Designing a method to attach

Fe3O4@Au nanoparticles uniformly to a

glass fiber tip to maximize Raman gain TEAM 01

2/16/2009 Drexel University

Brenay Major, Carlos Sanchez, Aneta Strus, Edwin Theosmy and Dr. Kambiz Pourrezai (Advisor)

1

Table of Contents

Lists of Figures and Tables ...................................................................................................................... 2

Lists of Abbreviations and Definitions ..................................................................................................... 2

Executive Summary ................................................................................................................................ 3

Introduction............................................................................................................................................. 4

Description of Prototype .......................................................................................................................... 6

Nanoparticle Preparation ..................................................................................................................... 6

Silanization Method ............................................................................................................................. 7

Induction of Magnetic Field ................................................................................................................. 8

Theory behind Magnetic Field Device ....................................................................................... 8

Overall look/Ideal Prototype Method ....................................................................................................... 9

Current State of Prototype ..................................................................................................................... 10

Problems/Issues ..................................................................................................................................... 11

Plan of Action – Continuation of Progress ............................................................................................. 11

Alternatives to Magnetic Field ............................................................................................................... 13

Societal and Environmental Impacts ...................................................................................................... 13

References ............................................................................................................................................ 16

Appendices ........................................................................................................................................... 18

Appendix A-Sonication ..................................................................................................................... 18

Appendix B- Water Bath Method ....................................................................................................... 19

Appendix C-Silanization .................................................................................................................... 20

Appendix D-Free Body Diagram ....................................................................................................... 22

Appendix E-Schedule ........................................................................................................................ 23

Appendix F- Resumes........................................................................................................................ 25

2

Lists of Figures and Tables

Figure 1 Prototype Design

Lists of Abbreviations and Definitions

Au Gold

CAD Computer-aided design (used for prototype visualization)

DNA Deoxyribonucleic acid

ELISA Enzyme-Linked Immunosorbent Assay

Fe3O4 Magnetite

Fe3O4@Au Gold coated magnetite

PCR Polymerase Chain Reaction

PDMS Polydimethylsiloxane

PEBBLE Probe Encapsulated by Biologically Localized Embedding

SAM Self-assembled Monolayer

SEM Scanning Electron Microscope

SERS Surface Enhanced Raman Spectroscopy

Silanization Method of modifying the tip of the probe to enhance adhesion of nanoparticles a substrate

such as a glass surface

TERS Tip-Enhanced Raman Spectroscopy

3

Executive Summary

There is currently no commercialized method of attaching nanoparticles to a nanotip that is

controlled and uniform. A nanotip-nanoparticle system that can be used in conjunction with Tip-enhanced

Raman Spectroscopy (TERS) will allow for the determination of the molecular composition of a biological molecule. The method will be used for TERS testing and have the ability to outrank other

diagnostic tools such as Polymerase Chain Reaction (PCR) and Enzyme-linked Immunosorbent Assay

(ELISA) in terms of precision, accuracy, cost, and portability. The design criteria include being able to

produce a Raman signal on the order of 1010

-1014

with 85% accuracy. The Raman signal output must also be precise, able to produce a signal within the range of 10

10-10

14. The components must also be small

enough to be incorporated into a portable system. (definition of what small enough is) Constraints on the

design include the use of a glass-fiber nanotip and the intrinsic density of the gold coated magnetite nanoparticle that cannot be modified. The nanotip tip must be between 30-50nm. Copper coil used to

induce magnetic field must be smaller than 1” in diameter.

The proposed method will allow for the controlled attachment of nanoparticles that will allow the nanotip to be used in conjunction with TERS. The orientation of the nanoparticles on the probe is

extremely important to allow for the highest Raman signal output. The highest Raman signal output will

be detected when gold coated magnetite nanoparticles are placed in a single layer surrounding the probe and less than 10nm apart. These nanoparticles will be placed on the probe by modifying the surface of

the probe, modifying the nanoparticle solution and inducing a magnetic field in the nanoparticle solution.

The probe will be modified by completing a silanization process. The nanoparticle solution will be modified by altering the concentration of the nanoparticles in solution. The induction of a magnetic field

to the nanoparticle solution will result in the movement of the nanoparticles onto the probe to enhance

even adhesion of the nanoparticles to the probe. The final deliverable of this design project will be a

method of modifying the nanotip and nanoparticle that will result in the optimal orientation of nanoparticles to a nanotip that can be used in conjunction with TERS testing. The benefits to this project

will include the ability of this method to be used in a portable system that can be used to diagnose

diseases quickly and in many different locations throughout the world. This could be extremely beneficial within third world countries where expensive diagnostic tools are not available.

