http://www.sciencemag.org/content/331/6021/1168.abstract
Once again, the James Tour's group.
They just put zinc metal onto the graphene sheets and dissolve the metal with HCl....
The metal and the topmost graphene sheet is removed without affecting the underlying sheets.
What a strange thing it is!
The the bonding between metal and graphene is unlikely stronger than the carbon-carbon network!
Well, they have given an resonable explanation for that. They attributed the ease of removal to the defect formed during sputtering process, so that the damaged region of graphene can be easily removed during metal dissolving process.
In addition, they pointed out the dissolving process that accompanied with hydrogen formation is also play a role in removing process.
They also dissolved gold and copper with KI/I2 and HCl/CuCl2, respectively, which no hydrogen is formed during these two reactions. As a result, no carbon layer was removed by these two method....
That's a really interesting work!
My first paper in ACS Nano
http://pubs.acs.org/doi/abs/10.1021/nn103221v
Several chemical approaches are known to form a p-n junction of graphene such as gas exposure, polymer-induced doping, and reaction with diazonium salts. These methods require e-beam lithography to define the pattern mask for selective area doping, which suffers from the residue of resist that may heavily affect the electrical properties and the following chemical doping process.
In this study, we report a facile way to modify the specific area of graphene devices by simply ultilizing a polydimethylsiloxane (PDMS) microfluidic channel. The PDMS channel has been widely used in biosensor application, which is capable of modifying the target object with solution-based modification. With the help of PDMS microchannel, the graphene was partially covered by PDMS and left uncovered region for solution passing through the channel. This simple approach have enabled us to achieve spatially selective functionalization or doping in graphene, resist-free p-n junction device. Taking advantage of microfluidic system, we can easily switch the dopant from one to another at will, along with noncovalent modification. We are able to create a high-quality graphene device with high carrier mobility and prominent QHE signature. Although this method seems to be only suitable for micron-scale fabrication, I think this partially-modified graphene devices can be futher patterned or narrowed down into nano-scale by some kind of nanoribbon formation process, such as nanowire-mask approach or e-beam lithography.
Boron Nitride and Graphene : the possible way toward band gap opening of graphene?
Now researchers have a new focus to pursue the band gap opening of graphene.
BN thin film, a two dimensional insulator, has a band gap > 5 eV and very similar structure to graphene. Some theoretical calculations have suggested the hybrid-BNC film and graphene on BN could be the potential way toward band gap engineering.
Besides, the BN layer can also be grown on copper by CVD synthesis, just like the graphene. I believe that the BN film and graphene should have some interesting interactions between them. For example, Philip Kim's group used BN as the substrate for making high mobility graphene devices, since the BN is an atomically smooth and dangling-bond-free insulator, which makes it an ideal dielectric substrate. However, the problem is still there, the creation of the band gap is usually accompanied with a decrease of carrier mobility.
It seems still a long way to go for making the effective graphene transistors.
Here are some of the recent works in BN research
http://www.nature.com/nmat/journal/v9/n5/full/nmat2711.html
http://www.nature.com/nnano/journal/v5/n10/full/nnano.2010.172.html
http://pubs.acs.org/doi/abs/10.1021/nl1022139
http://pubs.acs.org/doi/abs/10.1021/nl1023707
http://onlinelibrary.wiley.com/doi/10.1002/smll.201001628/abstract
http://pubs.acs.org/doi/abs/10.1021/jp110985w
BN thin film, a two dimensional insulator, has a band gap > 5 eV and very similar structure to graphene. Some theoretical calculations have suggested the hybrid-BNC film and graphene on BN could be the potential way toward band gap engineering.
Besides, the BN layer can also be grown on copper by CVD synthesis, just like the graphene. I believe that the BN film and graphene should have some interesting interactions between them. For example, Philip Kim's group used BN as the substrate for making high mobility graphene devices, since the BN is an atomically smooth and dangling-bond-free insulator, which makes it an ideal dielectric substrate. However, the problem is still there, the creation of the band gap is usually accompanied with a decrease of carrier mobility.
It seems still a long way to go for making the effective graphene transistors.
Here are some of the recent works in BN research
http://www.nature.com/nmat/journal/v9/n5/full/nmat2711.html
http://www.nature.com/nnano/journal/v5/n10/full/nnano.2010.172.html
http://pubs.acs.org/doi/abs/10.1021/nl1022139
http://pubs.acs.org/doi/abs/10.1021/nl1023707
http://onlinelibrary.wiley.com/doi/10.1002/smll.201001628/abstract
http://pubs.acs.org/doi/abs/10.1021/jp110985w
Nanofabrication of graphene
Patterning the graphene surface is a significant topic in the future graphene applications, since a number of functionalities of graphene were enabled by surface chemical modification; the two-dimensional structure of graphene offers an unique way to engineer the carriers by using surface modification.
