The sol-gel synthesis and photocatalytic activity of Gd-SiO2-TiO2 photocatalyst

Abstract:

The sol-gel method was used to synthesize Gd-SiO2-TiO2 composite

photocatalysts. The sample showes the optimal photocatalytic activity during the methylene blue (MB) degradation. When the calcination temperature was lower than 550 ºC, Gd-SiO2-TiO2 photocatalyst has an anatase crystal structure. After doping of Si and Gd, the absorption wavelength thresholds of the sample approached 407 nm. Gd-SiO2-TiO2 photocatalyst showed the degradation efficiency about 90% to methylene blue (MB) under irradiation of simulated sunlight.

. Introduction:

Now a days Environmental pollution becomes more and more serious problems . And organic pollution has become a serious problem in water environments. These pollutants could not be removed thoroughly by general physical and
chemical methods. Because of the mild reaction conditions, low cost and avoidance of secondary pollution. The photocatalytic oxidation technology s an important and potential applications in fields of pollutant degradation and decomposition of water to hydrogen.
 The synthesis and photocatalytic activity of TiO2 have been investigated widely. Various techniques were carried out to develop TiO2 with high photocatalytic activity . And some research results indicate that the TiO2/SiO2 mixed oxide has higher activity than pure TiO2 while used as the photocatalyst . The added SiO2
strengthens the thermostability of anatase TiO2, increases its specific area and enhances its photocatalytic activity. 



Reference:

https://www.sciencedirect.com/science/article/abs/pii/S0009261419306578

IR spectroscopy

Infrared Spectroscopy is the analysis of infrared light interacting with a molecule. This can be analyzed in three ways by measuring absorption, emission and reflection. The main use of this technique is in organic and inorganic chemistry. It is used by chemists to determine functional groups in molecules. IR Spectroscopy measures the vibrations of atoms, and based on this it is possible to determine the functional groups.5 Generally, stronger bonds and light atoms will vibrate at a high stretching frequency (wavenumber).
Topic hierarchy

How an FTIR Spectrometer Operates
FTIR spectrometers (Fourier Transform Infrared Spectrometer) are widely used in organic synthesis, polymer science, petrochemical engineering, pharmaceutical industry and food analysis. In addition, since FTIR spectrometers can be hyphenated to chromatography, the mechanism of chemical reactions and the detection of unstable substances can be investigated with such instruments.
Identifying the Presence of Particular Groups
This page explains how to use an infra-red spectrum to identify the presence of a few simple bonds in organic compounds.

Infrared: Application
Infrared spectroscopy, an analytical technique that takes advantage of the vibrational transitions of a molecule, has been of great significance to scientific researchers in many fields such as protein characterization, nanoscale semiconductor analysis and space exploration.

Infrared: Interpretation
Infrared spectroscopy is the study of the interaction of infrared light with matter. The fundamental measurement obtained in infrared spectroscopy is an infrared spectrum, which is a plot of measured infrared intensity versus wavelength (or frequency) of light.

Infrared: Theory
Infrared (IR) spectroscopy is one of the most common and widely used spectroscopic techniques employed mainly by inorganic and organic chemists due to its usefulness in determining structures of compounds and identifying them. Chemical compounds have different chemical properties due to the presence of different functional groups.

Interpreting Infrared Spectra
 The wavelengths found in infrared radiation are a little longer than those found in visible light. IR spectroscopy is useful for finding out what kinds of bonds are present in a molecule, and knowing what kinds of bonds are present is a good start towards knowing what the structure could be.

Gibb's Phase Rule

The Phase Rule describes the possible number of degrees of freedom in a (closed) system at equilibrium, in terms of the number of separate phases and the number of chemical constituents in the system. It was deduced from thermodynamic principles by J. W. Gibbs in the 1870s.
The Degrees of Freedom [F] is the number of independent intensive variables (i.e. those that are independent of the quantity of material present) that need to be specified in value to fully determine the state of the system. Typical such variables might be temperature, pressure, or concentration.
A Phase is a component part of the system that is immiscible with the other parts (e.g. solid, liquid, or gas); a phase may of course contain several chemical constituents, which may or may not be shared with other phases. The number of phases is represented in the relation by P.
The Chemical Constituents are simply the distinct compounds (or elements) involved in the equations of the system. (If some of the system constituents remain in equilibrium with each other whatever the state of the system, they should be counted as a single constituent.) The number of these is represented as C.
The rule is:
F = C - P + 2.


