Photosensitizer Using Visible Light: An Undergraduate Laboratory Experiment Utilizing an Affordable Photocatalytic Reactor

In this experiment, the visible light reactive photosensitizer (PS) derived from chlorophyllin sodium copper salt has been synthesized via a simple synthetic route. The enhanced photocatalytic activity for the decomposition of the pharmaceutical compound Diclofenac Potassium available as Voltfast sachets under visible light irradiation was demonstrated by comparing the photocatalytic decomposition of Diclofenac Potassium in the presence and absence of the new synthesized visible light photosensitizer under the same photocatalytic conditions. Based on the experimental results, higher activity was achieved for the sample composed of the new synthesized visible light photosensitizer. The photosensitized sample using the new derivative of chlorophyllin sodium copper salt exhibited approximately 21 times higher rate when compared with that of Chlorophyllin sodium copper salt sample. This photocatalytic activity can be attributed to the enhanced visible light harvesting of the new derivative of Chlorophyllin sodium copper salt. &nbsp

Synthesis, Structures, and Ethylene Oligomerization Activity of Bis(phosphanylamine)pyridine Chromium/Aluminate Complexes

A trivalent chromium complex of a PN­(pyridine) ligand system, {[(2,6-Ph₂P-NH)₂C₅H₃N]­CrCl₃}­(THF)₂ (<b>1</b>), was prepared and tested as a catalyst for ethylene oligomerization and polymerization, with the purpose of probing the ability of a pyridine ring substituent as a stabilizing factor on catalytically active intermediates. Its nonselective catalytic behavior indicated that ready reduction of the metal center to the divalent state occurred during the activation process. To substantiate this point, we have reacted <b>1</b> with a few common aluminate activators and isolated both the divalent complexes {[2,6-Ph₂PNHC₅H₃NAlClEt₂NPPh₂]­Cr­(μ-Cl)₂AlEt₂}­(toluene) (<b>3</b>) and {[2,6-Ph₂PNHC₅H₃NAlCl-<i>i</i>-Bu₂NPPh₂]­Cr­(μ-Cl)₂Al-<i>i</i>-Bu₂}₂ (toluene) (<b>4</b>) and the trivalent complexes {[2,6-Ph₂PNHC₅H₃NAlClMe₂NPPh₂]­CrMe­(μ-Cl)₂AlMe₂}­(toluene)_1.5 (<b>2</b>) and {[2,6-Ph₂PNHC₅H₃ NHNPPh₂]­CrEt­(μ-Cl)₂AlEt₂}­AlEtCl₃(hexane)_0.5 (<b>5</b>). The reaction of the ligand with the divalent chromium precursor CrCl₂(THF)₂ in the presence of alkylaluminum afforded {[2,6-Ph₂PNHC₅H₃NCl₂EtAlNPPh₂]­Cr­(μ-Cl)₂AlEt₂}₂(toluene) (<b>6</b>) containing aluminate residues, where the metal has preserved the initial divalent state. All of these species showed moderate to high activities toward ethylene oligomerization

Polymer-Free Ethylene Oligomerization Using a Pyridine-Based Pincer PNP-Type of Ligand