A group from Northwestern University, lead by Mark Hersam, had demonstrated the sub-5-nm nanofabrication can be realized by using the scanning tunneling microscopy.
A layer of PTCDA was served as a chemical resist which can be desorbed from the surface of graphene by controlling the bias voltage or the tunneling current. The PTCDA was firstly deposited onto graphene surface by thermal evaporation, and the PTCDI-C8 layer was formed following the PTCDA deposition. The outcome shows that the PTCDI-C8 prefer to stay in the remaining graphene area where lack of the PTCDA layer. Moreover, they employed the feedback-controlled lithography (FCL) to eliminate the ununiformity of desorption, thus they are able to define the clear pattern on PTCDA layer and fill up the desorbed area with PTCDI-C8. This work has revealed the possibilities of nanofarication, which could be used for the selective area functionalization or etching process in the future nanoelectronic devices. I think this technique is also good for the study of surface modified-graphene.
Turn PMMA into a sheet of graphene
http://www.nature.com/nature/journal/v468/n7323/full/nature09579.html
This work done by James M. Tour's group will certainly be a huge impact in graphene production.
They show that the graphene can be grown by solid state materials like polymer, more incredibly, they said that they can even control the layer number of synthesized graphene by tuning the annealing condition, such as the flow rate of Ar and H2 gas during the growth process.
They accounted for this effect by introducing an idea that H2 is able to serve as reducing agent as well as a carrier gas to remove carbon released from PMMA. And the hydrogen flow rate is essential since the remain carbon sources determined the number of layer will grow.
In addtion to the PMMA-derived graphene, they also used fluorene and sucrose to demonstrate the possible way to grow monolayer graphene.
Moreover, they blended melamine and PMMA and make them into N-type graphene by introducing some nitrogen atoms in the framwork of carbon.
They really did an incredible job, it seems that anything contain carbon can be used to grow the graphene. That sounds pretty amazing, doesn't it?
This work done by James M. Tour's group will certainly be a huge impact in graphene production.
They show that the graphene can be grown by solid state materials like polymer, more incredibly, they said that they can even control the layer number of synthesized graphene by tuning the annealing condition, such as the flow rate of Ar and H2 gas during the growth process.
They accounted for this effect by introducing an idea that H2 is able to serve as reducing agent as well as a carrier gas to remove carbon released from PMMA. And the hydrogen flow rate is essential since the remain carbon sources determined the number of layer will grow.
In addtion to the PMMA-derived graphene, they also used fluorene and sucrose to demonstrate the possible way to grow monolayer graphene.
Moreover, they blended melamine and PMMA and make them into N-type graphene by introducing some nitrogen atoms in the framwork of carbon.
They really did an incredible job, it seems that anything contain carbon can be used to grow the graphene. That sounds pretty amazing, doesn't it?
Self-aligned nanowire gate graphene transistor !
The groups who formed GNR with the aid of nanowire now have enormous advance in top-gated graphene transistor.
Their paper was published in Nature in just two days before.
They used a Co2Si–Al2O3 core–shell nanowire as a top gate electrode which is able to apply an electric field across the thin layer of Al2O3 that serve as a gate dielectric. Apparently, the gating effect would be far more large than that of back-gated configuration, since the dielectric layer is extremely thin and possess higher dielectric constant than SiO2. To fulfill the requirements of microwave measurement, they replaced the degenerate silicon substrate with highly resistive ones that could effectively reduce the dielectric loss at microwave frequency. And they found that the cutoff frequency could be up to 300GHz, which increases the usability of graphene transistor at high frequency.
Two groups drilled nano scale pores for DNA passing through !!!
As mentioned in my previous article, two groups, from Upenn and Netherlands, have already put this idea into practice. They really drill a nanopore on the sheets of graphene!!
both of them have been published in Nano Letters,
This one is from a famous group in the field of biosensor lead by Cees Dekker
And this one is from Upenn, Datta's previous lab lead by A.T. Charlie Johnson, they are the pioneer that found a way to sense the gas odor by DNA-decorated carbon nanotube
They realized this idea by recording the blocked current change while the DNA were passing through these holes, and they found the current change profile corresponding to the two states of DNA; the signals could be used to distinguish the DNA either folded or unfolded as it pass through a pore. These DNAs were driven by a potential difference across the graphene membrane, which allows the measurement of the passing of DNA.
