eChapters

Zerovalent (nZVI) Ionic Compounds

Although Ag⁺ contains a filled d¹⁰ shell, the structures of Ag compounds can in many instances be understood only if one assumes the existence of weak attractive Ag⁺ - Ag⁺ interactions. Similar attractive forces have been shown to be responsible for the formation of gold cluster compounds. In Ag⁺ solid state compounds the unoccupied 5s and 5p orbitals give rise to empty bands which may be partially occupied thus resulting in subvalent Ag compounds; examples are Ag₃O and Ag₂F. The compound Ag₅SiO₄ prepared from Ag and Si0₂ at 350 °C under a high pressure of oxygen, contains [Ag₆]⁴⁺ clusters (average oxidation state 2/3) and should be formulated at [Ag₆]⁴⁺ (Ag⁺)₄ (SiO₄ ^{4 -})₂.

Ag and Au forms numerous cluster compounds in which the metals are zero valent or subvalent. Examples are Ag₆ Fe₃ (CO)₁₂ {HC(PPh₂)₃} and paramagnetic cluster ions [Ag₁₃ Fe₈ (CO)₃ ²]^4-.

Introduction

Hydrogels are loosely cross-linked, highly hydrophilic, organic polymers. They can absorb and retain aqueous fluids up to 500 times of their own weight (Singh et al., 2011). In the field application, such absorbents exhibited a limited swelling capacity within the soil matrix.

Aim

To synthesize chitosan/nanosilica coating solution for fruit coating aiming at increasing shelf life.

Introduction

Application of edible coatings is promising to improve the quality and extend shelf life of fruits and vegetables (Lin et al., 2011). Chitosan, a versatile biopolymer derived from deacetylation of chitin had been widely applied in the fresh-keep field owing to its good biocompatibility, biodegradability, antibacterial activity and capacities to form film (Lin et al., 2011).

Aim

To synthesize silver (Ag) nanoparticle.

Introduction

The Ag nanoparticles easily interact with other particles and increases their antibacterial efficiency. The Ag nanoparticles can be synthesized using various methods: biological, chemical electrochemical, γ-radiation, photochemical, laser ablation etc (Udapudi et al., 2012). The most popular preparation of Ag colloids is chemical reduction of Ag salts by sodium borohydride or sodium citrate (Udapudi et al., 2012).

Aim

To synthesize iron (III) oxide (Fe₂O₃) nanoparticles

Introduction

Iron oxide nanoparticles have a number of applications in catalysis, sensors and high sensitive biomolecular magnetic resonance imaging (MRI) for medical diagnosis and therapeutics. They can be synthesize by the bottom-up approaches including the sol-gel technique.

Synthesis of Zn Oxide Nanoparticle

Aim

To synthesize Zn oxide nanoparticle

Introduction

Zinc oxide nanoparticle are effective anti-bacterial and antiodur agent. They can be synthesized by number of techniques including hydrothermal methods. Their synthesis using solvothermal process is described, (Aneesh et al., 2007).

Solid state materials can exists in various forms namely:

1. Single crystals (preferred for authentic characterization of structure and physical properties)
2. Polycrystalline powders that are agglomerates of large number of crystallites and are used for characterization when single crystal cannot be easily obtained
3. Nanocrystalline or nanostructured materials that posses large surface area
4. Thin films that can be grown in the best crystalline form for many applications
5. Amorphous systems that have no long-range translational order

History and Recent Developments

Richard P. Feynman in 1959 suggested that it should be possible to build machines small enough to manufacture objects with atomic precision. His talk “There is plenty of Room at the Bottom” is widely considered to be the foreshadowing of Nanotechnology. He delivered this talk at the annual meeting of the American Physical Society at California Institute of Technology (Caltech), In 1990, a team of IBM Physicists revealed that they could write (arrange) the letter IBM using 35 individual atoms of Xenon.

In 1992 a book entitled Nanosystems: Molecular Machinery, Manufacturing and Computation was published by Eric Drexler where he outlined a way to manufacture extremely high performance machines out of molecular carbon lattice (diamondoid).

Around year 2000, federal funding for Nanotechnology in the United States began with National Nanotechnology Initiative (NNI). NNI defined nanotechnology as dealing with materials with sizes between 1 and 100 nanometers exhibiting novel properties.

The Government of India, in May 2007 launched a mission on Nano sceince and nano technology (Nano Mission) with an allocation of `1,000 crores.

