Visible Absorption Maxima Research Articles

Chlorophyll Pigments and Their Synthetic Analogs.

Oxygenic phototrophs use chlorophylls (Chls) as photosynthetically active pigments. A variety of Chl molecules have been found in photosynthetic eukaryotes including green plants, algae, and cyanobacteria. Here we review their molecular structures with stereochemistry, occurrence in light-harvesting antennas and reaction centers, biosyntheses in the late stage, chemical stabilities, and visible absorption maxima in diethyl ether. The observed maxima are comparable to those of semisynthetic Chl analogs, methyl pyropheophorbides, in dichloromethane. The effects of their peripheral substituents and core π-conjugation on the maxima of the monomeric states are discussed. Notably, the oxidation along the molecular x-axis in Chl-a produces its accessory pigments, Chls-b/c, and introduction of an electron-withdrawing formyl group along the y-axis perpendicular to the x-axis affords far-red light absorbing Chls-d/f.

Extraction and characterization of anthocyanin pigments from Iris flowers and metal complex formation

Exploring the chemical processes and factors influencing the stability of the blue color derived from anthocyanins is a crucial objective in agricultural and food chemistry research. The ability of these compounds to bind with metals could potentially stabilize anthocyanins extracted from plant-based foods or enable modifying their hues for application as natural food colorants. This study had two core objectives - first, to extract and identify the major anthocyanin pigments responsible for iris flower coloration. Second, to selectively complex purified iris anthocyanins with aluminum (Al3+) and copper (Cu2+) ions, probing the coordination chemistry underlying synthetic metalloanthocyanin formation. Fresh iris flowers were collected and anthocyanins extracted using an optimized acidic solution. After separation, anthocyanins were complexed with metals Al3+ and Cu2+ at pH 5–6 to understand better the evolution of blue and green colors in anthocyanin-metal chelates. Characterization of anthocyanins and their metal complexes utilized UV–visible spectrometry, colorimetry (L\\* a\\*b\\* values), FTIR spectroscopy, and LC-MS. Metal complexation of anthocyanins exhibited bathochromic shifts of visible absorption maxima from 538 to 584 nm for Al-complex and 538–700 nm for Cu-complex. Color changes were accompanied by decreased lightness (L\\*, from 87 to 81) and color coefficients a\\* (+5.4 to −6.8) and b\\* (−12.2 to −4.8). LC-MS analysis identified five major anthocyanin aglycones: cyanidin (Cyd, m/z 289), delphinidin (Dpd, m/z 305), petunidin (Ptd, m/z 229), malvidin (Mv, m/z 329) and pelargonidin (m/z 273), along with various glycosylated derivatives. This work successfully isolated key iris anthocyanin pigments and elucidated their metal chelation interactions underlying expanded floral color production, bridging knowledge gaps about this underexplored genus.

Excited Charge Separation in a π-Interacting Phenothiazine-Zinc Porphyrin-Fullerene Donor-Acceptor Conjugate.

We have designed, synthesized, and characterized a donor-acceptor triad, SPS-PPY-C60, that consists of a π-interacting phenothiazine-linked porphyrin as a donor and sensitizer and fullerene as an acceptor to seek charge separation upon photoexcitation. The optical absorption spectrum revealed red-shifted Soret and Q-bands of porphyrin due to charge transfer-type interactions involving the two ethynyl bridges carrying electron-rich and electron-poor substituents. The redox properties suggested that the phenothiazine-porphyrin part of the molecule is easier to oxidize and the fullerene part is easier to reduce. DFT calculations supported the redox properties wherein the electron density of the highest molecular orbital (HOMO) was distributed over the donor phenothiazine-porphyrin entity while the lowest unoccupied molecular orbital (LUMO) was distributed over the fullerene acceptor. TD-DFT studies suggested the involvement of both the S2 and S1 states in the charge transfer process. The steady-state emission spectrum, when excited either at porphyrin Soret or visible band absorption maxima, revealed quenched emission both in nonpolar and polar solvents, suggesting the occurrence of excited state events. Finally, femtosecond transient absorption spectral studies were performed to witness the charge separation by utilizing solvents of different polarities. The transient data was further analyzed by GloTarAn by fitting the data with appropriate models to describe photochemical events. From this, the average lifetime of the charge-separated state calculated was found to be 169 ps in benzonitrile, 319 ps in dichlorobenzene, 1.7 ns in toluene for Soret band excitation, and ∼320 ps for Q-band excitation in benzonitrile.

