Layer-by-layer assembled multilayers of polyethylenimine-stabilized platinum nanoparticles and PEDOT:PSS as anodes for the methanol oxidation reaction

Wavelength-dependent photoelectrochemical response demonstrated by the determination of acetaminophen and rutin in differential molecularly imprinted polymers strategy

Herein, the excitation wavelength-dependent responses of the molecularly imprinted polymer (MIP) photoelectrochemical (PEC) sensors were investigated, using acetaminophen (AP), rutin (RT) and perfluorooctanoate (PFOA) as the model templates, pyrrole as functional monomer, CuInS2@ZnS/TiO2 NTs as the basic photoelectrode. With wavelength λ > 240 nm, the photocurrent of MIPPFOA enhanced at higher concentrations of PFOA. With increasing AP concentration, the photocurrents of MIPAP could decline with λ < 271 nm, not change at λ = 270 nm, or increase with λ > 270 nm. As RT concentration increased, the photocurrents of MIPRT could decrease (λ < 431 nm), not change (λ = 431 nm) or increase (λ > 431 nm). The PEC responses depend on the comprehensive interaction of two contrary mechanisms from the template molecules within the MIP membrane. The photocurrent is enhanced by the role of the electron donor for photo-generated holes but attenuated due to the steric hindrance effect and the excitation light intensity loss via absorption or scattering. The apparent molar absorption coefficient of AP and RT within MIP membranes are 9.1-19.4 folds of those measured from dilute solutions. By using a routine UV lamp as the light source, the photocurrents of MIPRT at 254 nm and MIPAP at 365 nm were used to determine RT and AP, with the detection limits of 5.3 and 16 nM, respectively. The interference from the non-specific adsorption of interferents on the surfaces of MIPAP and MIPRT was reduced by one order of magnitude via a differential strategy.

Ultrasmall Peptide-Coated Platinum Nanoparticles for Precise NIR-II Photothermal Therapy by Mitochondrial Targeting

Photothermal therapy (PTT) is considered an alternative for oncotherapy because it has less invasive damage to normal tissues than other methods, particularly in second near-infrared (NIR-II) PTT (1000-1350 nm) because of deeper biological tissue penetration, lower photon scattering, and higher maximum permissible exposure (1.0 W cm^-2). However, for achieving a higher therapeutic effect, the delivery of large amounts of NIR-sensitive agents has been pursued, which in turn enormously increases damage to normal cells. Herein, we developed peptide-coated platinum nanoparticles (TPP-Pt) to create violent damage for a given amount of hyperthermia by purposefully delivering TPP-Pt to the thermally susceptible mitochondria with minimal side effects. Mitochondrial peptide targeting endowed ultrasmall platinum nanoparticles (PtNPs) with monodispersity, high stability, biosafety, and enhanced uptake of cancer cells and priority of mitochondria, causing efficient PTT. Moreover, an in vivo experiment showed that the excellent tumor inhibitory effect and negligible side effects could be achieved with the preferentially striking thermosensitive mitochondria strategy. The mitochondria-based "win by one move" therapeutic platform of peptide-coated platinum nanoparticles (TPP-Pt) demonstrated here will find great potential to overcome the challenges of low therapeutic efficiency and strong systemic side effects in PTT.

Tuneable thermal expansion of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate

Linear coefficient of thermal expansion is calculated for a mixture of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT:PSS) using density functional theory and the Debye-Grüneisen model. The linear coefficient of thermal expansion is a key factor in thermal management (thermal conductivity, thermal stress and thermal fatigue) of microelectronic and energy devices, being common applications of the conjugated polymeric PEDOT:PSS system. The obtained value of 53  ×  10^-6 K^-1 at room temperature can be rationalised based on the electronic structure analysis. The PEDOT and PSS units are bonded by a dipole-dipole interaction between S in PEDOT and H in PSS. A C-C bond in a benzene ring (PSS) or thiophene (PEDOT) is up to 13 times stronger than the S-H bond. By adjusting the population of the S-H bonds by deprotonating PSS, the linear coefficient of thermal expansion can be enhanced by 57%. This allows for tuning the thermal properties of PEDOT:PSS in cutting-edge devices.

