Chemosynthesis (nanotechnology)

Last updated September 04, 2023

In molecular nanotechnology, chemosynthesis is any chemical synthesis where reactions occur due to random thermal motion, a class which encompasses almost all of modern synthetic chemistry. The human-authored processes of chemical engineering are accordingly represented as biomimicry of the natural phenomena above, and the entire class of non-photosynthetic chains by which complex molecules are constructed is described as chemo-.

Chemosynthesis can be applied in many different areas of research, including in positional assembly of molecules. This is where molecules are assembled in certain positions in order to perform specific types of chemosynthesis using molecular building blocks. In this case synthesis is most efficiently performed through the use of molecular building blocks with a small amount of linkages. Unstrained molecules are also preferred, which is when molecules undergo minimal external stress, which leads to the molecule having a low internal energy. There are two main types of synthesis: additive and subtractive. In additive synthesis the structure starts with nothing, and then gradually molecular building blocks are added until the structure that is needed is created. In subtractive synthesis they start with a large molecule and remove building blocks one by one until the structure is achieved.^[1]

This form of engineering is then contrasted with mechanosynthesis, a hypothetical process where individual molecules are mechanically manipulated to control reactions to human specification. Since photosynthesis and other natural processes create extremely complex molecules to the specifications contained in RNA and stored long-term in DNA form, advocates of molecular engineering claim that an artificial process can likewise exploit a chain of long-term storage, short-term storage, enzyme-like copying mechanisms similar to those in the cell, and ultimately produce complex molecules which need not be proteins. For instance, sheet diamond or carbon nanotubes could be produced by a chain of non-biological reactions that have been designed using the basic model of biology.

Use of the term chemosynthesis reinforces the view that this is feasible by pointing out that several alternate means of creating complex proteins, mineral shells of mollusks and crustaceans, etc., evolved naturally, not all of them dependent on photosynthesis and a food chain from the sun via chlorophyll.^[2] Since more than one such pathway exists to creating complex molecules, even extremely specific ones such as proteins edible to fish, the likelihood of humans being able to design an entirely new one is considered (by these advocates) to be near certainty in the long run, and possible within a generation.^[2]

Modern applications

Several methods of nanoscale chemosynthesis have been developed, a common variant of which is chemical bath deposition (CBD). This process enables large-scale synthesis of thin film layers of a variety of materials, and has been especially useful in providing such films for opto-electronics through the efficient creation of lead sulfide (PbS) films. CBD synthesis of these films allows for both cost-effective and accurate assemblies, with grain type and size as well as optical properties of the nanomaterial dictated by the properties of the surrounding bath. As such, this method of nanoscale chemosynthesis is often implemented when these properties are desired, and can be used for a wide range of nanomaterials, not just lead sulfide, due to the adjustable properties.^[3]

As explained previously, the usage of chemical bath deposition allows for the synthesis of large deposits of nanofilm layers at a low cost, which is important in the mass production of cadmium sulfide. The low cost associated with the synthesis of CdS through means of chemical deposition has seen CdS nanoparticles being applied to semiconductor sensitized solar cells, which when treated with CdS nanoparticles, see improved performance in their semiconductor materials through a reduction of the band gap energy.^[4] The usage of chemical deposition in particular allows for the crystallite orientation of CdS to be more favourable, though the process is quite time consuming. Research by S.A. Vanalakar in 2010 resulted in the successful production of cadmium sulfide nanoparticle film with a thickness of 139 nm, though this was only after the applied films were allowed to undergo deposition for 300 minutes.^[4] As the deposition time was increased for the film, not only was the film thickness found to increase, but the band gap of the resultant film decreased.^[4]

Related Research Articles

Nanotechnology, often shortened to nanotech, is the use of matter on atomic, molecular, and supramolecular scales for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabrication of macroscale products, also now referred to as molecular nanotechnology. A more generalized description of nanotechnology was subsequently established by the National Nanotechnology Initiative, which defined nanotechnology as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). This definition reflects the fact that quantum mechanical effects are important at this quantum-realm scale, and so the definition shifted from a particular technological goal to a research category inclusive of all types of research and technologies that deal with the special properties of matter which occur below the given size threshold. It is therefore common to see the plural form "nanotechnologies" as well as "nanoscale technologies" to refer to the broad range of research and applications whose common trait is size.

Nanosensors are nanoscale devices that measure physical quantities and convert these to signals that can be detected and analyzed. There are several ways proposed today to make nanosensors; these include top-down lithography, bottom-up assembly, and molecular self-assembly. There are different types of nanosensors in the market and in development for various applications, most notably in defense, environmental, and healthcare industries. These sensors share the same basic workflow: a selective binding of an analyte, signal generation from the interaction of the nanosensor with the bio-element, and processing of the signal into useful metrics.