Exploring the effects of saccharides on the solvation behaviour of L-Citrulline in aqueous medium: Volumetric, transition state theory, transfer parameters and spectroscopic approach

This study examines the volumetric, viscometric and UV–vis characteristics of L-Citrulline in water and aqueous saccharides at atmospheric pressure across the whole concentration range and the absorber operating temperature range of 293.15 K -313.15 K. Density, partial molar volume, apparent molar isobaric expansion, Hepler's constant and hydration number were among the examined volumetric parameters, and viscosity coefficients, viscosity deviation and free energy for viscous flow activation were among the examined viscometric parameters. Stronger interactions between L-Citrulline and L-Arabinose were indicated by the increase in the transfer characteristics in the following order: L-Arabinose > D-xylose. A comparison of the taste behaviours of L-Citrulline in water and in an aqueous solution of saccharides has also been attempted. L-Citrulline interacts with all solvents in a significant way, as evidenced by the UV–visible spectra suggested by the shift in UV–visible absorption maxima that correspond with a rise in L-Citrulline content in the solvent systems chosen.

Effect of perfluorination at the 3-ethyl group in chlorophyll-a derivatives on physical properties in solution

Methyl 3-perfluoroethyl-pyropheophorbide-a exhibited a redmost visible (Qy) absorption maximum in solution at a longer wavelength than that of the non-fluorinated counterpart, while the former Qy band was sharper and more intense than the latter. In addition, the other visible bands of the fluorinated compound were red-shifted from those of the non-fluorinated. The perfluoroethylated molecule was more fluorescent at a longer wavelength with a longer lifetime, comparing with the ethylated analog. Similar results as in the above free bases were obtained for the corresponding nickel, copper, and zinc complexes. Additionally, the nickel and copper complexes exhibited similar absorption behaviors. This observation was due to the electron-withdrawing perfluoroethyl group bonding directly to the core chlorin π-system.

Green multifunctional palladium nanoparticles from polysaccharide cordia myxa (CMY) gum: Synthesis, characterization, and antibacterial activity

BackgroundGreen synthesis has emerged as an environmentally friendly and highly effective method that has gained widespread application across various domains and biomedical research, particularly in healthcare. ObjectivesThe primary aim behind synthesizing CMY-PdNPs was to harness the potential of Cordia myxa gum to create multi-functional palladium nanoparticles, which could effectively prevent antimicrobial activity. MethodsIn this study, CMY-PdNPs were synthesized using Cordia myxa gum, a natural polysaccharide known for its non-toxic and environmentally friendly properties, marking the first reported instance of such green synthesis. Remarkably, this synthesis method demonstrated effectiveness in reaction time and nanoparticle stability, achieved without requiring external stabilizers or reducing agents. Green synthesized CMY-PdNPs characterization by different techniques, UV-Vis, FT-IR, FESEM, XRD, TEM, and XPS. ResultsThe synthesized CMY-PdNPs showed UV–Vis absorption maximum at around 278 nm. The crystalline nature of CMY-PdNPs was suggested by XRD patterns at (111), (200 (220), and (311) lattice planes, with a face-centered cubic structure depicting the formation of PdNPs. The chemical composition and product purity of green-produced CMY-PdNPs were determined by XPS analysis. As indicated by TEM micrographs, the uniform and spherical-shaped NPs with an average mean diameter of 15 nm were observed. The study investigated the antibacterial properties of PdNPs against Gram-positive and Gram-negative bacterial strains using the disc diffusion method to assess the zone of inhibition against various pathogenic microorganisms. ConclusionThis work demonstrates that eco-friendly technology can rival conventional physical/chemical methods for PdNP synthesis. Biogenic CMY-PdNPs show exceptional antimicrobial effectiveness and hold promise for biomedical applications, contributing significantly to medical research potential.