We will market our design as a design method that can be used in conjunction with TERS testing.

The method is different from other methods because there is currently no method of attaching

nanoparticles to a nanoprobe in a uniform method that has the ability to produce high Raman signal

output when used in conjunction with TERS testing.

4

Introduction

Molecular diagnostic tools are used to identify defects in inherited diseases. They are also

used to detect and monitor infectious diseases and have been increasing in demand over the past

ten years. Current diagnostic tools such as ELISA and polymerase chain reaction (PCR) have

several short-comings including: high level of complexity, sensitivity to contamination, difficulty

in detecting multiple targets in an assay, cost, and lack of portability (Merel, 2005). Diagnostic

tools that are composed of nanomaterials are ideal for complex analyte detection, but need

customization and further engineering before they can be applied to molecular diagnostics. For

example, Raman spectroscopy is a spectroscopic technique capable of providing information on

the chemical composition, molecular structure, and molecular interactions in cells and tissues.

Since disease leads to changes in molecular makeup of affected tissues, these changes should be

reflected in the spectra (Choo-Smith et al., 2002). Therefore, there is a need for nanotip-

nanoparticle systems that can be used in conjunction with tip enhanced Raman spectroscopy

(TERS) to identify biological molecules that are embedded in complex mixtures (i.e. cell

cytoplasm, cell membrane).

TERS is a diagnostic tool that ranks better overall than those currently used including,

polymerase chain reaction and enzyme-linked immunosorbent assay in terms of precision,

accuracy, cost, portability and ease of use (Merel, 2005). TERS, like all Raman spectroscopic

techniques relies on the excitations of localized surface plasmons (Au in this case). The method

utilizes a metal nanoparticle-coated tip to enhance the intrinsically weak Raman signals of

analytes. When attached to a nanotip, these nanoparticles contain electron clouds that interact

with each other. When the probe is inserted into an environment and light is focused on the tip,

photons excite the nearby molecular bonds from the ground state to a higher energy state (Elfick,

Downes, & Mouras, 2009). The molecule then emits a photon and returns to the ground state, at

5

a different vibrational state. Deformation of the electron cloud occurs as a result of the vibration

and allows for the observation of the Raman Effect. As a result, compounds can be identified by

the vibrations of its unique bonding structure (Elfick et al., 2009).

Currently there is no controlled, uniform method of attaching nanoparticles to a nanotip.

The proposed design will utilize a silanization method to modify the glass nanotip to enhance

adhesion of the nanoparticles to the probe. Magnetite nanoparticles coated with gold will be

adhered to the nanotips. Gold coating is used because it will produce a high Raman signal

output. Finally a magnetic field will be induced within the nanoparticle solution to force the

nanoparticles to move toward the silanized nanotip tip and increase the adhesion of the

nanoparticles to the nanotip tip.

A majority of groups attach nanoparticles to nanotips using an ink dip method where the

nanotip is silanized and dipped into an ink. This ink is a composed of a polymer with metal

nanoparticles dispensed throughout the polymer. While this does attach nanoparticles to the

nanotip, there is no control on the distance between each nanoparticle, since it relies completely

on Fickian Diffusion.

Criterion, Specifications, & Constraints

The design criterion is to maximize Raman scattering, achieving enhancement factors as much as

1010

-1014

. Design specifications include nanoparticle spacing and composition. Equation (1) demonstrates

how the Raman signal is enhanced:

where fSERS is the SERS enhancement factor, R the radius of the particle, and d is the distance

between the nanoparticles surface and the molecule. The equation demonstrates that the field

6

enhancement depends critically on the nanoparticles size and shape. To gain the maximum

Raman signal, studies show that nanoparticles must be attached to the nanotip with an average

spacing between the range of 5.5-10nm apart (Xu et al. 1999). This optimal spacing allows for

molecules to fit in between the particles with an optimal distance between the nanoparticles

surface and the molecules.

Constraints on the project include that the nanoparticles must be coated with gold. Gold

nanoparticles have been shown to produce

the highest possible Raman gain.

