Two-Dimensional Plasmonic Nanoparticle as a Nanoscale Sensor to Probe Polymer Brush Formation.

Conventional analysis and characterization of polymer brush formation relies on laborious methods that use a quartz crystal microbalance, atomic force microscope, microcantilever, or other tools that measure the concentration change of solutions. Herein we develop a simple and easy method that utilizes intrinsically flat two-dimensional (2D) plasmonic nanoparticles as sensors for unveiling the mechanism of polymer brush formation on surfaces. Via ultraviolet-visible spectroscopy, the plasmonic nanoparticles can be used to determine the amount of polymers near the surface in situ. As the amount of polymers increases near the surface, the nanoparticle characteristic localized surface plasmon resonance wavelength redshifts, and the shift amount corresponds linearly to the polymer density near the surface. By functionalizing the nanoparticles in solutions of thiolated polyethylene glycol (PEG-SH) with or without PEG disulfide (PEG-S-S-PEG), the three-regime kinetics of the polymer brush formation is confirmed. The fast adsorption and slow chain rearrangement in the first regime are found to be the causes of the latent regime. In the latent regime, the adsorbed polymer chains rearrange to anchor their ends onto the surface and contract to liberate space so that other polymer chains can graft onto the surface until saturation. The fundamental understanding gained herein enables the design of surfaces with complex chemistries and properties, which can find broad applications in responsive sensors, films, and coatings. Moreover, the novel analytical method of using 2D plasmonic nanoparticle as a sensor to understand the polymer brush formation is applicable to investigating the grafting of other molecules such as self-assembled monolayers, protein, and DNA.

Poly(vinylpyrrolidone)-Free Multistep Synthesis of Silver Nanoplates with Plasmon Resonance in the Near Infrared Range.

Herein, a poly(vinylpyrrolidone) (PVP)-free method is described for synthesizing Ag nanoplates that have localized surface plasmon resonance in the near-infrared (NIR) range. Citrate-capped Ag spherical nanoparticles are first grown into small Ag nanoplates that resonate in the range of 500-800 nm. The small Ag nanoplates are used as seeds to further grow into large Ag nanoplates with a lateral dimension of 100-600 nm and a plasmon resonance wavelength of 800-1660 nm and above. The number of growth steps can be increased as desired. Without introducing additional citrate into the solutions of small Ag nanoplate seeds, large Ag nanoplates can be synthesized within minutes. The entire synthesis is completely PVP free, which promotes the nanoparticle growth along the lateral direction to form large Ag nanoplates. The multistep growth and the minimum usage of citrate are essential for the fast growth of high-aspect-ratio Ag nanoplates resonating in the NIR range.

Covalent and Noncovalent Loading of Doxorubicin by Folic Acid-Carbon Dot Nanoparticles for Cancer Theranostics.

With special properties such as excellent fluoresce features, low toxicity, good biocompatibility, permeability, and easy clearance from the body, carbon dot (CD)-based nanoparticles (NPs) have the potential to deliver drugs and use in vivo diagnostics through molecular imaging. In this work, folic acid-CD (FA-CD) NPs were prepared to deliver doxorubicin (Dox) covalently and noncovalently as cancer theranostics. FA was conjugated to the surface of CDs for targeting cancer cells with overexpressing folate receptors. CDs prepared with various amounts of precursors lead to their associated NPs with different photoluminescence properties and drug release profiles. The loading of Dox and its releasing data depends on the linkage of drug Dox to FA-CD and CD composition. All NPs were characterized by UV-vis, Fourier transform infrared spectroscopy, and dynamic light scattering. The noncovalent FA-CD-Dox NPs were preferred with a simple preparation process, excellent photoluminescence, and in vitro drug release properties. The noncovalent FA-CD-Dox showed the best efficacy against MDA-MB-231 compared to the CD-Dox and covalent FA-CD-Dox.

Mutually Reinforced Polymer-Graphene Bilayer Membranes for Energy-Efficient Acoustic Transduction.

Graphene holds promise for thin, ultralightweight, and high-performance nanoelectromechanical transducers. However, graphene-only devices are limited in size due to fatigue and fracture of suspended graphene membranes. Here, a lightweight, flexible, transparent, and conductive bilayer composite of polyetherimide and single-layer graphene is prepared and suspended on the centimeter scale with an unprecedentedly high aspect ratio of 105 . The coupling of the two components leads to mutual reinforcement and creates an ultrastrong membrane that supports 30 000 times its own weight. Upon electromechanical actuation, the membrane pushes a massive amount of air and generates high-quality acoustic sound. The energy efficiency is ≈10-100 times better than state-of-the-art electrodynamic speakers. The bilayer membrane's combined properties of electrical conductivity, mechanical strength, optical transparency, thermal stability, and chemical resistance will promote applications in electronics, mechanics, and optics.