Reference 
http://kj-gibbs.uio.no/phase_rule.html

Corrosion and Its Prevention

The loss of material(metals or alloys) or its useful properties by chemical interaction with its environment is known as corrosion. Corrosion is an electrochemical process. Corrosion leads to a tremendous loss. Corrosion is the reverse of metal extraction.

Examples:

 Rusting of iron. 
Blackening of silver articles in atmosphere.
 Fogging of nickel.

Causes of corrosion

Most metals exist in nature in combined forms that is in the form of ore. So extraction of metal from its ores is an unnatural process in which component of a stable system is being separated. Ore extraction Metal corrosion corrosion product Stable gain es mteta stable loss of es stable During the process of extraction a number of steps like concentration, Roasting ,and Smelting are involved and finally the ore is reduced into metal. therefore metals in their finally refined state are highly unstable and have a tendency to revert back in their original state that is to stable state by the process of corrosion(oxidation).

Rusting of iron is the most popular example of corrosion.

Usually the Surface of metal is covered with a thin layer of oxide. When this layer is broken, bare surface is exposed to the environment and this area act as an anode while the remaining area act as cathode. since the medium is exposed to the atmosphere, it contain dissolved oxygen.

Types of corrosion

 Uniform corrosion:

This is also called general corrosion. The surface effect produced by most direct chemical attacks (e.g., as by an acid) is a uniform etching of the metal.

Galvanic Corrosion :
Galvanic corrosion is an electrochemical action of two dissimilar metals in the presence of an electrolyte and an electron conductive path. It occurs when dissimilar metals are in contact.

 Crevice or contact corrosion:

Crevice or contact corrosion is the corrosion produced at the region of contact of metals with metals or metals with nonmetals. It may occur at washers, under barnacles, under applied protective films.

Corrosion in Concrete Concrete is a widely-used structural material that is frequently reinforced with carbon steel reinforcing rods, post-tensioning cable or pre-stressing wires. The steel is necessary to maintain the strength of the structure, but it is subject to corrosion.

 Erosion corrosion :
Erosion corrosion is the result of a combination of an aggressive chemical environment and high fluid-surface velocities.

 Dealloying Dealloying is a rare form of corrosion found in copper alloys, gray cast iron, and some other alloys. Dealloying occurs when the alloy loses the active component of the metal and retains the more corrosion resistant component in a porous "sponge" on the metal surface.

Factors affecting corrosion

1. Presence of impurities in metals Speed of corrosion increases with the presence of impurities in the metals because these impurities help in setting up the voltaic cells.

 2. Presence of electrolyte Electrolytes present in water also increases the rate of corrosion e.g. corrosion of iron in sea water takes place in large extent than in distilled water because sea water contains salts i.e.electrolytes.

Position of metals in electrochemical series

Highly reactive metals undergo corrosion faster than least reactive metals. Reactivity of metals can be found from the electrochemical series. e.g.Au Cu Pb Fe Zn Al Mg Na K Reactivity increases 4. Presence of carbon dioxide in water Presence of carbon dioxide in natural water also increases the rusting of iron because it acts as an electrolyte and increases the flow of electron from one place to another.

 Presence of protective coating

When the iron surface is coated with the metal, which is more reactive than the iron, then the rate of corrosion is retarded e.g. when iron is coated with zinc, iron is protected from rusting.

PREVENTION OF CORROSION

Corrosion is slow but continuously eating away the metal and consequence of rusting. Rusting can be avoided by not letting moist air come in contact with the metal surface .Following methods could gain fully be adopted to minimize rusting and corrosion

 Methods of preventing corrosion and rusting

Tarring

 Painting

Enameling

 Galvanizing

 Sheradising

 Tin plating

 electroplating

 Tarring: metal is dipped in hot coal tar so that a film of it is sticks to the surface which protect the surface from rusting and corrosion. Pipes or ends of poles to be embedded in the earth are usually given this protective treatment.

 Painting: Paints usually the lead paints are applied on the surface to be protected. Exposed metal surfaces as in case of roof and bridge structure are given this treatment which has to be repeated after regular interval of time.

Enameling: Enamels consist of high grade bases like zinc oxide or lead oxide ground in oil or varnish. they dry slowly leaving a hard tough and elastic film which is smooth and durable.Enamle painted surfaces are washable and are not affected by acids,alkali,gases or steam. Even tough they are more costly than ordinary paints yet because of their durability. They are equally good for use both on external and internal work.