In my view, it is not dfficult to imagine that the ion distribution outside the giant biomolecules such as DNA and protein would somehow change to adapt these intruders and tend to maintain charge neutrality in the solution. As these molecules approach the surface of graphene, the graphene nanopore device can detect this considerable or even quantitative change in ionic condition in terms of the pulses that decrease in current. I believe that it is just the first step for DNA sequencing. The difficulty of this final goal is possible to be limited to rate of detection, since the transient signal is hard to be used in distinguishing the single-base pair differences.
CNT-FET controlled by an ion pump gate
The above is a very impressive work from Lawrence Livermore National Laboratory!
They utilized a lipid bilayer with ion pumps to cover the CNT-FET.
The ion pump as mentioned above, is made of ATPase which is powered by ATP hydrolysis; the ATPase is able to control the ion gradients across the membrane by metabolizing ATP.
They used a single semiconducting CNT to conduct this experiment and proved that the ATP can indeed act like a trigger to open the gate of ion pump, which is evidenced by the drain current change.
Moreover, they conjugated the head group of lipid with FITC which monitored the pH variation in the aqueous layer between CNT and lipid membrane. Finally, they explained that the drain current saturation is due to a small leak passage in the membrane or ion pump.
I think it is interesting to put a lipid on the top of CNT device, what if we put it on the graphene device?
Or maybe graphene itself can serve as a membrane or even we can even drill a hole on it to allow small biomolecules like DNA or RNA to pass through these holes, and we can monitor the ionic concentration change nearby the holes by recording the current change or something. It is not difficult to imagine that someone would think of this kind of idea, since in recent publication, the nanopore-related topics is also a very hot topic as graphene, both of them had appeared in Nano Letters or ACS Nano for many times.
Meet with Dr. Lain-Jong Li
Yesterday I was so excited about that I had a chance to meet with Dr. Lain-Jong Li.
He is an outstanding researcher in the field of graphene and carbon nanotube materials. His group published a total of 18 journal papers in 2009. And many of them are published in Advanced Materials, Small….and etc.. He was invited to give a talk about his research yesterday, during the presentation, he mentioned that the contact between carbon nanotube and metal electrode plays a more important role than the central region of the carbon nanotube network FET in biosensing application. He attributed this effect to Schottky barrier between metal and semiconducting nanotubes, so I asked him whether the same effect will happen in graphene devices. He told me graphene is metallic, and there should not be any barrier in the contact. That triggers me to think of a properties of graphene called of Klein tunneling. The tunneling probability of transport carriers is always 1 despite the mismatch in work function of these two part of graphene....
They also stress on chemical modification of graphene and CNT, just like the way we do. However, I have been spent one year studying this project, and it turns out that I didn't get very positive results. In the past year, I've read a lot of papers about graphene, but the experimental data still fluctuates for many unknown reasons. An increasing number of factors in our experiments need to be controlled--such like humidity control in KPM measurement and modification process control.... I don't know why I've encountered so many problems. Maybe this is the only route to the final success. I have so many questions need to be answered. So, when Dr. Li Lain-Jong came to our lab, I asked him lots of questions about the obstacles I met. After about an hour's discussion with him, I received quite a few valuable advice about our research project. I am so glad that I have such chance to discuss with him, which strongly inspired me in the field of materials research.
He is an outstanding researcher in the field of graphene and carbon nanotube materials. His group published a total of 18 journal papers in 2009. And many of them are published in Advanced Materials, Small….and etc.. He was invited to give a talk about his research yesterday, during the presentation, he mentioned that the contact between carbon nanotube and metal electrode plays a more important role than the central region of the carbon nanotube network FET in biosensing application. He attributed this effect to Schottky barrier between metal and semiconducting nanotubes, so I asked him whether the same effect will happen in graphene devices. He told me graphene is metallic, and there should not be any barrier in the contact. That triggers me to think of a properties of graphene called of Klein tunneling. The tunneling probability of transport carriers is always 1 despite the mismatch in work function of these two part of graphene....
