Nanoparticle‐Enhanced Silver‐Nanowire Plasmonic Electrodes for High‐Performance Organic Optoelectronic Devices

Improved performance in plasmonic organic solar cells (OSCs) and organic light‐emitting diodes (OLEDs) via strong plasmon‐coupling effects generated by aligned silver nanowire (AgNW) transparent electrodes decorated with core–shell silver–silica nanoparticles (Ag@SiO₂NPs) is demonstrated. NP‐enhanced plasmonic AgNW (Ag@SiO₂NP–AgNW) electrodes enable substantially enhanced radiative emission and light absorption efficiency due to strong hybridized plasmon coupling between localized surface plasmons (LSPs) and propagating surface plasmon polaritons (SPPs) modes, which leads to improved device performance in organic optoelectronic devices (OODs). The discrete dipole approximation (DDA) calculation of the electric field verifies a strongly enhanced plasmon‐coupling effect caused by decorating core–shell Ag@SiO₂NPs onto the AgNWs. Notably, an electroluminescence efficiency of 25.33 cd A^?1 (at 3.2 V) and a power efficiency of 25.14 lm W^?1 (3.0 V) in OLEDs, as well as a power conversion efficiency (PCE) value of 9.19% in OSCs are achieved using hybrid Ag@SiO₂NP–AgNW films. These are the highest values reported to date for optoelectronic devices based on AgNW electrodes. This work provides a new design platform to fabricate high‐performance OODs, which can be further explored in various plasmonic and optoelectronic devices.     

WO3 Nanofiber‐Based Biomarker Detectors Enabled by Protein‐Encapsulated Catalyst Self‐Assembled on Polystyrene Colloid Templates

A novel catalyst functionalization method, based on protein‐encapsulated metallic nanoparticles (NPs) and their self‐assembly on polystyrene (PS) colloid templates, is used to form catalyst‐loaded porous WO₃ nanofibers (NFs). The metallic NPs, composed of Au, Pd, or Pt, are encapsulated within a protein cage, i.e., apoferritin, to form unagglomerated monodispersed particles with diameters of less than 5 nm. The catalytic NPs maintain their nanoscale size, even following high‐temperature heat‐treatment during synthesis, which is attributed to the discrete self‐assembly of NPs on PS colloid templates. In addition, the PS templates generate open pores on the electrospun WO₃ NFs, facilitating gas molecule transport into the sensing layers and promoting active surface reactions. As a result, the Au and Pd NP‐loaded porous WO₃ NFs show superior sensitivity toward hydrogen sulfide, as evidenced by responses (R_air/R_gas) of 11.1 and 43.5 at 350 °C, respectively. These responses represent 1.8‐ and 7.1‐fold improvements compared to that of dense WO₃ NFs (R_air/R_gas = 6.1). Moreover, Pt NP‐loaded porous WO₃ NFs exhibit high acetone sensitivity with response of 28.9. These results demonstrate a novel catalyst loading method, in which small NPs are well‐dispersed within the pores of WO₃ NFs, that is applicable to high sensitivity breath sensors.     

Evaluation of the toxicities of silver and silver sulfide nanoparticles against Gram‐positive and Gram‐negative bacteria