<span class="mw-page-title-main">Nanomaterials</span> Materials whose granular size lies between 1 and 100 nm

Nanomaterials describe, in principle, materials of which a single unit is sized between 1 and 100 nm.

A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead.

A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale.

Nanomaterial-based catalysts are usually heterogeneous catalysts broken up into metal nanoparticles in order to enhance the catalytic process. Metal nanoparticles have high surface area, which can increase catalytic activity. Nanoparticle catalysts can be easily separated and recycled. They are typically used under mild conditions to prevent decomposition of the nanoparticles.

Nanochemistry is an emerging sub-discipline of the chemical and material sciences that deals with the development of new methods for creating nanoscale materials. The term "nanochemistry" was first used by Ozin in 1992 as 'the uses of chemical synthesis to reproducibly afford nanomaterials from the atom "up", contrary to the nanoengineering and nanophysics approach that operates from the bulk "down"'. Nanochemistry focuses on solid-state chemistry that emphasizes synthesis of building blocks that are dependent on size, surface, shape, and defect properties, rather than the actual production of matter. Atomic and molecular properties mainly deal with the degrees of freedom of atoms in the periodic table. However, nanochemistry introduced other degrees of freedom that controls material's behaviors by transformation into solutions. Nanoscale objects exhibit novel material properties, largely as a consequence of their finite small size. Several chemical modifications on nanometer-scaled structures approve size dependent effects.

<span class="mw-page-title-main">Nanoscopic scale</span> Structures with a length scale applicable to nanotechnology

The nanoscopic scale usually refers to structures with a length scale applicable to nanotechnology, usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter. The nanoscopic scale is a lower bound to the mesoscopic scale for most solids.

As the world's energy demand continues to grow, the development of more efficient and sustainable technologies for generating and storing energy is becoming increasingly important. According to Dr. Wade Adams from Rice University, energy will be the most pressing problem facing humanity in the next 50 years and nanotechnology has potential to solve this issue. Nanotechnology, a relatively new field of science and engineering, has shown promise to have a significant impact on the energy industry. Nanotechnology is defined as any technology that contains particles with one dimension under 100 nanometers in length. For scale, a single virus particle is about 100 nanometers wide.

Nanometrology is a subfield of metrology, concerned with the science of measurement at the nanoscale level. Nanometrology has a crucial role in order to produce nanomaterials and devices with a high degree of accuracy and reliability in nanomanufacturing.

The following outline is provided as an overview of and topical guide to nanotechnology:

<span class="mw-page-title-main">Nanomechanics</span>

Nanomechanics is a branch of nanoscience studying fundamental mechanical properties of physical systems at the nanometer scale. Nanomechanics has emerged on the crossroads of biophysics, classical mechanics, solid-state physics, statistical mechanics, materials science, and quantum chemistry. As an area of nanoscience, nanomechanics provides a scientific foundation of nanotechnology.

Green nanotechnology refers to the use of nanotechnology to enhance the environmental sustainability of processes producing negative externalities. It also refers to the use of the products of nanotechnology to enhance sustainability. It includes making green nano-products and using nano-products in support of sustainability.

Chemical Bath Deposition, also called Chemical Solution Deposition and CBD, is a method of thin-film deposition, using an aqueous precursor solution. Chemical Bath Deposition typically forms films using heterogeneous nucleation, to form homogeneous thin films of metal chalcogenides and many less common ionic compounds. Chemical Bath Deposition produces films reliably, using a simple process with little infrastructure, at low temperature (<100˚C), and at low cost. Furthermore, Chemical Bath Deposition can be employed for large-area batch processing or continuous deposition. Films produced by CBD are often used in semiconductors, photovoltaic cells, and supercapacitors, and there is increasing interest in using Chemical Bath Deposition to create nanomaterials.

A nanofountain probe (NFP) is a device for 'drawing' micropatterns of liquid chemicals at extremely small resolution. An NFP contains a cantilevered micro-fluidic device terminated in a nanofountain. The embedded microfluidics facilitates rapid and continuous delivery of molecules from the on-chip reservoirs to the fountain tip. When the tip is brought into contact with the substrate, a liquid meniscus forms, providing a path for molecular transport to the substrate. By controlling the geometry of the meniscus through hold time and deposition speed, various inks and biomolecules could be patterned on a surface, with sub 100 nm resolution.