They also stress on chemical modification of graphene and CNT, just like the way we do. However, I have been spent one year studying this project, and it turns out that I didn't get very positive results. In the past year, I've read a lot of papers about graphene, but the experimental data still fluctuates for many unknown reasons. An increasing number of factors in our experiments need to be controlled--such like humidity control in KPM measurement and modification process control.... I don't know why I've encountered so many problems. Maybe this is the only route to the final success. I have so many questions need to be answered. So, when Dr. Li Lain-Jong came to our lab, I asked him lots of questions about the obstacles I met. After about an hour's discussion with him, I received quite a few valuable advice about our research project. I am so glad that I have such chance to discuss with him, which strongly inspired me in the field of materials research.
Wrote to Sujit S. Datta
He is an outstanding student who made a lot of impressive work.
One of his previous work named "Surface Potentials and Layer Charge Distributions in Few-Layer Graphene Films" is an important reference for my KPM study.
When I found his website and blog, I am so excited because he also shared the idea and comments about scientific research just like me.
And I asked him some questions about the article I just mentioned, and I listed them as follows:
------------------------------------------------------------------------------------------------------------------------
(1) You mentioned that the surface potential of few layer graphene(FLGs) on SiO2 substrate is always positive, indicating hole doping in ambient.
But what about single layer graphene?
In our experiments, they sometimes exhibit higher potential than surrounding silica but sometimes lower than that. Could such variation be an evidence for doping tendency?
(2) The surface potential of FLGs increases with film thickness and approach to a finite value is resulted from "interlayer screening".
Is that means each graphene layer can "feel" positive charges on the bottom layer which is strongly doped by holes from silica?
And will each layer redistribute the electron density to adapt the positive surface charges of the bottom layer?
If the bottom layer is doped by negative electrons, instead of holes. Would it be possible that the potential of FLGs may decrease with layer thickness, or it still increases with film thickness?
-----------------------------------------------------------------------------------------------------------------------
Surprisingly, he replied me very fast !
In spite of some unanswered questions, I’m so grateful to him!
One of his previous work named "Surface Potentials and Layer Charge Distributions in Few-Layer Graphene Films" is an important reference for my KPM study.
When I found his website and blog, I am so excited because he also shared the idea and comments about scientific research just like me.
And I asked him some questions about the article I just mentioned, and I listed them as follows:
------------------------------------------------------------------------------------------------------------------------
(1) You mentioned that the surface potential of few layer graphene(FLGs) on SiO2 substrate is always positive, indicating hole doping in ambient.
But what about single layer graphene?
In our experiments, they sometimes exhibit higher potential than surrounding silica but sometimes lower than that. Could such variation be an evidence for doping tendency?
(2) The surface potential of FLGs increases with film thickness and approach to a finite value is resulted from "interlayer screening".
Is that means each graphene layer can "feel" positive charges on the bottom layer which is strongly doped by holes from silica?
And will each layer redistribute the electron density to adapt the positive surface charges of the bottom layer?
If the bottom layer is doped by negative electrons, instead of holes. Would it be possible that the potential of FLGs may decrease with layer thickness, or it still increases with film thickness?
-----------------------------------------------------------------------------------------------------------------------
Surprisingly, he replied me very fast !
In spite of some unanswered questions, I’m so grateful to him!
Can we exfoliate graphene with the aid of solution?
The most common preparation of graphene is to exfoliate the graphite with scotch tape.
On the other hand, the researchers try to seek an alternative way to exfoliate the graphite stacks, that is, using various kinds of solvent to intercalate the graphite and exfoliate the stacks.
The most representational work is
Since the experiments in this paper seems to be relatively simple. I made a test immediately.
The solvent I chose is NMP (N-Methyl-2-pyrrolidone) which is the best solvent they concluded.
The mechanism is easily comprehended by the solvent-graphene interaction, but the main problem is that NMP is hard to evaporate in ambient condition. It can only be removed in vacuum with heat assistance.
After drying the solvent, the graphene flakes is so small to the extent that are difficult to process.
Meanwhile, something came to my mind, can we exfoliate the graphene sheets by similar technique used for dispersing CNT bundle?
So I test this idea with a surfactant called NaDDBS (sodium dodecylbenzenesulfonate) which were used in our previous study of CNT-FET biosensor. The results is better, I was so happy with that !
Immediately, I searched the literature to see whether it has been published or not....
And then.......I found this one.....
I was so depressed about it..............
It was too late, they already published their work in Feb, 2009.
The early bird catches the worm.......
Terpyridine and Graphene
A paper published at 2005 discussed the interaction between terpyridine and CNT.
That triggered me to think what if we put terpyridine on the top of graphene?