In this study, the endogenous lipid signalling molecules, N ‐myristoylethanolamine, were explored as a capping agent to synthesise stable silver nanoparticles (AgNPs) and Ag sulphide NPs (Ag₂ S NPs). Sulphidation of the AgNPs abolishes the surface plasmon resonance (SPR) maximum of AgNPs at 415 nm with concomitant changes in the SPR, indicating the formation of Ag₂ S NPs. Transmission electron microscopy revealed that the AgNPs and Ag₂ S NPs are spherical in shape with a size of 5–30 and 8–30 nm, respectively. AgNPs and Ag₂ S NPs exhibit antimicrobial activity against Gram‐positive and Gram‐negative bacteria. The minimum inhibitory concentrations (MIC) of 25 and 50 μM for AgNPs and Ag₂ S NPs, respectively, were determined from resazurin microtitre plate assay. At or above MIC, both AgNPs and Ag₂ S NPs decrease the cell viability through the mechanism of membrane damage and generation of excess reactive oxygen species.Inspec keywords: cellular biophysics, biomembranes, transmission electron microscopy, nanomedicine, microorganisms, molecular biophysics, antibacterial activity, nanofabrication, silver, biomedical materials, surface plasmon resonance, nanoparticles, materials preparation, silver compounds, lipid bilayersOther keywords: Gram‐negative bacteria, Gram‐positive bacteria, endogenous lipid signalling molecules, N‐myristoylethanolamine, capping agent, silver nanoparticles, Ag sulphide NPs, sulphidation, surface plasmon resonance, concomitant changes, transmission electron microscopy, minimum inhibitory concentrations, resazurin microtitre plate assay, cell viability, membrane damage, reactive oxygen species, Ag toxicities, Ag, Ag₂ S     

Gap‐Mode Surface‐Plasmon‐Enhanced Photoluminescence and Photoresponse of MoS2

2D materials hold great potential for designing novel electronic and optoelectronic devices. However, 2D material can only absorb limited incident light. As a representative 2D semiconductor, monolayer MoS₂ can only absorb up to 10% of the incident light in the visible, which is not sufficient to achieve a high optical‐to‐electrical conversion efficiency. To overcome this shortcoming, a “gap‐mode” plasmon‐enhanced monolayer MoS₂ fluorescent emitter and photodetector is designed by squeezing the light‐field into Ag shell‐isolated nanoparticles–Au film gap, where the confined electromagnetic field can interact with monolayer MoS₂. With this gap‐mode plasmon‐enhanced configuration, a 110‐fold enhancement of photoluminescence intensity is achieved, exceeding values reached by other plasmon‐enhanced MoS₂ fluorescent emitters. In addition, a gap‐mode plasmon‐enhanced monolayer MoS₂ photodetector with an 880% enhancement in photocurrent and a responsivity of 287.5 A W^?1 is demonstrated, exceeding previously reported plasmon‐enhanced monolayer MoS₂ photodetectors.     

Formation of a Monolayer Protein Corona around Polystyrene Nanoparticles and Implications for Nanoparticle Agglomeration

Nanoparticle (NP) interactions with cells and organisms are mediated by a biomolecular adsorption layer, the so‐called “protein corona.” An in‐depth understanding of the corona is a prerequisite to successful and safe application of NPs in biology and medicine. In this work, earlier in situ investigations on small NPs are extended to large polystyrene (PS) NPs of up to 100 nm diameter, using human transferrin (Tf) and human serum albumin (HSA) as model proteins. Direct NP sizing experiments reveal a reversibly bound monolayer protein shell (under saturating conditions) on hydrophilic, carboxyl‐functionalized (PS‐COOH) NPs, as was earlier observed for much smaller NPs. In contrast, protein binding on hydrophobic, sulfated (PS‐OSO₃H) NPs in solvent of low ionic strength is completely irreversible; nevertheless, the thickness of the observed protein corona again corresponds to a protein monolayer. Under conditions of reduced charge repulsion (higher ionic strength), the NPs are colloidally unstable and form large clusters below a certain protein–NP stoichiometric ratio, indicating that the adsorbed proteins induce NP agglomeration. This comprehensive characterization of the persistent protein corona on PS‐OSO₃H NPs by nanoparticle sizing and quantitative fluorescence microscopy/nanoscopy reveals mechanistic aspects of molecular interactions occurring during exposure of NPs to biofluids.     