Alternative boronic acids in the detection of Mycolactone A/B using the thin layer chromatography (f-TLC) method for diagnosis of Buruli ulcer

BackgroundMycobacterium ulcerans is the causative agent of Buruli ulcer. The pathology of M. ulcerans disease has been attributed to the secretion of a potent macrolide cytotoxin known as mycolactone which plays an important role in the virulence of the disease. Mycolactone is a biomarker for the diagnosis of BU that can be detected using the fluorescent-thin layer chromatography (f-TLC) technique. The technique relies on the chemical derivatization of mycolactone A/B with 2-naphthylboronic acid (BA) which acts as a fluorogenic chemosensor. However, background interferences due to co-extracted human tissue lipids, especially with clinical samples coupled with the subjectivity of the method call for an investigation to find an alternative to BA.MethodsTwenty-six commercially available arylboronic acids were initially screened as alternatives to BA using the f-TLC experiment. UV–vis measurements were also conducted to determine the absorption maximum spectra of mycolactone A/B and myco-boronic acid adducts followed by an investigation of the fluorescence-enhancing ability of the boronate ester formation between mycolactone A/B and our three most promising boronic acids (BA15, BA18, and BA21). LC–MS technique was employed to confirm the adduct formation between mycolactone and boronic acids. Furthermore, a comparative study was conducted between BA18 and BA using 6 Polymerase Chain Reaction (PCR) confirmed BU patient samples.ResultsThree of the boronic acids (BA15, BA18, and BA21) produced fluorescent band intensities superior to BA. Complexation studies conducted on thin layer chromatography (TLC) using 0.1 M solution of the three boronic acids and various volumes of 10 ng/µL of synthetic mycolactone ranging from 1 µL – 9 µL corresponding to 10 ng – 90 ng gave similar results with myco-BA18 adduct emerging with the most visibly intense fluorescence bands. UV–vis absorption maxima (λmax) for the free mycolactone A/B was observed at 362 nm, and the values for the adducts myco-BA15, myco-BA18, and myco-BA21 were at 272 nm, 270 nm, and 286 nm respectively. The comparable experimental λmax of 362 nm for mycolactone A/B to the calculated Woodward-Fieser value of 367 nm for the fatty acid side chain of mycolactone A/B demonstrate that even though 2 cyclic boronates were formed, only the boronate of the southern side chain with the chromophore was excited by irradiation at 365 nm. Fluorescence experiments have demonstrated that coupling BA18 to mycolactone A/B along the 1,3-diols remarkably enhanced the fluorescence intensity at 537 nm. High-Resolution Mass Spectrometer (HR-MS) was used to confirm the formation of the myco-BA15 adduct. Finally, f-TLC analysis of patient samples with BA18 gave improved BA18-adduct intensities compared to the original BA-adduct.ConclusionTwenty-six commercially available boronic acids were investigated as alternatives to BA, used in the f-TLC analysis for the diagnosis of BU. Three (3) of them BA15, BA18, and BA21 gave superior fluorescence band intensity profiles. They gave profiles that were easier to interpret after the myco-boronic acid adduct formation and in experiments with clinical samples from patients with BA18 the best. BA18, therefore, has been identified as a potential alternative to BA and could provide a solution to the challenge of background interference of co-extracted human tissue lipids from clinical samples currently associated with the use of BA.

N'-(3,4-dimethoxybenzylidene)-4-methylbenzenesulfonohydrazide derivatives: Synthesis, quantum chemical method, in silico ADMET, molecular docking and molecular dynamic simulations

