A Simple and Green Method for Synthesis of Ag and Au Nanoparticles Using Biopolymers and Sugars as Reducing Agents.

A Simple and Green Method for Synthesis of Ag and Au Nanoparticles Using Biopolymers and Sugars as Reducing Agents. German Ayala, Luci Cristina O. Vercik, Leticcia G. Ferreira, Andres Vercik and Thiago A. Villa Menezes. Nanotechnology Biosensors Devices Laboratory NANOBIODEV Basic Sciences Department FZEA, Pirassununga SP University of São Paulo USP Brazil MRS Fall Meeting 2011 Symposium D11.3 12/1 11:15 AM /22

Metallic nanoparticles D Au Ag Cu Pt Pd Si O 2 Nanometer range 1 to few hundreds. Single metal, alloy or metallic oxides (conducting or semiconducting). Optical, electrical, quantum and magnetic properties. 2/22

(Some) Applications Imaging of tumors and infections. Theranostics of cancer. Immobilization of biological molecules. Sensing (optic, electric). Our focus is on the last two by using gold and silver NPs. We! 3/22

Gold Nanoparticles (AuNP) Lys Au NH 2 (amine) SH (thiol) Long known interaction between amine and thiol groups and gold NPs. Gole et al., Langmuir 2001, 17, 1674-1679. Proteins contain lysine and cysteine aminoacid residues in their chains. Cy s AuNP can be used to immobilize antibodies, enzymes and structural proteins. 4/22

Silver Nanoparticles (AgNP) Cy s Protein SH SH Silver NP is most known by its antibacterial properties. Ag Protein S It is believed that they catalyze disulfide bond formation, what denatures enzymes and proteins. S Yan et al., Chi. J. Cataly. 2009, 30 (9), 856-858 5/22

Nanoparticles Synthesis Physical Electrochemical, Thermolysis, Radiation etc. Chemical Chemical reduction. Photochemical reduction, Radiolysis etc. CA + RA + RA O Metal ion (solution ) Electron donor Nanoparticl e (colloid) What are the choices for RA and CA? Oxidized agent 6/22

Current RAs and CAs Most used NaBH4 N,N-dimethylformamide Citrate Trace amounts of those and their solvents might hinder applications in biomedicine or as biomaterials. Less solvents/reagents Mild temperature and ph Environmental friendly processes GREEN CHEMISTRY Can we use green chemistry principles to obtain NPs? 7/22

Green Reducing Agents Wei et al., Coll. Surf. B 2008, 62, 136-142. Wei uses chitosan as both reducing and capping agents. Can we extend that method to different reducing sugar and biopolymers? Chitosan as RA and CA NH3+ Au or Ag ph ~ Acetic acid 85 C Few hours NH3+ NH3+ 8/22

Reducing Sugar Closed open ring equilibrium in solution Reducing sugar must have an aldehyde in open form to be oxidized to carboxilic acid 9/22

Objectives We further developed the method by Wei, extending it to other cheap and readily available green reducing agents as carbohydrates, and evaluated what's the relation between ph, temperature, reducing agent and metal ion parameters. Wei et al., Coll. Surf. B 2008, 62, 136-142. 10/22

1 Metal ion Flowchart Diagram Wei's methodology. 2 HAuCl 4 (8.1 mm) AgNO 3 (52 mm) Sugar 6.92 mg/ml ph adjustment 3 4 Heating 40, 60, 80 and 90 C Reaction time 3 h for Au 12 h for Ag 5 SPR UV-Vis spectrum Next slide. 11/22

Carbohydrates Used as RAs Size Name Structure Reducing? Mono Glucose --- Yes Galactose --- Yes Fructose --- Yes Di Maltose Glu Glu Yes Lactose Glu Gal Yes Sucrose Glu Fru No Poly Starch (Glu)n Yes Chitosan (DA-Chitin)n Yes Table 1. Summary of sugars used as reducing agents for NP synthesis. 12/22

Wei's Method for Other Sugars Ag 12h 90 C Fig. 1. UV-Vis for different sugars and Wei's method. Chitosan diluted 50%. Wei's method works for different sugars, but with less efficiency 1 Chitosan is still the best. 2 13/22

Influence of Sugar (for Ag) Expecte d Obtaine d Ag 12h 90 C Ga l Gl u Mono Fru La c Ma l Di Su c Sta Ch i Polymers Fig. 2. Digital image for Ag NPs synthesized with different sugars. Some results were not as efficient as expected. 1 We started to investigate parameters. 2 14/22

Influence of Temperature Ag 12h Starch 1 Higher temperature yields more NPs for fixed time, metal and RA. Fig. 3. UV-Vis for influence of temperature on AgNPs with starch. Size dispersion seems to be narrow. 2 15/22

Influence of Sugar (for Au) Au 3h 90 C Fig. 4. Only soluble chitosan worked (ph 3-4 due to acetic acid) 1 Is ph influencing charge transport in redox reaction? 2 Expecte d Obtaine d Fig X. UV-Vis for AuNP Ga l Gl u Mono Fru La c Ma l Di Su c Sta Ch i Polymers Fig. 5. 16/22

Influence of ph (glu) Au 3h There is an optimal ph range for which synthesis occurs. 1 25 C Glucose ph allows synthesis at room temperature. No further synthesis for increasing temperature. 2 3 Fig. 6. UV-Vis for influence of ph on AuNP synthesis using glucose. NaOH 0.1M added 17/22

Au 3h Influence of ph (suc) For sucrose, ph and temperature are necessary. 1 90 C Sucrose Maybe sucrose is going alkaline thermal hydrolysis? 2 Glu Fru Glu + Fru Fig. 7. UV-Vis for influence of ph on AuNP synthesis using sucrose. NaOH 0.1M added 18/22

Influence of ph (sta) Au 3h Higher ph enables proper synthesis of AuNP using starch (previously not possible). 1 90 C Starch Hydrolisis of starch yields several glucoses. 2 Fig. 8. UV-Vis for influence of ph on AuNP synthesis using starch. NaOH 0.1M added 19/22

Sugars from Extracts Au 25 C 1 min! (a) Mentha piperita 10 min! Fig. 9. UV-Vis for AuNP reduced by leaves extracts of herbs and fruits. (b) Pineapple (c) Banana (d) Passion fruit (e) Mandarin orange Faster synthesis employing common food industry byproducts. 20/22

Metal ion Same set of parameters doesn't work for different metal ions. Sugars Similar sugars behave differently. Glucose was the best reducing agent. ph Extracts Reaction time ph is one key parameter in stabilizing/allowing synthesis. Leaf and fruit peel extracts are viable reducing agents when NaOH stabilized. Advancement in relation to Wei's: we went from few hours to few minutes using other sugars (glucose). 21/22

We gladly thank: You for listening. Nanotechnology Biosensors Devices Laboratory NANOBIODEV Thiago A. Villa Menezes thi.avm@gmail.com /22