Nanotechnology impressions

Nanotechnology impressions

info on quantum dots continued

I know what you’re thinking-“Rich, what’s with all this about toxicity and ee-king? We can’t have our imaging material causing more problems.” And, you’re right. The scientists have also thought of this and have done experiments mirroring the body’s environment to make sure quantum dots and their coatings are stable over a broad range of PH and salt conditions- Even hydrochloric acid. And they passed with (ahem) flying colors.

Carbon nanotubes also have this fluorescence quality. R.Bruce Welsman and his group at Rice University have determined that semi-conducting carbon nano-tubes fluoresce in the near –infrared spectrum and can be fine-tuned to different wavelengths by varying the nano-tube diameter. The near infrared spectrum is particularly important for biomedical applications but nothing in the human body fluoresces in this region of the spectrum: in effect, human tissue is fairly transparent. It’s especially handy that nanotubes also maintain their fluorescent properties inside living cells, with no adverse effects to the cell.

Down the road ,such carbon nanotube technology may be used along the same lines as the quantum dots.- you could end up wrapping the tubes with a specific protein allowing them to target cells (such as tumors) Along these lines a proposal by Michael Stranto and his team at the University of Illinois Urbana/Champaign(involving a glucose-detection optical sensor) looks especially promising. Here nanotubes are wrapped in a glucose oxidase and placed inside a small porous capillary (20 microns across by 1cm in length) the capillary pores are only big enough for glucose to penetrate. Once through the glucose promptly reacts with the oxidation solution changing the fluorescence properties of the nanotubes. This capillary is subsequently inserted just underneath the skin, but within range of being able to detect the near –infrared fluorescence, Imagine a patient with diabetes wearing a watch that periodically checks the fluorescence /glucose and sounds an alert if levels are too low or high- all without needles.

Unlike quantum dots, nanotubes don’t contain heavy metals, so they don’t raise any toxic issues. Additionally nanotubes can be fine-tuned to very narrow wavelength, providing fluorescence in a greater number of wavelengths, giving us greater flexibility( in other words nano colors to our palette) Such properties may give nano-tubes the advantage among products marketed as laboratory imaging markers.

More info on quantum Dots

We describe quantum dots, semi conducting nanocrystals roughly 5nm in size. They also have applications in the biological world as fluorescent tags Quantum dots are nanometer-scale nanocrystals composed of a few hundred to a few thousand semiconductor atoms made out of bio-inert materials – meaning they are non intrusive and non toxic to the body additionally unlike fluorescent dyes (which tend to decompose and lose their ability to fluorescence), quantum dots maintain their integrity withstanding more cycles of excitation and light emission before they start to fade. Changing their size or composition allows scientist to cater their compositions allows the scientist to cater the optical properties.-Which means they can fluoresce in a multitude of colors. This effect is called quantum confinement (hence the name the quantum dots)- they have quantized discrete energy levels that are directly related to their size.

Interestingly enough, quantum dots can even be tuned to fluorescence in different colors with the same wavelength of light. In other words it can choose quantum dots sizes where the frequency of light to make one group of dots fluoresce is an even multiple of the frequency required to make another group of dots fluoresce: both dots then fluoresce with the same wavelength of light. This allows for multiple tags to be tracked while using a singe light source.

A paul alivistos and his company (Quantum Dots corporation) have used these concepts in their Qdot product- a quantum dot surrounded by an inorganic shell that amplifies its optical properties while protecting the dot from its environment. The Qdot can have a variety of attachments to its shell. allowing it to attach to specific cell walls.- or even penetrate a cell and light it up from the inside. In the summer of 2003, This company joined forces with matsustha Electronic Industrial co(Panasonic) and sumitomo Corporation Biosciences to develop advanced optical and image processing technologies that utilize the Qdot. Products under this agreement are expected to generate revenue of more than $100 million per year for quantum dot Corporation by 2007.(Tiny product, big bucks)

An example of quantum dots in action involves targeting and imaging cancer cells. Researchers at Emory University, Georgia Tech and Cambridge Research and instrumentation have used quantum dots to identify tumors in mice. These quantum dots were made of cadmium selenide- zinc sulphide each 5nm in diameter. They were coated with polymers to prevent both the body from attacking the quantum dot and to keep the dots themselves from leaking toxic Cadmium and selenium ions.(Eek! Toxic! Read on...) Finally they attached antibodies to the outer shell that was first targeted and then attached themselves to a prostrate tumor cell surface. The scientist injected the quantum dots into the circulatory system and the dots accumulated at the tumor, which could then be detected by fluorescence imaging. As an added benefit, these quantum dots have a large surface area allowing for a dual role of both diagnostics and therapy.- the surface is big enough to attach both diagnostic and therapeutic antibodies to the surface.

