COMPREHENSIVE STUDIES ON AMINO ACID BASED ORGANOMETALLIC L-THREONINUM COBALT (II) SULFATE (LTCS) SINGLE CRYSTAL

By the most widely used slow evaporation technique at room temperature, L-Threoninum Cobalt (II) Sulfate Heptahydrate (LTCS) materials were grown for various applications. The structure of orthorhombic LTCS was identified by X-Ray Diffraction studies (Powder X-Ray Diffraction and Single crystal X-Ray Diffraction), this analysis has also reported the crystallinity, cell parameters (a= 5.35, b= 7.93, c=13.71), and space group (non-centrosymmetric) of the grown material. Functional groups were affirmed by FTIR analysis. Optical analysis straightforwardly confirms LTCS crystals has greater optical transparency, and Eg = 5.6 eV demonstrates the appropriateness of prepared crystals to optical applications. The mechanical properties were validated with the aid of Vickers' microhardness measurement and that also suggests LTCS belongs to the class of hard material. In this respect, the SHG efficiency of the LTCS crystal grown is 1.25 times greater than that of the KDP crystal because Co + ions boost the SHG efficiency of LTCS and it was tested by Kurtz and Perry's technique. Electrical results documented the good conducting properties of LTCS crystal. The LTCS substance used to treat fungal and bacterial infections and this bacterial and fungal destroying property was validated by an antimicrobial assay.


INTRODUCTION
In the newest scenario, crystal growth plays an interdisciplinary activity in numerous areas of physics, chemistry, and molecular biology due to its notable benefits. In the age of informatics; in multidisciplinary nature of technology (information) is handled at high speed by integrated circuits built on a single crystal. On the other hand, in microelectronics, communication technology, energy and space technology single crystal with high quality is required, because single crystals are capable of changing their properties under the influence of light, electric and magnetic field, temperature and pressure, etc. Among various organic and inorganic materials, semi-organic materials cater to an innumerable scope in various practical applications. At present amino acids combined with a variety of inorganic materials single crystals can be formed and they have received broad attention for the above-mentioned applications, because in the zwitterionic state amino acid may produce an added betterment in various practical applications [1,2]. Unlike other amino acids, L-threonine is capable of forming compounds with organic and inorganic compounds, and also it is an essential amino acid often used to support the production of connective tissue [3,4]. Inorganic Cobalt (II) Sulfate has lot of applications such as preparation of pigments and manufacture of other cobalt salts etc., and also it may play a vital role in various biological activities [5,6].

Materials and crystal growth
A comfortable slow evaporation solution growth mechanism was used at a constant temperature for the production of high quality LTCS material. The equimolar ratio of L-Threonine and Cobalt (II) Sulfate heptahydrate was chosen to take for the production of LTCS substance and it is dissolved in the solvent (distilled water). For the removal of contaminants, the very well mixture solution was filtered and wrapped in perforated foil, and preserved in uninterrupted condition for evaporation. The high transparency LTCS single crystal was gathered after 25-30 days without defects, and is being shown in Fig.1. .

Characterization techniques
Only for the determination of unit cell parameters of the titular crystals, the Bruker Kappa APEXII X-ray diffractometer was used. By using the XPERT-PRO diffractometer with Cu kα radiation (λ= 1.5406 Å), the crystallinity of the LTCS crystal was checked. Functional groups of the LTCS crystals are trialed by Thermo Nicolet Avatar 370 spectrometers in the frequency region 400-4000 cm -1 . By UV-1700 Series Spectrophotometer optical character of LTCS crystal was measured in the range of 200-800 nm. The mechanical behavior of LTCS was investigated by an HMV-2T microhardness tester. The mechanical behavior of grown crystals was validated by an HMV-2T microhardness tester. By the Tonghui TH2826 Precision LCR Meter, the dielectric behavior was observed. To assess the presence of antibacterial activity of LTCS was carried out by the Agar disk diffusion method with aminoglycoside antibiotics Amikacin as a control for antibacterial activity and Nystatin was used as a control for fungicide activity studies of the grown material.

Single crystal X-ray diffraction analysis (SXRD)
The data obtained from SXRD measurement are unit cell parameters, crystal system, and space group. A system with orthorhombic structured LTCS was identified along with this analysis and also SXRD confirms the LTCS crystal belongs to non-centrosymmetric space group P212121. The unit cell parameters of grown sample collected from SXRD measurement are presented in Table 1. Radiation wavelength λ=0.71073Å

Powder X-ray diffraction analysis (PXRD)
The grown LTCS crystal has been subjected to PXRD measurement because it provides information about the symmetry of unit cell, atom position, and displacements of crystalline material via the position and intensities of the diffraction reflection [7,8].

FTIR analysis
FTIR is a non-destructive powerful analytical technique for producing a unique fingerprint of the sample. Herein the bonding structure and the diverse functional groups for the synthesized crystal were analyzed by FTIR technique. The resulting FTIR spectrum of LTCS has been illustrated in Fig.3 and it shows that LTCS molecules exist in the zwitter ionic state due to the presence of amine group, carboxylate group, and hydrogen bonding [9]. The observed wavenumbers and the proposed assignments of the LTCS crystal's FTIR spectrum band are given in Table 2.

