Nanotechnology Future Of Todays Present

1

NANOTECHNOLOGY

NANOTECHNOL OGY “Characterization & synthesis of ZnO Nanoparticles Synthesized by wet chemical Process”

2

NANOTECHNOLOGY

SUBMITTED BY:- RAHUL JAISWAL B.Sc LIFE SCIENCES 2ND YEAR

3

NANOTECHNOLOGY

ACKNOWLEDGEMENT

I would like to express my gratitude to Dr.VINAY GUPTA, Department of Physics and Astrophysics, University of Delhi for giving me permission to commence this project in the first instance, to do the necessary research work and to use departmental data. I have furthermore to thank ANJALI MADAM, AMIT SIR who helped & encouraged me to go ahead with my project. I am deeply indebted Prof. Dr. HARISH whose help, stimulating suggestions and encouragement helped me in all the time of research for and writing of this project. Especially, I would like to give my special thanks to my parents whose patient love enabled me to complete this work.

4

NANOTECHNOLOGY

DECLARATION

I hereby certify that the matter embodied in the project entitled “Characterization & synthesis of ZnO Nanoparticles

Synthesized

by

wet

chemical

Process” has been carried out by RAHUL JAISWAL at the Department of Physics and Astrophysics under the supervision of Prof. Dr.VINAY GUPTA for his shortterm programmed in Nanotechnology and that it has not been submitted elsewhere for award of any degree or diploma.

5

NANOTECHNOLOGY

CONTENTS NANOTECHNOLOGY a) NANOMETER b) HISTORRY c) PIONEERS OF NANOTECHNOLOGY NANOPARTICLES a) HISTORY b) PROPERTIES FABRICATIONS OF NANOTECNOLOGY CHARECTERIZATION TECHNIQUES a) UV-VIS SPECTROSCOPY b) X-RAY DIFFRACTION WHY I CHOOSE ONLY ZnO NANOPARTICLES SYNTHESIS OF ZnO NANOPARTICLES RESULT

6

CONCLUSION BIBLIOGRAPHY

NANOTECHNOLOGY

7

NANOTECHNOLOGY

NANOTECHNOLOG Y Nanotechnology is the creation of USEFUL/FUNCTIONAL materials, devices and systems (of any useful size) through control/manipulation of matter on the nanometer length scale and exploitation of novel phenomena and properties which arise because of the nanometer length scale:

NANOMETER: •

One billionth (10-9) of a meter

Hydrogen atom 0.04 nm • Proteins ~ 1-20 nm • Diameter of human hair ~ 10 µm •

BRIEF REMINDING OF THE HISTORY RELATED TO NANOTECHNOLOGY:

8

NANOTECHNOLOGY

1959 Feynman gives after-dinner talk describing molecular machines building with atomic precision 1974 Taniguchi uses term "nano-technology" in paper on ion-sputter machining 1977 Drexler originates molecular nanotechnology concepts at MIT 1981 First technical paper on molecular engineering to build with atomic precision STM invented 1985 Buckyball discovered 1986 First book published, AFM invented, First organization formed 1987 First protein engineered , First university symposium 1988 First university course 1989 IBM logo spelled in individual atoms , First national conference 1990 First nanotechnology journal

9

NANOTECHNOLOGY

1991 Japan''s MITI announces bottom-up "atom factory" Carbon nanotube discovered 1992 First textbook published 1993 First Feynman Prize in Nanotechnology awarded First coverage of nanotech from White House "Engines of Creation" book given to Rice administration, stimulating first university nanotech center 1996 NASA begins work in computational nanotech First nanobio conference 1997 First company founded: Zyvex First design of nanorobotic system 1998 First NSF forum , First DNA-based nanomechanical device 1999 First Nanomedicine book published 2000 President Clinton announces U.S. National Nanotechnology Initiative First state research initiative: $100 million in California

10

NANOTECHNOLOGY

2001 First report on nanotech industry U.S. announces first center for military applications 2003 Drexler/Smalley debate is published in Chemical & Engineering News 2004 First policy conference on advanced nanotech First center for nanomechanical systems 2005 At Nanoethics meeting, Roco announces nanomachine/nanosystem project count has reached 300 2006 National Academies nanotechnology report calls for experimentation toward molecular manufacturing

11

NANOTECHNOLOGY

PIONEERS OF NANOTECHNOLOGY Richard Feynman: Was an American physicist. For his contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965.He for the first time introduced the concept of nanotechnology. His famous books are called There's Plenty of Room at the Bottom, and Physics. Feynman is also known for his semiautobiographical books Surely You're Joking, Mr. Feynman! and What Do You Care What Other People Think?

