Recent achievements in sonochemical synthesis of bina Mqreifrjni/; nides ecturer: assist, prof. dr. Matjaž Kristl University of Maribor, Slovenia culty of Chemistry and Chemical Engineering )epartment of Inorganic Chemistry Syllabus > Introduction: Applications of metal chalcogenides Fundamentals of the sonochemical method Overview of the work done up to now > Experimental: synthesis and characterization > Results: ^Ag2S, Ag2Se, Ag2Te > Summary Introduction Nanocrystalline transition metal chalcogenides: Receiving growing attention due to their unique physical, chemical, semiconducting and optical properties Applications: photodiodes, thermoelectrical devices, semiconducting materials, solar cells, optical devices Classical methods: high T, long reaction times, poor control, use of highly toxic precursors (H2S H2Se) Use of silver chalcogenides, Ag2E (E = S, Se, Te) Ag2S: interesting semiconducting material for production of photocells, photoconductors / photo resistors, IR detectors Ag2Se: solar cells, optical filters, superionic conductors Ag2Te: material with great magnetic resistance (magnetic reluctance, MR) Some classical methods of synthesis > Solid - state synthesis from elements • high T (500 - 600 °C), long reaction times, vacuum or inert atmosphere • difficult to obtain nanosized products, especially in the case of Ag2S (tends to form agglomerates) > Reaction between aqueous solutions of metal ions and gaseous H2E (E = S, Se, Te) • Working with gaseous, highly poisonous reagents! ransition meta cha coaenides > Safer, avoiding toxic reactants > Milder reaction conditions —► easier to control! Inverse (revers) micelles Sol - gel method Synthesis in liquid ammonia Hydrothermal syntheses Solvothermal syntheses in aqueous NH3 and ithylenediamim Basic principles of sonochemical reactions Ultrasound: cyclic sound pressure with fequencies between 20 kHz and 10 MHz Medical and Destructive Lowbass notes Animals and Chemistry 2QKHz| Diagnostic and NDE 2MHsl 20QMHE Infrasound Acoustic Ultrasound Effect of ultrasound to molecules: indirect, most probable through the mechanism called acoustic cavitation: formation, growth and implosive collapse of gas/vapour bubbles inside the liquid Extreme conditions at the collapse1 ('hot - spot'): t > 5000°C. P > 2000 bar. AT / At ~ 109 K/s «wwi 1-K S SiiQlir.k Sr.ipnr.P 947 MQQm 143Q Polniei mehurčkov í|imf Kavitacijska jedra 1: :| '■* ;j 100 200 300 Čas (ms) 400 500 600 Photograph of a collapsing bubble during 0 million frames / s msm m m m m Some new theories of theoretical sonochemistry: There are two reaction sites during the bubble collapse: • Gaseous / volatile reagents: the reaction takes place inside the collapsing bubble in the gaseous phase, T > 25000°C, AT / At ~ 1011 K/s -► products are always amorphous • Non volatile reagents: the reaction takes place in the liquid phase (~ 200 nm) just outside the collapsing bubble, T ~ 1900°C —► products are either amorphous or nanoc 2: A. Gedanken, Ultrason. Sonochem. 11 (2004), Sonochemical syntheses of transition metal sulfides: literature review Compound Year Reactants M"*2 1998 Mo(CO)6+S 1999 2000 Zn(Ac)2 + thioacetamide Hg(Ac)2 + S Pb(Ac)2 + S 2000 Solvent tetramethyl-benzene water RuCI3 + thiourea water air ethylenediamine air 1 - decanethiol 2002 W(CO)6 + S diphenylmethane Ar Compound Year Reactants Solvent Atm. 2003 Au(Ac)3 + S decaline 2004 Hg(Ac)2 + Na2S203 water + TEA Hg(Ac)2 + thiourea water 2005 Zn(Ac)2 + S ethylenediamine air 1-decanethiol 2006 Cd(Ac)2 + S ethylenediamine air 1-decanethiol 2008 Hg(N03)2 + S water / EDTA air 3: M. Kristl, M. Drofenik, Ino 4: M. Kristl, M. d -- =' m. Commun TorsruiY, UJEJ OQ8), S9S Sonochemical syntheses of transition metal selenides and tellurides: literature review Compound Year Reactants Solvent \Atm. 1 Ag2Se CuSe PbSe 1999 AgN03 + Se ethylenediamine air Cul + Se PbCI2 + Se Cu4Te Cu7Te ZnSe 2000 2000 CuCI2 + Te Zn(Ac)2 + selenourea ethylenediamine air en + N2H4 water Compound Year Reactants Cu2.xSe ß - CuSe Cu3Se2 2001 Cul + NaoSeSO. 