Di- and trivalent chromium complexes of the pyridine-based ligand [2,6-(Ph₂PCH₂)₂ C₅H₃N]­CrCl₃ (<b>1</b>) and {[2,6-(Ph₂CH₂)₂C₅H₃N]­CrCl₂}.(THF) (<b>2</b>) and their aluminate aggregates [2,6-(Ph₂CH₂)₂C₅H₃NCrCl­(μ-Cl)­AlClMe₂] (<b>3</b>), {[(2,6-(Ph₂CH₂)₂C₅H₃NCrCl­(μ-Cl)­AlClEt₂]}. (toluene)_0.5 (<b>4</b>), {2,6-(Ph₂CH₂)₂C₅H₃NCrEt­(μ-Cl)₂AlEt₂}­{AlCl₃Et} (<b>5</b>), {2,6-(PPh₂CH₂) C₅H₃N (PPh₂CH)­Al­(<i>i</i>-Bu)₂(μ-Cl)­Cr­(μ-Cl)₂Al­(<i>i</i>-Bu)₂}.(toluene)_1.5 (<b>6</b>), and {[2,6-(PPh₂CH₂)₂C₅H₃ N]₂Cr} {(μ-Cl)­[Al­(<i>i</i>-Bu)₃]₂} (<b>7</b>) were prepared, isolated, and their activities toward ethylene oligomerization tested. While complexes <b>3</b>, <b>5</b>, and <b>6</b> were directly accessible by reacting catalyst precursor <b>1</b> with Me₃Al, DEAC, and TIBA, respectively, complexes <b>4</b> and <b>7</b> were prepared using catalyst precursor <b>2</b> with DEAC and TIBA, respectively. All these complexes, with the exception of <b>7</b>, showed good activities for a polymer-free ethylene oligomerization. Complex <b>7</b> contains cationic chromium in its monovalent state and its encapsulation in an octahedral ligand field as defined by two ligands is probably responsible for its failure as a catalyst

Reactivity with Alkylaluminum of a Chromium Complex of a Pyridine-Containing PNP Ligand: Redox N–P Bond Cleavage

The ligand 2,6-[(Ph₂)₂PN]₂C₅H₃N based on the popular PNP motif has been used to generate the corresponding chromium adduct {2,6-[(Ph₂)₂PN]₂C₅H₃N}­CrCl₃·2.5THF (<b>1</b>). Its reaction with Et₂AlCl and Cl₂AlEt afforded the two nearly isostructural complexes {2,6-(Ph₂PNH)­[(Et₂ClAl)­NPPh₂]­C₅H₃N}­CrCl­(PEtPh₂)·0.5­(toluene) (<b>2</b>) and {2,6-(Ph₂PNH)­[(EtCl₂Al)­NPPh₂]­C₅H₃N}­CrCl­(PEtPh₂)·0.5­(toluene) (<b>3</b>). The formation of these two species is the result of a multiple attack of the activator at both the ligand system and the metal center. During the reaction, the two nitrogen atoms lost one phosphine residue each, the metal was reduced, one of the two nitrogens was protonated, and one EtPPh₂ molecule was formed and retained by the metal center. The three complexes characterized in this work display activity for catalytic and nonselective ethylene oligomerization

Reactivity with Alkylaluminum of a Chromium Complex of a Pyridine-Containing PNP Ligand: Redox N–P Bond Cleavage

The ligand 2,6-[(Ph₂)₂PN]₂C₅H₃N based on the popular PNP motif has been used to generate the corresponding chromium adduct {2,6-[(Ph₂)₂PN]₂C₅H₃N}­CrCl₃·2.5THF (<b>1</b>). Its reaction with Et₂AlCl and Cl₂AlEt afforded the two nearly isostructural complexes {2,6-(Ph₂PNH)­[(Et₂ClAl)­NPPh₂]­C₅H₃N}­CrCl­(PEtPh₂)·0.5­(toluene) (<b>2</b>) and {2,6-(Ph₂PNH)­[(EtCl₂Al)­NPPh₂]­C₅H₃N}­CrCl­(PEtPh₂)·0.5­(toluene) (<b>3</b>). The formation of these two species is the result of a multiple attack of the activator at both the ligand system and the metal center. During the reaction, the two nitrogen atoms lost one phosphine residue each, the metal was reduced, one of the two nitrogens was protonated, and one EtPPh₂ molecule was formed and retained by the metal center. The three complexes characterized in this work display activity for catalytic and nonselective ethylene oligomerization