Putting Quantum dots to work

Quantum dots apart from being neat things in and of themselves-could be put to some very interesting uses. The first application of quantum dots will be for biological labels used in medical imaging. Researchers tag proteins and nucleic acids with quantum dots. When they shine ultraviolet ray on the sample, the quantum dots glow at a specific wavelength and indicate the locations of attached proteins. Quantum dots have advantages over materials currently used for this application. For example they glow longer.

Researchers are also hoping that quantum dots could eventually provide energy efficient lighting for general use, in your house, office or neighborhood street lamps. In these applications a light emitting diode (LED) or other source of UV light would shine on quantum dots, which would then light up. By mixing different sizes (and the associated colors) of quantum dots together, you could generate white light. Generating light from quantum dots would work like generating fluorescent light but without the bulky fluorescent tube. This method would also avoid the wasted heat that you get with your typical incandescent light bulb.

Passing an electrical current through an LED also generates light. A company called Q vision is attempting to use techniques developed MIT to design a quantum dot LED: A layer of quantum dots sandwiched between conductive organic layers. Passing a c

Flat panel TV displays using quantum dots LEDs may provide more vibrant colors than current flat panel displays based on liquid crystals Display (LCD) Technology.

urrent through the dots generates light

Getting quantum dot energized

Quantum dots are useful because when you add energy to their electrons, the electrons act they’re in one big atom.- and (as any physicist could tell you) When you add electrons in any atom, what you get is light. This occurs hen an electron moves to a higher energy level and then falls back again to it’s normal energy level. The same is true for quantum dots – zap them they will glow. One way to add energy to quantum dots is to shine an ultraviolet light on them

It turns that the smaller the quantum dot, larger the gap between energy levels. Which means more energy is packed into photons – which means more energy is packed into the photon that’s emitted when an electron falls from a higher energy level to it’s normal energy level.A small quantum dot emits higher energy photons – with a shorter wavelength than a large Q-dot can.
Think of this light in terms of color: a quantum dot of a particular size- a relatively larger size, to be exact- emits red light, which is the longest wave length of visible light: smaller quantum dots produce different colors. If you keep going smaller and smaller, you’ll eventually get to a tiny quantum dots that produce blue light.- the shortest wavelength of visible light. If you come up with really large quantum dots you might get them to emit infrared light: incredibly teensy quantum dots might emit ultra violet light, outside the visible spectrum.

So where do you get quantum dots (No you cant find them in one stop shops store at least not yet) It turns out that it is possible to grow a large number of quantum dots in a chemical reactions. But the methods used range from simple wet –chemical setups. (In which you precipitate zinc sulphide crystals) to complicate methods such as chemical-vapor deposition.(Which is also used to grow carbon Nanotubes). You can control the size of the particular batch of quantum dots- ensuring that they all emit the same wavelength of light- by controlling the length of time you allow the reaction to run. But what do you do with them once you have got them?

Making quantum leaps with quantum dots

Quantum dots are nano-size crystals that emit light; the wavelength they emit depends on the size of the crystal.

Quantum dots are composed of various materials such as lead sulfide, Zinc sulfide, cadmium selenide, and indium phosphide.

Quantum dots are useful because, depending on their size and composition they emit particular wavelength or color of light after an outside source such as the ultra violet light, excites the electron in them. Quantum dot produces light in a way similar to atoms. The ability to tailor the color of light emitted by a group of quantum dots is very useful in medical diagnostics

The rules that describe electron orbital (also called energy levels) and dictate that electrons are only allowed to be in certain energy levels within an atom are called quantum mechanics. Because electrons in this nano size crystals behave in a similar way they are called quantum dots.

Artificial atoms

The three-dimensional (3D) spherically symmetric potential around atoms yields degeneracies known as shells, 1s, 2s, 3s, 3p,... Each shell can hold a specific number of electrons. The electronic configuration is particularly stable when these shells are completely filled wih electrons, occurring at 'magic' atomic numbers 2, 10, 18, 36,... In a similar way, the symmetry of a two-dimensional (2D), disk-shaped quantum dot leads to a shell structure with magic numbers 2, 6, 12, 20,... The lower degree of symmetry in 2D results in a different sequence of magic numbers than in 3D.

By measuring electron transport through quantum dots, a periodic table of artificial 2D elements can be obtained. For this purpose, dots are connected via potential barriers to source and drain contacts. If the barriers are thick enough , the number of electrons on the dot, N, is a well defined integer. This number changes when electrons tunnel to and from the dot. However, due to Coulomb repulsion between electrons, the energy of a dot containing N+1 electrons is larger than when it contains N electrons. Extra energy is therefore needed to add an electron to the dot. Consequently, no current can flow which is known as the Coulomb blockade.