Furthermore, gold nanoparticles have high

surface reactivity and biocompatibility

properties ideal for in vivo applications

Another constraints is that the glass fiber

tip used must have diameters between 30-50nm, in order to minimize the impact on the cell’s membrane

and maintain its integrity after insertion. Another constraint is portability: the device that controls the

attachment method must be able to be transported to various locations including battlefields and poor

third-world countries, unlike the large, complex equipment needed for techniques such as ELISA and

PCR. Ideally, the final attachment device should be able to attach to a portable Raman Spectroscopic

device (Figure 1) or be carried around in a separate bag.

Description of Prototype

Nanoparticle Preparation

Magnetite (Fe3O4) nanoparticles were obtained from Vivenano in a hydrophilic solvent. It was

necessary for the solvent to be hydrophilic in order to coat the nanoparticles with a gold shell because

HAuCl4 acts best in a hydrophilic solution. There are two possible procedures to implement in order to

produce gold-coated nanoparticles. One uses a sonicator, which is available for our use by Dr. Wheatley’s

7

lab. The other uses a water bath heating procedure and seems easier but may not be as efficient. Both

protocols are attached in Appendix A. The magnetite nanoparticles obtained from Vivenano range from 1

to 10 nm in diameter, and once coated with the gold will increase by about 10 to 15 nm in diameter,

giving a range of nanoparticles 11-25 nm in size. The expected size is consistent with the nanoparticle

size necessary for nano-probe coating.

Silanization Method

An important step in the attachment of the nanoparticles to the nanotip is the modification of the

glass surface of the probe. Silanization is a process that is being used increasingly to attach nanoparticles

to different substrates for different types of Raman Spectroscopy. Glass acts as a hydroxyl bearing

substrate and is “derivatized by a bifunctional organosilane” (Hajdukova et. al 2007). A self-assembled

monolayer (SAM) is formed on the glass when the organosilane binds to the hydroxyl groups within the

glass. Once the SAM is formed the glass can be submerged into an ink solution containing metal

nanoparticles. The nanoparticles attach to the terminal groups of the organosilane. The silane used for

our proposed solution is thiol-terminated, as thiol binds to the gold coating of the nanoparticles. The

silanization method used can differ in the organosilane concentration and duration of silanization.

Generally, an increase in organosilane concentration and duration of silanization increase the attachment

of nanoparticles (Hajdukova et. al 2007). The level of silanization and further treatment will be adjusted

to ensure that a favorable density is obtained (where the nanoparticles are on average between 5.5-10nm

apart).

Silanization will be carried out using APTMS (3-aminopropyltrimethoxysilane). Samples will be

washed in Piranha solution (H2SO4:H2O2, 7:3 v/v) above 80oC for 1 hour. Samples will then be washed

with distilled water/methanol , until all H2SO4 is removed and placed in 10% APTMS in anhydrous

methanol for 1-4 hours. Sample will be washed with anhydrous methanol followed with water and air

dried for 24 hours in a clean, particle-free enclosed storage space.

8

Induction of Magnetic Field

Theory behind Magnetic Field Device

In order to control the movement of the Fe3O4@Au nanoparticles within the aqueous solvent (that

solvent being water), the magnetite cores of the Fe3O4@Au nanoparticles were subjected to a gradient (or

varying) magnetic field. This gradient magnetic field creates a force, which allows the Fe3O4@Au

nanoparticles of similar charge to attract to one another, ultimately aggregating together in solution. The

shape of the gradient holds the purpose of focusing the Fe3O4@Au nanoparticle aggregation at the tip of

the tapered glass fiber.

According to Bischof et al. who have performed studies on solvated nanoparticles in a magnetic

field, the relation between a magnetic field and the force experienced by a magnetite particle is governed

by:

…where F(mag) is the force (represented in Newtons) of one nanoparticle in solution, M is the

magnetization (max moment per volume), and B is the Magnetic Field (Tesla per unit length) (2005).