Norio Taniguchi (27 May1912 - 15

November 1999): was a professor of Tokyo Science University. He coined the term nanotechnology in 1974 to describe semiconductor processes such as thin film deposition and ion beam milling exhibiting characteristic control on the order of a nanometer: "‘Nano-technology’ mainly consists of the processing of separation, consolidation, and deformation of materials by one atom or one molecule."

12

NANOTECHNOLOGY

Professor Taniguchi was the recipient of Euspen's 1st Lifetime Achievement Award which was presented in Bremen, May 1999.

Kim Eric Drexler (born April 25, 1955) Is an American engineer best known for popularizing the potential of molecular nanotechnology (MNT), from the 1970s and 1980s. His 1991 doctoral thesis at MIT was revised and published as the book "Nanosystems Molecular Machinery Manufacturing and Computation" (1992), which received the Association of American Publishers award for Best Computer Science. Drexler in his 1986 book Engines of Creation: The Coming Era of Nanotechnology to describe what later became known as molecular nanotechnology (MNT).He proposed the idea of a nanoscale "assembler" which would be able to build a copy of itself and of other items of arbitrary complexity. He also coined the term grey goo.

13

NANOTECHNOLOGY

NANOPARTICLES NANOPARTICLE is defined as a small object that behaves as a whole unit in terms of its transport and properties. It is further classified according to size: In terms of diameter, fine particles cover a range between 100 and 2500 nanometers, while ultrafine particles, on the other hand, are sized between 1 and 100 nanometers.

HISTORY OF NANOPARTICLES: Nanoparticles were used by artisans as far back as the 9th century in Mesopotamia for generating a glittering effect on the surface of pot

PROPERTIES OF NANOPARTICLES: Properties of nanoparticles both chemical & physical are different from than those of bulk materials. The change in properties is not always desirable. Like

14

1.

2.

3.

4.

NANOTECHNOLOGY

Different colour of metal’s nanoparticles than bulk like gold nanoparticles appears red. Copper nanoparticles smaller than 50 nm are considered super hard materials that do not exhibit the same malleability and ductility as bulk copper. The reduction in incipient melting temperature of nanoparticles Sintering can take place at lower temperatures, over shorter time scales than for larger particles.

REASONS BEHIND THE DIFFERENT PROPERTIES OF NANOPARTICLES FROM THAT OF BULK MATERIALS Drastic increase in the surface to volume ratio as the particle size is reduced below 100nm leading to:-1.Restriction in delocalization of electron with reduced size 2. Ability of surface to make larger excursions from their equilibrium position leading to a change in structure with size. E.g. gold nanoparticles when smaller <=5 nm

15

3.

NANOTECHNOLOGY

becomes isohedral instead of the bulk FCC arrangement Dominance of the interfacial phenomenon.

FABRICATION OF NANOPARTICLES

Characterization Technique 1. 2. 3. 4. 5.

Ultraviolet-visible spectroscopy. powder x-ray diffractometry [XRD]. atomic force microscopy [AFM]. electron microscopy [TEM,SEM]. Fourier transform infrared spectroscopy [FTIR]

Ultraviolet-visible spectroscopy

16

NANOTECHNOLOGY

A beam of light from a visible and/or UV light source (colored red) is separated into its component wavelengths by a prism or diffraction grating. Each monochromatic (single wavelength) beam in turn is split into two equal intensity beams by a half-mirrored device. One beam, the sample beam (colored magenta), passes through a small transparent container (cuvette) containing a solution of the compound being studied in a transparent solvent. The other beam, the reference (colored blue), passes through an identical cuvette containing only the