Leaf Spot

Colletotrichum capsici

Economic Importance

• The disease is common in many parts of South India, and in recent years has become very severe, causing much damage to the crop.
• The yield losses occur due to leaf spot infection is through the loss of photosynthetic green surface.
• During the period of heavy infestation, yield loss could be as much as 50%.

Damping Off

Pythium aphanidermatum

Economic Importance

• The disease is reported from China, Indonesia, South Africa and the USA.
• It causes extensive damage in the tobacco tracts of Andhra Pradesh, Maharashtra and Gujarat in India.
• The damage in some areas can be hundred percent, in the absence of protective sprays.

Wilt

Fusarium oxysporum f.sp. vasinfectum

Economic Importance

• Wilt is one of the major diseases of cotton, found wherever this crop is grown like Mexico, African countries, France, Italy, Yugoslavia, India and West Indies.
• In India, the disease was first reported from Nagpur by Evans in 1908.
• It appears in almost every cotton tract of the country. However, it is more or less absent in the loamy soils of Indo Gangetic plains and sandy loams of Maharashtra, Tamil Nadu, Karnataka and other States.
• In affected susceptible varieties yield losses exceed 45-50%.

Red Rot

Colletotrichum falcatum (Perfect stage: Physalospora tucumanensis)

Economic Importance

• The disease is so devastating in nature that it has been referred to as cancer of sugarcane.
• Red rot occurs in all sugarcane growing tracts of India and several epiphytotics have been recorded in the past from states like U.P., Bihar, Haryana, Punjab, Andhra Pradesh and Kerala.
• In U.P and Bihar, the two popular varieties, namely, CO 213 and CO 312 were badly hit by the epidemics of 1938-40 and 1946-47.
• There have been reports of red rot epidemics in many other countries viz., USA, Mauritius, Australia, Hawaii and Myanmar.
• Red rot also causes appreciable damage to canes in Bangladesh, Taiwan and Pakistan.
• The loss in cane yield has been estimated 12 to 44.5% and 35 to 86 % in cane yield of ratoon over preceding plant crops have different levels of disease.

Root Rot or Stem Rot or Charcoal Rot

Macrophomina phaseolina (Sclerotial stage: Rhizoctonia bataticola)

Economic Importance

• Root rot is an important disease of sesame as infection occurs from seed germination and emergence to adult plant stage.
• The losses incurred are even up to 100 per cent, if conditions are favorable.

Wilt

Fusarium oxysporum f.sp. carthami

Economic Importance

• The disease was reported for the first time from America in 1950.
• Wilt is a devastating disease infecting the crop right from seedling to maturity resulting in crop losses to varied degrees depending on the severity of infection.
• The disease incidence has been reported in India to the tune of 80 percent under favorable condition.

Wilt

Fusarium oxysporum f.sp. carthami

Economic Importance

• The disease was reported for the first time from America in 1950.
• Wilt is a devastating disease infecting the crop right from seedling to maturity resulting in crop losses to varied degrees depending on the severity of infection.
• The disease incidence has been reported in India to the tune of 80 percent under favorable condition.

Ozonium Wilt

Ozonium texanum var. parasiticum Thirum / Guizotia abyssinica

Economic Importance

• The disease was reported around Varanasi.
• Heavy losses are incurred as the diseased plants dry.

Wilt

Fusarium oxysporun lini

Economic Importance

• The wilt is very serious disease and occurs in almost all the countries where linseed is grown.
• Continuous cropping in the infected field makes the soil sick.
• Yield losses upto 80 percent has been reported due to this disease. However, in severe cases crop is destroyed completely.

Seedling Blight

Phytophthora parasitica

Economic Importance

• Seedling blight is wide spread in Africa, India and other Asian countries.
• The average economic loss due to the disease has been 10%.

White Rust

Albugo candida

Economic Importance

• White rust is an important disease affecting mustard crop in world.
• Countries where the disease occurs include the Brazil, Canada, Fiji, Germany, India, Japan, New Zealand, Pakistan, Turkey and UK.
• Up to 60 per cent or more yield losses on B. rapa and B. juncea from this disease have been reported in India.

Root Rot or Charcoal Rot

Rhizoctonia bataticola

(Pycnidial stage: Macrophomina phaseolina)

Economic Importance

• Charcoal rot is of great economic importance in the World and has been found to reduce head weight and diameter, stem height and weight and in particular, the stem girth and root weight of sunflower plants.
• The first report of the occurrence of charcoal rot on sunflower was from Sri Lanka by Small (1927).
• Under favourable condition, losses can reach 60-90%.
• Infected plants generally die before seed set is finished.