Atoms

||Electrons

Atomic level resolution is possible due to the created tunneling current between the STM tip and the sample. The current is measured and displayed as an image. The same method may also be used to charge and move individual atoms.

By arranging two ultra-short laser light pulses, it is found that an electron takes 40 attoseconds to pass through one layer of magnesium atoms.

||Molecular structure

Similar to EDX, a gas electron diffractometer can be used to analyze molecules in their gaseous states. Angstrom precision on electron diffraction and bond lengths are readily achievable (additionally to angle measurements).

||Reactions – chemical

The binding energy of the outer shell electrons determine the chemical reaction affinity. The ionization potential may assist in the quantification of this energy by, for example, laser excitation.

Once atoms combine to form compounds, it may be possible to image their coordination and planar bond structures. In AFM non-contact mode, individual covalent bonds of oligo-(phenylene-1,2-ethynylenes) were imaged as they underwent a series of reaction-induced changes.

||Reactions – mechanical

A force of approximately 42 yoctonewtons (exp-24) is the smallest force measured. This is still four times larger than the Standard Quantum Limit defined by the Heisenberg uncertainty principle which is the most sensitive measurement that can be made. In this measurement, gas of 1200 rubidium atoms was optically trapped by 840 and 860nm wavelengths and chilled to nearly absolute zero. Probe beam at 780nm registered the oscillatory reaction of modulating the 840nm wavelength.

||Reactions – quantum tunneling

In ultra-cold reactions, the activation barriers are too high for the cold atoms and cannot exchange electrons to bind together. These temperatures are near absolute zero at μK or nK. Lasers may be used to trap and hold these slow moving atoms.

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Methods

||Atomic force microscopy (AFM)

Considered as one of the few ways to “feel” a nano patterned surface, AFM techniques rely on surface forces and electronic feedback loops to convert mechanical interference of the scanning probe into an electrical signal. Interferences are usually atomic forces such as van der Waals. Magnetic and electrostatic effects may also be registered, as well as surface reactions to applied voltages (e.g. Kelvin probe) and forces (e.g. nano-indentation). Both organic and inorganic substances have found their way under the AFM scans.

A new friction mechanism has been discovered in part due to AFM. The expected sticking and sliding of a polymer chain was accompanied by a desorption stick: that is independent of normal force, velocity, and adsorbed polymer length.

A variation of AFM is also being developed as hydrothermal AFM. In this case, the scanning probe is submerged. The novelty of this method is being able to study surface interactions at 250 deg C and at a pressure of 80 atm, including hydrofracturing and storage of radioactive wastes.

The micro-AFM tip has also been developed as a possible liquid despencer by 2013. The liquid drops may be delivered in the microscale to specific areas of interest during the scanning procedure.

||Cold ion laser spectroscopy

Molecules are cooled close to absolute zero and ionized. Angle variant IR and UV laser excitation produces specific of molecular fragments which may ultimately reveal information about the different energy levels. Two isomers may be differentiated due to unique vibrational frequencies and light absorption characteristics.

||Computer simulation

An effective way to simulate a nano device’s electrical properties is to derive the electrical properties from the first-principles method, which accurately calculates the behavior of each atom. A massively parallel supercomputer is required for this task and is still limited to models on the scale of 3,000 atoms.

Density Functional Theory (DFT) is a modeling tool as useful as a hammer and screwdriver around the house. It assists chemists and physicists at understanding the properties of matter on the nanoscale. It must still be used with caution. For one, it is based on the Schrödinger formalism (complex valued wave-functions which have no counterpart in the real world). Secondly, finite element and/or difference solutions make is difficult to scale these deterministic algorithms.

Monte Carlo is often a competitive simulation tool to DFT. Monte Carlo is a mathematical method relying on independent number generation to solve complex integro-differential equations.

||Electron diffraction

A gas electron diffractometer can be used to measure the undisturbed molecular bond lengths and angles. It is more accurate than solid state experimentation because of reduced crystal packing interactions. About halfway to costing half a billion USD, equipment owners include Europe, Japan, New Zealand, the USA and two for Russia.

||Fluorescence spectroscopy

If an electron is excited, it may hop into a different energy state. On the return path, an electron may emit different kinds of energies. The collection of such energies is the basis of many spectroscopy techniques, including one of the most popular being fluorescence. Ultra-fast techniques can resolve changes in fluorescence on 60 – 450 fs time scales.

||Near-field/far-field measurements

Often compared with EM simulations for the presence of localized plasmonic resonance. Near-field allows measurement of individual parts of a system. Such is also possible when coupled with atomic force microscopy.

