UV Technique - an overview (2023)

4 Conclusion

We have developed a novel MALDI technique, UV/FEL-MALDI, in which a sample is exposed to FEL and nitrogen laser pulses simultaneously. The principle of UV/FEL-MALDI was examined by using a hair keratin sample prepared under a strong denaturing condition. The molecule-related ions of keratins, i.e. their total masses, have been analyzed by mass spectrometry for the first time, along with an evidence of their clustering. The remarks are as follows: firstly, the FEL macro-pulse with 15 μs width was utilized for MALDI-TOFMS without an extra instrumentation, such as the Pockels cell, to obtain a sliced micro-pulse train; secondly, extremely heavy ions (> m/z 800,000) can be generated in the gas-phase by UV/FEL-MALDI; lastly, the present approach allows a solubilizing agent to be used in a high concentration for sample preparations.

5 Conclusions

The deep investigation of the structure and electronic structure studies on biguanides has clearly shown that the structural misrepresentation is not of minor significance as there is indeed “a lot in the structure”. Structure elucidation of biguanides with the aid of X-Ray diffraction and spectroscopic techniques (UV, ¹H and ¹⁵N NMR) has been discussed which confirmed the existence of 1b. The analysis of electronic structure studies also corroborates the same. The electronic structure analysis also revealed the presence of an unusual electronic character i.e. divalent N^I character. This character needs to be explored further as it may open new avenues for its applications. A thorough understanding of structure and electronic structure will give a correct perspective to the scientific community for further studying and modulating this moiety for better chemical and biological applications.

Abstract

A new Cobalt (III) complex salt [Co(bpy)₂CO₃](ONP)·3H₂O (1) where ONP= Orthonitrophenolate/C₆H₄NO₃ has been synthesized to explore [Co(bpy)₂CO₃]⁺ cation as a new host for orthonitrophenolate anion. The newly synthesized complex salt was then characterized by elemental analysis, spectroscopic techniques (UV–Visible, FT-IR, ¹H NMR) and solubility product measurement. Single crystal X-ray structure studies of 1 revealed the presence of one 2-nitrophenolate anion, one [Co(bpy)₂CO₃]⁺cation and three water molecules of crystallization in the solid state. The structural studies revealed that a strong network of hydrogen bonding interactions O–H⋯O (water/phenolate), O–H⋯O (water/water), O–H⋯O (water/carbonate) stabilize the crystal lattice. Newly synthesized complex 1 was scrutinized for antimicrobial activity and the results revealing a modest activity. The synthesized compound was screened for anticancer activity against PANC-1 cells using MTT colorimetric assay.

3 Synthesis of metal complexes

The complexes of [Fe(III),Cr(III),Mn(II)&Ni(II) were prepared when 1.27 g of sulfamethoxazole were dissolved in 25 mL of water in the presence of basic media. Then solution of ligand was poured into 10 mL aqueous solution of metal salts [Fe (III), Cr (III), Mn (II),and Ni(II)] with constant stirring. The precipitate that was obtained was filtered washed and dried. The complexes that were formed were characterized by spectral studies (UV–Visible, IR& H NMR), magnetic and thermal studies The yield of metal complexes in these reactions was found to be in the range 60–80%.. [5,27,40].

The absence of vibrational bands at 3300 cm⁻¹ in metal complexes show that sulfonamide NH group was deprotonated during the complex formation. The vibrational band at 1620 cm⁻¹ may be assigned to isoxazolyl ring C–N stretching vibration of ligand and this remain un-shifted in the metal complexes. The un-shifted vibrational bands due to sulfonyl oxygen in case of Fe(III) suggest little bonding between sulfonyl oxygen and metal [5].

Sulfamethoxazole has been shown to form a complex with Ag (I) where co-ordination occurred through the Nitrogen atom of the sulfonamide group and also through the Nitrogen atom of the 5-membered N-heterocyclic ring[Fig.1]. The complex formed a dimeric structure. The complex was formed by the reaction of 5.0 mL aqueous solution containing 0.1015 g of SMX and 1.0 mL aqueous solution contacting 0.0476 g of KOH with 1.0 mL aqueous solution containing 0.0685 g of AgNO₃. The stirring was carried at room temperature. The white precipitate that was obtained was filtered, washed and dried. The yield of the synthesis was 90%.{{}}

Cobalt and Cadmium has also been shown to form complexes with sulfamethoxazole when 2 mmol of SMX was dissolved in hot water in the presence of basic media. Then this solution was mixed with 1 mmol solution of Cobalt acetate and cadmium acetate separately with constant stirring. The compound formed was filtered, washed with distilled water and dried at room temperature. The prepared complexes were characterized by IR spectral studies [9,21,41].