A new N'-(3,4-dimethoxybenzylidene)-4-methylbenzenesulfonohydrazide derivatives were prepared from a condensation reaction between 4-methylbenzenesulfonohydrazide and 3,4-dimethoxybenzaldehyde. The structure of DMSH was elucidated using various spectral techniques including FT-IR, 1HNMR and 13CNMR. The structure of DMSH bond parameters also confirmed by single crystal XRD analysis of related derivatives and optimized bond parameters are calculated by density functional theory (DFT) method at B3LYP/6–311 G (d, p) level of theory. The optimized geometrical parameters obtained by DFT calculation are in good agreement with single crystal XRD data. The experimentally observed FT-IR bands were assigned to different normal modes of the molecule. The results show a good agreement with each other when these computed bond parameters are compared to XRD values of related compounds. The stability, chemical reactivity and charge transfer within the molecule was explained by frontier molecular orbital calculations. Atomic charges on the various atoms of DMSH obtained by Mulliken population analysis. Potential reactive sites of the DMSH compound have been identified by MEP which is mapped to the electron density surfaces. The reported molecule is used as a potential NLO material since it has a high μβ0 value. The theoretical UV–vis spectrum of the compound is used to study the visible absorption maxima (λ max). The molecular docking mechanism between DMSH ligand and COVID-19/6WCF and COVID-19/6Y84 receptors were studied to investigate the binding modes of this compound at the active sites. Molecular docking outcomes have shown that the DMSH molecule can be considered as a potential agent against COVID-19/6WCF-6Y84 receptors. In addition, the theoretical parameters of the bioactive molecules were calculated to establish their drug-likeness qualities and ADME/T analysis was carried out to examine the drug properties of the synthesized compound. Molecular dynamics simulation was performed for COVID-19 main protease (Mpro: 6WCF/6Y84) to understand the elements governing the inhibitory effect and the stability of interaction under dynamic conditions. The resultant complex structures were subjected to 100 ns simulation run to estimate their binding stabilities using GROMACS. The molecular dynamics simulation studies provided essential evidence that the systems were stable during the progression of 100 ns simulation run.

Green synthesis of zinc oxide nanoparticles using Cocos nucifera leaf extract: characterization, antimicrobial, antioxidant and photocatalytic activity.

Zinc oxide nanoparticles (ZnO NPs) have been successfully prepared using Cocos nucifera leaf extract and their antimicrobial, antioxidant and photocatalytic activity investigated. The structural, compositional and morphological properties of the NPs were recorded and studied systematically to confirm the synthesis. The aqueous suspension of NPs showed an ultraviolet-visible (UV-Vis) absorption maxima of 370 nm, indicating primarily its formation. X-ray diffraction analysis identified the NPs with a hexagonal wurtzite structure and an average particle size of 16.6 nm. Fourier transform infrared analysis identified some biomolecules and functional groups in the leaf extract as responsible for the encapsulation and stabilization of ZnO NPs. Energy-dispersive X-ray analysis showed the desired elemental compositions in the material. A flower-shaped morphology of ZnO NPs was observed by scanning electron microscopy, with a grain size of around 15 nm. The optical properties of the NPs were studied by UV-Vis spectroscopy, and the band gap was calculated as 3.37 eV. The prepared ZnO NPs have demonstrated antimicrobial activity against T. harzianum and S. aureus, with a zone of inhibition of 14 and 10 mm, respectively. The photocatalytic behaviour of ZnO NPs showed absorbance degradation at around 640 nm and it discoloured methylene blue dye after 1 h, with a degradation maximum of 84.29%. Thus, the prepared ZnO NPs could potentially be used in antibiotic development and pharmaceutical industries, and as photocatalysts.

Lanthanum doped corannulenes with enhanced static and dynamic nonlinear optical properties: A first principle study

In this work, lanthanum doping on corannulene (C20H10) buckybowls has been explored for their geometrical, electronic and nonlinear optical (NLO) properties via DFT simulations. The interaction energies of −21.75 to −40.01 kcal/mol reflect that A-D complexes are thermodynamically stable. The HOMO-LUMO energy gaps of designed complexes are decreased significantly up to 48.92%. A maximum charge transfer of 1.452 |e| is observed for complex A as revealed by natural bond orbital analysis. Non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses have confirmed the presence of various interactions in the complexes. The complexes are transparent in UV–Visible region and absorption maxima fall near infrared region (1123–2032 nm). The highest nonlinear optical response in terms of first hyperpolarizability value of 5.08 × 104 au is observed for complex C. The hyper-Rayleigh scattering (βHRS) and frequency dependent hyperpolarizability coefficients including electro-optical Pockel's effect and second harmonic generation are also computed theoretically.