UV-Visible spectral analysis
The improvements that light travels throughout the substance by altering its vector of propagation or strength with a specific material are described as the optical characteristics of that substance [10]. Including a very well, the most important optical properties: absorption, propagation, reflection, and refraction. Some optical constants such as refractive index (n) and extinction coefficient (K) are correlated with these properties and can be calculated by calculating the reflectance of a material. The transmittance spectrum of the LTCS crystal in Fig. 4.1 shows a wide transparency window from 235 to 800 nm and no absorbance in the entire wavelength indicating that the LTCS crystal possess greater optical transparency and the prepared crystals were suitable for NLO applications [11][12][13]. In this present work the value of Eg=5.6 eV obtained from Fig. 4.2. The optical absorption coefficient (α) and Eg according to Tauc's relationship is given by [14] 2.303 1 log tT   1 where T is the transmittance and t is thickness of crystal.
where A is a constant, Eg the optical band gap, h the plank's constant and ν the frequency of incident photons and value of n is depend upon the nature of transition.

Hardness measurement
Hardness is a simple parameter to measure the resistance of the material to permanent deformation.
For most materials hardness measurements can be made at low loads < 200 gram is called microhardness.
This low load hardness is a major parameter to evaluate the mechanical property such as Hardness (Hv), if the material high quality, defect free, the hardness is high. The mechanical parameters of the titular material are presented in Table 6.3.
For LTCS material Hv increase with rising load indicates RISE (reverse indentation size effect RISE) which is presented in Fig.5 Where P is the applied load in kg and d is the diagonal length of the indentation mark in mm.

Fig. 5.2 Log P versus Log d of LTCS crystal
Fracture toughness is the property of materials able to resist the fracture and the following relation is used to calculate Kc (Fracture toughness), Increase in Kc with applied load indicates high mechanical stability of the LTCS material (Fig.5.3).

.4 Brittleness index versus load P of LTCS crystal
In device manufacturing and construction technology, yield strength seems to be a very significant mechanical property and it is calculated by using the relation [20,21] where n is the microhardness index.
The increase in yield strength (Fig. 5.5) indicates the selection of materials for the field of engineering.

Fig. 5.5 Yield Strength versus load P of LTCS crystal
The stiffness constant C11 can determine using Wooster's empirical formula, Due to the high bonding nature of grown material, stiffness constant (C11) increased by increasing load ( Fig.5.6).

SHG measurement
The titular material was illuminated by the Q-switched Nd: YAG laser of λ=1064nm and the output energy (green light of λ = 532 nm) were analyzed for the nonlinear SHG efficiency of the LTCS. Thus, obtained results were compared with standard reference KDP [22][23][24]. It is evident from the observation that Co + ion raises the SHG performance of grown LTCS crystal because the results obtained were 1.25 times higher than that of standard KDP crystal and it confirms LTCS can be used for numerous NLO applications [25,26].

Dielectric studies
The dielectric analysis is indispensable for characterizing the electrical properties of the crystal and it also provides information related to the nature of defects in the crystal [27,28]. The frequency dependent plot of εr in Fig.7.1 explains dielectric constant high at lower frequency side because the presence of all type of polarization and it gradually decreased at high frequency is due to the reduction of space charge polarization The relative permittivity or the dielectric constant εr is calculated by the following relation Where all the symbols have their own significance The dielectric loss depends very much on temperature and frequency and measured by the following relation, The tan δ is referred to as the dielectric loss. demonstrates also that loss tangent has a similar trend with dielectric constant. The high value of tanδ at a low frequency can attribute to the high resistivity of the grain boundaries [29]. Fig.7.3 shows the variation of AC conductivity of LTCS material for 120 0 C within the 100Hz to 2MHz frequency range. It was observed that with an increase in frequency, the AC conductivity was slowly rising up to 100 kHz and a rapid linear increase thereafter. This study unambiguously identifies the grown crystal is less defective, good quality material [30,31].  Table 5. Among the two bacteria, Staphylococcus aureus showed high antibacterial activity (31 mm) than the control (28 mm) and also Pseudomonas aeruginosa have nearly equal activity of control.
According to the results of this study, LTCS crystal has substantial antibacterial activity on Staphylococcus aureus than Pseudomonas aeruginosa. However, in this present study confirms the grown material is used to treat various bacterial infections produced by the given microorganism [34][35][36].
To access the antifungal activity of the grown sample using Candida albicans and Aspergillus flavus as test organisms. Some health problems caused by Aspergillus flavus include allergic reactions, lung infections, and infections in other organs. Candida albicans is not problematic at normal levels, when it grow uncontrollably the healthy bacteria levels are minimized this causes fungal infections in humans [37].
Antifungal susceptibility activity of LTCS crystal is shown in Fig.8.2 (a & b) and the obtained results are presented in Table 5 and this study confirms the grown material makes high resistance to the most prevalent opportunistic fungal pathogens Aspergillus flavus than Candida albicans. In the context of above concern, the grown material is used to treat wide verity of fungal infection.