Galvanizing: Depositing a fine film of zinc on the iron/steel surfaces is termed as galvanizing. The surfaces to be galvanizing is first cleared of all foreign matter by giving it an acid wash to be followed by a wash of clean water. the surface is then dried and dipped in molten zinc.The fine film of zinc that get deposited protect the surface from contact with atmosphere and consequence oxidation. Removal of the zinc film caused by scratches.

Sheradising: Surface to be treated is cleaned of all foreign deposits by washing it with acid solution and then with clean water. It is then dried and covered with zinc dust and enclosed in steel boxes to be heated in a furnace under controlled temperatures. Molten zinc spreads over the whole surface and on cooling forms a thin protective layer. Sherading gives better protection than galvanizing.

Tin plating: After cleaning the surface with acid wash followed by wash with clean water and drying, it is dipped in a bath of molten tin. A protective covering of tin layer if left on the surface.

Electroplating: By the process of electrolysis a thin film of nickel,cromium,copper or zinc is deposited on the surface to be protected. The surface to be protected is made the cathode and the metal to be deposited is made the anode.

 https://slideplayer.com/slide/5705698/

TiO2 photocatalysis: Design and applications

 Abstract:

 

TiO2 photocatalysis is widely used in a variety of applications in the environmental and energy fields, self-cleaning surfaces, air and water purification systems, sterilization, hydrogen evolution etc.,.

 The dimensionality associated with the structure of a TiO2 material can affect its properties and functions, including its photocatalytic performance, and also more specifically its surface area, adsorption, reflectance, adhesion, and carrier transportation properties. TiO2 photocatalysts can be classified into zero-, one-, two-, and three-dimensional structures.

Introduction:

                  Photocatalysis is focusing area in recent years. Photocatalysis currently used in a various products across a wide range of research areas, such as  environmental and energy fields. The photocatalytic properties of certain materials have been used to convert solar energy into chemical energy to oxidize or reduce materials to obtain useful materials including hydrogen and hydrocarbons, and to remove pollutants and bacteria.

TiO2 has been the most widely studied and used in many applications because of its strong oxidizing abilities for the decomposition of organic pollutants, superhydrophilicity (A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water), chemical stability, long durability, non toxicity, low cost, and transparency to visible light. The photocatalytic properties of TiO2 are derived from the formation of photogenerated charge carriers (hole and electron) which occurs upon the absorption of UV light corresponding to the band gap. The photogenerated holes in the valence band diffuse to the TiO2 surface andreact with adsorbed water molecules, forming hydroxyl radicals (•OH). The photogenerated holes and the hydroxyl radicals oxidize nearby organic molecules on the TiO2 surface. Meanwhile, electrons in the conduction band typically participate in reduction processes, which are typically react with molecular oxygen in the air to produce superoxide radical anions((a radical is an atom, molecule, or ion that has an unpaired valence electron.With some exceptions, these unpaired electrons make radicals highly chemically reactive).


 TiO2 surfaces become superhydrophilic with a contact angle of less than 5◦ under UV-light irradiation.The majority of the holes are subsequently consumed by reacting directly with adsorbed organic species or adsorbed water, producing •OH radicals .a small proportion of the holes is trapped at lattice oxygen sites and may react with TiO2 itself, which weakens the bonds between the lattice titanium and oxygen ions.The construction of TiO2 nano- or micro-structures with interesting morphologies and properties has recently attracted considerable attention. Many TiO2 nanostructural materials, such as spheres, nanorods, fibers, tubes, sheets, and interconnected architectures, have been fabricated. Nanostructured TiO2 materials are widely used not only in photocatalysis, but also in dye-sensitized solar cells, lithium-ion batteries.It is well known that there are many factors which can exert significant influence on photocatalytic performance, including the size, specific surface area etc..,. the development of performance improvements by adjusting these factors remains the focus of photocatalysis research. Structural dimensionality is also a factor which can affect the photocatalytic performance and also has a significant impact on the properties of TiO2 materials. For example, a sphere with zero dimensionality has a high specific surface area, resulting in a higher rate of photocatalytic decomposition of organic pollutants.