17

NANOTECHNOLOGY

solvent. The intensities of these light beams are then measured by electronic detectors and compared. The intensity of the reference beam, which should have suffered little or no light absorption, is defined as I0. The intensity of the sample beam is defined as I. Over a short period of time, the spectrometer automatically scans all the component wavelengths in the manner described. The ultraviolet (UV) region scanned is normally from 200 to 400 nm, and the visible portion is from 400 to 800 nm. IF the sample compound does not absorb light of of a given wavelength, I = I0. However, if the sample compound absorbs light then I is less than I0, and this difference may be plotted on a graph versus wavelength, as shown on the right. Absorption may be presented as transmittance (T = I/I0) or absorbance (A= log I0/I). If no absorption has occurred, T = 1.0 and A= 0. Most spectrometers display absorbance on the vertical axis, and the commonly observed range is from 0 (100% transmittance) to 2 (1% transmittance). The wavelength of maximum absorbance is a characteristic value, designated as λmax. Different compounds may have very different absorption maxima and absorbance. Intensely absorbing compounds must be examined in dilute solution, so that significant light energy is received by the detector, and this requires the

18

NANOTECHNOLOGY

use of completely transparent (non-absorbing) solvents. The most commonly used solvents are water, ethanol, hexane and cyclohexane. Solvents having double or triple bonds, or heavy atoms (e.g. S, Br & I) are generally avoided. Because the absorbance of a sample will be proportional to its molar concentration in the sample cuvette, a corrected absorption value known as the molar absorptivity is used when comparing the spectra of different compounds. This is defined as:

Molar Absorptivity, ε = A/ c l ( where A= absorbance, c = sample concentration in moles/liter & l = length of light path through the cuvette in cm.)

Molar absoptivities may be very large for strongly absorbing compounds (ε >10,000) and very small if absorption is weak (ε = 10 to 100).

X-ray Diffraction

19

NANOTECHNOLOGY

X-rays are electromagnetic radiation with typical photon energies in the range of 100 eV - 100 keV. For diffraction applications, only short wavelength x-rays (hard x-rays) in the range of a few angstroms to 0.1 angstrom (1 keV - 120 keV) are used. Because the wavelength of x-rays is comparable to the size of atoms, they are ideally suited for probing the structural arrangement of atoms and molecules in a wide range of materials. The energetic x-rays can penetrate deep into the materials and provide information about the bulk structure. Powder XRD (X-ray Diffraction) is perhaps the most widely used x-ray diffraction technique for characterizing materials. As the name suggests, the sample is usually in a powdery form, consisting of fine grains of single crystalline material to be studied. The technique is used also widely for studying particles in liquid suspensions or polycrystalline solids (bulk or thin film materials). The term 'powder' really means that the crystalline domains are randomly oriented in the sample. Therefore when the 2-D diffraction pattern is recorded, it shows concentric rings of

20

NANOTECHNOLOGY

scattering peaks corresponding to the various d spacings in the crystal lattice. The positions and the intensities of the peaks are used for identifying the underlying structure (or phase) of the material. Powder diffraction data can be collected using either transmission or reflection geometry, as shown below. Because the particles in the powder sample are randomly oriented, these two methods will yield the same data. In the MRL xray facility, powder diffraction data are measured using the Philips XPERT MPD diffractometer, which measures data in reflection mode and is used mostly with solid samples, or the custom built 4-circle diffractometer, which operates in transmission mode and is more suitable for liquid phase samples.

The peaks in an x-ray diffraction pattern are directly related to the atomic distances. Let us consider an incident x-ray beam interacting with the atoms arranged in a periodic manner as

21

NANOTECHNOLOGY

shown in 2 dimensions in the following illustrations. The atoms, represented as green spheres in the graph, can be viewed as forming different sets of planes in the crystal (colored lines in graph on left). For a given set of lattice planes with an inter-plane distance of d, the condition for a diffraction (peak) to occur can be simply written as

2dsinθ = n λ This is known as the Bragg’s law, after W.L. Bragg, who first proposed it. In the equation, λ is the wavelength of the x-ray, θ the scattering angle, and n an integer representing the order of the diffraction peak. The Bragg's Law is one of most important laws used for interpreting x-ray diffraction data. Bragg's Law applies to scattering centers consisting of any periodic distribution of electron density. In other words, the law holds true if the atoms are replaced by molecules or collections of

22

NANOTECHNOLOGY

molecules, such as colloids, polymers, proteins and virus particles.

WHY I CHOOSE ONLY ZnO NANOPARTICLES? BECAUSE: ZnO has large band gap of 3.2eV - 3.4eVat room temperature and large exciton-binding energy of 60meV so can be used for excitonrelated optical devices. 2.ZnO is a semi-conducting, photo-conducting and piezoelectric material had widely used as transparent electrodes in solar cells, active 1.

