Inclusion complexation of 4,4′-dihydroxybenzophenone and 4-hydroxybenzophenone with α- and β-cyclodextrins

<div><p>The inclusion complexation behaviours of 4,4′-dihydroxybenzophenone (DHBP) and 4-hydroxybenzophenone (HBP) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) were investigated using UV–visible fluorescence, time-resolved fluorescence, molecular modelling, scanning electron microscopy (SEM), FTIR, differential scanning calorimeter, X-ray diffraction, ¹H NMR and molecular modelling techniques. In both molecules, biexponential decay was observed in water, whereas triexponential decay was observed in the CD medium. The DSC thermogram of the DHBP/α-CD and DHBP/β-CD inclusion complex nanomaterials shows the endothermic peak at 60.8, 101.9, 119.6 and 112.8°C. The upfield chemical shift observed for HBP protons reveal that the phenyl ring (without hydroxyl substitution) entered the CD cavity and the hydroxyl group of HBP is exposed outside the CD cavity. The SEM image of DHBP appears as needle-shaped crystals on the micrometre scale, whereas the irregular bar shape was observed for HBP. Transmission electron microscopy images show that both guest molecules formed nano vesicles with α-CD and formed nano rods with β-CD.</p></div

Nanorod formation of cyclodextrin-covered sudan dyes through supramolecular self-assembly

<div><p>Cyclodextrin-covered sudan III (SDIII) and sudan IV (SDIV) dyes produced various nanostructures such as pseudorotaxanes through supramolecular self-assembly, studied by absorption, fluorescence, time-resolved fluorescence, SEM, TEM, FT-IR, DSC, PXRD and ¹H NMR. Solvent study shows that azo–hydrazo tautomer is present in sudan dyes. Absorption and fluorescence spectroscopy data gave evidence for the formation of 1:2 inclusion complexes. Big nanorod (∼36 nm) surrounded by small nanorod (∼3 nm) was identified in SDIV/α-CD complexes. This confirms that the rigid molecular nanorod aggregates of α-CD and β-CD complexes are formed through the initial formation of smaller nanorods. An unequal morphology noticed in SDIII/CD suggests that the 1:2 inclusion complexes were self-assembled into irregular arrangement. The thermodynamic parameters (Δ<i>H</i>, Δ<i>G</i> and Δ<i>S</i>) of inclusion processes were determined from semi-empirical PM3 calculations.</p></div

Encapsulation of ciprofloxacin, sparfloxacin, and ofloxacin drugs with α- and β-cyclodextrins: spectral and molecular modelling studies

<div><p></p><p>Inclusion complexation of ciprofloxacin (CIP), sparfloxacin (SPA), and ofloxacin (OFL) drugs with α-CD and β-CD was studied by UV-visible, fluorescence, time-resolved fluorescence, Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (¹HNMR), scanning electron microscopy (SEM), and molecular modelling techniques. Changes in the absorbance and fluorescence intensities and fluorescence lifetime of the drugs in the cyclodextrin (CD) solutions suggest the formation of inclusion complexes. Carbonyl stretching frequency moved to higher wave numbers and broadening of the N–H stretching band indicated the formation of inclusion complex. Cyclohexane ring protons of the drugs show remarkable upfield or downfield shift in the ¹HNMR spectrum, indicating that the cyclohexane part of the guest molecule is entrapped inside CD cavities. SEM images of CIP/CD, SPA/CD, and OFL/CD complexes have a crystal structure with different morphology from the isolated CIP, SPA, OFL, and CDs. Investigations of the energetic, thermodynamic, and electronic properties of parametric model number 3 computational calculations confirmed the stability of the inclusion complex.</p></div

Excimer emission of caffeine with α- and β-cyclodextrins: spectral and molecular modelling studies

<p>Excimer emission of caffeine with α-CD and β-CD were studied by UV-visible, fluorescence, time-resolved fluorescence, FTIR, ¹H NMR and molecular modelling techniques. Changes in the absorbance and fluorescence and lifetime of the caffeine with cyclodextrin (CD) solutions indicate (i) caffeine shows dual emission in the CD solutions, (ii) normal emission originates from a monomer and the longer wavelength emission is due to excimer and (iii) in both CDs caffeine forms 1:2 inclusion complex. Carbonyl stretching frequency moved to higher wave numbers and broadening of the N–H stretching band indicated the formation of inclusion complex. The resonance of the methyl protons of caffeine show remarkable upfield or downfield shift in the ¹H NMR, which indicates imidazole ring of the caffeine entrapped in the CD cavities. Investigations of energetic, thermodynamic and electronic properties of PM3 computational calculations confirmed the stability of the inclusion complex.</p

Nanochain and vesicles formed by inclusion complexation of 4,4′-diaminobenzanilide with cyclodextrins

<div><p>The nanochain-like agglomerates and spherical nanovesicles were formed from supramolecular self-assembly of 4,4′-diaminonenzanilide (DABA) with α- and β-cyclodextrins. The DABA with α-CD and β-CD inclusion complex nanomaterials were prepared and characterised by transmission electron microscopy, scanning electron microscopy, FTIR, differential scanning calorimetry, ¹H NMR and powder X-ray diffraction. ¹H NMR analysis indicated that the benzamido ring of DABA was encapsulated into the cyclodextrin (CD) cavity. Absorption and fluorescence spectral studies suggested that DABA forms different types of nanomaterials in α-CD and β-CD solutions. Higher occupied molecular orbital, lower unoccupied molecular orbital, and thermodynamic parameter values confirmed DABA dye entrapped in the CD cavities.</p></div

Green Synthesized Silver and Gold Nanoparticles for Colorimetric Detection of Hg²⁺, Pb²⁺, and Mn²⁺ in Aqueous Medium

In this study, we report a simple and green method for the synthesis of l-tyrosine-stabilized silver (AgNPs) and gold nanoparticles (AuNPs) in aqueous medium under ambient sunlight irradiation. The nanoparticles (NPs) are characterized by UV–visible spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and dynamic light scattering (DLS) techniques. The size and shape of the metal NPs could be controlled by changing the concentration of the substrate, metal precursors, and pH of the medium. The synthesized AgNPs are found to be highly sensitive to Hg²⁺ and Mn²⁺ ions with the detection limit for both ions as low as 16 nM under optimized conditions. However AuNPs are found to be sensitive to Hg²⁺ and Pb²⁺ ions with a detection limit as low as 53 and 16 nM, respectively. The proposed method was found to be useful for colorimetric detection of heavy metal ions in aqueous medium