Also in accordance with Bischof et al. there is a counter force, Fvisc, that acts against the moving

nanoparticle represented by:

…where is the viscosity of the solvent, d is the diameter of the nanoparticle, and is the velocity of the

particle. These two equations, upon assuming that the magnetic force will only move the nanoparticles in

one dimension, can be combined to produce:

All of these forces from the above equations have been considered and a free body diagram of these

forces acting on the nanoparticles when they are introduced to a magnetic field can be seen in Appendix

C. On a further note, the magnetization, M, of equation 3 can be further represented as:

H

9

Table 1: This table displays the parameters that can be varied in order to meet design criteria along with their effect

on velocity of the Fe3O4@Au nanoparticles. Velocity ultimately correlates to the effect on Interparticle Spacing,

assuming the Magnetization time remains constant.

…where x is equal to the magnetic susceptibility of the magnetite and H being the corresponding

magnetic field at which the magnetic susceptibility of the magnetite is saturated. This equation behaves

similarly to Michaelis-Menten kinetics, since the magnetization becomes saturated after a certain amount

of Tesla is added. For this project, we are only interested in the maximum magnetization; a figure

modeling this equation can be seen in Appendix D. Based on the equations above, the factors that we

have control over are viscosity, diameter, and magnetic field strength (which in turn correlates to the

speed of the particle). Increasing the intensity of the magnetic field has been shown to successfully

correlate with a decrease in interparticle spacing of magnetite nanoparticles in one dimension (Wang et al,

2009). A table on the effects of varying each parameter, while holding the other two constant, on the

main factors behind achieving our goal of rapid, uniformly spaced Fe3O4@Au nanoparticles adhesion to

the glass fiber tip (velocity and interparticle distance) can be seen in Table 1.

Overall look/Ideal Prototype Method

The ideal prototype method will consist of a methodical process that will ultimately result in a

tapered glass fiber tip coated with Fe3O4@Au nanoparticles. The first step in this method will be

functionalizing the glass fiber tips (meaning giving them the ability to bond to the Fe3O4@Au via

Increasing

Factor

(below)

Effect on Velocity

Ultimate Effect on Interparticle Spacing

Viscosity Decrease Increase

Diameter Increase Decrease

Magnetic Field Strength

Increase Decrease

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hydroxyl bonds). This is done through the silanization process we have detailed above and in the

Appendix. Once the glass fiber tip has been functionalized, the nanoparticle solution will then be poured

into the cylindrical tube of the magnetic device. Once the nanoparticle solution is in place, the current

wired to the shaped solenoids at either side of the cylindrical tube will be turned on, inducing a magnetic

flux through the copper tubing of the solenoids which will translate to a magnetic field being produced in

the area between the two solenoids (where the nanoparticles are located within the cylindrical tube).

After some time, the glass fiber tip will be introduced into the system. The magnetic field, hopefully, will

cause the nanoparticles in solution to aggregate towards the tip of the glass fiber. After an hour, the

current to the solenoids will be switched off, and the glass fiber tip will be removed. The glass fiber tipp

will then be rinsed with water to wash out the excess nanoparticles. Once dry, this glass fiber tip will

now be ready to be used as a probe to be injected into an object, then removed from the object, and finally

used in conjunction with Raman Signaling hardware and software to produce a characteristic spectrum of

the object that was probed. The intensity of the Raman signal output will be on the order of magnitude of

1010

-1014

, which is sufficient enough to detect bonds in the biological compound of interest.

Current State of Prototype

The wooden support base, copper wiring, glass tubing, corks, and necessary power tools

to create the prototype magnetic field device are contained in Disque. We were waiting on the

delivery of the copper tubing, which arrived a few days ago in order to finish the creation of the

magnetic field device, so we are now in our final stages of making the prototype for the magnetic

field. As of now, the prototype consists of the cylindrical glass tube being situated in a 12” by

12” wooden base; this glass tube, as stated earlier, will contain the nanoparticle solution and will

be the location where the glass fiber tip will meet the solution (as the tip in being held in place by

a cork).

The process of pulling glass fiber tips has been completed. We managed to get

satisfactory feedback from the fiber puller, indicating that our tips are between 30 - 50nm in

11

diameter; however, we still need to confirm the tip size by imagining the manufactured fibers

with SEM. The protocol for the silanization process has been written up and is awaiting the

finish of the magnetic device prior to silanization of the glass fiber tips.

As for the nanoparticles, every compound needed to make the gold-coated nanoparticles

has arrived. These include Fe3O4 (magnetite) nanoparticles, D-glucose reducing agent, sodium

citrate reducing agent, and distilled water. The protocols have also been written and are ready to

be implemented. The scheduled date for coating the magnetite nanoparticles is Wednesday,

March 3; however the nanoparticle solution will not be needed until silanization is complete.

