Highly ordered arrays of hat-shaped hierarchical nanostructures with different curvatures for sensitive SERS and plasmon-driven catalysis

Regulation of hot spots exhibits excellent potential in many applications including nanolasers, energy harvesting, sensing, and subwavelength imaging. Here, hat-shaped hierarchical nanostructures with different space curvatures have been proposed to enhance hot spots for facilitating surface-enhanced Raman scattering (SERS) and plasmon-driven catalysis applications. These novel nanostructures comprise two layers of metal nanoparticles separated by hat-shaped MoS2 films. The fabrication of this hybrid structure is based on the thermal annealing and thermal evaporation of self-assembled polystyrene spheres, which are convenient to control the metal particle size and the curvature of hat-shaped nanostructures. Based on the narrow gaps produced by the MoS2 films and the curvature of space, the constructed platform exhibits superior SERS capability and achieves ultrasensitive detection for toxic molecules. Furthermore, the surface catalytic conversion of p-nitrothiophenol (PNTP) to p, p′-dimercaptobenzene (DMAB) was in situ monitored by the SERS substrate. The mechanism governing this regulation of hot spots is also investigated via theoretical simulations.

Three-Dimensional Superhydrophobic Hollow Hemispherical MXene for Efficient Water-in-Oil Emulsions Separation

A superhydrophobic macroporous material composed of hollow hemispherical MXene (HSMX) was synthesized by the thermal annealing of MXene-wrapped cationic polystyrene spheres (CPS@MXene). Notably, the spherical MXene shells exhibited highly efficient catalysis of the carbonization of CPS into carbon nanoparticles. Their insertion into the interlayer of MXene increased the d-spacing and created hollow hemispheres. The as-prepared HSMX with nanoscale walls had a lower packing density than MXene, but higher porosity, total pore volume, and total pore area. Moreover, the stacking of hollow hemispheres promoted the formation of a highly undulating macroporous surface and significantly improved the surface roughness of the HSMX-based 3D membrane, resulting in superhydrophobicity with a water contact angle of 156.4° and a rolling angle of 6°. As a result, the membrane exhibited good separation efficiency and flux for emulsifier-stabilized water-in-paraffin liquid emulsions, which was dependent on its superhydrophobic performance and strong demulsification ability derived from the razor effect originating from the ultrathin walls of HSMX. This work provides a facile approach for the transformation of highly hydrophilic 2D MXene into superhydrophobic 3D HSMX, and opens a new pathway for the development of advanced MXene-based materials for environmental remediation applications.

Cell size matters: nano- and micro-plastics preferentially drive declines of large marine phytoplankton due to co-aggregation

Marine plastic pollution represents a key environmental concern. Whilst ecotoxicological data for plastic is increasingly available, its impact upon marine phytoplankton remains unclear. Owing to their predicted abundance in the marine environment and likely interactions with phytoplankton, here we focus on the smaller fraction of plastic particles (~50 nm and ~2 μm polystyrene spheres). Exposure of natural phytoplankton communities and laboratory cultures revealed that plastic exposure does not follow traditional trends in ecotoxicological research, since large phytoplankton appear particularly susceptible towards plastics exposure despite their higher surface-to-volume ratios. Cell declines appear driven by hetero-aggregation and co-sedimentation of cells with plastic particles, recorded visually and demonstrated using confocal microscopy. As a consequence, plastic exposure also caused disruption to photosynthetic functioning, as determined by both photosynthetic efficiency and high throughput proteomics. Negative effects upon phytoplankton are recorded at concentrations orders of magnitude above those estimated in the environment. Hence, it is likely that impacts of NPs and MPs are exacerbated at the high concentrations typically used in ecotoxicological research (i.e., mg L-1).

APPLICATION OF COPPERED POLYSTYRENE SPHERES IN CASTING PRODUCTS

A technological scheme for obtaining an experimental foam aluminum material with a fixed arrangement of closed pores inside the casting is presented. As a blowing agent, polystyrene foam granules were used on the surface of which a copper galvanic coating was applied in several ways.