Anticancer therapeutic potential of 5-fluorouracil and nisin co-loaded chitosan coated silver nanoparticles against murine skin cancer

Cancer is a major health concern worldwide as conventional treatment modalities face several limitations such as drug resistance, toxicity etc. To overcome such deficits, combination therapy involving anticancer peptides and chemodrugs is being considered as an attractive strategy. Therefore, present study developed, characterized and evaluated the anticancer potential of a single nanoconstruct comprising of oligomeric chitosan coated silver nanoparticles co-loaded with nisin and 5-florouracil (5-FU/nisin-CHI-AgNPs) against DMBA/TPA-induced murine skin cancer. It was fabricated using wet reduction method of silver salt to form silver nanoparticles followed sequentially by oligomeric chitosan coating, nisin conjugation to deacetylated units of chitosan oligomers (EDC/NHS chemistry) and physical loading of 5-FU. Biophysical characterisation studies revealed that the developed nanoconstruct had UV–visible absorption maxima at 420 nm, zeta potential of + 32.90 mV and 72.39 nm particle size (TEM analysis). In vivo anticancer therapeutic potential was assessed in terms of tumor statistics, histopathological, scanning electron microscopic analyses and testing oxidant/antioxidant status which exhibited marked reduction both in mean tumor volume (68.34 %) and mean tumor burden (82.39 %); restored skin histoarchitecture and improved oxidant/antioxidant status. Interestingly, anticancer therapeutic potential of nisin and 5-florouracil was found to be enhanced in vivo when bound on single composite nanoconstruct. The study forms a basis for developing synergetic single platforms against variety of cancers.

Investigations on spectroscopic characterizations, molecular docking, NBO, drug-Likeness, and ADME properties of 4H-1,2,4-triazol-4-amine by combined computational approach

In this study, the spectroscopic characterization, frontier molecular orbital analysis, and natural bond orbital analysis (NBO) analysis were executed to determine the movement of electrons within the molecule and the stability, and charge delocalization of the 4H-1,2,4-triazol-4-amine (4-AHT) through density functional theory (DFT) approach and B3LYP/6-311++G(d,p) level of theory. Surface plots of the hybrids’ Molecular Electrostatic Potential (MEP) revealed probable electrophilic and nucleophilic attacking sites. The discussed ligand were observed to be characterized by various spectral studies (FT-IR, UV-Vis). The calculated IR was found to be correlated with experimental values. The UV-Vis data of the molecule was used to analyze the visible absorption maximum (λmax) using the time-dependent DFT method. Since the principle of drug-likeness is usually used in combinatorial chemistry to minimize depletion in pharmacological investigations and growth, drug-likeness and ADME properties were calculated in this research to establish 4-AHT molecule bioavailability. Furthermore, molecular docking studies were carried out. Molecular docking analysis was performed for the title ligand inside the active site of the Epidermal Growth Factor Receptor (EGFR). The title compound’s anti-tumor activity against the cancer cell, in which EGFR is strongly expressed, prompted us to conduct molecular docking into the ATP binding site of EGFR to predict whether this molecule has an analogous binding mode to the EGFR inhibitors (PDB: ID: 1M17).

Towards synthetic unimolecular [Fe2S2]-photocatalysts sensitized by perylene dyes

A new set of perylene-based [Fe2S2(CO)6] photocatalyst dyads was synthesized and characterized. Four different strategies were employed to facilitate photoinduced electron transfer from the chromophore to the catalytically active site, increasing the chance for successful photocatalytic proton reduction. X-ray photoelectron spectroscopy measurements demonstrated the covalent attachment of the catalyst and provided insights on oxidation states of the iron. Visible light absorption maxima of the presented complexes reached up to 550 nm with reduction potentials between −1.14 V and −1.20 V because of increased electron density of the photoactive moiety. Quantum chemical calculations were performed to evaluate the employed design strategies based on the energy levels of the frontier orbitals and allowed to elucidate the electronic states involved in the initial photoactivation as well as to assess the charge transfer phenomena within the Franck-Condon point.