Radical chemistry of alkyl aluminum with quinoxaline ligands

<p>The behavior of organo-aluminum species with 2,3-bis(2-pyridyl) quinoxaline (DPQ), a well-known polyazine capable of performing interesting radical transformations, was examined in the presence and absence of chromium. In spite of proving the presence of chromium as essential for reactivity, only organic radicals, coupled to aluminum-containing residues, have been isolated and characterized. The electronic structure of the organic radicals has been elucidated by a combination of crystallographic, DFT calculations and EPR studies. Experimental and computational work has highlighted the co-existence of both singlet and triplet forms in one di-radical complex.</p

Challenges and Recent Advances in Enzyme-Mediated Wastewater Remediation—A Review

Different classes of artificial pollutants, collectively called emerging pollutants, are detected in various water bodies, including lakes, rivers, and seas. Multiple studies have shown the devastating effects these emerging pollutants can have on human and aquatic life. The main reason for these emerging pollutants in the aquatic environment is their incomplete removal in the existing wastewater treatment plants (WWTPs). Several additional treatments that could potentially supplement existing WWTPs to eliminate these pollutants include a range of physicochemical and biological methods. The use of enzymes, specifically, oxidoreductases, are increasingly being studied for their ability to degrade different classes of organic compounds. These enzymes have been immobilized on different supports to promote their adoption as a cost-effective and recyclable remediation approach. Unfortunately, some of these techniques have shown a negative effect on the enzyme, including denaturation and loss of catalytic activity. This review focuses on the major challenges facing researchers working on the immobilization of peroxidases and the recent progress that has been made in this area. It focuses on four major areas: (1) stability of enzymes upon immobilization, enzyme engineering, and evolution; (2) recyclability and reusability, including immobilization on membranes and solid supports; (3) cost associated with enzyme-based remediation; and (4) scaling-up and bioreactors

Combined effect of tungsten inert gas welding and roller expansion processes on mechanical and metallurgical characteristics of heat exchanger tube-to-tubesheet joints

Tube-to-tubesheet joints are one of the major vulnerable locations prone to cracks in heat exchangers. The manufacturing processes of these joints have an important role in providing structural integrity to the heat exchangers. The main objective of this work is to study the impact of the combined effect of tungsten inert gas weld and expansion percentages of 3%, 5% and 7% on the structural integrity of carbon steel-based tube-to-tubesheet joints. The results show that the pull-out strength of hybrid welded and expanded using 3%, 5% and 7% expansion percentages has exceeded the tube axial strength. The minimum leak path of the welds was satisfactorily above two-thirds of the tube wall thickness. Vickers hardness was restricted at the adjacent regions of weld to below 250 HV. The microstructural studies indicate that the higher the expansion percentage, the smaller the grains at the inner tube surface and the higher the extent the fine grains formed from the inner tube surface. The effect of expansion on the grains at the inner and outer tube surfaces of the transition zone and the unexpanded zone was found negligible. The absence of grain refinement on the outer tube surface using light expansion at a 3% expansion percentage indicated that the contact pressure was inadequate on the tube-to-tubesheet interface. The hardness at the expanded zone and transition zone of the inner tube surface was higher than at the outer tube surface due to the plastic deformation caused by the intensive roller expansion pressure

Bismuth-Based Metal–Organic Framework as a Chemiresistive Sensor for Acetone Gas Detection

Analyzing acetone in the exhaled breath as a biomarker has proved to be a non-invasive method to detect diabetes in humans with good accuracy. In this work, a Bi-gallate MOF doped into a chitosan (CS) matrix containing an ionic liquid (IL) was fabricated to detect acetone gas with a low detection limit of 10 ppm at an operating temperature of 60 °C and 5 V operating bias. The sensor recorded the highest response to acetone in comparison to other test gases, proving its high selectivity along with long-term stability and repeatability. The sensor also exhibited ultra-fast response and recovery times of 15 ± 0.25 s and 3 ± 0.1 s, respectively. Moreover, the sensor membrane also exhibited flexibility and ease of fabrication, making it ideal to be employed as a real-time breath analyzer