Citation
Bimodal Molecular Weight Polyvinyl Pyrrolidone-Synthesized Silver Nanoparticles for Use as Low-Curing Temperature Conductive Materials

Material Information

Title:
Bimodal Molecular Weight Polyvinyl Pyrrolidone-Synthesized Silver Nanoparticles for Use as Low-Curing Temperature Conductive Materials
Creator:
Flores, Glen Patrick
Place of Publication:
[Gainesville, Fla.]
Publisher:
University of Florida
Publication Date:
Language:
english
Physical Description:
1 online resource; 151 pages

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Materials Science and Engineering
Committee Chair:
Batich, Christopher D.
Committee Members:
Hummel, R. E.
Sigmund, Wolfgang M.
El-Shall, Hassan E.
Bashirullah, Rizwan
Graduation Date:
8/8/2009

Subjects

Subjects / Keywords:
Ablation techniques ( jstor )
Antennas ( jstor )
Electrical resistivity ( jstor )
Inkjet prints ( jstor )
Inks ( jstor )
Nanoparticles ( jstor )
Particle size classes ( jstor )
Printing ( jstor )
Silver ( jstor )
Sintering ( jstor )
Materials Science and Engineering -- Dissertations, Academic -- UF
Genre:
Electronic Thesis or Dissertation
Materials Science and Engineering thesis, Ph. D.

Notes

Abstract:
In the past quarter century, many researchers have begun materials investigations into low-curing temperature metallizations. These low-temperature metallizations may allow for the design of complex electronic circuits on low-melting temperature substrates. Metal nanoparticles are of great interest due to their ability to begin sintering at temperatures as low as 150masculine ordinalC. The small size of and environmental stability of gold and silver nanoparticles allows them to be economically and rapidly printed from industrial and commercial printing equipment to form electronic metallizations. Upon heat treatment above their sintering temperature, these nanoparticles form a continuous metallic film. Gold and silver conductive line widths as small as a few micrometers have been made using nanoparticles in inkjet and pad printing techniques. Such techniques may also help decrease the high manufacturing costs associated with other metallization techniques such as photolithography. Electronic devices that utilize low-glass transition temperature substrates (such as many polymers or organic substrates) require metallizations to form at curing temperatures even lower than the sintering temperature of gold and silver nanoparticles. These metallizations must also exhibit low electrical resistivity (smaller than 10-4 W-cm). One application of such low-curing temperature metallizations is in the production of electronic pill antennas that can be used for the monitoring of medical compliance. Such antennas will require materials with very low electrical resistivity to reach the radiation efficiency necessary to transmit signals from within the human body. Gelatin is the predominant material that forms capsules used to administer medication. Gelatin quickly becomes brittle or degrades when heated to temperatures above 100masculine ordinalC. Therefore, electronic pills will require the curing of antenna metallizations at temperatures below that at which gelatin begins to crack or deform. To address these needs, silver nanoparticles were produced from the formaldehyde reduction process in the presence of polyvinylpyrrolidone (PVP) and sodium hydroxide. Using a novel bimodal molecular weight PVP-protection reaction system, these silver nanoparticles were able to achieve a lower electrical resistivity than was previously reported in the literature for silver nanoparticles cured at temperatures below their sintering temperature. Silver nanoparticles could be produced in the size range of 20-200 nm and could be pad printed into high-resolution antenna patterns. The electrical resistivity of silver nanoparticles at low curing temperatures (room temperature to 150masculine ordinalC) has been scarcely reported and characterized in the literature. Such an investigation was performed on a new and novel silver nanoparticle synthesis system that used two molecular weights of PVP simultaneously. After applying heat at a temperature of 60masculine ordinalC for 10 minutes, the electrical resistivity of silver nanoparticles was as low as 4.0(10)^-3 Ohm-cm. Electrical resistivity as low as 7.4(10)^-5 Ohm-cm could be achieved in these nanoparticles at a sintering temperature of 190masculine ordinalC for a sintering time of as little as 10 min. Silver nanoparticle films also exhibited large differences in electrical resistivity depending on the respective molecular weight of PVP used during nanoparticle synthesis. After 10 minutes of a 115masculine ordinalC heat treatment, a four orders of magnitude (or greater) difference in resistivity could be observed between silver nanoparticles synthesized by either PVP of molecular weight 10,000 or PVP of molecular weight 40,000. To identify the reasons for the difference in electrical resistivity between silver nanoparticles produced by each respective molecular weight, the surface topology of silver nanoparticles was imaged using atomic force microscopy. Atomic force microscopy revealed that, upon drying at room temperature, silver nanoparticles decorated with PVP of molecular weight 10,000 had numerous areas of exposed silver. These exposed silver areas could then allow silver-to-silver contact between nanoparticles, which would allow for a highly conductive electrical pathway between particles. Silver nanoparticles decorated with PVP of molecular weight 40,000, however, exhibited very few areas of exposed silver, indicating that PVP coated the samples extensively. Thus, highly conductive pathways were unavailable in these nanoparticles, leading to poor electrical conduction.
Statement of Responsibility:
by Glen Patrick Flores