Waste fruit peel – Mediated green synthesis of biocompatible gold nanoparticles

Gold nanoparticles (AuNPs) have many applications in biomedical science due to their small size, large surface area, inertness, stability, high dispersity, and biocompatibility. However, the preparation of biocompatible and non-toxic AuNPs is very important issue. Biological synthesis of AuNPs presents to be simple, cost-effective, and non-toxic, which is unlike the chemically synthesized AuNPs. The aim of this study was to synthesize biocompatible AuNPs using waste fruit peel. We developed green method for AuNP synthesis by reducing gold (III) chloride trihydrate (HAuCl 4 ) with an aqueous fruit peel extract of Ananas comosus (pineapple) and Passiflora edulis (passion fruit). Such fruit peels are usually considered a waste material but contain many chemical components including proteins, minerals, lipids, vitamin, phenolic compounds, flavonoids and carotenoid, which act as reductants and nanoparticle stabilizers. Gold nanoparticles obtained using pineapple peel (Pi-AuNPs) and passion fruit peel extracts (Pa-AuNPs) exhibit a characteristic red coloration and UV–visible spectral absorption maximum around 545 nm attributable to surface plasmon resonance. TEM imaging confirmed that the AuNPs were spherical, with XRD patterns indicating that the gold atoms adopt a face-centered cubic structure. Cell viability assays in normal African green monkey kidney epithelial cells (Vero) and breast cancer cells (MCF-7) imply that the synthesized AuNPs have no biological cytotoxicity, even at high concentration (400 μg/mL). This study thus highlights the potential benefit of employing fruit peel extracts as reducing and stabilizing agents for the synthesis of non-cytotoxic AuNPs, with the greenness of the production process being particularly important for their utility in biomedical applications.

Theoretical investigation on tautomerism and NLO properties of salicylideneaniline derivatives

In this work, a comprehensive investigation of the salicylideneaniline derivatives is carried out using density functional theory to determine their linear and nonlinear optical (NLO) properties. Geometry optimizations, for gas and solvent phases, of the tautomers (enol and keto forms) are calculated using B3LYP levels with 6-31G(d,p) basis set. An intramolecular proton transfer, for 1SA-E and 2SA-E, is performed by a PES scan process at the B3LYP/6-31G(d,p) level. The optical properties are determined and show that they have extremely high NLO properties. In addition, the RDG analysis, molecular electrostatic potential (MEP), and gap energy are calculated. The low energy gap value indicates the possibility of intramolecular charge transfer. The frontier molecular orbital calculations clearly show the inverse relationship of HOMO–LUMO gap with the first-order hyperpolarizability (β = 59.6471 × 10–30 esu), confirming that the salicylideneaniline derivatives can be used as attractive future NLO materials. Therefore, the reactive sites are predicted using MEP and the visible absorption maxima are analyzed using a theoretical UV–Vis spectrum. Natural bond orbitals are used to investigate the stability, charge delocalization, and intramolecular hydrogen bond.

Influence of the Protonation State on the Excited-State Dynamics of Ruthenium(II) Complexes with Imidazole π-Extended Dipyridophenazine Ligands.

Ruthenium(II) complexes, like [(tbbpy)2Ru(dppz)]2+ (Ru-dppz; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, dppz = dipyrido-[3,2-a:2',3'-c]phenazine), have emerged as suitable photosensitizers in photoredox catalysis. Since then, there has been ongoing interest in the design of π-extended Ru-dppz systems with red-shifted visible absorption maxima and sufficiently long-lived excited states independent of the solvent or pH value. Herein, we explore the photophysical properties of protonation isomers of the linearly π-extended [(tbbpy)2Ru(L)]2+-type complexes bearing a dppz ligand with directly fused imidazole (im) and methyl-imidazole units (mim) as L. Steady-state UV-vis absorption, resonance Raman, as well as time-resolved emission and transient absorption spectroscopy reveal that Ru-im and Ru-mim show desirable properties for the application in photocatalytic processes, i.e., strong visible absorbance and two long-lived excited states in the 3ILCT and 3MLCT manifold, at pH values between 3 and 12. However, protonation of the (methyl-)imidazole unit at pH ≤ 2 unit causes decreased excited-state lifetimes and an emission switch-off.