 Reference :
https://www.sciencedirect.com/science/article/pii/S1389556712000421

Photocatalysis and it's mechanism

The term can be generally used to describe a process where light is  used to activate a substance.The photocatalyst that modifies the rate of a chemical reaction without itself being involved in the chemical transformation. Thus, the main difference between a conventional thermal catalyst and photocatalyst is that  the former is activated by heat whereas the latter is activated by photons of appropriate energy. The principle of photocatalysis is based on the activation of a semiconductor particulate material by the action of radiation with an appropriate wavelength.  Photocatalysis is used for the elimination of several pollutants ( alkanes, alkenes, phenols, aromatics, pesticides) and complete mineralization of the organic compounds.

When a photocatalyst is irradiated with a light of suitable wavelength, an electron is excited to the conduction band (CB), leaving behind a positive hole in the valence band (VB). The electron in the CB can be utilized to reduce any substrate, whereas the hole in the VB can be used for oxidizing some compounds.

Reference: Photocatalysis principles and applications by Rakshit ametha

Page number 9-11

TiO2 photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including self-cleaning surfaces, air and water purification systems, sterilization, hydro- gen evolution, and photoelectrochemical conversion. The development of new materials, however, is strongly required to provide enhanced performances with respect to the photocatalytic properties and to find new uses for TiO2 photocatalysis. In this review, recent developments in the area of TiO2 photo- catalysis research, in terms of new materials from a structural design perspective, have been summarized. The dimensionality associated with the structure of a TiO2 material can affect its properties and func-
tions, including its photocatalytic performance, and also more specifically its surface area, adsorption, reflectance, adhesion, and carrier transportation properties.


https://www.sciencedirect.com/science/article/pii/S1389556712000421

Operators in quantum mechanics

The principal
mathematical difference between classical mechanics and quantum mechan-
ics is that whereas in the former physical observables are represented by
functions , in quantum mechanics they
are represented by mathematical operators.

 An operator is a symbol for an
instruction to carry out some action, an operation, on a function. In most of
the examples we shall meet, the action will be nothing more complicated than
multiplication or differentiation.

Linear operator:

Schrödinger equation

The Schrödinger equation, sometimes called the Schrödinger wave equation, is a partial differential equation. It uses the concept of energy conservation (Kinetic Energy + Potential Energy = Total Energy) to obtain information about the behavior of an electron bound to a nucleus. It does this by allowing an electron's wave function, Ψ, to be calculated.
Solving the Schrödinger equation gives us Ψ and Ψ2. With these we get the quantum numbers and the shapes and orientations of orbitals that characterize electrons in an atom or molecule.

The Schrödinger equation gives exact solutions only for nuclei with one electron: H, He+, Li2+, Be3+, B4+, C5+, etc. In mathematical language, we say that analytic solutions for Ψ are possible only for one-electron systems. One-electron systems are often described as hydrogenic - meaning "like hydrogen.For all other atoms, ions, and molecules, no analytic solutions for Ψ are possible;


There is a time-dependent Schrödinger equation and a time-independent Schrödinger equation.

The time-independent equation considers the electron's quantum state to be unchanging, hence it considers the electron as a standing wave. The time-independent equation allows electron densities (i.e. the sizes and shapes of atomic and molecular orbitals) to be found using Ψ2, the square of the wave function.

The p orbitals below are examples of Ψ2:px,py,pz.



https://www.chemicool.com/definition/schrodinger_equation.html

Electronic structure

Electrons are the “glue” that holds the nuclei together in the chemical bonds of
molecules and ions. It  is the nuclei’s positive charges that bind the electrons to
the nuclei. Electronic structure theory deals with the quantum states of the electrons, usually within the Born- Oppenheimer approximation .It also addresses the forces that the electrons’ presence creates on the nuclei; it is these forces that determine the geometries and energies of various stable structures of the molecule as well as transition states connecting these stable structures. Because there are ground and excited
electronic states, each of which has different electronic properties, there are different
stable-structure and transition-state geometries for each such electronic state. Electronic
structure theory deals with all of these states, their nuclear structures, and the
spectroscopies.

Reference
http://simons.hec.utah.edu/NewUndergradBook/Chapter6

Effect of Li Adsorption on the Electronic and Hydrogen Storage Properties of Acenes

Due to the presence of strong static correlation effects and noncovalent interactions, accurate prediction of the electronic and hydrogen storage properties of Li-adsorbed acenes with n linearly fused benzene rings (n = 3-8) has been very challenging for conventional electronic structure methods.To meet this challenge using developed thermally-assisted-occupation density functional theory (TAO-DFT) with dispersion corrections.