Two procedures for nanoparticle coating can be referenced in appendix A. Although both

procedures have shown promising results, we will be using the Water Bath Method because it is

easier; however, if this procedure does not work properly, we will use the Sonication Method.

Problems/Issues

The preliminary testing to be performed on micrometer-sized magnetite (as stated in the Progress

to Date section) in order understand the behavior of the particles in a magnetic field has reached a

standstill due to the unforeseen inability of micrometer-sized magnetite particle to be solvated in water.

We are currently researching alternative solutions and/or alternative methods in order to test the behavior

of the magnetite particles. Theoretical data has been found that show magnetite particles aggregating

together in the presence of a magnetic field (Wang et al, 2009, Jang et al, 2007), however visualizing this

for ourselves will certainly aid in the confidence of using the magnetic field to accomplish our goals.

Thus, the prototype devices being used in our method are still being constructed as planned, but strictly

on theoretical data.

Plan of Action – Continuation of Progress

12

We are currently working on several projects at once, with each team member focused on

a specific task. Member I is working on manufacturing the nanofibers that will be used as

nanotips after complete modification. Member I is pulling quartz fibers into nanosized tips using

a Model P-2000 fiber puller, modifiying the tip surface using a silanization process, and

checking the tip size using SEM to make sure it ranges between 30-50nm. The procedure for

obtaining the appropriate size tip has been previously implemented and proven successful.

Member II is working on creating a magnetic field system for fast and uniform attachment of the

nanoparticles. The system will first be tested on micro-sized magnetite particles and pipette to

demonstrate the behavior and attachment on a larger scale before it can be implemented on the

nano scale. We have magnetite powder that we will suspend in a liquid in order to observe how it

reacts to the magnetic field. We will use the field to manipulate how the magnetite powder

travels through the liquid and coats the glass microprobe. Once we observe a uniform attachment

of the particles to the probe, we will move on to using the magnetic field for nanoparticle

attachment. Member III is working on constructing a CAD drawing of the prototype, this will

give a visual representation of how the nanoparticles act in the magnetic field, since they are

unable to be seen with the naked eye. Member IV is working on the preparation of the

nanoparticles by implementing the most effective procedure to coat the nano-sized magnetite

particles with gold. There have been studies that have successfully made gold-coated magnetite

nanoparticles and we will be using modified a version of their procedures (Mandal et al 2005, Lo

et al 2007). The gold particles will be suspended in a solution so that they can be ready for

coating the glass fiber after silinization is completed and magnetic field is created.

After members I, II, and IV are finished with their respective assignments, nanotips will

be created using the magnetic field. SEM will be used to check nanoparticle size, attachment,

and spacing. Although magnetite nanoparticles were purchased and exact size is known, coating

the particles with gold will increase and vary each particle’s size according to how much gold

attaches to the particle’s surface. Attachment of particles with 5-10nm spacing between each

13

particle arranged in a monolayer will confirm that the silinization process, nanoparticle solution

and magnetic field were effective. Further modification of magnetic field and nanoparticle

solution concentration will be done if optimal size, attachment, and spacing is not achieved. If

particle spacing is too dense, we will dilute the nanoparticle solution; however if the coating is

too sparse, we will create a more concentrated solution. The final step will be to perform TERS

to determine the magnification obtained with the manufactured nanotip. TERS will also be used

on biomolecule testing on butter (a source of animal fat). This procedure is simple and easy to do

because all of the equipment that we need for testing including the laser and computer interface

are already in Dr. Pourrezaei’s lab. We will insert the completed nanoprobe into a vial of melted

butter and shine the laser through it. We will then compare the Raman signal to the output

received by published papers (Baeten et al 1998). Exact protocol details of TERS testing are still

being finalized.

A complete schedule is listed in Appendix D.

Alternatives to Magnetic Field

We are looking at an alternative method to space the nanoparticles on the nanofiber that

does not utilize a magnetic field. Addition of 2-aminothiophenol and varying its concentration

will have an effect on particle spacing variance. Adjustment of the pH of the solution will also

have an effect on spacing. Increasing 2-aminothiophenol concentration will bring particles closer

together, whereas a more basic pH will allow the particles to be spaced further apart (Basu et al

2008). This method is a secondary option because it has no affect on the time it takes for the

particles to coat the probe, where the magnetic field will potentially speed the coating process

up.

