Non-Resonant Large Format Surface Enhanced Raman Scattering Substrates for Selective Detection and Quantification of Xylene Isomers

Non-Resonant Large Format Surface Enhanced Raman Scattering Substrates for Selective Detection and Quantification of Xylene Isomer

Investigating Unexpected Magnetism of Mesoporous Silica-Supported Pd and PdO Nanoparticles

The synthesis and magnetic behavior of matrix-supported Pd and PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal columnal packing is selected as a template, and the impregnation method with thermal annealing is used to obtain supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary to the general belief that smaller Pd NPs or cluster size particles have higher magnetization, matrix-supported Pd NPs in this study maintain the highest magnetization with room temperature ferromagnetism when the size is the largest. (2) Twin boundaries along with stacking faults are more pronounced in these large Pd NPs and are believed to be the reason for this high magnetization. Similarly, supported PdO NPs were prepared under air conditions with different heating rates. Their phase is tetragonal (P4₂/mmc) with cell parameters of <i>a</i> = 3.050 Å and <i>c</i> = 5.344 Å, which are slightly larger than in the bulk phase (<i>a</i> = 3.03 Å, <i>c</i> = 5.33 Å). Faster heating rate of 30 °C/min also produces larger particles and larger magnetic hysteresis loop, although magnetization is smaller and few twin boundaries are observed compared to the supported metallic Pd NPs

Selective Magnetic Evolution of Mn_<i>x</i>Fe_1–<i>x</i>O Nanoplates

Iron–manganese oxide (Mn_<i>x</i>Fe_1–<i>x</i>O) nanoplates were prepared by the thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of Mn_<i>x</i>Fe_1–<i>x</i>O and MnFe₂O₄ is achieved by controlling the annealing conditions. Rock-salt structure of Mn_<i>x</i>Fe_1–<i>x</i>O (space group <i>Fm</i>3̅<i>m</i>) is observed in as-synthesized nanoplates, while MnFe₂O₄ and Mn_<i>x</i>Fe_1–<i>x</i>O with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn_0.48Fe_2.52O₄ with Mn_<i>x</i>Fe_1–<i>x</i>O are observed. It is assumed that the differential and early development of crystalline phase of Mn_<i>x</i>Fe_1–<i>x</i>O and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time of 15 h which enables ordering are also thought to contribute to these irregularities

Compositing Polyetherimide with Polyfluorene Wrapped Carbon Nanotubes for Enhanced Interfacial Interaction and Conductivity

A novel approach to chemically functionalize multiwalled carbon nanotubes (MWCNTs) for making superior polyetherimide (PEI) nanocomposites with polyfluorene polymer is presented. In this approach, MWCNTs are non-covalently functionalized with poly­(9,9-dioctyfluorenyl-2,7-diyl) (PFO) through π–π stacking as confirmed by UV-vis, fluorescence, and Raman spectra. Atomic force microscopy as well as scanning and transmission electron microscopy shows the PFO coated MWCNTs, which provides excellent dispersion of the latter in both solvent and PEI matrix. The strong interaction of PFO with PEI chains, as evidenced from fluorescence spectra, supports the good adhesion of dispersed MWCNTs to PEI leading to stronger interfacial interactions. As a result, the addition of as little as 0.25 wt % of modified MWCNTs to PEI matrix can strongly improve the mechanical properties of the composite (increase of 46% in storage modulus). Increasing the amount of MWCNTs to 2.0 wt % (0.5 wt % PFO loading) affords a great increase of 119% in storage modulus. Furthermore, a sharp decrease of 12 orders of magnitude in volume resistivity of PEI composite is obtained with only 0.5 wt % of PFO modified MWCNT

Histidine–dialkoxyanthracene dyad for selective and sensitive detection of mercury ions

<p>Histidine-dialkoxyanthracene (HDA) was synthesised as a turn off type fluorescent sensor for fast and sensitive detection of mercury ions (Hg²⁺) in aqueous media. The two histidine moieties act as ‘claws’ to selectively complex Hg²⁺. The binding ratio of HDA to Hg²⁺ was 1:1 (metal-to-ligand ratio). The association constant for Hg²⁺ towards the receptor HDA obtained from Benesi–Hildebrand plot was found to be 3.22 × 10⁴ M⁻¹ with detection limit as low as 4.7 nM (0.94 μg/L).</p

Surface Modification of Multiwalled Carbon Nanotubes with Cationic Conjugated Polyelectrolytes: Fundamental Interactions and Intercalation into Conductive Poly(methyl methacrylate) Composites