Advanced Biomaterials Accumulation of Citrate‐Coated Magnetic Iron Oxide Nanoparticles by Cultured Brain Astrocytes

Magnetic iron oxide nanoparticles (Fe‐NP) are considered for various applications in the brain. However, little is known so far on the uptake and the metabolism of such nanoparticles in brain cells. Since astrocytes are strategically localized between capillaries and neurons, astrocytes are of particular interest concerning uptake and fate of nanoparticles in the brain. Using astrocyte‐rich primary cultures as model system we have investigated the accumulation of citrate‐coated Fe‐NP by astrocytes. Viable cultured astrocytes accumulate iron from citrate‐coated Fe‐NP in a time‐, concentration‐, and temperature‐dependent manner. The cellular iron content determined after 4 h of incubation increases proportional to the concentration of Fe‐NP, if the particles were applied in concentrations of up to 1000 × 10^?6 M of total iron. The iron accumulation from 500 or 1000 × 10^?6 M iron as Fe‐NP is significantly slowed by lowering the incubation temperature from 37 to 4 °C. Transmission electron microscopy of the cells revealed that most of the cellular Fe‐NP are present in intracellular vesicles. These data demonstrate that astrocytes accumulate efficiently citrate‐coated Fe‐NP, most likely by an endocytotic pathway.     

Ordered Arrangement and Optical Properties of Silica‐Stabilized Gold Nanoparticle–PNIPAM Core–Satellite Clusters for Sensitive Raman Detection

Gold–polymer hybrid nanoparticles attract wide interest as building blocks for the engineering of photonic materials and plasmonic (active) metamaterials with unique optical properties. In particular, the coupling of the localized surface plasmon resonances of individual metal nanostructures in the presence of nanometric gaps can generate highly enhanced and confined electromagnetic fields, which are frequently exploited for metal‐enhanced light–matter interactions. The optical properties of plasmonic structures can be tuned over a wide range of properties by means of their geometry and the size of the inserted nanoparticles as well as by the degree of order upon assembly into 1D, 2D, or 3D structures. Here, the synthesis of silica‐stabilized gold–poly(N‐isopropylacrylamide) (SiO₂‐Au‐PNIPAM) core–satellite superclusters with a narrow size distribution and their incorporation into ordered self‐organized 3D assemblies are reported. Significant alterations of the plasmon resonance are found for different assembled structures as well as strongly enhanced Raman signatures are observed. In a series of experiments, the origin of the highly enhanced signals can be assigned to the interlock areas of adjacent SiO₂‐Au‐PNIPAM core–satellite clusters and their application for highly sensitive nanoparticle‐enhanced Raman spectroscopy is demonstrated.     

Surface Plasmon‐Enhanced Photodetection in Few Layer MoS2 Phototransistors with Au Nanostructure Arrays

2D Molybdenum disulfide (MoS₂) is a promising candidate material for high‐speed and flexible optoelectronic devices, but only with low photoresponsivity. Here, a large enhancement of photocurrent response is obtained by coupling few‐layer MoS₂ with Au plasmonic nanostructure arrays. Au nanoparticles or nanoplates placed onto few‐layer MoS₂ surface can enhance the local optical field in the MoS₂ layer, due to the localized surface plasmon (LSP) resonance. After depositing 4 nm thick Au nanoparticles sparsely onto few‐layer MoS₂ phototransistors, a doubled increase in the photocurrent response is observed. The photocurrent of few‐layer MoS₂ phototransistors exhibits a threefold enhancement with periodic Au nanoarrays. The simulated optical field distribution confirms that light can be trapped and enhanced near the Au nanoplates. These findings offer an avenue for practical applications of high performance MoS₂‐based optoelectronic devices or systems in the future.     