Societal and Environmental Impacts

14

The development of a method for placing nanoparticles on a nanoparticle nanoprobe in a manner

that will yield the highest Raman signal output for TERS testing can have a variety of implications for

biologists and cellular analysis. This method could allow for better testing and analysis of the effects of

exogenous molecules on organelles within cells and the cell itself. The method of uniformly attaching

nanoparticles to a nanoprobe will yield high Raman signal during TERS testing. TERS can also be used

to classify the cellular components and molecules within a cell. The method of adhering the nanoparticles

to the nanoprobe will require a variety of different techniques including silanization and the induction of a

magnetic field to the nanoparticle solution. These techniques may require additional training within labs

who do not currently use these techniques. The aim of the proposed method is to make it similar to that

of other cellular analysis techniques so that it will be accepted by those in the field; we are doing this by

using a combination of techniques that are widely used and accepted in the science community. The

method will however be slightly different because there will be different types of methods (sonification,

silanization, and apply of a magnetic field) put together. Though the individual methods that comprise

our proposed method are not generally used together they are methods that are currently used within the

science community. The costs of the nanoparticle inks and other components of the proposed method

will not be a major factor in the acceptance of this method. The costs of the materials needed for this

method are relatively cheap compared to other tests such as PCR and ELISA. The disposal of the

nanoparticle ink and nanoprobes could potentially negatively impact the environment. If disposed of

improperly nanoparticles can be taken up by animals and bacteria in bodies of water. A study by Nowack

and Bucheli suggests that nanoparticles introduced to the water with different types of organisms, the

organisms took up the nanoparticles. Many organisms have the potential to take up the organism and

could therefore be affected by the nanoparticles. (Nowack and Bucheli 2007) The current method of

disposal of nanoparticle ink is similar to that of other hazardous wastes. The inks must be disposed by

licensed waste disposal services and treated as combustible material .This procedure will not affect the

routine of a majority of lab users. (Nowack and Bucheli 2007) The system also has the potential to be

15

used in portable systems for disease diagnosis. The components of this device are small and can be used

in a machine that is portable. Other diagnostic tools currently do not have the potential to be portable.

16

References

Baeten, V., Hourant, P., Morales, M.T., Aparicio, R. (1998) Oil and Fat Classification by FT-

Raman Spectroscopy. J Agric. Food Chem. 46 (7) 2638-2646

Basu, S., Pande, S., Jana, Subhra, Bolisetty, S., Pal, T. (2008) Controlled Interparticle Spacing

for Surface-Modified Gold Nanoparticle Aggregates. Langmuir 24: 5562-5568

Bischof JC, Hammer BE, Han B, Kalambur VS, Shield TW. “In vitro characterization of

movement, heating and visualization of magnetic nanoparticles for biomedical applications”.

(2005). Nanotechnology 16; 1221-1233.

Bruckbauer, A., James, P., Zhou, D., Yoon, J.M.,Klenerman, D., et al (2007) Nanopipette

Delivery of Individual Molecules to Cellular Compartments for Single-Molecule

Fluorescence Tracking Biophysical J 93, 3120-3131

Chen, X., Kis, A., Zettl, A., and Bertozzi, C. “A Cell Nanoinjector based on Carbon

Nanotube”.(2007). Proceedings of the National Academy of Sciences of the United States of

America. 104(20) 8218-8222.

Choo-Smith, L., Edwards, H. G. M., Endtz, H. P., Kros, J. M., Heule, F., Barr, H., et al. (2002).

Medical applications of raman spectroscopy: From proof of principle to clinical

implementation. Biopolymers - Biospectroscopy Section, 67(1), 1-9.

Hajukova, N., Prochazka, M., Stepanek, . and Spirkova, M. “Chemically reduced and laser-

ablated gold nanoparticles immobilized to silanized glass plates: Preparation, characterization

and SERS spectral testing”.(2007) Colloids and SurfacesA: Physicochemical Engineering

Aspects. 301, 264-270.

