Nanodiamonds Synthesis Fluorescent nanoparticles are highly sought after. They have broad applications, but their use in macroscopic arrays allows them efficient in applications of
plasmonics,
photonics, and
quantum communications. While there are many methods in assembling nanoparticles array, especially
gold nanoparticles, they tend to be weakly bonded to their substrate so they can't be used for wet chemistry processing steps or
lithography. Nanodiamonds allow for greater variability in access that can subsequently be used to couple plasmonic waveguides to realize quantum
plasmonic circuitry. cells
Nanodiamonds can be synthesized by employing nanoscale carbonaceous seeds created in a single step by using a mask-free electron beam-induced position technique to add amine groups. This assembles nanodiamonds into an array. The presence of dangling bonds at the nanodiamond surface allows them to be functionalized with a variety of
ligands. The surfaces of these nanodiamonds are terminated with
carboxylic acid groups, enabling their attachment to amine-terminated surfaces through carbodiimide coupling chemistry. This process affords a high yield that relies on covalent bonding between the
amine and carboxyl functional groups on amorphous carbon and nanodiamond surfaces in the presence of EDC. Thus unlike gold nanoparticles, they can withstand processing and treatment, for many device applications.
Fluorescent (nitrogen vacancy) Fluorescent properties in nanodiamonds arise from the presence of
nitrogen-vacancy (NV) centers, nitrogen atoms next to a vacancy. Fluorescent nanodiamond (FND) was invented in 2005 and has since been used in various fields of study. The invention received a US patent in 2008 , and a subsequent patent in 2012 . NV centers can be created by irradiating nanodiamonds with high-energy particles (electrons, protons, helium ions), followed by vacuum-annealing at 600–800 °C. Irradiation forms vacancies in the diamond structure while vacuum-annealing migrates these vacancies, which will get trapped by nitrogen atoms within the nanodiamond. This process produces two types of NV centers. Two types of NV centers are formed—neutral (NV0) and negatively charged (NV–)—and these have different emission spectra. The NV– the center is of particular interest because it has an
S = 1 spin ground state that can be spin-polarized by optical pumping and manipulated using electron paramagnetic resonance. Fluorescent nanodiamonds combine the advantages of semiconductor
quantum dots (small size, high photostability, bright multicolor fluorescence) with biocompatibility, non-toxicity, and rich surface chemistry, which means that they have the potential to revolutionize
Vivo imaging applications.
Drug-delivery and biological compatibility Nanodiamonds can self-assemble and a wide range of small molecules, proteins antibodies, therapeutics, and nucleic acids can bind to its surface allowing for drug delivery, protein-mimicking, and surgical implants. Other potential biomedical applications are the use of nanodiamonds as support for solid-phase peptide synthesis and as sorbents for detoxification and separation and fluorescent nanodiamonds for biomedical imaging. Nanodiamonds are capable of biocompatibility, the ability to carry a broad range of therapeutics, dispersibility in water and scalability, and the potential for targeted therapy all properties needed for a drug delivery platform. The small size, stable core, rich surface chemistry, ability to self-assemble, and low
cytotoxicity of nanodiamonds have led to suggestions that they could be used to mimic
globular proteins. Nanodiamonds have been mostly studied as potential injectable therapeutic agents for generalized drug delivery, but it has also been shown that films of Parylene nanodiamond composites can be used for localized sustained release of drugs over periods ranging from two days to one month.
Nanolithography Nanolithography is the technique to pattern materials and build devices under nano-scale. Nanolithography is often used together with thin-film-deposition, self-assembly, and self-organization techniques for various nanofabrications purpose. Many practical applications make use of nanolithography, including
semiconductor chips in computers. There are many types of nanolithography, which include: •
Photolithography •
Electron-beam lithography •
X-ray lithography •
Extreme ultraviolet lithography •
Light coupling nanolithography •
Scanning probe microscope •
Nanoimprint lithography •
Dip-Pen nanolithography •
Soft lithography Each nanolithography technique has varying factors of the resolution, time consumption, and cost. There are three basic methods used by nanolithography. One involves using a resist material that acts as a "mask", known as photoresists, to cover and protect the areas of the surface that are intended to be smooth. The uncovered portions can now be etched away, with the protective material acting as a stencil. The second method involves directly carving the desired pattern. Etching may involve using a beam of
quantum particles, such as electrons or light, or chemical methods such as
oxidation or
Self-assembled monolayers. The third method places the desired pattern directly on the surface, producing a final product that is ultimately a few nanometers thicker than the original surface. To visualize the surface to be fabricated, the surface must be visualized by a nano-resolution microscope, which includes the
scanning probe microscopy and the
atomic force microscope. Both microscopes can also be engaged in processing the final product.
Photoresists Photoresists are light-sensitive materials, composed of a polymer, a sensitizer, and a solvent. Each element has a particular function. The polymer changes its structure when it is exposed to radiation. The solvent allows the photoresist to be spun and to form thin layers over the wafer surface. Finally, the sensitizer, or inhibitor, controls the photochemical reaction in the polymer phase. Photoresists can be classified as positive or negative. In positive photoresists, the photochemical reaction that occurs during exposure, weakens the polymer, making it more soluble to the developer so the positive pattern is achieved. Therefore, the masks contains an exact copy of the pattern, which is to remain on the wafer, as a stencil for subsequent processing. In the case of negative photoresists, exposure to light causes the polymerization of the photoresist so the negative resist remains on the surface of the substrate where it is exposed, and the developer solution removes only the unexposed areas. Masks used for negative photoresists contain the inverse or photographic "negative" of the pattern to be transferred. Both negative and positive photoresists have their own advantages. The advantages of negative photoresists are good adhesion to silicon, lower cost, and a shorter processing time. The advantages of positive photoresists are better resolution and thermal stability. Research conducted on the optical properties of MoS2 nanoclusters compared them to their bulk crystal counterparts and analyzed their absorbance spectra. The analysis reveals that size dependence of the absorbance spectrum by bulk crystals is continuous, whereas the absorbance spectrum of nanoclusters takes on discrete energy levels. This indicates a shift from solid-like to molecular-like behavior which occurs at a reported cluster the size of 4.5 – 3.0 nm.
Nanothermodynamics The idea of nanothermodynamics was initially proposed by T. L. Hill in 1960, theorizing the differences between differential and integral forms of properties due to small sizes. The size, shape, and environment of a nanoparticle affect the
power law, or its proportionality, between nano and macroscopic properties. Transitioning from macro to nano changes the proportionality from exponential to power. Therefore, nanothermodynamics and the theory of statistical mechanics are related in concept. Building on these ideas, recent research has shown that, in finite nanosystems, the spatial dependence of intensive variables persists even in the thermodynamic limit. == Notable researchers ==