Nano structures.pptx

Nanoscience introduction, nanostructures, significance of nanostructures. classification of nanostructures based on origin, dimension, and structure. Natural nanostructures. Biomimetic materials inspired by natural nanomaterials. 0D, 1D, 2D, and 3D materials, their properties, and applications. discrete energy levels of these structures. Density of states. The density of states in metals and semiconducting nanomaterials, Color changes in nanostructure due to decreased size. Variation in the number of electrons and density of states with energy

1. Nanoscience is the study of phenomena and manipulation of materials at atomic, molecular, and macromolecular scales, where properties differ significantly from those at a larger scale. Nanotechnology is the design, characterization, production, and application of structures, devices, and systems by controlling the shape and size at the nanometer scale.

2. A Nanostructured material(or a nanomaterial) is defined as a solid material characterized by at least one dimension in the nanometer range. A nanostructure basically comprises an atom (nanoparticle) or an aggregate of atoms forming a cluster of dimensions less than 100nm. The cluster formed can be viewed as a subdivision of a Bulk material, and having dimensions less than the Characteristic length of certain phenomena Nano structures are those which have a characteristic length scale within 100nm. Particle diameter, grain size, layer thickness, or width of a conduction line on a device are examples of length scales. Nanostructures

3. Nanostructure materials are materials with different structures in the range of nanometers (typically 1–100 nm) Nano surfaces, cylindrical nanotubes, and nanospheres are common nanostructures . Nanostructure materials exhibit novel and astonishing properties that are entirely different from their bulk material counterparts The properties of nanostructures always depend on the size, shape, and morphology of the nanostructures, and hence they can be tuned Therefore nanostructure materials are garnering great attention for their potential to advance and improve currently existing devices as well as to develop future ones

4. In recent years, nanosized structures have attracted much attention from the research community owing to their extraordinary physical, chemical, mechanical, and electrical properties. Significance of Nanostructures: In nanoelectronics, silicon may soon be replaced by carbon nanotubes to develop lighter yet efficient microchips and devices With growing energy demands, solar panels and hydrogen fuel cells can be developed using nano structural components to increase their efficiency In the field of nanomedicine, biocompatible tunneling nanotubes can help to deliver drugs to precise targets and monitor health conditions. Creating functional organic or synthetic nano-structural components for medically implanted devices is certainly challenging,. 

5. To improve air quality, catalysts made from nanoparticles are used to transform hazardous gases released from industries and automobiles into harmless gases Nanoscale structures (nanoscale rods, rings, beams, plates, and shells) have been implemented in fundamental structural parts of various nanoelectromechanical systems (NEMS). NEMS-based devices include nanomechanical resonators, nanoscale mass sensors, electromechanical nanoactuators, and nano energy harvesters

6. Nanoscience is not just the science of the small, but the science in which materials with small dimension show new physical phenomena called quantum effects

7.   Classification of nanostructure materials is based on Origin Dimension And Structure Classification on the basis of Origin Natural nanomaterial : coming from resources of nature, these are viruses, proteins, and antibodies. Some minerals like clay, gelatin, natural colloids, shells, coral, etc are natural nanomaterials. Artificial nanomaterials : those which are prepared deliberately through well-defined mechanical and fabrication processes, like carbon nanotubes, quantum dots, and semiconductor nanoparticles

8. Classification on the basis of Materials Carbon-based material : mostly carbon-composed , hollow spheres (fullerenes) or tubes (nanotubes), these have wide potential applications. Metal-based materials : Quantum dots, nanogold, nano silver, and metal oxides like TiO2 are examples of it. Dendrimers : nanosized polymers built from branched units are dendrimers. Surfaces of dendrimers have branch ends performing a special function. They are used in drug delivery. Composites : these are bulk-type materials

9. A nanomaterial is an object that has at least one dimension in the nanometer scale

10. Nanoscience in Nature: a great starting point

11. Nanoscience in Nature: a great starting point The interaction of light, water, and other materials with these nanostructures gives the natural materials some remarkable properties which can be appreciated at the macro scale. The chemical identity and properties of a substance depend upon its molecular structure