||Mass

A suspended nanochannel resonator (SNR) measures the mass of particles as they flow through a 400 nm channel. It is possible to weigh small viruses, extracellular vesicles, and most of the engineered nanoparticles that are being used for nanomedicine. Nearly 30,000 particles in about 90min could be measured.

||Particle accelerator

Half a billion electrons to can now be accelerated to 2 giga-electronvolts over a distance of about 1 inch, a size reduction of approximately 10,000. This energy may be converted to hard x-rays on a femtosecond time resolution. What made this possible is the laser-plasma acceleration which involves firing a brief but intensely powerful (petawatt) laser pulse into a puff of gas.

||Pulsed laser

Pulsed laser light offers a wide array of imaging and synthesis options. Ultra-short pulses provide the ability to measure responses at small time scales. Compressing femtosecond and attosecond is possible through optical design. More recently another complimentary method was developed by modifying the fiber amplification class of lasers with nanostructured basket-weave cores that are filled with noble gas. The nonlinear interaction between the gas and the pulses generate a variety of pulse rates that act to compress into shorter pulses.

||Raman spectroscopy

Modes of vibration are experienced not only by macroscopic objects like cars, but also by nanoscopic species like molecules. The vibrations occur due to excitation (usually by visible light) that will shift the energy of the excitation source by amounts proportional to the molecular bond energies.

Hyperspectral imaging adds more information to Raman scanning as it allows spatial data to be collected simultaneously. An added benefit is that larger areas may be sampled: square cm and larger vs. square micrometre with traditional equipment. The resultant images are then typically scaled as an intensity graph based on a selected wavenumber.

||Scanning electron microscopy (SEM)

SEM is essentially the bread and butter of many nano investigations. It is a microscope that is not limited by diffraction as optical microscopes are and hence may comfortably reach 50,000x magnification as opposed to a common 100x by a basic light microscope. With electron microscopy, individual planes of atoms may actually be resolved. Much like Galileo saw the defects on the moon with his telescope, we can now see defects on coherent twin boundaries, often described as “perfect,” appearing like a perfectly flat, one-atom-thick plane in computer models and electron microscope images. It is also becoming more common to scan in 3D and provide corresponding computer models with a resolution as small as 25 nm.

A variation of SEM is Scanning Transmission Electron Holography Microscope (STEHM). Au atoms were scanned with a resolution of 35 picometres deeming it the world’s most powerful microscope (2013, 7 tonne, 4.3m tall, $9.2 M CAD, Hitachi).

For monitoring catalytic reactions, in-situ aberration corrected environmental scanning transmission electron microscopy technology (in-situ AC-ESTEM) is developed. Reactions up to 500 degC could be facilitated under transient conditions.

Quotes

The true sign of intelligence is not knowledge but imagination.”

Albert Einstein, German-born theoretical physicist

If you have always done it that way, it is probably wrong.”

Charles Kettering, American inventor

By leadership we mean the art of getting someone else to do something that you want done because he wants to do it.”

Dwight Eisenhower, American president

Spoon feeding in the long run teaches us nothing but the shape of the spoon.”

Edward Forster, British writer

Men stumble over pebbles, never over mountains.”

H. Emilie Cady, American author

No effort that we make to attain something beautiful is ever lost.”

Helen Keller, American author and activist

Nothing is really work unless you would rather be doing something else.”

James Barrie, Scottish dramatist

A ship in harbor is safe, but that is not what ships are built for.”

John Shedd, American writter

A good objective of leadership is to help those who are doing poorly to do well and to help those who are doing well to do even better.”

Jim Rohn, American entrepreneur

Don’t be afraid to give up the good to go for the great.”

John D. Rockefeller, American industrialist

We choose our joys and sorrows long before we experience them.”

Khalil Gibran, Lebanese-American artist, poet and writer

How much time he saves who does not look to see what his neighbor says or does or thinks.”

Marcus Aurelius, Roman emperor

Our opinion of people depends less upon what we see in them than upon what they make us see in ourselves.”

Sarah Grand, British writer and women’s rights activist

There is no greater impediment to the advancement of knowledge than the ambiguity of words.”

Thomas Reid, Scottish philosopher

Judge a man by his questions rather than by his answers.”

Voltaire, French writer and historian

Hazards

The Nanotechnology Industries Association (NIA) maintains a Regulatory Monitoring Database of nanotechnology related topics. Regulations and standards are gathered from around the world.