Magneto-optical properties of borophosphate glasses co-doped with [formula omitted] and [formula omitted]ions

Glasses from lithium-aluminum-zinc-boron-phosphorous oxide system co-doped with terbium (Tb3+) and dysprosium (Dy3+) oxides were studied for magneto-optical applications in lasers. The Fourier Transform Infrared and Raman Spectroscopy complementary analysis suggested the depolymerization of the boro-phosphate glass network by adding and increasing the rare-earth (RE) oxide content. Main UV–vis absorption maxima of Tb and Dy ions were identified at 348 and 1266 nm. Spectroscopic ellipsometry indicated a maximum refractive index of 1.56, at 400 nm, for the highest RE content. The Verdet constant amplified by increasing the RE content, reaching for the 9 mol% RE co-doped sample a value of -0.075 min/Oe/cm at 630 nm. The Faraday rotation angle was additionally confirmed by using a Faraday Cell Device, being also related to the specific paramagnetic behavior evidenced by Superconducting Quantum Interference Device magnetometry. The magneto-optical properties recommend such vitreous co-doped materials for magneto-optical devices.

3D printed reactor-in-a-centrifuge (RIAC): Making flow-synthesis of nanoparticles pump-free and cost-effective

It is widely recognised that flow-reactors offer greater control over the stoichiometry of chemical reactions when compared to batch methods, since they provide finer and more predictable regulation over the transport of fluids and chemical species. These characteristics are of critical importance in the context of nanoparticle production, since the physical and chemical properties of the fluidic environment within a reactor strongly influence the size and/or shape of the end-product. In the past decade, replica moulding techniques (e.g., based on soft-lithography) have been developed to manufacture flow-reactors in a relatively cost-effective and efficient fashion. However, devices are often operated using multiple syringe pumps, and several of these techniques require laborious and multi-step procedures. In this study, we developed rapidly prototyped reactors embedded within a cylindrical structure that are designed for actuation using a laboratory centrifuge (herein referred to as reactor-in-a-centrifuge, or RIAC). Using RIACs of different architecture, we demonstrated production of nanoscale liposomes of therapeutically relevant size (in the diameter range 80 – 300 nm) under varying operating conditions. We also demonstrated production of silver nanospheres (with UV–vis absorption maxima of 404 nm) at selected operating conditions. The novel concept proposed in this study has the potential to significantly simplify the synthesis of nanomaterials over more commonly used microfluidic techniques, as it relies on a cost-effective and single-step reactor manufacturing process (using a desktop 3D printer) and employs widely available laboratory centrifuges to drive reagents through the reactor. In this paper we describe RIAC’s design, manufacturing, and actuation protocols, and demonstrate its applicability to the flow synthesis of nanoparticles without relying on highly specialised instrumentation or costly procedures.

Effects of photophysical properties of 1,4-cyclohexadiene derivatives on their [2 + 2] photocycloaddition reactivities: Experimental and theoretical studies

To study the relationship between the [2 + 2] photocycloaddition reactivities of 1,4-cyclohexadiene derivatives (1,4−CHDs) and their structures, photophysical properties of a series of 1,4−CHDs were studied experimentally and by performing theoretical calculations. Specifically, UV–vis absorption spectra of these compounds in diluted solutions were acquired and the theoretical calculations were performed at the density functional theory (DFT) level. Their UV–vis absorption maxima were found to be related to the substituents on the 1,4-cyclohexadiene ring. To describe the [2 + 2] photocycloaddition reactivities of the 1,4−CHDs, time-dependent density functional theory (TDDFT) was used to optimize their ground- and excited-state structures, and their electronic excitation energies were calculated at the M062X/def-TZVP level. Frontier molecular orbitals and electron-hole distribution analyses were used to illustrate the electron transition modes of the 1,4−CHDs. The differences between the ground- and excited-state structures of the different 1,4−CHDs were characterized by carrying out a root-mean-square-deviation (RMSD) analysis. The results showed that the photophysical properties of 1,4−CHDs are meaningful for explaining their [2 + 2] photocycloaddition reactivities.

Efficient Photogeneration of Hydrogen Boosted by Long-Lived Dye-Modified Ir(III) Photosensitizers and Polyoxometalate Catalyst

Efficient Photogeneration of Hydrogen Boosted by Long-Lived Dye-Modified Ir(III) Photosensitizers and Polyoxometalate Catalyst