12. Nanoscience in Nature: a great starting point

13. LOTUS LEAF

14. Zoom On Lotus Leaf

15. Cl a y s Clays are a type of layered silicate that is characterized by a fine 2D crystal structure

16. Natural colloids Colloid Invisible to the naked eye Can’t be separated by filtration Do not settle down Usually particle size 1 – 1000 nanometer Visible to the naked eye Can be separated by filtration Dispersed material is usually solid Particles can be settled down Usually particle size larger than 1 micrometer Su s pension There are different types of dispersed material

17. Natural colloids such as milk and blood All these materials have the characteristic of scattering light and often their color (as in the case of blood and milk) is due to the scattering of light by the nanoparticles that make them up.

18. Natural colloids

19. Natural colloids

20. Paper and cotton high strength, durability , and absorbency of cotton are due to the nanoscale arrangement of the fibers.

21. Spider silk

22. Gecko feet

23. Gecko feet

24. Gecko feet

25. Gecko feet

26. Gecko feet

27. Classification on the basis of Dimensions

28. Classification on the basis of Dimensions 1. Zero-dimensional : These are the materials wherein all the dimensions are within the nanoscale. The most common representation of 0D nanomaterials are Nanoparticles – Quantum Dots They have no dimension or 0-D, outside the nanoscale ( larger than 100nm) These are nanoparticles that might be crystalline, amorphous, single crystalline, or polycrystalline. The term nanoparticles encompass all 0-D nanosized building blocks (regardless of size and morphology ).

29. They are composed of single or multi-chemical elements They exhibit various shapes and forms They exist individually or incorporated in a matrix They may be metallic, ceramic, or polymeric . In the past 10 years, significant progress has been seen in 0-D nanoparticles. In well-controlled dimensions a variety of properties has been developed for the fabrication of 0-D NMs. Recently, 0-D such as uniform particle arrays (quantum dots) and heterogenous particle arrays, core-shell quantum dots have been used in LEDs, solar cells, and single electron transistors

30. 23 Electrons confined in all the 3Ds Discrete Energy levels

31. One-dimensional (1-D) : These are the materials with one dimension that is outside the nanoscale This leads to needle-like-shaped nanomaterials. 1D materials include Nanotubes, Nanorods, and Nanowires These materials could be Amorphous or Crystalline Single crystalline or Polycrystalline Chemically pure or impure Stand-alone materials or embedded in within another medium Metallic, ceramic, or polymeric

32. The one-dimensional materials have been extensively studied because of both their functional properties and highly controllable morphology. From the past decade, they have been used in research and development. They play an important role as both interconnects and the key units in fabricating electronic, optoelectronic nanoscale dimensions,

33. Electrons confined in 2ds as in quantum wires : electrons can freely and easily move in 1D 25

34. Two-dimensional (2D): These are the materials with two of the dimensions that are not confined to the Nanoscale or two dimensions of the material are outside the Nanoscale . 2D Nanomaterials exhibit plate-like shapes which include Nanofilms, Nanolayers, and Nanocoating. 2D nanostructures have two dimensions outside the nanometric size range (100nm). They are made up of various compositions like multi and single-layered structures . They are also integrated into the surrounding matrix material Interesting structures for the investigation and development of novel applications in sensors, photocatalysts, nanocontainers, nanoreactors, and templates for 2D structures of materials.

35. These materials could be Amorphous or Crystalline Made up of various chemical compositions Used as a single layer or as multilayer structures Deposited on a substrate Integrated in a surrounding matrix material Metallic, ceramic, or polymeric

36. 27 2D nanostructure – If 1D is Confined to nano range While another 2D remains Large – Quantum well (thin Films . Electrons can easily move i n 2 d imension s .