Could Terpy serve as a nanoparticle template for graphene?
To test this idea, I've tried to immerse the graphene-contained silicon chip into the 50 mM ethanolic solution for 1 hr just like the way they do. But turns out, the outcome is far beyond what I expected.
The Raman spectroscopy results showed that the peaks does not change at all, neither does the electrical properties.
Furthermore, I also tried to immerse the Terpy-modified samples into metal ions solution for the nanoparticle formation test. And I scanned the surface with AFM and tried to find the nanoparticles that should be formed on the surface of graphene. But the result was not as good as I anticipated. Only little amount of nanoparticles were formed and located everywhere without spatial selectivity.
The paper claimed that the terpyridine would associate CNT through nitrogen-mediated interactions instead of the π-π interactions. But if this statement is true, why it can not be applied in the case of graphene?
The possible reason is that the curvature of CNT is the crucial character for the interaction between Terpy and CNT.
Reducing GO with Flash light !??
Although the use of camera lash has been reported in CNT, Si nanowire and conducting polymer. This work still gave me a big shock.
http://pubs.acs.org/doi/abs/10.1021/ja902348k
Researchers from Northwestern University (the alma mater of my master adviser) had invented a new way to reduce graphite oxide. They used the commercial camera's flash light to irradiate the GOs and make them back to graphite and accounted for this effect by using photothermal heating mechanism. They found that the flash method is effective enough to compare with themal annealed samples. The basic principle is about the water evaporation from the GO, and the enough photo energy to trigger the deoxygenating process.
Taking advantage of flash light, they even make a photomask to define the device region. This is a very useful method for GO approach, and they demonstrated again that the camera flash is able to be a tool for reduction proecess.
I just wondering why the flash light irradiation in ambient condition could be a reducing agent for GO while being a oxide agent in other cases. @_@
http://pubs.acs.org/doi/abs/10.1021/ja902348k
Researchers from Northwestern University (the alma mater of my master adviser) had invented a new way to reduce graphite oxide. They used the commercial camera's flash light to irradiate the GOs and make them back to graphite and accounted for this effect by using photothermal heating mechanism. They found that the flash method is effective enough to compare with themal annealed samples. The basic principle is about the water evaporation from the GO, and the enough photo energy to trigger the deoxygenating process.
Taking advantage of flash light, they even make a photomask to define the device region. This is a very useful method for GO approach, and they demonstrated again that the camera flash is able to be a tool for reduction proecess.
I just wondering why the flash light irradiation in ambient condition could be a reducing agent for GO while being a oxide agent in other cases. @_@
Over 1 square centimeter graphene debut!!
No doubt this accomplishment is definitely an enormous progress for graphene research.
A famous group from UT Austin, lead by Rodney S. Ruoff, a leader who first carved up graphite into graphene in 1998, he also wrote a review article in Nature Nanotechonlogy in just few months earlier.
They found if the growth substrate for CVD graphene is replaced by a copper foil, the growth of graphene would be self-limited, which means it is hard to build the second layer on the top of the first layer graphene. With the help of the poor carbon solubility in copper during the synthesis process, the graphene is formed continuously across a vast area of substrate. Eventually, they concluded that the precipitation process of carbon on the surface of copper is suppressed at the high temperature, which enabled a large continuous graphene to be obtained.
The realization of getting a wafer scale and atomically thin graphene is a great progress, however, the absence of band gap in SLG has strongly limited the potential application in electronic industry. Nowadays, a vigorous trend is to open a band gap in graphene electronic device without degrading the transport properties. As far as I know, there are many groups are eagerly working on band gap engineering of graphene, one of these possibility is bilayer graphene, which has been shown to be able to get a band gap under the dual gate configuration. I believe that one day the dream of wafer scale CVD bilayer graphene will be realized. Unfortunately, in spite of my previous work is related to build a CVD system, I don't have chance and enough time to work on it...
Raman spectroscopy in our lab again !!
In fact, we have a confocal Raman system in the lab already, but the alignment is completely lost...
In order to dealing with our new baby--graphene, I told to my boss that I want to refurbish the previous Raman system in the lab. Since it is has long fallen into disuse. And once again, I gave myself a challenge, just like the previous work in redesigning the CVD system.
But I have to say this is definitely a wearing job to save this old Raman system.