Sulfamethoxazole was treated with Au (III), Pd(II) and Pt(IV) in the presence of alcoholic media in order to prepare a series of new metal complexes. The complexes were characterized by FTIR, UV–Visible, elemental analysis, conductivity and magnetic measurements [8]. The mixture of metal salts (NaAuCl₄·2H₂O, CaCl2 and ZnCl₂) and sulfamethoxazole were heated at 60–70 °C and refluxed for 3 h with constant stirring. The precipitate obtained were filtered, washed with methanol and dried. {{}}{{}}

4.3 Urea compounds

The general structure of a phenylurea herbicides is (substituted) phenyl–NH–C(O)–NR₂. The phenyl ring is substituted e.g. with chlorine atom, methyl-, or 2-propyl groups. Most phenylurea herbicides are N-dimethyl derivatives, but combinations of a methyl substituent and another group (e.g O–CH₃) are also used.

The rate coefficient for the basic compound urea (Masuda et al., 1980) is very low 7.5×10⁵mol⁻¹dm³s⁻¹. The low value, obtained in gamma radiolysis, is due to the absence of C=C double bond. When an aromatic ring is attached to the carbamide part, the k_OH’s are above 1×10⁹mol⁻¹dm³s⁻¹. For phenylurea Canle Lopez et al. (2005) determined (2.02±0.08)×10¹⁰mol⁻¹dm³s⁻¹ in pulsed H₂O₂ photolysis. This k_OH is higher than k_diff. The k_OH published for 3,4-dichloroaniline by the same authors is also too high, 1.7×10¹⁰mol⁻¹dm³s⁻¹, much higher than the k_OH of aniline: 8.6×10⁹mol⁻¹dm³s⁻¹ (Qin et al., 1985).

We can say the same about the k_OH given by Canle Lopez et al. (2005) for fenuron (methyl groups on N-atom), (1.6±0.1)×10¹⁰mol⁻¹dm³s⁻¹. The recent value of Oturan et al. (2010) is 1.2×10¹⁰mol^–1dm³s^–1. Acero et al. (2002) and Dao and De Laat (2011) based on Fenton reaction and Mazellier et al. (2007) using the H₂O₂/UV technique published 7.4×10⁹mol⁻¹dm³s⁻¹, 7.0×10⁹mol⁻¹dm³s⁻¹ and (7±1)×10⁹mol⁻¹dm³s⁻¹, respectively. We recommend using the average of the last four values, 8.3×10⁹mol⁻¹dm³s⁻¹.

Monuron and diuron differ from fenuron by one or two chlorine atoms in position 4 or in 3 and 4 on the ring. For the k_OH of monuron Canle Lopez et al. (2005) published (3.1±0.4)×10⁹mol⁻¹dm³s⁻¹ in pulsed photolysis experiments, while Oturan et al. (2010) in electro-Fenton experiments obtained 7.3×10⁹mol^–1dm³s^–1. For diuron a large number of measurements are available, they are in the range of 2.9×10⁹mol^–1dm³s^–1 and 7.6×10⁹mol^–1dm³s^–1, with a centre at 6.0×10⁹mol⁻¹dm³s⁻¹ (De Laat et al., 1996; Gallard and De Laat, 2001 (relative to atrazine); Canle Lopez et al., 2005; Shemer et al., 2006; Benitez et al., 2007, 2009; Chen et al., 2008; Elovitz et al., 2008; Oturan et al., 2010).

Linuron is similar to diuron but one of the methyl groups on N atom is replaced by a methoxy group. The rate coefficient was determined by several groups using high variety of techniques, the k_OH’s are in a relatively narrow range between 2.74×10⁹mol^–1dm³s^–1 and 6.5×10⁹mol^–1dm³s^–1, with an average of 5.2×10⁹mol⁻¹dm³s⁻¹ (De Laat et al., 1996; Canle Lopez et al., 2005; Shemer et al., 2006; Benitez et al., 2007, 2009; Chen et al., 2008; Elovitz et al., 2008; Rao and Chu, 2009). For monolinuron, which has only one chlorine atom on the ring, Canle Lopez et al. (2005) published a k_OH of (2.6±0.1)×10⁹mol⁻¹dm³s⁻¹.

The published rate coefficients for isoproturon (in para position isopropyl group) are 5.2×10⁹mol^–1dm³s^–1 (H₂O₂/O₃, De Laat et al., 1996), (7.9±0.1)×10⁹mol^–1dm³s^–1 (H₂O₂/O₃, Benitez et al., 2007) and 5.7×10⁹mol^–1dm³s^–1 (Benitez et al., 2009). Gallard and De Laat (2001) determined a rate coefficient ratio: k_{OH,isoproturon}/k_OH,atrazine=2.55. Using the recommended absolute value for atrazine in Table 3 we obtain (6.1±0.5)×10⁹mol^–1dm³s^–1. Canle Lopez et al. (2005) found (1.3±0.7)×10¹⁰mol^–1dm³s^–1; because of the large uncertainty, this value is not in disagreement with the previously mentioned rate coefficients. We recommend using the average of all values: 7.6×10⁹mol^–1dm³s^–1.