Woodward's rules

Woodward's rules, named after Robert Burns Woodward and also known as Woodward–Fieser rules are several sets of empirically derived rules which attempt to predict the wavelength of the absorption  maximum (λmax) in an ultraviolet visible spectrum of a given compound. Inputs used in the calculation are the type of chromophores present, the substituents on the chromophores, and shifts due to the solvent. Examples are conjugated carbonyl compounds,conjugated dienes, and polyenes.

Example

Reference 

https://en.m.wikipedia.org/wiki/Woodward's_rules

Infrared spectroscopy

Infrared spectroscopy or vibrational spectroscopy involves the interaction of infrared radiation with matter. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic techniques, it can be used to identify and study chemical substances. Samples may be solid, liquid, or gas. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer.

Reserpine

Reserpine is a drug that is used for the treatment of high blood pressure.

Reserpine has also been used for relief of psychotic symptoms.Reserpine is one of dozens of indole alkaloids  isolated from the plant Rauvolfia serpentina. In the rauwolfia plant, tryptophan is the starting material in the biosynthetic pathway of reserpine.

Reference https://en.m.wikipedia.org/wiki/Reserpine

Glycogen

Glycogen is a multibranched polysaccharide  of glucose that serves as a form of energy storage in animals,fungi, and bacteria.The polysaccharide structure represents the main storage form of glucose in the body.In humans, glycogen is made and stored primarily in the cells of the liver and skeletal muscle. In the liver, glycogen can make up 5–6% of the organ's fresh weight, and the liver of an adult weighing 70 kg can se roughly 100–120 grams of glycogen.In skeletal muscle, glycogen is found in a low concentration  and the skeletal muscle of an adult weighing 70 kg stores roughly 400 grams of glycogen. The amount of glycogen stored in the body—particularly within the muscles and liver—mostly depends on physical training, basal metabolic rate, and eating habits. Small amounts of glycogen are also found in other tissues and cells, including the kidneys, red blood cells,white blood cells,and glial cells in the brain.
Glycogen is the analogue of starch, a glucose polymer that functions as energy storage in plants. It has a structure similar to amylopectin,  but is more extensively branched and compact than starch. Both are white powders in their dry state. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle.

Oligomer

Oligomers are low molecular weight polymers comprising a small number of repeat units whose physical properties are significantly dependent on the length of the chain.In biochemistry, an oligomer usually refers to a macromolecular complex formed by non-covalent bonding of a few macromolecules like proteins or nucleic acids. In this sense, a homo-oligomer would be formed by few identical molecules and by contrast, a hetero-oligomer would be made of more than one, different, macromolecules. Collagen is an example of a homo-oligomeric protein that is composed of three identical protein chains.

Caffeine

Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is the world's most widely consumed psychoactive drug.

Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).Caffeine can have both positive and negative health effects. It can treat and prevent the premature infant breathing disorders bronchopulmonary dysplasia of prematurity and apnea of prematurity.Caffeine can increase blood pressure and cause vasoconstriction.Coffee and caffeine can affect gastrointestinal motility  and gastric acid secretion.

Reference  

https://en.m.wikipedia.org/wiki/Caffeine

Cyanocobalamin

Cyanocobalamin is a manufactured form of vitamin B 12. It used to treat vitamin B12 deficiency. This may occur in pernicious anemia and  bowel cancer.It is used by mouth, by injection into a muscle.

Possible side effects of cyanocobalamin injection include allergic reactions such as hives, difficult breathing; redness of the face; swelling of the arms, hands, feet, ankles or lower legs; extreme thirst; and diarrhoea. Less-serious side effects may include headache, dizziness, leg pain, itching, or rash.Cyanocobalamin is one of the most widely manufactured vitamers in the vitamin B
12  family  because cyanocobalamin is the most air-stable of the B 12 forms. It is the easiest[citation needed] to crystallize and therefore easiest  to purify after it is produced by bacterial fermentation, or synthesized in vitro. It can be obtained as dark red crystals or as an amorphous red powder. Cyanocobalamin is hygroscopic in the anhydrous form, and sparingly soluble in water. Cyanocobalamin is commercially prepared by bacterial fermentation. Fermentation by a variety of microorganisms yields a mixture of methyl-, hydroxo- and adenosylcobalamin. These compounds are converted to cyanocobalamin by addition of potassium cyanide in the presence of sodium nitrite and heat.