Characterizing the Lateral Friction of Nanoparticles on On‐Chip Integrated Black Lipid Membranes

The use of nanoparticles (NPs) in biomedical applications creates a need for appropriate model systems to systematically investigate NP–membrane interactions under well‐defined conditions. Black lipid membranes (BLMs) are free‐floating membranes with defined composition that are ideally suited for characterizing NP–membrane interactions free of any potential perturbation through a supporting substrate. Herein, arrays of microfabricated BLMs are integrated into a chip‐based platform that is compatible with high‐speed optical NP tracking. This system is used to investigate the lateral diffusion of 40 nm gold spheres tethered to biotinylated lipids through antibody‐functionalized ligands (single‐stranded DNA or polyethylene glycol). Although the NPs show an almost free and ergodic diffusion, their lateral motion is subject to substantial drag at the membrane surface, which leads to systematically smaller diffusion coefficients than those obtained for lipids in the membrane through fluorescence recovery after photobleaching. The lateral mobility of the NPs is influenced by the chemical composition and salt concentration at the NP‐membrane interface, but is independent of the ligand density in the membrane. Together with the observation that nanoprisms, which have a larger relative contact area with the membrane than spherical NPs, show an even slower diffusion, these findings indicate that the lateral mobility of NPs tethered in close vicinity to a membrane is significantly reduced by the friction at the NP‐membrane interface.     

Enhancement of photoinduced transformations in amorphous chalcogenide film via surface plasmon resonances

Laser-matter coupling results specific structural changes in amorphous chalcogenide semiconductor layers which originate from electron-hole excitations, defect creation or modification and subsequent atomic motions. These changes can be influenced by plasmon fields. Plasmon enhanced photo-darkening and bleaching, optical recording in thin As_xSe_1 − x films have been demonstrated in this paper, specifically in As₂₀Se₈₀ and As₂Se₃ compositions which revealed the best effects of stimulated expansion or optical darkening respectively due to the He-Ne laser (λ = 633 nm) illumination. Gold nanoparticles deposited on the silica glass substrate and covered by an amorphous chalcogenide film satisfy the conditions of efficient surface plasmon resonance in this spectral region. These experimental results support the importance of localized electric fields in photo-structural transformations of chalcogenide glasses as well as suggest better approaches for improving the performance of these optical recording media.     

A Microwell Array Platform for Picoliter Membrane Protein Assays

A novel microwell chip is developed that can be used to detect protein binding in a liquid environment, together with a liquid handling system that allows the performance of assays with picoliter volumes. A PDMS well structure is cast on a planar optical waveguide, providing reaction containers combined with a high‐sensitivity fluorescence readout system. Individual wells of the array can be addressed, filled, and rinsed using a contact‐mode pin and ring spotter. This allows for immunoassays in a heavily multiplexed way, as all steps of the assay can be individually chosen per well. An array density of over 1000 wells cm^?2 is used for the current experiments. The wells provide a protected liquid environment in which the handling of proteins in their natural state is possible, thus maintaining their activity. The membrane protein annexin V is chosen as a model protein to demonstrate the current possibilities. Annexin V binds to phosphatidylserine (PS) head groups of lipids in a Ca²⁺‐dependent manner and is often chosen as a marker for cell apoptosis. Lipid vesicles with and without PS are spotted in individual wells and spontaneously formed a planar lipid bilayer on the bottom of the buffer‐filled wells. Annexin V can be used to distinguish between wells containing PS groups previously incorporated in the membrane patches and reference wells without PS head groups. Also, the dependence on the calcium concentration can be shown. Fluorescence readout of the assays is performed using a highly sensitive system based on a planar optical waveguide.     

Rubber-crumb modified polystyrene

The strain energy release rate,G _c, of polystyrene (PS) containing rubber crumb has been examined. It was found that for unmodified crumb, addition of small amounts (5%) leads to 100% increase inG _c. This is attributed to crazing in the PS. However, further addition of crumb leads to reductions inG _c, as the crumb-PS adhesion is low and interfacial failure results. If the crumb is modified with PS its adhesion to the matrix PS increases and internal rupture of the rubber occurs.G _c for these composites increases linearly with crumb loading, and is due to matrix crazing as well as rupture of the rubber phase.     