Chlortoluron is similar to diuron, in this molecule in position 4 there is a methyl group. The published k_OH’s hardly differ from each-other (De Laat et al., 1996; Benitez et al., 2007, 2009; Kesraoui-Abdessalem et al., 2008), the average is 5.9×10⁹mol^–1dm³s^–1.

Shape memory thermoset polymers

Shape memory thermoset polymers can be directly 3D printed with different printing techniques [15,49–51]. For example, soybean oil epoxidized acrylate was laser printed for the fabrication of biomedical scaffolds [15]. The ink was developed using soybean oil epoxidized acrylate with bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide as a photopolymerizer. A table top stereolithography (STL) system, based on the existing Solidoodle^® 3D printer platform, was utilized to print the scaffolds [52]. The ink was cured by activating the laser and drawing lines at various print speeds.

An interesting technique, UV curing of jet sprayed materials, has been utilized to fabricate shape memory structures. The inks are commercially available from the 3D printing company Stratasys (Edina, MN, USA) [53–55]. By combining two model materials VeroWhite^® and Tangoblack^®, the so-called digital materials were created. Varying compositions of these two materials leads to different thermomechanical properties. By 3D printing hinges using various T_g digital materials, adaptive structures capable of self-expanding and self-shrinking were created [53]. When the structure is subjected to a uniform temperature, temporal sequencing of activation was achieved by the time-dependent behavior of each polymer, which was illustrated via a series of 3D printed structures that respond rapidly to a thermal stimulus and self-fold to specified shapes in a controlled shape-changing sequence (Fig. 5b) [53]. By integrating both material design and the shape memory digital materials, active structures were further developed [55]. Glassy shape memory polymer fibers were directly printed in an elastomeric matrix; after a programmed lamina and laminate architecture and a subsequent thermomechanical training process, the shape memory effect transformed a thin plate into complex three-dimensional configurations including bent, coiled, and twisted strips, folded shapes, and complex contoured shapes with non-uniform, spatially varying curvature [55]. By heating these structures, they recovered their original shape. By 3D printing shape memory polymers and hydrogels in prescribed 3D architectures, a new, reversible, shape-changing component design concept was realized [35]. The swelling of the hydrogel was used to drive the shape change while the temperature-dependent modulus of a shape memory polymer was used to regulate the time of such shape change. Via the controlled interplay between the active materials and the 3D printed architectures, specific shape changing scenarios were achieved (Fig. 5c).

In addition to STL and DLP based printing techniques, extruding techniques are also used to fabricate thermoset shape memory structures. UV cross-linking poly(lactic acid)-based inks were used to print shape memory structures by direct-write printing [50]. Poly lactic acid (PLA), benzophenone and dichloromethane were mixed to create the ink; benzophenone acts as the UV cross-linking agent. All of the fabricating processes proceeded in light resistant conditions at room temperature (25±2°C). A system consisting of a microdepositing robot was used to direct write the ink. During the printing process, the fast evaporation of dichloromethane was used to harden the 3D structures; shape memory behavior was enhanced by subsequent UV irradiation. Excellent shape memory behavior, which enables multi-dimensional and combinatorial configurations and transformations, was demonstrated. By adding iron oxide, the fabricated structures exhibited fast, remotely actuated, and magnetically guidable properties.

All of the previously described shape memory polymers are cross-linked thermosets which are insoluble and do not flow at high temperature, making them difficult to process [51]. In this regard, resin-based 3D printers (STL or DLP) are preferred for fabrication; liquid monomers or oligomers are placed in a resin bath and photopolymerization is performed layer by layer [15]. As a matter of fact, many thermoset polymers are obtained through a thermal curing process, but most of these types of thermosets are unprintable [56–64].

One solution to use currently unprintable thermoset polymers to construct 3D structures is using sacrificial materials. A mold structure can be 3D printed with sacrificial materials, such as poly lactic acid (PLA) and polyvinyl alcohol (PVA). The monomers for synthesizing the thermoset polymers can then be poured into the mold. After a curing process, the desired scaffolds can be obtained by removing the sacrificial mold material; the mold is leached and the crosslinked thermoset is left. For example, biomimetic gradient tissue scaffolds with highly biocompatible naturally derived smart polymers were fabricated [65]. A series of novel shape memory polymers with excellent biocompatibility and tunable shape changing effects were synthesized and cured in the presence of 3D printed sacrificial PLA molds, which were subsequently dissolved to create controllable, graded porosity within the scaffold. The smart polymers display finely tunable recovery speed and exhibit greater than 92% shape fixing at −18°C or 0°C and full shape recovery at physiological temperature. A graded microporous structure was fabricated, which mimics the non-uniform distribution of porosity found within natural tissues. The finely controlled structure illustrates the feasibility of this strategy for precisely fabricating complex structures. Another advantage of this approach is that this mold-guided technique provides different pore morphologies, facilitating physiologically appropriate, biomimtetic conditions [65].