The blockade can be lifted by means of a third electrode closeby, known as the gate contact. A negative voltage applied to this gate is used to supply the extra energy and thereby change the number of free electrons on the dot. This makes it possible to record the current flow between source and drain as the number of electrons on the dot, and hence its energy, is varied. The Coulomb blockade leads to a series of sharp peaks in the measured current (see figure below). At any given peak, the number of electrons on the dot alternates between N and N+ 1. Between the peaks, the current is zero and N remains constant. The distance between consecutive peaks is proportional to the so-called addition energy, which is the difference in energy between dots with N+1 and N electrons. The magic numbers can be identified because significantly higher voltages are needed to add the 2nd, 6th and 12th electron.

Quantum dots are 2D analogies for real atoms. But since they have much larger dimensions they are suitable for experiments that can not be carried out in atomic physics. It is especially interesting to observe the effect of a magnetic fieldd, B, on the atom-like properties. A magnetic flux-quantum in an atom requires typically a B-field as high as 10^6 T, whereas for dots this is of the order 1 T, which is experimentally accessible.

http://qt.tn.tudelft.nl/grkouwen/qdotsite.html this website is under contruction and quite interesting to read have a look at it ....

Quantum dots

When I went through the Interview on Quantum dots, programmable matter, and Wellstone (with Author Wil McCarthy by Rocky Rawstern Editor Nanotechnology Now - June 2003) I understood the intricacies of quantum dots with much of clarity and inquest.In the interview when questioned about the quantum dots McCarthy answers as follows

“Can you give our readers a brief explanation of "artificial atoms" and "quantum dots," and how they - when produced en mass - can create "programmable matter"?
A quantum dot is a device which traps electrons in a very small region of space, forcing them to behave like tiny standing waves, just as they do in atoms. An "artificial atom" is a cloud of electrons trapped in this way. Although it has no nucleus of its own, the artificial atom behaves in many ways like a real atom does. Producing large numbers of artificial atoms inside a bulk material, such as a semiconductor, will alter its properties dramatically so that, for example, it can be made to appear and behave like a metal, or an insulator. The material's color, transparency, reflectance, thermal and magnetic properties can also be altered, in real time.”

To go still more I browsed through the internet and could find many more interesting definitions and dimensions in context to quantum dots. From a very basic understanding to applications I would like to share some essences of my reading as well given the concerned urls for your further reading let me start to go further into the basics of quantum dots

“Quantum dots are small devices that contain a tiny droplet of free electrons. They are fabricated in semiconductor materials and have typical dimensions between nanometers to a few microns. The size and shape of these structures and therefore the number of electrons they contain, can be precisely controlled; a quantum dot can have anything from a single electron to a collection of several thousands. The physics of quantum dots shows many parallels with the behavior of naturally occurring quantum systems in atomic and nuclear physics. As in an atom, the energy levels in a quantum dot become quantized due to the confinement of electrons. Unlike atoms however, quantum dots can be easily connected to electrodes and are therefore excellent tools to study atomic-like properties. There is a wealth of interesting phenomena that have been measured in quantum dot structures over the past decade. This page shows a few examples from our group. The next blog will first discuss briefly the parallels between atoms and quantum dots.

My students Nanotech info for this week

Dear students I happen to read many interesting things on Nano and one of the sample i would like to share with you all...
http://www.nanotech-now.com/
In the site an introductory stuff to beginer is presented very nicely...browse through the session and come prepared...It starts as
"Truly revolutionary nanotechnology products, materials and applications, such as nanorobotics, are years in the future (some say only a few years; some say many years). What qualifies as "nanotechnology" today is basic research and development that is happening in laboratories all over the world. "Nanotechnology" products that are on the market today are mostly gradually improved products (using evolutionary nanotechnology) where some form of nanotechnology enabled material (such as carbon nanotubes, nanocomposite structures or nanoparticles of a particular substance) or nanotechnology process (e.g. nanopatterning or quantum dots for medical imaging) is used in the manufacturing process. In their ongoing quest to improve existing products by creating smaller components and better performance materials, all at a lower cost, the number of companies that will manufacture "nanoproducts" (by this definition) will grow very fast and soon make up the majority of all companies across many industries. Evolutionary nanotechnology should therefore be viewed as a process that gradually will affect most companies and industries........"
Have the habit of going through the latest trends in nanotechnology through internet

Size matters much that is Nano

SIZE

Let's start BIG to explain about Nano-size

A meter is about the distance from the tip of your nose to the end of your hand (1 meter = 3.28 feet). One thousandth of that is a millimeter.
Now take one thousandth of that, and you have a micron: a thousandth of a thousandth of a meter. Put another way: a micron is a millionth of a meter, which is the scale that is relevant to - for instance - building computers, computer memory, and logic devices.