This research investigates the modification and dispersion and of pristine multiwalled carbon nanotubes (MWCNTs) through a simple solution mixing technique based on noncovalent interactions between poly­(phenylene ethynylene)-based conjugated polyelectrolytes functionalized with cationic imidazolium solubilizing groups (PIM-2 and PIM-4) and MWCNTs. Spectroscopic studies demonstrated the ability of PIMs to strongly interact with and efficiently disperse MWCNTs in different solvents, mainly due to π interactions between the PIMs and the MWCNTs. Transmission electron microscopy and atomic force microscopy revealed the coating of the polyelectrolytes on the walls of the nanotubes. Scanning electron microscopy (SEM) studies confirm the homogeneous dispersion of PIM-modified MWCNTs in the poly­(methyl methacrylate) (PMMA) matrix. The addition of 1 wt % PIM-modified MWCNTs to the matrix has led to a significant decrease in DC resistivity of the composite (13 orders of magnitude). The increase in electrical conductivity and the improvement in the thermal and mechanical properties of the membranes containing the PIM-modified MWCNTs is ascribed to the formation of MWCNT networks and cross-linking sites that provided channels for the electrons to move in throughout the matrix and reinforced the interface between MWCNTs and PMMA

Colorimetric Peroxidase Mimetic Assay for Uranyl Detection in Sea Water

Uranyl (UO₂²⁺) is a form of uranium in aqueous solution that represents the greatest risk to human health because of its bioavailability. Different sensing techniques have been used with very sensitive detection limits especially the recently reported uranyl-specific DNAzymes systems. However, to the best of our knowledge, few efficient detection methods have been reported for uranyl sensing in seawater. Herein, gold nanoclusters (AuNCs) are employed in an efficient spectroscopic method to detect uranyl ion (UO₂²⁺) with a detection limit of 1.86 μM. In the absence of UO₂²⁺, the BSA-stabilized AuNCs (BSA-AuNCs) showed an intrinsic peroxidase-like activity. In the presence of UO₂²⁺, this activity can be efficiently restrained. The preliminary quenching mechanism and selectivity of UO₂²⁺ was also investigated and compared with other ions. This design strategy could be useful in understanding the binding affinity of protein-stabilized AuNCs to UO₂²⁺ and consequently prompt the recycling of UO₂²⁺ from seawater

“Light-on” Sensing of Antioxidants Using Gold Nanoclusters

Depletion of intracellular antioxidants is linked to major cytotoxic events and cellular disorders, such as oxidative stress and multiple sclerosis. In addition to medical diagnosis, determining the concentration of antioxidants in foodstuffs, food preservatives, and cosmetics has proved to be very vital. Gold nanoclusters (Au-NCs) have a core size below 2 nm and contain several metal atoms. They have interesting photophysical properties, are readily functionalized, and are safe to use in various biomedical applications. Herein, a simple and quantitative spectroscopic method based on Au-NCs is developed to detect and image antioxidants such as ascorbic acid. The sensing mechanism is based on the fact that antioxidants can protect the fluorescence of Au-NCs against quenching by highly reactive oxygen species. Our method shows great accuracy when employed to detect the total antioxidant capacity in commercial fruit juice. Moreover, confocal fluorescence microscopy images of HeLa cells show that this approach can be successfully used to image antioxidant levels in living cells. Finally, the potential application of this “light-on” detection method in multiple logic gate fabrication was discussed using the fluorescence intensity of Au-NCs as output

Photoresponsive Bridged Silsesquioxane Nanoparticles with Tunable Morphology for Light-Triggered Plasmid DNA Delivery

Bridged silsesquioxane nanocomposites with tunable morphologies incorporating <i>o</i>-nitrophenylene–ammonium bridges are described. The systematic screening of the sol–gel parameters allowed the material to reach the nanoscale with controlled dense and hollow structures of 100–200 nm. The hybrid composition of silsesquioxanes with 50% organic content homogeneously distributed in the nanomaterials endowed them with photoresponsive properties. Light irradiation was performed to reverse the surface charge of nanoparticles from +46 to −39 mV via a photoreaction of the organic fragments within the particles, as confirmed by spectroscopic monitorings. Furthermore, such nanoparticles were applied for the first time for the on-demand delivery of plasmid DNA in HeLa cancer cells via light actuation

Photoresponsive Bridged Silsesquioxane Nanoparticles with Tunable Morphology for Light-Triggered Plasmid DNA Delivery

Bridged silsesquioxane nanocomposites with tunable morphologies incorporating <i>o</i>-nitrophenylene–ammonium bridges are described. The systematic screening of the sol–gel parameters allowed the material to reach the nanoscale with controlled dense and hollow structures of 100–200 nm. The hybrid composition of silsesquioxanes with 50% organic content homogeneously distributed in the nanomaterials endowed them with photoresponsive properties. Light irradiation was performed to reverse the surface charge of nanoparticles from +46 to −39 mV via a photoreaction of the organic fragments within the particles, as confirmed by spectroscopic monitorings. Furthermore, such nanoparticles were applied for the first time for the on-demand delivery of plasmid DNA in HeLa cancer cells via light actuation