Jang S, Kong W, Zeng Hao.“Magnetotransport in Fe3O4 nanoparticle arrays dominated by

noncollinear surface spins.” (2007). PHYSICAL REVIEW B 76, 212403

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Lo, C.K., Xiao, D., Choi, M.F. (2007) Homocystein-protected gold-coated magnetic

nanoparticles: synthesis and characterization. J Materials Chemistry 17: 2418-2427

Mandal, M., Kundu, S., Ghosh, S.K., Panigrahi, S., Sau, T.K., Yusuf, S.M., Pal, T. (2005)

Magnetite nanoparticles with tunable gold or silver shell. J Colloid and Interface Science

286: 187-194

Merel, P. (2005). Perspectives on molecular diagnostics automation. JALA - Journal of the

Association for Laboratory Automation, 10(5), 342-350.

Nowack, B. And Bucheli, T. (2007) ”Occurence, behavior and effects of nanoparticles in the

environment”. Environmental Pollution, 150(1), 5-22.

Piezosystem Jena <http://www.piezojena.com/en/site/site/xyz-positioner/TRITOR-38__257/>

Salata, OV. (2004) “Applications of Nanoparticles in Biology and Medicine”. Journal of

Nantechnology. 2(3) 1-6

Schrlau, M., Falls, E., Ziober, B., and Bau, H. “Carbon Nanopipettes for Cell Probes and

Intracellular Injection” 29 Nov 2007. Nanotechnology. 19 1-4

Wang, A. and Rothberg, L.J. “Silver nanoparticle coverage dependence of surface-enhanced

Raman Scattering”.(2006) Applied Physics B. 84, 289-293

Wang H, Chen QW, Sun LX, Qi H, Xi Y, Zhou S, Xiong J. “Magnetic-Field-Induced Formation

of One-Dimensional Magnetite Nanochains”. (2009). Langmuir 2009, 25(12), 7135–7139.

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4357-4360

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Appendices

Appendix A-Sonication

PROCEDURE: Magnetite-core Au-shell Nano-particle Formation – SONICATION METHOD

NOTE:

Magnetite to Au ratio can range from 1:0.5 to 1:1 in order to obtain particles that are fully coated;

however, thinner gold coating produces smaller nanoparticles. For example, particles with magnetite

diameter of 13 0.5-nm increased to 25 0.5-nm for 1:0.5 ratio, and 30 0.5-nm for 1:1 ratio. Because the

purchased magnetite particles are 1-10 nm in diameter, less gold can be used to obtain coated particles

with a smaller diameter.

MATERIALS:

o D-glucose (reducing agent)

o HAuCl4

o Double-distilled H2O o Fe3O4 particles (Magnetite), Purchased from Vivenano: 1-10nm 1.5mg/mL nanoparticles

suspended in water (200mL)

METHOD:

Prepare a 1:0.5 molar ratio of Fe3O4 to HAuCl4 (Fe3O4= 231.535 g/mol, HAuCl4= 338.782 g/mol)

10mL Fe3O4 has 15mg Fe3O4 and 0.000065 mol Fe3O4

Need 0.0000325 mol HAuCl4, so 11mg HAuCl4 (0.011 g)

Add ~100mg D-glucose (excess)

Sonicate for 15-min

Heat in waterbath for 1-hr with slow stirring

OBSERVATIONS:

The added Au ions are reduced to metallic state and subsequently wrap around the Fe3O4 particles

producing Fe3O4@Au structures. The supernatant of the liquid turned transparent when complete

reduction occurs; however incomplete reductions leave the supernatant slightly colored. The dry black

mass of Fe3O4 turns reddish brown after Au coating.

19

Appendix B- Water Bath Method

PROCEDURE: Magnetite-core Au-shell Nano-particle Formation – WATER BATH METHOD

METHOD:

Prepare 15mL aqueous solution of HAuCl4 – 2.0mg/mL (Need 30 mg HAuCl4)

Add solution to 105mL DI water and heat to boiling

Add 5mL (CONCENTRATION UNKNOWN!!!) Fe3O4

I think that we could use the same 1:1 Fe3O4 to HAuCl4 ratio as here to conserve magnetite. We

would need 20.5mg Fe3O4 Since our magnetite concentration is 1.5mg/mL, we would need 13.67mL of Fe3O4

Add 5mL Sodium Citrate (80 mmol dm-3

) while stirring

Boil for about 5 minutes while stirring

OBSERVATION:

Reaction mixture turns from brown to burgundy

NOTE*** Both procedures could be up-scaled by an order of magnitude.