Nanoparticles are classified as having at least one of its dimensions in the range of 1-100 nanometers (nm). The small size of nanoparticles allows them to have unique characteristics which may not be possible on the macro-scale. Self-assembly is the spontaneous organization of smaller subunits to form larger, well-organized patterns. For nanoparticles, this spontaneous assembly is a consequence of interactions between the particles aimed at achieving a thermodynamic equilibrium and reducing the system’s free energy. The thermodynamics definition of self-assembly was introduced by Professor Nicholas A. Kotov. He describes self-assembly as a process where components of the system acquire non-random spatial distribution with respect to each other and the boundaries of the system. This definition allows one to account for mass and energy fluxes taking place in the self-assembly processes.

The characterization of nanoparticles is a branch of nanometrology that deals with the characterization, or measurement, of the physical and chemical properties of nanoparticles. Nanoparticles measure less than 100 nanometers in at least one of their external dimensions, and are often engineered for their unique properties. Nanoparticles are unlike conventional chemicals in that their chemical composition and concentration are not sufficient metrics for a complete description, because they vary in other physical properties such as size, shape, surface properties, crystallinity, and dispersion state.

There are many water purifiers available in the market which use different techniques like boiling, filtration, distillation, chlorination, sedimentation and oxidation. Currently nanotechnology plays a vital role in water purification techniques. Nanotechnology is the process of manipulating atoms on a nanoscale. In nanotechnology, nanomembranes are used with the purpose of softening the water and removal of contaminants such as physical, biological and chemical contaminants. There are variety of techniques in nanotechnology which uses nanoparticles for providing safe drinking water with a high level of effectiveness. Some techniques have become commercialized.

Zinc oxide (ZnO) nanostructures are structures with at least one dimension on the nanometre scale, composed predominantly of zinc oxide. They may be combined with other composite substances to change the chemistry, structure or function of the nanostructures in order to be used in various technologies. Many different nanostructures can be synthesised from ZnO using relatively inexpensive and simple procedures. ZnO is a semiconductor material with a wide band gap energy of 3.3eV and has the potential to be widely used on the nanoscale. ZnO nanostructures have found uses in environmental, technological and biomedical purposes including ultrafast optical functions, dye-sensitised solar cells, lithium-ion batteries, biosensors, nanolasers and supercapacitors. Research is ongoing to synthesise more productive and successful nanostructures from ZnO and other composites. ZnO nanostructures is a rapidly growing research field, with over 5000 papers published during 2014-2019.

This glossary of nanotechnology is a list of definitions of terms and concepts relevant to nanotechnology, its sub-disciplines, and related fields.

References

↑ Merkle, Ralph (2000). "Molecular building blocks and development strategies for molecular nanotechnology". Nanotechnology. 11 (2): 89–99. doi:10.1088/0957-4484/11/2/309. S2CID 250914545.
1 2 Jannasch, H. W.; Mottl, M. J. (1985-08-23). "Geomicrobiology of Deep-Sea Hydrothermal Vents". Science. 229 (4715): 717–725. Bibcode:1985Sci...229..717J. doi:10.1126/science.229.4715.717. ISSN 0036-8075. PMID 17841485. S2CID 24859537.
↑ Pawar, S.B.; Shaikh, J.S.; Devan, R.S.; Ma, Y.R.; Haranath, D.; Bhosale, P.N.; Patil, P.S. (2011). "Facile and low cost chemosynthesis of nanostructured PBS with tunable optical properties". Applied Surface Science. 258 (5): 1869–1875. Bibcode:2011ApSS..258.1869P. doi:10.1016/j.apsusc.2011.10.069.
1 2 3 Vanalakar, S.A. "Quantum Size Effects in Chemosynthesized Nanostructured CdS Thin Films." Digest Journal of Nanomaterials and Biostructures.

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[1] Merkle, Ralph (2000). "Molecular building blocks and development strategies for molecular nanotechnology". Nanotechnology. 11 (2): 89–99. doi:10.1088/0957-4484/11/2/309. S2CID 250914545.

[:1-2] 1 2 Jannasch, H. W.; Mottl, M. J. (1985-08-23). "Geomicrobiology of Deep-Sea Hydrothermal Vents". Science. 229 (4715): 717–725. Bibcode:1985Sci...229..717J. doi:10.1126/science.229.4715.717. ISSN 0036-8075. PMID 17841485. S2CID 24859537.

[3] Pawar, S.B.; Shaikh, J.S.; Devan, R.S.; Ma, Y.R.; Haranath, D.; Bhosale, P.N.; Patil, P.S. (2011). "Facile and low cost chemosynthesis of nanostructured PBS with tunable optical properties". Applied Surface Science. 258 (5): 1869–1875. Bibcode:2011ApSS..258.1869P. doi:10.1016/j.apsusc.2011.10.069.

[:0-4] 1 2 3 Vanalakar, S.A. "Quantum Size Effects in Chemosynthesized Nanostructured CdS Thin Films." Digest Journal of Nanomaterials and Biostructures.

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