Thiamine

Thiamine is a vitamin, also called vitamin B1. Vitamin B1 is found in many foods including yeast, cereal grains, beans, nuts, and meat. It is often used in combination with other B vitamins, and found in many vitamin B complex products. Vitamin B complexes generally include vitamin B1, vitamin B2 , vitamin B3 ,vitamin B5 , vitamin B6  (pyridoxine), vitamin B12  and folic acid. However, some products do not contain all of these ingredients and some may include others, such as biotin, para-aminobenzoic acid (PABA), choline bitartrate, and inositol.

 It is a nutrient that is not synthesized in the human body. Food sources of thiamine include whole grains, legumes, and some meats and fish. Grain processing  removes much of the thiamine content, so in many countries cereals and flours are enriched with thiamine. Thiamine is a building block required for energy production and glucose metabolism.

Thiamine is used to treat thiamine deficiency  which when severe can prove fatal. In less severe cases, non-specific signs include malaise, weight loss, irritability and confusions.

Reference  https://www.webmd.com/vitamins/ai/ingredientmono-965/thiamine-vitamin-b1

https://en.m.wikipedia.org/wiki/Thiamine

Carbon nanotube

Carbon nanotubes (CNT) are a class of nanomaterials that consist of a two-dimensional hexagonal lattice of carbon atoms, bent and joined in one direction so as to form a hollow cylinder.
Carbon nanotubes are composed of carbon atoms linked in hexagonal shapes, with each carbon atom covalently bonded to three other carbon atoms. Carbon nanotubes have diameters as small as 1 nm and lengths up to several centimeters. Although, like buckyballs, carbon nanotubes are strong, they are not brittle. They can be bent, and when released, they will spring back to their original shape.

One type(a) of carbon nanotube has a cylindrical shape with open ends.

Another type (b)of nanotube has closed ends, formed by some of the carbon atoms combining into pentagons on the end of the nanotube.

 (a)

(b)

Reference 

https://www.understandingnano.com/what-are-carbon-nanotubes.html

Coronene

Coronene is a polycyclic aromatic hydrocarbon (PAH) comprising six peri-fused benzene rings. Its chemical formula is C 24H 12. It is a yellow material that dissolves in common solvents including benzene, toluene, and dichloromethane.  It has been used as a solvent probe, similar to pyrene.

It can be described by 20 resonance structures or by a set of three mobile Clar sextets. Coronene occurs naturally as the very rare mineral carpathite, which is characterized by flakes of pure coronene embedded in sedimentary rock. Coronene is produced in the petroleum-refining process of hydrocracking, where it can dimerize to a fifteen ring PAH, trivially named "dicoronylene".

 Coronene has been used in the synthesis of graphene. For example, coronene molecules evaporated onto a copper surface at 1000 degrees Celcius will form a graphene lattices.

Reference https://en.m.wikipedia.org/wiki/Coronene

Nitrogen fixation

Nitrogen fixation is a process by which nitrogen in the air is converted into ammonia  (NH3) or related nitrogenous compounds. Biological nitrogen fixation converts N2 into ammonia, which is metabolized by most organisms. Nitrogen fixation is essential for life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds, such as amino acids and proteins. As part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all chemical compounds that contain nitrogen, which includes explosives, most pharmaceuticals, and dyes. Nitrogen fixation is carried out naturally in the soil by a wide range of microorganisms.Nitrogen fixation also occurs between some termites and fungi. It also occurs naturally in the air by means of NOx  production by lightning. All biological nitrogen fixation is effected by enzymes called nitrogenases. These enzymes contain iron.


Reference https://en.m.wikipedia.org/wiki/Nitrogen_fixation

Biomolecule

A biomolecule or biological molecule is a loosely used term for molecules and ions  present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development.Biomolecules include large macromolecules  such as proteins, carbohydrates, lipids, and nucleic acids, as well as small molecules such as primary metabolites, secondary metabolites, and natural products. A more general name for this class of material is biological materials. Biomolecules are usually endogenous, produced within the organisms. Most biomolecules are organic compounds, and just four elements—oxygen, carbon, hydrogen, and nitrogen—make up 96% of the human body's mass. But many other elements, such as the various biometals, are present in small amounts.


Reference https://en.m.wikipedia.org/wiki/Biomolecule

Acenes

The acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons made up of linearly fused benzene rings.