Block copolymer-based porous carbon fibers.

Carbon fibers have high surface areas and rich functionalities for interacting with ions, molecules, and particles. However, the control over their porosity remains challenging. Conventional syntheses rely on blending polyacrylonitrile with sacrificial additives, which macrophase-separate and result in poorly controlled pores after pyrolysis. Here, we use block copolymer microphase separation, a fundamentally disparate approach to synthesizing porous carbon fibers (PCFs) with well-controlled mesopores (~10 nm) and micropores (~0.5 nm). Without infiltrating any carbon precursors or dopants, poly(acrylonitrile-block-methyl methacrylate) is directly converted to nitrogen and oxygen dual-doped PCFs. Owing to the interconnected network and the highly optimal bimodal pores, PCFs exhibit substantially reduced ion transport resistance and an ultrahigh capacitance of 66 µF cm-2 (6.6 times that of activated carbon). The approach of using block copolymer precursors revolutionizes the synthesis of PCFs. The advanced electrochemical properties signify that PCFs represent a new platform material for electrochemical energy storage.

Spectral-Selective Plasmonic Polymer Nanocomposites Across the Visible and Near-Infrared.

State-of-the-art commercial light-reflecting glass is coated with a metalized film to decrease the transmittance of electromagnetic waves. In addition to the cost of the metalized film, one major limitation of such light-reflecting glass is the lack of spectral selectivity over the entire visible and near-infrared (NIR) spectrum. To address this challenge, we herein effectively harness the transmittance, reflectance, and filtration of any wavelength across the visible and NIR, by judiciously controlling the planar orientation of two-dimensional plasmonic silver nanoplates (AgNPs) in polymer nanocomposites. In contrast to conventional bulk polymer nanocomposites where plasmonic nanoparticles are randomly mixed within a polymer matrix, our thin-film polymer nanocomposites comprise a single layer, or any desired number of multiple layers, of planarly oriented AgNPs separated by tunable spacings. This design employs a minimal amount of metal and yet efficiently manages light across the visible and NIR. The thin-film plasmonic polymer nanocomposites are expected to have a significant impact on spectral-selective light modulation, sensing, optics, optoelectronics, and photonics.

Impact of specialist neurovascular care in subarachnoid haemorrhage.

BACKGROUND: The management of neurosurgical disorders has become increasingly specialised. The care of patients with subarachnoid haemorrhage (SAH) has generally been part of core neurosurgical practice, provided by general neurosurgeons whatever their specialist interest. The aim of this present study therefore is to ascertain if, and to what extent care provided by a dedicated neurovascular team (compared to care provided by a general neurosurgical team) change patient disposition in SAH. METHODS: This is a retrospective analysis of SAH patients, identified from a departmental database of a single neurosurgical centre. In 2008, the service was reorganised such that a neurovascular team cared for all SAH patients. We compared clinical outcome in people admitted prior to this service reorganisation (Period A, 2004-2007) with patients admitted afterwards (Period B, 2009-2011). Survival and recovery were assessed according to the Glasgow Outcome Scale (GOS). Multi-factorial logistic regression analysis was performed to determine the injury and age adjusted incidence of complications, odds of survival at discharge, discharge home, mortality, good recovery (GOS 5) and favourable outcome, by dichotomising GOS (GOS 4-5 vs. GOS 1-3) at 3 months. RESULTS: 1114 patients were included in the study. The mean age of patients presenting in Period A (n = 543) was younger [50 years (SD 13.5)] than those in Period B (n = 571) [53 years (SD 13)]. Patients admitted in Period B were more likely to present as poor grade (World Federation of Neurological surgeons (WFNS) grades 4 and 5) compared to Period A (26.5% vs. 21.3%). No statistical differences between the groups in the incidence of pre-operative re-bleeding (3% vs. 5%) or rates of delayed cerebral ischaemia (16.1% vs. 16.1%) were observed. After adjustment for age, sex and injury severity, the odds of patient time to discharge, discharge home and good recovery (GOS 5) were 27% (p < 0.001), 45% (p = 0.001) and 93% (p < 0.001) higher respectively in Period B than Period A. CONCLUSIONS: The data presented here demonstrates that management of SAH by a dedicated neurovascular team improves the potential for patient recovery.