Controlling the aggregation behavior of gold nanoparticles

The aggregation of Au nanoparticles (NPs) in solution is influenced by cationic and oligocationic species. The polarization of the conduction electron oscillations in adjacent gold nanoparticles causes a new red-shifted plasmon absorbance attributed to the coupling of the plasmon absorbance of the particles. This appearance of an additional plasmon band is of particular interest to the field of SERS and has led to research works directed at the stabilization of small colloid aggregates in solution. The surface plasmon coupling can be tuned by controlling the aggregation of gold nanoparticles by the addition of some “cross-linking” agent. Here we develop a simple method to fabricate linear-chainlike aggregates of gold nanoparticles (so-called nanochains), tuning the linear optical properties in a wide wavelength range from visible to the near-infrared. The aggregation behavior and linear self-assembly mechanism of citrate-stabilized gold colloids as provoked by the addition of cetyltrimethylammonium bromide (CTAB) and 11-mercaptoundecanoic acid (MUA) are also analyzed. The line-assembly mechanism of gold nanochain is attributed to the preferential binding of CTAB molecules on a certain facet of gold NPs and the Au NP electrostatic interactions. We also found that the 11-mercaptoundecanoic acid was effective to prevent the further aggregation of CTAB-modified gold colloids.     

Protein Toxin Chaperoned by LRP‐1‐Targeted Virus‐Mimicking Vesicles Induces High‐Efficiency Glioblastoma Therapy In Vivo

Glioblastoma is a most intractable and high‐mortality malignancy because of its extremely low drug accessibility resulting from the blood–brain barrier (BBB). Here, it is reported that angiopep‐2‐directed and redox‐responsive virus‐mimicking polymersomes (ANG‐PS) (angiopep‐2 is a peptide targeting to low‐density lipoprotein receptor‐related protein‐1 (LRP‐1)) can efficiently and selectively chaperone saporin (SAP), a highly potent natural protein toxin, to orthotopic human glioblastoma xenografts in nude mice. Unlike chemotherapeutics, free SAP has a low cytotoxicity. SAP‐loaded ANG‐PS displays, however, a striking antitumor activity (half‐maximal inhibitory concentration, IC₅₀ = 30.2 × 10^?9m ) toward U‐87 MG human glioblastoma cells in vitro as well as high BBB transcytosis and glioblastoma accumulation in vivo. The systemic administration of SAP‐loaded ANG‐PS to U‐87 MG orthotopic human‐glioblastoma‐bearing mice brings about little side effects, effective tumor inhibition, and significantly improved survival rate. The protein toxins chaperoned by LRP‐1‐targeted virus‐mimicking vesicles emerge as a novel and highly promising treatment modality for glioblastoma.     

Photoinduced enhancement of optical second harmonic generation in LiB3O5 nanocrystallites embedded between the Ag/ITO electrodes

It is reported that there is substantial enhancement of the optical second harmonic generation (SHG) at 1064 nm Nd:YAG laser wavelength for LiB₃O₅ nanocrystatllites embedded into the electric field aligned photopolymer oligoetheracrylate matrices. The borate nanocomposite was put between the electrodes containing Ag/ZnO NP with silver sizes 20, 40 and 60 nm. We study an influence of the Ag NP sizes on the output SHG. It is clearly seen that only excitation by the green continuous wave 532 nm laser with power about 350–400 mW with beam diameter about 4 mm give significant effect. The latter confirms a principal role of the surface plasmon resonances spectrally overlapped with the nonlinear excitations responsible for the observed changes of the SHG.     

Design und Herstellung selektiver Dünnschichtabsorber auf Silberinselbasis. Design and fabrication of selective multilayer absorber based on silver island films

The combination of a metal island film with a dielectric multilayer represents a novel approach for preparation of spectrally selective absorbers. Metal island films show exceptional optical properties caused by the optical excitation of surface plasmon modes. The plasmon resonance frequency depends on the size and shape of the islands and is influenced by the deposition parameters. The first type of samples represents a silver island film in an ultra thin Al₂O₃ film. We analyzed these samples by means of spectrophotometry. The recorded spectra allow the calculation of the optical constants of the silver island films. These show a maximum absorptance up to 40 %. Finally, we incorporated ultrathin metal‐dielectric‐composite films on a silver/alumina basis into multilayer stacks to design tailored spectrally selective absorber coatings. The stack absorptance comes close to 100 %.     