Due to their increased conjugation length the larger acenes are also studied.Theoretically, a number of reports are available on longer chains using density functional methods. They are also building blocks for nanotubes  and graphene. Unsubstituted octacene (n=8) and nonacene (n=9.


Reference -https://en.m.wikipedia.org/wiki/Acene

Electrons shielding

The shielding effect sometimes referred to as atomic shielding or electron shielding  describes the attraction between an electron  and the nucleus in any atom with more than one electron. The shielding effect can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces on the electrons in the atom. It is a special case of electric-field screening.

Crystal Field theory

Many transition-metal complexes are coloured. This other spectroscopic properties, such as magnetism and hydration enthalpies, can be explained with the so-called crystal field theory (CFT). The CFT describes the degeneration of the d- and f-orbitals in transition-metal complexes. It does not attempt to describe any type of chemical bonds. CFT is based on the interaction of a positively charged cation and the nonbinding (negatively charged) electrons of the ligand. The general principle is that the five d orbitals are degenerated, meaning that they do not occupy the same energy level anymore. Once the ligands approach the central positively charged cation,
the electrons of the ligands will become closer to some of the d orbitals of the metal. This results in the degeneration of the d orbitals. Electrons in d orbitals that are closer to the ligands will occupy a higher energy level as the negatively charged electrons will repel each other.



Reference - Essential inorganic chemistry by katja
Page number 128

Valence Bond theory

This theory was proposed by Linus Pauling. He was awarded the Nobel  Prize for Chemistry in 1954. The theory was very widely used in the period 1940-1960. It provides a basis for simple description of small inorganic molecules.  Atoms with unpaired electrons tend to combine with other atoms which also have an unpaired electrons. In this way the unpaired electrons are paired
up, and the atoms involved all attain a stable electronic arrangement. This is usually a foll shell of electrons ( a noble gas configuration). Two
electrons shared between two atoms constitute a bond. The Number of Bond is formed by an atom is usually the same as the number of unpaired
electrons in the ground state.


Concise inorganic chemistry by JDLee

Atom bomb

Atomic bomb, also called atom bomb, weapon with great explosive power that results from the sudden release of energy upon the splitting, or fission, of the nuclei of a heavy element such as plutonium or uranium.
Structure:
An atom bomb consists of a piece of fissile material whose mass is subcritical. This piece has a cylindrical void. It has a cylindrical fissile material which can fit into this void and its mass is also subcritical. When the bomb has to be exploded, this cylinder is injected into the void using a conventional explosive.  Now, the two pieces of fissile material join to form the supercritical mass, which leads to an explosion. During this explosion tremendous amount of energy in the form of heat, light and radiation is released. A region of very high temperature and pressure is formed in a fraction of a second along with the emission of hazardous radiation like γ rays, which adversely affect the living creatures. This type of atom bombs were exploded in 1945 at Hiroshima and Nagasaki in Japan during the World War II.

 

Reference   https://www.britannica.com/technology/atomic-bomb

https://en.wikipedia.org/wiki/Nuclear_weapon

Quercetin

Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, and grains; red onions and kale are common foods containing appreciable content of quercetin. Quercetin has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.

Quercetin is a flavonoid widely distributed in nature.The name has been used since 1857, and is derived from quercetum.It is a naturally occurring polar auxin transport inhibitor.

Quercetin is one of the most abundant dietary flavonoids,with an average daily consumption of 25–50 milligrams.

In red onions, higher concentrations of quercetin occur in the outermost rings and in the part closest to the root, the latter being the part of the plant with the highest concentration. One study found that organically grown tomatoes had 79% more quercetin than non-organically grown fruit.Quercetin is present in various kinds of honey  from different plant sources.

Reference.https://en.m.wikipedia.org/wiki/Quercetin

Types of bonds

Atoms may attain a stable electronic configuration in three different ways: 
by losing electrons, by gaining electrons, or by sharing electrons. 
Elements may be divided into: 
I. Electmpositive elements, whose atoms give up one or more electrons 
fairly readily. 
2. electronegative elements. which will accept electrons. 
3. Elements which have little tendency to lose or gain electrons. 
Three different types of bond may be formed, depending on the electropositive or electronegative character of the atoms involved.

Ionic bonding involves the complete transfer of one or more electrons from one atom to another. Covalent bonding involves the sharing of a pair 
of electrons between two atoms, and in metallic bonding the valency electrons are free to move throughout the whole crystal.