37. Three-dimensional (3D): Bulk nanomaterials are materials that are not confined to the nanoscale in any dimension. (all 3D are above 100nm. 3D nanostructures have three dimensions outside/above the nanometric size range (100nm). Bulk Materials possess a nanocrystalline structure can be composed of multiple arrangements of nanosize crystals, most typically in different orientations. With respect to the presence of features at the nanoscale, 3D nanomaterials can contain dispersions of nanoparticles, bundles of nanowires and nanotubes as well as multi- nanolayers

38. Due to their large surface area, these Bulk materials have attracted considerable research interest. These are very much important materials due to their wide range of applications in areas of catalysis, magnetic material, and electrode material for batteries. Due to their large surface area these have been used in research for transporting of molecules due to their porosity.

39. The density of states 29 The density of states of a system describes the number of states of each energy level that is available to be occupie d by an electron per unit interval of energy

40. 30

41. 31

42. 32 and QUANTUM CONFINEMENT DIME N SION A LITY

43. Meta l ( c o n d u c t o r) , I n s u l a t o r, and Semiconductor C o n d u c tion band (empty ) Val e n ce band (fu ll) ll ) ba n d gap ba n d gap E l ectro n i c b a n d t h eory

44. When a Bulk metal particle is reduced to a size of a few tens or hundreds of atoms, the density of states changes dramatically. The changes observed in the electronic structure during the transition of a bulk material to a large nanocluster and then to a small nanocluster of tens of atoms are as per the figure. Bulk material Large cluster Small cluster

45. When the particle size is reduced such that it has a few hundred atoms or less, the continuous density of states changes to a set of discrete energy levels In small nanocrystals, the electronic energy levels are not continuous as in the bulk but are discrete (finite density of states), because of the confinement of the electronic wavefunction to the physical dimensions of the particles This phenomenon is called quantum confinement and therefore nanocrystals are also referred to as quantum dots (QDs).

46. In any material, substantial variation of fundamental electrical and optical properties with reduced size will be observed when the energy spacing between the electronic levels exceeds the thermal energy (kt) The small cluster is analogous to a molecule having discrete energy levels Moreover, nanocrystals possess a high surface a rea and a large fraction of the atoms in a nanocrystal are on its surface. Since this fraction depends largely on the size of the particle (30% for a 1-nm crystal, 15% f or a 10-nm crystal), it can give rise to size effects in the chemical and p hysic a l p rop ertie s of th e n a noc r y s t a l

47. Decrease in the size of the nanoscale structure cause a color change

48. The number of electrons plotted as a function of energy for conduction electrons delocalized in one, two, and three dimensions provide the density of states which is given by the slopes of the curves N(E) Vs E. Density of states D(E) = dN/dE. This means the number of electrons in an interval of energy is proportional to the density of states at that energy

49. N(E) Energy E 3D 2D 1D Energy E D(E) 1 Dim 2 Dim 3 Dim

50. It is observed that the density of states decreases with increasing energy for one dimension, remains constant for two dimensions, and increases with increasing energy for three dimensions. Thus the density of states is different for all three cases.

51. E n e r g y l e v el s i n m e t al l i c a n d s e m icon ductor nanoparticles The density of stat e s in m e ta l (A ) a n d semiconductor (B) nanocrystals. In each case, t h e de n sity of states is discrete at the band edges. The F e r m i l e v e l is in th e c e n t e r o f a ba n d in m e tal , so kT w ill e xce e d t h e l e v e l sp acing ev e n a t l o w t e mperat u r e s a n d small si z e s. Ne v e rthe l e ss, metal n a n o particl e s o f v e ry small si z e c an e xhibit insulating properties .

52. Dependence of density of states and number of electrons on energy The Number of electrons N(E) increases with the energy E for all four structures. Which means they differ only qualitatively The density of states differs dramatically for each of the nanostructure types The nature of dimensionality and the confinement associated with each of the nanostructures have a profound effect on the properties The above considerations can be used to predict the properties On the other hand, we can also identify the structure based on the properties