Let’s go smaller to the nanometer
A nanometer is one thousandth of a micron, and a thousandth of a millionth of a meter (a billionth of a meter). Imagine: one billion nanometers in a meter.


Click image for larger version. Courtesy and © Quantum Dot Corporation


Another perspective: a nanometer is about the width of six bonded carbon atoms, and approximately 40,000 are needed to equal the width of an average human hair. Another way to visualize a nanometer: 1 inch = 25,400,000 nanometers Red blood cells are ~7,000 nm in diameter, and ~2000 nm in heightWhite blood cells are ~10,000 nm in diameterA virus is ~100 nmA hydrogen atom is .1 nmNanoparticles range from 1 to 100 nmFullerenes (C60 / Buckyballs) are 1 nmQuantum Dots (of CdSe) are 8 nmDendrimers are ~10 nmDNA (width) is 2 nmProteins range from 5 to 50 nmViruses range from 75 to 100 nmBacteria range from 1,000 to 10,000 nmFor our purposes, nanometers pertain to science, technology, manufacturing, chemistry, health sciences, materials science, space programs, and engineering.

Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering and technology, nanotechnology involves imaging, measuring, modeling, and manipulating matter at this length scale. At the nanoscale, the physical, chemical, and biological properties of materials differ in fundamental and valuable ways from the properties of individual atoms and molecules or bulk matter. Nanotechnology R&D is directed toward understanding and creating improved materials, devices, and systems that exploit these new properties. From What is Nanotechnology?


Powers of 10 From 10-15 meters (a fermi), in steps of 10, to 10 -9 meters (nanometer), all the way out to 10 +16 meters (a lightyear), and finally, to 10 +23 meters (10 million light years). If you have not seen this really neat series of viewpoints, it can help to put scale into perspective! "View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons." New Scientist has a great illustration on size.
Metric Prefix Table Units Conversion Tool 1 Units Conversion Tool 2

Nanotechnology - impressions

What is Nanotechnology?
Nanotechnology is the act of purposefully manipulating matter at the atomic scale, otherwise known as the "nano-scale." Coined as "Nanotechnology" in a 1974 paper by Norio Taniguchi at the University of Tokyo, and encompassing a multitude of rapidly emerging technologies, based upon the scaling down of existing technologies to the next level of precision and miniaturization. Taniguchi approached nanotechnology from the 'top-down' standpoint, from the viewpoint of a precision engineer. Foresight Nanotech Institute Founder K. Eric Drexler introduced the term "nanotechnology" to the world in 1986, using it to describe a 'bottom-up' approach. Drexler approaches nanotechnology from the point-of-view of a physicist, and defines the term as "large-scale mechano-synthesis based on positional control of chemically reactive molecules." Broadly speaking however, Answers differ depending on who you ask, and their background.

It uses a basic unit of measure called a "nanometer" (abbreviated nm). Derived from the Greek word for midget, "nano" is a metric prefix and indicates a billionth part (10-9). There are one billion nm's to a meter. Each nm is only three to five atoms wide. They're small. Very small. ~40,000 times smaller than the width of an average human hair. One aspect of nanotechnology is all about building working mechanisms using components with nanoscale dimensions (MNT), such as super small computers (think bacteria-sized) with today's MIPS capacity, or supercomputers the size of a sugar cube, possessing the power of a billion laptops, or a regular sized desktop model with the power of trillions of today's PC's. Some of the most promising potential of nanotechnology exists due to the laws of quantum physics. Quantum physics laws take over at this scale, enabling novel applications in optics, electronics, magnetic storage, computing, catalysts, and other areas. Regardless of the diverse opinions on the rate at which nanotechnology will be implemented, people who make it a habit of keeping up with technology advances agree on this: it is a technology in its infancy, and it holds the potential to change everything. Read this great Introduction from the Center for Responsible Nanotechnology for a better understanding of what nanotechnology is and is not, the social and business implications, and some steps being considered to control misuse. Related and interwoven fields include, but are not limited to: Nanomaterials, Nanomedicine, Nanobiotechnology, Nanolithography, Nanoelectronics, Nanomagnetics, Nanorobots, Biodevices (biomolecular machinery), AI, MEMS (MicroElectroMechanical Systems), NEMS (NanoElectroMechanical Systems), Biomimetic Materials, Microencapsulation, and many others.