Reference-- consiceInorganic chemistry by JDLee

Page number  30-31

Cholesterol

Cholesterol is an organic molecule. It is a sterol or a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell membranes.

 Cholesterol also serves as a precursor for the biosynthesis of steroid hormones,and vitamin D. In vertebrates, hepatic cells typically produce the greatest amounts. It is absent among prokaryotes, although there are some exceptions, such as Mycoplasma, which require cholesterol for growth.
According to the lipid hypothesis, elevated levels of cholesterol in the blood lead to atherosclerosis which may increase the risk of heart attack, stroke, and peripheral vascular disease.


Reference 
https://en.m.wikipedia.org/wiki/Cholesterol

Vanadium

Vanadium, with chemical symbol V and atomic number 23, is a member of the d-block metals and belongs to group 5 of the periodic table of elements. Vanadium can be found in the earth’s crust in numerous minerals and is isolated from ores mostly as a by-product. Its main application is in the steel industry, where it is used as an alloy in combination with iron. Vanadium pentaoxide is also being used as a catalyst for the production of sulfuric acid. The metal vanadium has very similar properties to titanium. Therefore, it is not surprising that its metallocene, vanadium dichloride, was also subjected to research as a potential anticancer agent.


Reference -Wikipedia

Ionization energy

A small amount of energy is supplied to an atom, then an electron may  be promoted to a higher energy .level, but if the amount of. energy supplied 
is sufficiently large the electron may be completely removed. The energy required to remove the most loosely bound electron from an isolated 
gaseous atom is called the ionization energy. 
Ionization energies are determined from spectra and are measured in kJ mo1- 1. It is possible to remove more than one electron from most 
atoms. The first ionization energy is the energy required to remove the first electron and convert M to M+; the second ionization energy is the energy 
required to remove the second election arid convert M+ to M2+; the third ionization energy converts M2+ to M3+, and so on.

The factors that influence the ionization energy are: 
1. The size of the atom. 
2. The charge on th,e nucleus. 
3. How effectively the inner electron shells screen the nuclear charge. 
4. The type of electron involved (s. p, d or/).

Reference Inorganic chemistry by Huhee

Biology and toxicology of lanthanides

lanthanoids are used in the production of batteries, lasers and other technological devices. Some lanthanoids salts, such as the salts of lanthanum, cerium and gadolinium  are
increasingly used in a clinical setting, for example, as a phosphate binder in the treatment of renal osteodys- trophy or as MRI (magnetic resonance imaging) contrast agents. Lanthanoids (Ln) show a biological behaviour very similar to that of Ca2+, as they have similar ionic radii. Lanthanoids are mostly trivalent and therefore possess a higher charge than Ca2+. Lanthanoids display a high
binding affinity to calcium-binding sites in biological molecules and to water molecules. The coordination number for lanthanoids varies from 6 to 12. Mostly, eight or nine water molecules are coordinated to the lanthanoid ion. This is a significantly lower coordination number compared to that of calcium, which is 6.

Copper containing drug

Copper-containing drugs
Copper is a valuable metal and has been mined for more than 2000 years. It has had many uses throughout
history. Initially, copper was mainly used to make alloys such as brass and bronze, which are harder and
stronger than copper itself. Nowadays, copper is mainly used because it conducts heat and electricity  and it is corrosion-resistant.
Historically, copper was used for the treatment of a variety of diseases, including chronic ulcers, headaches,
ear infections, rheumatoid arthritis (RA), and so on. In 1832, copper workers were found to be immune to an
outbreak of cholera in Paris, which stimulated further research into the medicinal use of copper. Almost every
cell in the human body uses copper, as most contain copper-dependent enzymes. Unfortunately, excessive
amounts of copper are toxic for the human body, whereas low amounts of copper also lead to health problems,
manifested in Menkes disease.
Copper ions from food sources are processed by the liver, and transported and excreted in a safe manner.
Inorganic metallic copper from sources such as drinking water mainly enters the blood directly and can be
toxic as it can penetrate the blood–brain barrier. Typically, 50% of the daily copper intake is absorbed in the GI
tract and transported to the liver from where it is transported to the peripheral tissue bound to ceruloplasmin, a
copper-binding glycoprotein. A smaller amount of copper is also bound to albumin. Excess copper is mainly
excreted in bile into the gut and then the faeces.
Copper is an essential trace metal, and copper .