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Glen Patrick Flores. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Embargo Date:
8/31/2011

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PAGE 14

14 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy BIMODAL MOLECULAR WEIGHT POLYVINYL PYRROLIDONE-SYNTHESIZED SILVER NANOPARTICLES FOR USE AS LOW-CURING TEMPERATURE CONDUCTIVE MATERIALS By Glen Patrick Flores August 2009 Chair: Christopher D. Batich Major: Materials Science and Engineering In the past quarter century, many researchers have begun materials investigations into lowcuring temperature metallizations. These low-temperature metallizations may allow for the design of complex electronic circuits on low-melting temperature substrates. Metal nanoparticles are of great interest due to their ability to begi n sintering at temperatures as low as 150C. The small size and environmental stability of gold and silver nanoparticles allows them to be economically and rapidly printed from industrial and commercial printing equipment. Upon heat treatment above their sintering temperature, these printed nanoparticles form continuous metallic lines. Gold and silver conductive line widths as small as a few micrometers have been made using nanoparticles in inkjet and pad prin ting techniques. Such techniques may also help decrease the high manufacturing costs associated with other metallization techniques such as photolithography. Electronic devices that utilize low-glass transition temperature substrates (such as many polymers or organic substrates) require metallizations to form at curing temperatures even lower than the sintering temperature of gold and silver nanoparticles. These metallizations must also exhibit low electrical resistivity (smaller than 10-4 -cm). One application of such low-curing

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Research in Silver Nanoparticle Synthesis Using the PVP -Protection Mechanism

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PVP Protection Mechanism

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sp sp sp

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Silver Nanoparticle Reduction Systems The Polyol Process

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Formaldehyde Reduction

PAGE 34

Other Silver Nanoparticle Synthesis Reactions

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Other Nanoparticle Systems

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Current Silver Printing Applications

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Pad Printing

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Screen Printing

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Inkjet Printing V = 4/3r3 V r

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Review of Printing Methods Biocompatibility of Various Silver Compounds and Particles

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General Health Effects Silver Compounds Silver and silver alloys

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Studies of Specific Silver Exposure type dose manner of silver absorption or method of silver intake. metallic, high dose, ingested Silver acetate gum

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Food -grade silver foil

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Solid silver biomedical implants

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Application of Biocompatibility Analysis to E -pills

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Ink Preparation SNPs below 200 nm Relatively high solution molarity No non-biocompatible elements or compounds Re agents were to be low cost Reaction time was constrained to be less than 3 hours Final PVP content in SNP ink was to remain below 5% Ink from SNPs had to show good printability SNP in k should be re -suspendable in a variety of solvents SNPs should be stable and suspendable for extended periods

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Basic Ink Synthesis All reaction steps are t o be performed in a fume hood due to toxic volatile compounds.

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Analysis Techniques Transmission Electron Microscopy

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Scanning Electron Microscopy Thermal Gravimetry

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Particle Size Analysis Techniques Four -Point Probe

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Rs = 4.532(V/I) Rs V I 4.532 Current Voltage Analysis Atomic Force Microscopy

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Visual Observations

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Inquiry into Visual Observations Effects of PVP Amount

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Coil Confo rmation Importance

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l n l

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Solution Colors

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Other Observations

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Experimental Desi gn

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Microtrac Nanotrac Results

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DOE Repeatability

PAGE 95

Statistical Analysis of DOE i i j

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TEM Images

PAGE 109

Summary of DOE Results Bimodal PVP MW Reaction Systems and Effects on SNP Properties

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CPSC for SNPs

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TGA of SNPs

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TEM Im ages of SNPs

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Electrical Resistivity of SNPs

PAGE 128

SEM Images of Cured SNPs

PAGE 133

Summary of Bimodal PVP MW SNPs Explanation of Electrical Resistivity of SNPs Cured at Temperatures Below Their Sintering Temperature

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Current Voltage Analysis of SNP Thin Films

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-1.5E-08 -1.0E-08 -5.0E-09 0.0E+00 5.0E-09 1.0E-08 1.5E-08 -6-4-2 0246 Voltage (V) Current (I)

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-1.5 -1 -0.5 0 0.5 1 1.5 -3 -2 -1 0 1 2 Voltage (V) Current (A) Atomic Force Microscopy of SNPs

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stiffer surfaces are distinguished by a large phase shift with abrupt edges

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Summary of Electrical Resistivity of SNPs Cur ed at Temperatures Below Their Sintering Temperature

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Printing of SNPs

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Conclusions

PAGE 144

Future Work

PAGE 147

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PAGE 150

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