and semiconducting Zn S

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Synthesis of metallic Ag and semiconducting Zn. S nanoparticles in self-assembled polyelectrolyte templates M.

Synthesis of metallic Ag and semiconducting Zn. S nanoparticles in self-assembled polyelectrolyte templates M. Logar, B. Jančar and D. Suvorov Institute Jožef Stefan, Advanced materials department, Slovenia

Introduction Inorganic nanoparticle properties v v Large surface / volume ratio Quantum confinement effect

Introduction Inorganic nanoparticle properties v v Large surface / volume ratio Quantum confinement effect The control over the particle shape, size and concentration In-situ nanoparticle synthesis methodology - nanoparticles are synthesized in-situ in polymer template - the surrounding polymer chains limits particle aggregation - the size and volume fraction of the particles in composite films is manipulated by varying the synthesis conditions

Polyelectrolyte multilayer (PEM) template formation Layer-by-layer self- assembly method Driving force for the multilayer

Polyelectrolyte multilayer (PEM) template formation Layer-by-layer self- assembly method Driving force for the multilayer buildup PAA PAH Electrostatic interaction between appositively charged polyelectrolyte

Properties of the PEM film v type of the PE v p. H value

Properties of the PEM film v type of the PE v p. H value of the PE assembly Weak polyelectrolyte - PAA [COO- ]= f (p. H) v. Thickness controllable in nanometer range p. H=3. 5 PEM thickness (nm) 250 200 p. H=3. 0 150 100 Substrate effect p. H=2. 5 50 0 0 5 10 15 number of polyelectrolyte bilayers

In-situ synthesis of inorganic nanoparticles C O O- m+ Metal salt solution p. H=5.

In-situ synthesis of inorganic nanoparticles C O O- m+ Metal salt solution p. H=5. 5 Metal ion Ag+, Zn 2+ Recharge Reduction/sulfidication Inorganic nanoparticle Ag, Zn. S

In-situ Ag nanoparticle synthesis p. H = 2. 5 p. H = 3. 0

In-situ Ag nanoparticle synthesis p. H = 2. 5 p. H = 3. 0 p. H = 3. 5 Ag acetate solution Ag nanoparticle p. H=5. 5 PEM film Ag+ n Na. BH 4 solution PS substrate Ag nanoparticle HAADF - STEM image

Volume fraction and size of the Ag nanoparticles in PEM are p. H- dependent

Volume fraction and size of the Ag nanoparticles in PEM are p. H- dependent p. H=2. 5 p. H=3. 0 p. H=3. 5 p. H value of PEM assembly Ag volume fraction (%) Average Ag particle diameter (nm) Ag particle concentrations (particles/cm 3) 2. 5 33 4. 5± 1. 5 6. 9∙ 1018 3. 0 27 6. 1± 1. 6 5. 2∙ 1018 3. 5 22 7. 4± 2. 5 1. 1∙ 1018

UV-vis absorption spectrum Red shift Surface plasmon resonance effect 0, 022 Absorbance [a. u.

UV-vis absorption spectrum Red shift Surface plasmon resonance effect 0, 022 Absorbance [a. u. ]/nm 0, 020 0, 018 0, 016 0, 014 0, 012 p. H=2. 5 0, 010 0, 008 p. H value of PEM assembly SPR wavelenght Λmax (nm) FWHM (nm) 2. 5 440 110 3. 0 427 97 3. 5 414 90 p. H=3 0, 006 p. H=3. 5 0, 004 0, 002 0, 000 200 400 600 Wavelenght [nm] 800

p. H=2. 5 n=1 p. H=2. 5 n=3 Absorbance (arbitrary units) Volume fraction and

p. H=2. 5 n=1 p. H=2. 5 n=3 Absorbance (arbitrary units) Volume fraction and size of the Ag nanoparticles in PEM are n- dependent 4, 0 Red shift 3, 5 3, 0 2, 5 n 2, 0 1, 5 1, 0 0, 5 0, 0 200 400 600 800 1000 1200 Wavelength (nm) Number of the reaction cycles Ag volume fraction (%) Average Ag particle diameter (nm) Ag particle concentrations (particles/cm 3) 1. 0 33 4. 5± 1. 5 6. 9∙ 1018 3. 0 65 6. 7± 1. 6 4. 1*1018

In-situ Zn. S nanoparticle synthesis p. H = 2. 5 n=1 da= 3. 2

In-situ Zn. S nanoparticle synthesis p. H = 2. 5 n=1 da= 3. 2 ± 0. 3 nm Na. Cl solution Zn acetate solution 20 nm p. H=5. 5 p. H = 3. 0 Zn 2+ n=1 da= 4. 1 ± 0. 9 nm n Na 2 S solution Zn. S nanoparticles in PEM Zn. S nanoparticle 20 nm

Zn. S nanoparticle crystal structure p. H = 2. 5 n=2 da= 3. 7

Zn. S nanoparticle crystal structure p. H = 2. 5 n=2 da= 3. 7 ± 0. 4 nm Wurtzite - hexagonal [100] [111] [202] Sphalerite - cubic SAED pattern BF – TEM image

UV-vis absorption spectrum Quantum confinement effect 0. 8 Red shift 0. 7 absorbance (a.

UV-vis absorption spectrum Quantum confinement effect 0. 8 Red shift 0. 7 absorbance (a. u. )/ nm 0. 025 p. H 0. 020 0. 015 Red shift 0. 6 n 0. 5 0. 4 0. 3 0. 2 0. 1 0. 010 0. 0 220 240 260 280 wavelength (nm) 300 320

Conclusions The thickness of PEM template is controlled in nanometer range by: v p.

Conclusions The thickness of PEM template is controlled in nanometer range by: v p. H value of the PE solution and v number of adsorbed layers With the In-situ synthesis method the control over the inorganic particle volume fraction and size is obtained by: v p. H value of the PEM assembly and v number of the reaction cycles - By increasing the p. H value and number of the reaction cycles larger size and lower volume fraction of inorganic nanoparticles in composite films were obtained Control over the optical properties of the composite film