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A WheatstoneBridge-type chemistor was fabricated to measure the sensitivty of electrospun PANI fiber. Several electrospinning parameters were varied to produce fibers with nanometer diameter. Fiber morphology and composition were analyzed as parameters were adjusted.
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A TERMINAL REPORT
Office of the Vice Chancellor for Research and Extension Building
February 23, 2011, 8:30AM
forging the foundations for the future
Fabrication of Polyaniline
Nanofiber via Electrospinning
for the Development of
Carbon Monoxide Sensor
People
Project leader Marvin U. Herrera
Proponent IMSP IC
Prof. Emmanuel A. Florido
Ms. Melody Joy Gamboa
Ms. Diane Denise Tabernilla
Mr. Francis Emralino
Mr. John Cerry dela Rosa
Dr. Ernesto J. del Rosario, Jr.
Mr. Jesse Cervantes
Materials Physics Laboratory, Physics Division
Institute of Mathematical Sciences and Physicson study leave for PhD at Kyoto University
Funding Details
Implementing Unit Institute of Mathematical Sciences and Physics
Cooperating Unit Institute of Chemistry
Funding Source PCASTRD Fellowship Grant
Project Duration February 1, 2009 to January 31, 2010
Total Budget PhP 500,000.00
WALKTHROUGHPolyaniline Nanofiber via Electrospinning for the Development of Carbon Monoxide Sensor
A Terminal Report
PANI SYNTHESIS
STUDIES
PEOPLE/FUND
SPINNER eSPUN FIBERS
WB-type CHEMISTOR
V
Resistor 1
Resistor 2
PANI fiber
Resistor 3
power supply
ABSTRACTA WheatstoneBridge-type
chemistor was fabricated to
measure the sensitivty of
electrospun PANI fiber.
Several electrospinning
parameters were varied to
produce fibers with nanometer
diameter. Fiber morphology
and composition were
analyzed as parameters were
adjusted.
AbstractDevelopment of a Wheatstone Bridge-type Chemistor
Characterization of electrospun fibers
Fabrication of electrospinning set-up
PANI synthesis
Abstract
syringe pump
PANI synthesis
Development of a Wheatstone Bridge-type Chemistor
Characterization of electrospun fibers
Fabrication of electrospinning set-up
syringe
aluminum foil (anode)
needle (cathode)
DC power supply
AbstractFabrication of electrospinning set-up
Characterization of electrospun fibers
Development of a Wheatstone Bridge-type Chemistor
V
Resistor 1
Resistor 2
PANI fiber
Resistor 3
power supply
AbstractFabrication of electrospinning set-up
Development of a Wheatstone Bridge-type Chemistor
Characterization of electrospun fibers
Pictures insert here
PANI synthesis
Polyaniline-emeraldine was synthesized following standard oxidative
polymerization by Stejskal (2005).
APS
aniline HClO4mixed while in ice bath
added dropwise
polyaniline solution
stored under 4oC
washed
filtered
vacuum dried
PANI powder
The Spinner
Custom-built vertical electrospinning set-up
The Spinner
Syringe pump
The syringe pump controls the flow rate being
ejected from the needle.
INSERT UNIT
The Spinner
Syringe
Contained in the syringe was the solution of certain
concentration. Needle gauge was chosen so as to
produce the desired fiber diameter. The needle
was connected to the positive terminal of the
power supply.
The Spinner
Collector
The collector used in the study is a commercially
available aluminum foil. This allowed the
researchers flexibility in setting the area for
collection of electrospun fibers. It also gave ease in
extraction/harvesting of fibers. The aluminum foil
served as ground which was connected to the
negative terminal of the high power supply.
The Spinner
Collector holder
To vary the distance between electrodes (needle
tip and collector), the aluminum foil was fixed to an
adjustable holder. The holder could be translated
along the vertical position.
The Spinner
Power supply
A high voltage power supply (AHV 100) was utilized
in the study. The instrument is capable of providing
constant voltage supply from 0 to 100kV.
The Spinner
Stand
The stand supports the components described
earlier into place. It is made of wood to prevent
short circuiting and unwanted random deposition of
fibers onto it.
The Spinner
Cover
A plastic sheet for safety covers the entire anode-
cathode system. It contains off-course fibers from
flying off. This also prevented accidental contact
with the electrodes while running an experiment.
The Spinner and its parameters
Parameters varied
1.voltage
2. tip to collector distance
3.viscosity
Wheatstone Bridge-Type Chemistor
V
Resistor 1
Resistor 2
PANI fiber
Resistor 3
power supply
Schematic diagram of Wheatstone bridge-type chemiresistor
Wheatstone Bridge-Type Chemistor
V
Variable resistors
Three variable resistors (R1, R2, and R3) along with the
PANI fiber were connected to form a Wheatstone bridge.
The resistances were adjusted to balance the bridge.
Voltage across the bridge was measured using a high
precision nanovoltmeter (Keithley).