2001 AgN03 + Te a-CuSe 2002 Cu(Ac)2+Se HgSe 2002 Hg(Ac)2 + Na2SeSO. Solvent Atm. water + EtOH water + hexanole ethylenediamine EtOH DMSO water + NH3 / en / triethanolamine Compound Year Reactants Solvent 2003 CdCI2 + Na2SeSO; water + NH air 2003 Hg(Ac)2 + Se PEG 2003 Mo(CO)6 + Se decaline 2004 Bi(N03)3 + Na2SeS03 air water + EDTA air 2004 Hg(CI04)2 + Te ethylenediamine air 5: M. Kristl, M r O Compound Year CdSe 2007 HgSe ro 2008 HgTe w 2008 Reactants Cd(Ac)2 + Na2SeS03 Hg(N03)2 + Se Hg(N03)2 + Te Solvent water + tartaric acid EDTA (0.1 M) + NaOH (2.5 M) EDTA (0.1 M) + NaOH (5M) air air 4: M. Kristl, M. Drofenik, Ultrason. Sonochem. 15 (2008), 695 perimental: Synthesis of Ag2E Used chemicals: AgCHgCOO, 99%, Sigma - Aldrich ethylenediamine, p.a., Aldrich elemental S, Merck Se, 99.5%, 100 MESH, Aldrich Te, 99.8%, 200 MESH, Aldrich _ Synthesis of Ag2S: 0.005 mol ( = 0.8345g) AgCH3COO + 25 mL en dissolving on a magnetic stirrer + 0.0025 mol ( = 0.080g) S stirring 10-15 min sonication with high - intensity ultrasound (15 -120 min) separation with a centrifuge 5 min (5000 min-1), washing 2x with water + 1x EtOH (absolute) rying, 24-48 I Synthesis of Ag2Se in Ag2Te: Identical procedure as described before, except for: • m (Se) = 0.1975 g (n = 0.0025 mol) • m (Te) = 0.3190 g (n = 0.0025 mol) • at some experiments cooling of the reaction mixture • at some experiments 10% or 20% excess of Te • replacing AgCH3COO with AgN03: m = 0.849 g (n = 0.005 mol) Used ultrasoni Sonics & Materials VCX 750 1.25 cm2 Ti - probe 20 KHz 100 W/cm2 50 m L beaker Characterization: X - ray powder diffractometer (XRD): AXS-Bruker/Siemens D5005, CuKa radiation, graphite monochromator (X = 1.54178 A) Transmission electron microscope (TEM): JEOL JEM-2100, working voltage 200 kV, Cu -grid Energy dispersive X-ray spectroscopy (EDS) ResuH Different reaction times Main product: Ag2S, PDF No. 00-014-0072 EDS: Ag2S +Ag ts - Ag2S ^LwwvV \wwAJ w vw w V Wvv u WU ř 90 min 60 min 30 min ^ 15 min f® Results - Ag2Se Reaction time: 1 h pure Ag2Se, PDF No 00-024-1041 EDS: 65 at % Ag + 35 at % Se 4000 3000 03 | 2 2000 N C (D 1000 H ■Y^^MwJ M W^ y l^ 20 30 40 50 29 60 70 80 Results - Ag2Te • Reaction time: 1 h • Ag2Te, PDF No. 00-034-0142 • EDS:64at%Ag + 36 at % Te • cooling reduces the presence of Ag! Conclusion Overview of recent achievements in the area of sonochemical syntheses of transition metal chalcogenides Rapid growth of publishing: sono* + nanop* = > 2 hits (1994+ 1995), > 59 hits (2002), >124 hits (2007) comparatively simple method for the synthesis of silver sulphide, -selenide and -telluride. mditions further investigations underway! Acknowledgme > Ministry of Higher Education, Science and Technology of the Republic of Slovenia for the financial support > Sašo Gyergyek, M. Sc, for TEM images and EDS spectra > Tina Kelc, prof, ke - bio, for helping in laboratory work Supplement: formulae of some reagents Thioacetamide: CH3CSNH: Thiourea: (NH2)2CS H2N NH2i 1 -decanethiole: CH3(CH2)9SH Diphenylmethane: (C6H5)2CH Ethylenediamine: C2H4(NH2); Ethylene glycol: C2H4(OH> Triethanolamine: NrC*H HO OH P^3^ÖH N S OH