Furthermore, the  National Institute for Occupational Safety and Health (NIOSH) has recently published recommendations on safety when working with nanomaterials, named “Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes”. The IOSH in the UK has also granted funds for nanotech health of market and potential market materials. The Institute of Demolition Engineers and the National Federation of Demolition Contractors is further involved to determine potential methods for demolition and recycling of such products.

||Cell damage

Substantial damage from commercially available Ag and ZnO NPs is found. These NPs produce free radicals (i.e. reactive oxygen species or ROS). In turn, cells can experience cancerous mutations or even death. The threshold concentration is currently found to be 10 micrograms per milliliter. Ag is further found to be significantly toxic when penetrating cells. These findings are in contradiction to the benefits of traditionally using Ag colloid potions for their antiseptic properties. Along the same lines, traditionally beneficial Au used for drug delivery can disrupt the production of progesterone and affect a woman’s fertility.

SiO2 NPs are found to be toxic and have significant adverse effects on macrophages (failure to take up lipids) This leads to atherosclerotic lesion development and its consequent cardiovascular events, such as heart attack or stroke.

Astrocytes help regulate the exchange of signal-carrying neurotransmitters in the brain and supplying their energy. TiO2 NPs are found to cause abo 67% mortality of these cells at 100 ppm.

||Personal protection

Gloves of different thicknesses made of nitrile, latex, neoprene and butyl were exposed to the passage of commercial TiO2 NPs. With the exception of butyl, a higher risk of penetration was seen with colloidal NPs, especially when subject to biaxial dynamic deformation.

||Product end-of-life cycle

Thermal, biological, or mechanical-biological waste treatment plants are not entirely familiar on how waste containing nanomaterials would behave in their facilities. These facilities need to handle all nano waste cycles, including by-products, contamination, and end-of-life. With incineration processes, it is so far believed that CNTs degrade almost completely. Graphene is also suseptible to hydroxyl radicals as a part of an oxidation process (such as TiO2-UV). However, most inorganic oxides are still present in the form of bottom ash, slag, or filter residue. Understanding of nano exposure limits is still being developed and any handling with these products should be exercised with caution. In summary:

  • when incinerated, nanomaterials can be destroyed, remain unchanged, or converted into oxides, chlorides or other
  • nanomaterials >100 nm are efficiently filtered
  • nanomaterials <100 nm are partially retained by filters, possibly up to 80%

Education

Richard Feynman is one of the first people to which the era of “nano” may be attributed. The Feynmann Lectures on Physics from the late 1950’s to the early 1960’s are now available online on the Caltech and The Feynman Lectures Website.

Topics in nanotechnology are not only on a project basis in graduate school at universities. They are now full degrees. A sample of major universities and their programs is provided here:

  • University of Albany, nanoscale engineering and nanoscience: BASc, MASc, PhD (U.S.A.)
  • University of Israel, nanotechnology and nanoscience: MSc, PhD (IL)
  • University of Waterloo, nanotech engineering: BASc, MASc, PhD (CAN)
  • University of Toronto, nanoengineering: BASc (CAN)

Recently, a Molecular Theme Park by NanoSpace was also opened online to stimulate interest in elemetary to middle school students. In addiditon, Scientix in their May 2014 newsletter made approaches to teaching nanotechnology to pupils their main theme.

ASTM published two standards to educate workers on nanotechnology ( E2996 and E3001). These standards were initiated by the Nanotechnology Applications and Career Knowledge Network (NACK).

Energy

||Batteries

The basic components of a battery include:

  1. an electrolyte to provide electrons,
  2. an anode to discharge those electrons, and
  3. a cathode to receive them.

A pure lithium anode would significantly improve efficiency over currently available lithium electrolyte products with graphite of Si as the anode. One barrier to a lithium anode has been the swelling of lithium and the creation of dendrites that short the circuit and reduce battery life. A protective layer for a lithium metal anode is under development that needs to be chemically stable to protect against the chemical reactions with the electrolyte and mechanically strong to withstand the swelling.

Sodium is more environmentally benign than lithium as used in rechargeable batteries. Diffusing sodium ions through tin anodes often weaken the tin’s connection to its base material. However, the wood fibers are soft enough to serve as a mechanical buffer, and thus can accommodate the swelling and shrinking of the tin nanocoating up to 400 cycles. Additionally, wood fibers that make up a tree once held mineral-rich water, and so are ideal for storing liquid electrolytes.

||Flexible electronics

In an effort to replace silicon wafers, flexible polymers (i.e. organic field-effect transistors) need to pack into crystalline structures containing regular pathways for charge carriers. It is found that fluorenone carbonyl units have the following advantages:

  • makes electrons in the co-polymer’s highest energy states less accessible and therefore less susceptible to air-based impurities;
  • helps to stick to aromatic hydrogen atoms; and
  • improves solid state packing.