Wheatstone Bridge-Type Chemistor
Power supply
A constant dc voltage (Keithley 2410C) is supplied
across the bridge.
Wheatstone Bridge-Type Chemistor
Chemiresistor
Electrospun PAni fibers fixed on an interdigitated
copper tracks.
etch PCB
Interdigitated circuit
fix e-spun pani
Wheatstone Bridge-Type Chemistor
Sensing
Gas chamber
to the bridge and voltmeter
CO generator
valve
reaction chamber
Electrospun PAni fibers fixed on an
interdigitated copper tracks.
Wheatstone Bridge-Type Chemistor
Sensing
Electrospun PAni fibers fixed on an
interdigitated copper tracks.
Voltage difference before and during
exposure to CO is measured across the
bridge.
Sensitivity of the device is determined
following
S = |VCO-Vi| / Vi X 100%
VCO voltage across the bridge in the
presence of CO
Vi voltage before exposure
S sensitivity
Gas chamber
to the bridge and voltmeter
CO generator
valve
static gas chamber
Electrospun Fibers
Electrospinning
PAni powder were dissolved in NMP were mixed with different polymers (i.e. PVC, PVAc).
Binder Solvent Mixture (volume) Stirring time
PANI:binder
polyvinyl acetate none varied 20-30 minutes
polyvinyl chloride tetrahydrofuran 1:2 10 minutes
Elastomer none 1:1 ~
Electrospun Fibers
Morphology
PAni-PVC PAni-PVAc Pani-elastomer
Scanning electron microscope images of composite fibers.
Electrospun Fibers
Morphology: Electrode voltage and fiber diameter of Pani-elastomer
Electrospun Fibers
Morphology: Electrode distance, solution conductivity, and
fiber diameter of PAni-PVC
Electrospun Fibers
Morphology: Viscosity and fiber diameter of PAni-PVAc
Electrospun Fibers
Sensitivity: Solution conductivity and sensitivity
FIBER 1
FIBERS
high fiber gap suggests high barrier gap prevents conduction
Active material Pani-EB Pani-ES
CO sensitivity (%) 93.45 29.72
Standard deviation 8.10 1.31
|Stdev/Sensivity| (%) 8.67 4.40
FIBER 1
FIBERS
Electrospun Fibers
Sensitivity: Solution conductivity and sensitivity
Active material Pani-EB Pani-ES
CO sensitivity (%) 93.45 29.72
Standard deviation 8.10 1.31
|Stdev/Sensivity| (%) 8.67 4.40
COCO
COCO
CO CO
COCO
CO
CO
COCO
COCO
CO
CO CO
COCO
CO
CO
CO “connects” the fibers thus changing the bulk electric resistance
FIBER 1
FIBERS
Electrospun Fibers
Sensitivity: Solution conductivity and sensitivity
Active material Pani-EB Pani-ES
CO sensitivity (%) 93.45 29.72
Standard deviation 8.10 1.31
|Stdev/Sensivity| (%) 8.67 4.40
COCO
COCO
CO CO
COCO
CO
CO
COCO
COCO
CO
CO CO
COCO
CO
CO
Or, CO blocks oxidation sites in the PAni structure, thus, decreases
resistance
FIBER 1
FIBERS
Electrospun Fibers
Sensitivity: Solution conductivity and sensitivity
Active material Pani-EB Pani-ES
CO sensitivity (%) 93.45 29.72
Standard deviation 8.10 1.31
|Stdev/Sensivity| (%) 8.67 4.40
COCO
COCO
CO CO
COCO
CO
CO
COCO
COCO
CO
CO CO
COCO
CO
CO
Lastly, CO acts as dopant.
Summary
A custom-built electrospinning set-up was assembled. The set-up was
made such that electrospinning parameters like voltage and tip-to-
collector distabce could be varied.
A Wheatstone Bridge-type chemiresistor was successfully fabricated as
CO sensor.
Fiber diameter are as follows: PAni-PVAc, 100 nm; PAni-PVC, 200nm,
and PAni-elastomer, 250nm.
Fiber diameter grows exponentially with electrode voltade in Pani-
elastomer.
Summary
Decrease in fiber diameter as distance between electrodes was varied in
PAni-PVC. Smallest fiber diameter was observed at 16-cm tip-to-
collector distance.
Bead formation was observed in PAni-PVAc with low viscosity.
PAni-EB was observed to be more sensitive in detecting CO than
H2SO4-doped PAni.
Studies conducted
Student
Ms. Melody Joy Gamboa
Ms. Diane Denise Tabernilla
Mr. Francis Emralino
Mr. John Cerry dela Rosa
Mr. Jesse Cervantes
Mr. Nathaniel Carolina
Ms. Stephanie Tumampos
Acknowledgement
PCASTRD for the grant.
Dr. EJ del Rosario for allowing the students to work in his lab at the Institute of
Chemistry-UPLB.
Prof. AKG Tapia for continuing and supervising the work on heme assisted CO
sensing.