The confocal Raman system has several parts, laser, confocal microscope, spectrometer, CCD, the most difficult task is how to adjust the laser spot and make it align to the identical light path of signal from sample. I spent almost two weeks adjusting a small piece of filter, namely "notch filter" which is an essential part of confocal Raman system. This small filter is responsible for filtering out the original laser signal from the reflected Raman signal of sample. Even the most subtle adjustment of this filter could lead to significant change in the position of light spot. That's why no one in the lab want to solve this thorny problem!
Anyway, through this experience of refurbishing our old Raman system, I have learned the alignment of optical path, and the basic sense of the optical component as well. After about 1 month wearing job of alignment, the Raman started to work normally with graphene.
Graphene Times !?
Incredibly, I found a website named "Graphene Times"!!
The guy who built this website is almost doing the same thing as me!!
But, the difference is that I catch the RSS feeds with a software called "Newsfire" (Mac only). NewFire is the best RSS reader I ever used, since it has the major and most important function -- filter. The filter just as the name implies, it filters out the unwanted and huge amount of RSS feeds except the keyword I set, for example, graphene as a keyword. With the help of filter in NewsFire, I can easily follow the newest publication related to graphene which were just updated in each journal website all around the world.
In comparison with "Graphene Times", my solution is even better, because the number of journal I monitored is more than he did, in addition, I could set more keywords to seek more research combination with graphene.
Substrate engineering of graphene?
I always think that the substrate has enormous effect on the graphene.
It is not difficult to imagine because the vast area of graphene have contacted with substrate, and the substrate has long been considered as major source of charge impurities. (though no one knows where they came from)The clues can be found from the previous work done by Andrei group in Rutgers, they reported that they could approach ballistic transport by suspending the graphene and measured the highest mobility ever in low-temperature about 200,000 cm2/ Vs.
http://www.nature.com/nnano/journal/v3/n8/full/nnano.2008.199.html
And the work related to Raman Spectroscopy
http://pubs.acs.org/doi/abs/10.1021/nn900130g
And the work that focus on the doping effect of the substrate
http://prb.aps.org/abstract/PRB/v79/i11/e115402
Since the previous work I focused is the surface modification of silica surface.
One of the various kinds modification I did is that I capped the silanol groups with HMDS which make silica to be hydrophobic.
And I analyzed the sensing signal change when I injected the buffer with stepwise concentration.
I found that the influence of surface silanol groups is quite important, since they are greatly responsible for the surface potential change in SiNW-FET biosensor. Moreover, I think the ionic behavior is quite different when we replaced the surface groups or capped them.
So, a question has now appeared--
If the so called "charge impurity" mainly came from the ions or ion-like molecules that associated with substrate, what would happen if I capped the surface silanol groups of SiO2 substrate with trimethylsilane?
I think it would be better, at least the mobility should increase, since the ion-like charge impurities would reduce the amount of them which associated with silica prior to the graphene attaching.
Can graphene quench the light from FITC?
I found that when I try to excite an FITC-tag protein linked to graphene with blue light, it seems graphene quench the light every time. No matter how many times I tried, it still became the darkest one on the screen. In order to find the answers, I've searched the literature and only found these two.
http://link.aip.org/link/JCPSA6/v130/i8/p086101/s1http://link.aip.org/link/JCPSA6/v129/i5/p054703/s1
I also repeated this experiment with almost identical condition simply by replacing graphene with CNT.
The results is quite different from graphene, it emitted green light normally.
But I think this may be due to some of CNTs are semiconductor which would not quench the light so effectly whereas the metallic one would do.
Maybe graphene behaves just like a metal, since the metal marks in the surrounding area were able to quench all the light as well.
But, what would happen if we put the FITC-tag protein on the top of the GO?
GO should have a band gap due the disruption of the π network, but it seems to depend on some specially distributed oxidized sites to open the "gap". I believe that one day the GO will be a band gap controllable materials in the future, but now, still long way to go.
UCLA researchers found the way to form GNR by Si-NW etching mask!!
I have to say this is really a brilliant idea to form a GNR by simply applying the nanowire as a mask.
Two groups from UCLA, lead by Yu Huang and Xiangfeng Duan, published this work in Nano Letters
I think it is very suitable for us to produce GNR in this way, since we have plenty of Si nanowires. In order to test it, I try to disperse Si nanowires by suspending them in an enthanolic solution. I found that it is hard to control the distribution and orientation of nanowires. Even though the nanowire has been deposit on the top of graphene, it is no guarantee that the nanowire would firmly contact the graphene to the extent that is able to protect the underlying graphene, which is hard to verify as well.
I think I would try to use some physical ways to deposit the nanowire if I have time to test it.