TiO2 Inverse Opals Modified by Ag Nanoparticles: A Synergic Effect of Enhanced Visible-Light Absorption and Efficient Charge Separation for Visible-Light Photocatalysis

This work reports on the synthesis, characterization, and photocatalytic performance of the TiO2 inverse opal nanostructure (IP-TiO2) and the IP-TiO2 modified by Ag nanoparticles (Ag@IP-TiO2). The IP-TiO2 is fabricated using polystyrene spheres as the template and TiCl4 as the precursor, and the Ag@IP-TiO2 is realized by photoreduction method. The morphological, structural, and optical properties of the materials are investigated by scanning electron microscopy, X-ray diffraction, ultraviolet–visible (UV-VIS) absorption spectroscopy, and photoluminescence spectroscopy. Their photocatalytic performances are studied by the degradation of rifampicin antibiotic under the visible-light irradiation generated by an LED lamp. The results demonstrate that the IP-TiO2 is composed of mesopores arranged in the honeycomb structure and strongly absorbs visible light in the wavelength range of 400–500 nm. This facilitates the visible-light catalytic activity of IP-TiO2, which is further enhanced by the surface modification by Ag nanoparticles. Our studies on the UV-VIS absorption and photoluminescent properties of the materials reveal that the presence of Ag nanoparticles not only enhances the visible-light absorption of IP-TiO2, but also reduces the recombination of photogenerated electrons and holes. These two factors create a synergic effect that causes the enhanced photocatalytic performance of Ag@IP-TiO2.

Chemical Imaging of Single Anisotropic Polystyrene/Poly (Methacrylate) Microspheres with Complex Hierarchical Architecture

Monodisperse polystyrene spheres are functional materials with interesting properties, such as high cohesion strength, strong adsorptivity, and surface reactivity. They have shown a high application value in biomedicine, information engineering, chromatographic fillers, supercapacitor electrode materials, and other fields. To fully understand and tailor particle synthesis, the methods for characterization of their complex 3D morphological features need to be further explored. Here we present a chemical imaging study based on three-dimensional confocal Raman microscopy (3D-CRM), scanning electron microscopy (SEM), focused ion beam (FIB), diffuse reflectance infrared Fourier transform (DRIFT), and nuclear magnetic resonance (NMR) spectroscopy for individual porous swollen polystyrene/poly (glycidyl methacrylate-co-ethylene di-methacrylate) particles. Polystyrene particles were synthesized with different co-existing chemical entities, which could be identified and assigned to distinct regions of the same particle. The porosity was studied by a combination of SEM and FIB. Images of milled particles indicated a comparable porosity on the surface and in the bulk. The combination of standard analytical techniques such as DRIFT and NMR spectroscopies yielded new insights into the inner structure and chemical composition of these particles. This knowledge supports the further development of particle synthesis and the design of new strategies to prepare particles with complex hierarchical architectures.

Detection, counting and characterization of nanoplastics in marine bioindicators: a proof of principle study

Plastic particulates in the environment pose an increasing concern for regulatory bodies due to their potential risk to higher organisms (including humans) as they enter the food chain. Nanoplastics (defined here as smaller than 1 μm) are particularly challenging to detect and analyze at environmentally relevant concentrations and in biological matrices. The tunicate Ciona Robusta is an effective bioindicator for microplastics and nanoplastic contamination in the marine environment, due to its capacity to filter substantial volumes of water and to accumulate particulates. In this proof-of-principle study that demonstrates a complete methodology, following controlled exposure using spiked samples of a model nanoplastic (100 nm diameter polystyrene spheres) the nanoparticles were separated from an enzymatically digested biological matrix, purified and concentrated for analysis. The described method yields an approximate value for nanoplastic concentration in the organism (with a limit of detection of 106 particles/organism, corresponding to 1 ng/g) and provides the chemical composition by Raman spectroscopy. Furthermore, this method can be extended to other biological matrices and used to quantitatively monitor the accumulation of nanoplastics in the environment and food chain.