23

NANOTECHNOLOGY

channel in thin film transistor, varistors, and chemical & gas sensors. 3.Recently, ZnO is main attention among the research community because of the tailoring of its optical and electrical properties using doping and find applications in the area of spintronics, p-n junction, short wave length optoelectronics devices

SYNTHESIS OF ZnO NANOPARTICLES My approach of synthesis of ZnO nano particles is a wet chemical route, as reported by Spanhel & Anderson. This synthesis consists of two major steps: 1.

2.

Preparing the precursor by reacting Zinc acetate with ethanol Hydrolyzing the precursor to form ZnO colloid by using lithium hydroxide.

24

NANOTECHNOLOGY

Zinc acetate dihydrate ((CH3COO)₂Zn.2H2O, molecular weight= 219.50 from Thomas Baker) and absolute ethanol (spectrochem) were used to prepare the precursors without any further purification, and Lithium hydroxide monohydrate (LiOH.H2O, molecular weight = 41.96 from Thomas Baker), was used to hydrolyze the precursor. Following flowchart represents the steps involved in the synthesis of nanoparticles through wet chemical route When zinc acetate is heated at 75°C to prepare an intermediate species through hydrolysis and condensation, acetic acid is also produced, which reacts with ethanol and results in the generation of additional water through an esterification process. One of the immediate species formed by hydrolysis and condensation is Zn₁₀O₄ (Ac)₁₂ which turns to zinchydroxy double salt by following reactions: Zn-OAc + HOH

Zn-OH +

HOAc Zn-OH + Zn-OAc + HOAc

Zn-O-Zn

25

NANOTECHNOLOGY

Zn-O-Ac + HOH

Zn-OH

+ Zn-OH The addition of LiOH to the transparent precursor leads to the formation of ZnO nanoparticles sol along with the reaction products like lithium acetate and H₂O through hydrolysis. Presence of water plays an important role in growth of ZnO nanoparticles, and therefore presence of water is strictly controlled during the reaction and during precipitation to obtain nanopowders. The use of hydrocarbon with long chain, such as hexane and heptane were reported to be suitable for the precipitation of nanoparticles. Heptane is preferable because of its less toxic in nature. The size of ZnO nanoparticles can be varied by varying the time of addition of n-heptane, by increasing the time size of ZnO nanoparticles are expected to increase.

In present experiment sample was prepared by adding n-heptane after 1 hr.

RESULT: ZnO SOL under UV LIGHT

26

NANOTECHNOLOGY

FIG: 1 FIG: 1 Clear ZnO sol when observed under UV light .Green florescence indicates the presence of ZnO nanoparticles.

FIG: 2 FIG: 2 ZnO nanoparticles under UV after adding nheptane & keeping it over night. ZnO particles settle down when n-heptane is added.

27

NANOTECHNOLOGY

FIG: 3 FIG: 3 ZnO nanoparticles under UV after adding ethanol & centrifuged (washing of ethanol)

RESULT BY UV-VISIBLE SPECTROSCOPY Optical transmission spectra of the ZnO sol was recorded at room temperature in the wavelength range 250 to 900 nm. The measurements were made with reference to the ethanol medium to cancel the effect of solvent. The onset of fundamental absorption edge, which is obtained by extrapolating the steep part of the transmission curve, is found to be

28

NANOTECHNOLOGY

CONCLUSION: During the experiment, we reported the synthesis of ZnO nanoparticles by WET CHEMICAL METHOD using ethanol as solvent. The green colour observed under UV shows the presence of good nanoparticles. The green emission is related to the singly ionized oxygen vacancy, and this emission results from the recombination of a photo-generated hole with a singly ionized charge state of the specific defect. Moreover the UV-VIS confirmed the presence of ZnO nanoparticles.

29

NANOTECHNOLOGY

BIBLIOGRAPHY http://en.wikipedia.org/wiki/Norio_Taniguc hi http://en.wikipedia.org/wiki/K._Eric_Drexl er http://en.wikipedia.org/wiki/Richard_Feyn man http://en.wikipedia.org/wiki/Nanoparticles http://en.wikipedia.org/wiki/Nanotechnology http://www.iop.org/EJ/journal/Nano