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Appendix C-Silanization

Silanization Protocol

21

22

Appendix D-Free Body Diagram

Free Body Diagram of Fe3O4@Au nanoparticle in solution

Figure B1. A simple free body diagram displaying the

major forces (the magnetic force due to the magnetic

field, the gravitational force, and the viscous drag force of

the solvent) acting on a Fe3O4@Au nanoparticle in

solution.

23

Appendix E-Schedule

Schedule

Fall Term DUE (Tuesdays) Activity

Week 1 (9/21-

9/27)

Week 2 (9/28-

10/4)

Project ID Draft

Week 3 (10/5-

10/11)

Project ID Final Research Nanopipettes

Week 4 (10/12-

10/18)

Meet with Dr. Pourrezaei to discuss project

Week 5 (10/19-

10/25)

Research current methods and materials used

to make nanopipettes

Week 6 (10/26-

11/1)

Outline Draft Research lab techniques for making

nanopipettes

Meet with Dr. Pourrezaei

Week 7 (11/2-

11/8)

Outline Final Redefine Research Objective; Research

Raman Spectroscopy, Glass-Fiber Nanotips;

Contact Dr. Pourrezaei about starting to

make nano-probe; Contact Dr. Lec about nanotechnology; Modify and resubmit outline;

work on Proposal Draft

Week 8 (11/9-

11/15)

Proposal Draft Lab – Learn to make glass fiber nano-probe; work on completing proposal, Meet with

Professors; Research gold ink properties

Week 9 (11/16-

11/22)

Lab – glass fiber nano-probe; Research gold-

ink properties to optimize Raman spectroscopy

Week 10 (11/23-

11/29)

Proposal Final Break – continue research

Week 11 (11/30-

12/6)

Oral Presentation

Uploaded Monday 9-AM

Lab – glass fiber nano-probe – start

experimenting with how to make different shapes/sizes of probe

Finals Week

(12/7-12/13)

Finals – continue research for optimization of

Raman Spectroscopy

Break Week 1

(12/14-12/20)

Break – continue research for optimization of Raman Spectroscopy

Break Week 2

(12/21-12/27)

Break – continue research for optimization of

Raman Spectroscopy

Break Week 3

(12/28-1/3)

Break – continue research for optimization of

Raman Spectroscopy

Winter Term

Week 1 (1/4-

1/10)

Discuss Design Project Plan – Due week 4

Week 2 (1/11-1/17)

Learn how to attach nanoparticles of ink to probe

Meet with Edward Keough (Merck)

Week 3 (1/18- Probe manufacturing

24

1/24) Meet with Manuel

Week 4 (1/25-

1/31)

Design Project Plan Probe manufacturing

Meet with Manuel Week 5 (2/1-2/7) Progress Report

Outline

Probe manufacturing

Meet Dr. Pourrezaei, Dr. Tyagi, Dr. Solomon

Week 6 (2/8-

2/14)

Probe manufacturing, surface modification,

create magnetic field system Week 7 (2/15-

2/21)

Progress Report Test magnetic field system on larger

magnetite particles, Surface modification of

probe, SEM Week 8 (2/22-

2/28)

Test magnetic field system on larger

magnetite particles, Surface modification of

probe, SEM

Week 9 (3/1-3/7) Progress Report HAuCl4 arrives – coat nano magnetite particles

Week 10 (3/8-

3/14)

HAuCl4 arrives – coat nano magnetite

particles, use magnetic field to attach particles Finals Week

(3/15-3/21)

SEM

Prototype Complete, ready or modifications.

Break Week (3/22-3/28)

Break – Attachment of Nanoparticles

Spring Term

Week 1 (3/29-

4/4)

Raman, modification of attachment

Week 2 (4/5-4/11)

Raman, modification of attachment, SEM Work on Presentation and Paper

Week 3 (4/12-

4/18)

Biomolecule testing

Work on Presentation and Paper Meet with Dr. Pourrezaei to discuss progress

Week 4 (4/19-

4/25)

Biomolecule testing

Work on Presentation and Paper

Week 5 (4/26-5/2)

Work on Presentation and Paper

Week 6 (5/3-5/9) Work on Presentation and Paper

Week 7 (5/10-5/16)

Work on Presentation and Paper

Week 8 (5/17-

5/23)

Presentation

25

Appendix F- Resumes

26

27

28

29

30

31