Flexible and wearable electronics may allow for a wide variety of human-machine interfacing applications. To overcome the difficulty of using brittle Si, the textile may the dipped into an aluminum solution that will form metal fibrous networks with the help of a Ti catalyst. Polymers may also have embedded NPs of gold that align as they the material is stretched. This provides the material a conductivity of 35 S/cm even when stretched at 5.8 times its original length (enough for small devices).

Graphene inks are also an alternative and can be printed on paper. Carbon in general is an attractive material because wires made from carbon are 10 times lighter and up to 30 times stronger than copper. Carbon wires also have the added benefits of corrosion resistance, a higher current capacity and lower losses in transmission efficiency with increasing temperature. Their conductivity is yet to match copper, however, due to the discontinuity of the individual CNTs.

||Friction

Super-lubricity is a theoretical concept  in overcoming friction on the microscopic scale. It is found that along a twist boundary (shear interface) of carbon, the atoms are misaligned which avoids crystal locking. The result is being able to translate at 25m/s (90km/h) on a micrometre squared area.

Friction is also found to be tunable at the nanoscale. By varying the thickness of the SiO2 layer, the forces experienced by AFM scanning could vary up to 30%.

||Hydrogen

Unlike hydrocarbon fuels, such as oil, coal and natural gas, where carbon dioxide and other contaminants are released into the atmosphere when used, hydrogen fuel usage produces pure water as the only byproduct. Nanoscale water electrosis may be facilitated by nanoparticles that mimic photosynthesis. In essence, an efficient separation of hydrogen from water occurs.

||Light

Biological systems on Earth demand light for energy, including the critical photosynthesis process. Solar energy harvesting is a ready application of nanomaterials. This is because it has most to do with surface science. The bandgap of a material is found to be affected by nanostructuring. For example, arsenic NP absorption from deep infrared to green is controllable by varying degrees of dimensional structuring. Core-shell gold NPs have also been found to convert a broad visible-invisible spectrum of light into heat that can be used for steam generation.

Synthesize the DNA of an Arabidopsis plant with genes from a firefly, and the result is natural luminosity. May or may not replace street lamps, let alone a table lamp, but applications are still vast for low cost or free electricity.


||Computers

Skyrmions are new magnetic structures which were discovered as a grid of magnetic eddies in a silicon manganese crystal. Individual eddies can also be generated on surfaces and moved electronically. Researchers are interested in using skyrmions to transfer magnetic information directly to materials through electric current alone, since they require 100 000 times less current and significantly less atoms per bit of information. Such an advancement would result in more compact and energy-efficient computers, but the method is still limited to very low temperatures.

Inorganics

||Acoustics

Standing waves have node locations that do not move. This principle was used in a demonstrative example to align nanowires into a square array. Alternating current was delivered to four piezoelectric transducers oriented in a square.

||Oragami

Typically becoming popular for micro-structures, oragami type assembly of connected template-like objects could be carried out in several ways. One instance is where silicon could be folded and unfolded with the introduction of water droplets to the wafer.

||Self Assembly

At the nanoscale, it is difficult to manually manipulate and arrange certain entities of interest. Therefore, in most cases, we rely on physics and chemistry to do the work for us. In the more simple case of nanoparticles, we can functionalize their surface and in essence create tethers or molecular links. These links can interact to bring the nanoparticles closer together in a determined manner.

||Self Assembly – Light Induced

Some molecules may greatly absorb incident electromagnetic energy. Upon doing so, the energy level of the molecule may change and cause a subsequent isomer transformation. In the case of a gold single-nanoparticle chain, the dicyanide trimer was directly observed to be responsible for the bent-to-linear transformation as well as linking into longer oligomers.

A tweezer effect may also be used to position nanostructures and quantum dots. The action is related to the accumulated recoil of incident photon momentum. Biologists, for example, use this effect in optical tweezers to fix cells and rotate them at the focus of a microscope. Physicists can also use the tweezer effect to isolate and collide Rb atoms at a velocity of about 1m/s and temperatures of one millionth of a degree above absolute zero.

Furthermore, gold nanorods may be positioned more regularly outside of their normal bonding symmetry by light induced plasmonic vibration. This process was found to occur in aqueous solutions although could readily explain ablation-generated plasmonic nanostructure.

||Self Assembly – DNA Mediated

DNA is composed of two complementary strands which are attracted to each other through matching base pairs. This attraction between the two strands can be used for the DNA-mediated self-assembly of two different nanoparticles into large-scale nanocomposite arrays. Synthetic DNA strands are attached to the nanoparticles of interest and the strands are allowed to naturally pair up, causing the nanoparticles to self-assemble into 3-D superlattices. This technique makes it possible to mix nanoparticles with different magnetic, optical or chemical properties and their self-assembly can be controlled to produce new enhanced or multifunctional materials.