A novel colorimetric paper sensor based on the layer-by-layer assembled multilayers of surfactants for the sensitive and selective determination of total antioxidant capacity

A new colorimetric paper sensor, (TBABr/SDS)₃/PAD, was successfully fabricated to detect TAC. Good selectivity and sensitivity toward TAC were achieved. The (TBABr/SDS)₃/PAD sensor has been applied for TAC detection in food samples.

The in situ growth of ultrathin Fcc-NiPt nanocrystals on graphene for methanol and formic acid oxidation

Due to the increasing demand for energy, improving the current density of fuel cells is an urgent issue. Here we report a bifunctional electrocatalyst for fuel cells involving methanol or formic acid oxidation. A nanocomposite consisting of 7.2 nm NiPt nanocrystals, which are grown in situ on graphene nanosheets (NiPt/GN), has been prepared via a solution thermal decomposition method. The NiPt/GN nanocatalyst presents specific activities as high as 41.1 mA cm-2 and 42.9 mA cm-2 for methanol oxidation and formic acid oxidation, respectively, outperforming most reported catalysts. Moreover, it retains 76.3% of this activity after 900 cycles of methanol oxidation. Additionally, in comparison with general NiPt nanoparticles, the NiPt/GN nanocatalyst shows higher electrocatalytic activity in methanol and formic acid oxidation. All these results indicate that ultrathin NiPt nanocrystals grown in situ on graphene nanosheet substrates can significantly improve performance as a bifunctional electrocatalyst.

Electrodeposition of PtNPs on the LBL assembled multilayer films of (PDDA-GS/PEDOT:PSS)n and their electrocatalytic activity toward methanol oxidation

In the present work, PDDA-functionalized graphene sheets (PDDA-GS) were prepared by reduction with hydrazine hydrate in situ in the presence of poly(diallyldimethylammonium chloride) (PDDA).

Lanthanide-Functionalized Hydrophilic Magnetic Hybrid Nanoparticles: Assembly, Magnetic Behaviour, and Photophysical Properties

The lanthanide-functionalized multifunctional hybrid nanoparticles combining the superparamagnetic core and the luminescent europium complex were successfully designed and assembled via layer-by-layer strategy in this work. It is noted that the hybrid nanoparticles were modified by a hydrophilic polymer polyethyleneimine (PEI) through hydrogen bonding which bestowed excellent hydrophilicity and biocompatibility on this material. A bright-red luminescence was observed by fluorescence microscopy, revealing that these magnetic-luminescent nanoparticles were both colloidally and chemically stable in PBS solution. Therefore, the nanocomposite with magnetic resonance response and fluorescence probe property is considered to be of great potential in multi-modal bioimaging and diagnostic applications.

Layered Metal Nanoparticle Structures on Electrodes for Sensing, Switchable Controlled Uptake/Release, and Photo-electrochemical Applications

Layered metal nanoparticle (NP) assemblies provide highly porous and conductive composites of unique electrical and optical (plasmonic) properties. Two methods to construct layered metal NP matrices are described, and these include the layer-by-layer deposition of NPs, or the electropolymerization of monolayer-functionalized NPs, specifically thioaniline-modified metal NPs. The layered NP composites are used as sensing matrices through the use of electrochemistry or surface plasmon resonance (SPR) as transduction signals. The crosslinking of the metal NP composites with molecular receptors, or the imprinting of molecular recognition sites into the electropolymerized NP matrices lead to selective and chiroselective sensing interfaces. Furthermore, the electrosynthesis of redox-active, imprinted, bis-aniline bridged Au NP composites yields electrochemically triggered "sponges" for the switchable uptake and release of electron-acceptor substrates, and results in conductive surfaces of electrochemically controlled wettability. Also, photosensitizer-relay-crosslinked Au NP composites, or electrochemically polymerized layered semiconductor quantum dot/metal NP matrices on electrodes, are demonstrated as functional nanostructures for photoelectrochemical applications.