Sensitivity Tuning through Additive Heterogeneous Plasmon Coupling between 3D Assembled Plasmonic Nanoparticle and Nanocup Arrays

Plasmonic substrates have fixed sensitivity once the geometry of the structure is defined. In order to improve the sensitivity, significant research effort has been focused on designing new plasmonic structures, which involves high fabrication costs; however, a method is reported for improving sensitivity not by redesigning the structure but by simply assembling plasmonic nanoparticles (NPs) near the evanescent field of the underlying 3D plasmonic nanostructure. Here, a nanoscale Lycurgus cup array (nanoLCA) is employed as a base colorimetric plasmonic substrate and an assembly template. Compared to the nanoLCA, the NP assembled nanoLCA (NP‐nanoLCA) exhibits much higher sensitivity for both bulk refractive index sensing and biotin–streptavidin binding detection. The limit of detection of the NP‐nanoLCA is at least ten times smaller when detecting biotin–streptavidin conjugation. The numerical calculations confirm the importance of the additive plasmon coupling between the NPs and the nanoLCA for a denser and stronger electric field in the same 3D volumetric space. Tunable sensitivity is accomplished by controlling the number of NPs in each nanocup, or the number density of the hot spots. This simple yet scalable and cost‐effective method of using additive heterogeneous plasmon coupling effects will benefit various chemical, medical, and environmental plasmon‐based sensors.     

Multifunctional Magnetic–Optical Nanoparticle Probes for Simultaneous Detection,Separation, and Thermal Ablation of Multiple Pathogens

Multifunctional nanoparticles possessing magnetization and near‐infrared (NIR) absorption have warranted interest due to their significant applications in magnetic resonance imaging, diagnosis, bioseparation, target delivery, and NIR photothermal ablation. Herein, the site‐selective assembly of magnetic nanoparticles onto the ends or ends and sides of gold nanorods with different aspect ratios (ARs) to create multifunctional nanorods decorated with varying numbers of magnetic particles is described for the first time. The resulting hybrid nanoparticles are designated as Fe₃O₄? Au_rod? Fe₃O₄ nanodumbbells and Fe₃O₄? Au_rod necklacelike constructs with tunable optical and magnetic properties, respectively. These hybrid nanomaterials can be used for multiplex detection and separation because of their tunable magnetic and plasmonic functionality. More specifically, Fe₃O₄? Au_rod necklacelike probes of different ARs are utilized for simultaneous optical detection based on their plasmon properties, magnetic separation, and photokilling of multiple pathogens from a single sample at one time. The combined functionalities of the synthesized probes will open up many exciting opportunities in dual imaging for targeted delivery and photothermal therapy.     

Effect of particle size on in vitro cytotoxicity of titania and alumina nanoparticles

Aluminium oxide (Al₂O₃) and titanium dioxide (TiO₂) nanoparticles (NPs) have been widely used in nanotechnology-based products. Recently, researchers and the public have raised concerns about the adverse effects of these NPs in biological systems, particularly in humans. The aim of this study was to investigate the possible adverse effects of these two common metal oxide NPs on human lung epithelium cells (A549) and to investigate NP size-dependent effects on these cells, considering both the primary and hydrodynamic particle size. NPs were found to inhibit cell viability and proliferation at the highest concentration level (10?mg/mL) included in this study, as measured by a clonogenic assay. Moreover, cell viability, proliferation and metabolism were impaired to a greater extent by the smaller NPs (5?nm TiO₂ and 10?nm Al₂O₃) relative to the larger particles (200?nm TiO₂ and 50?nm Al₂O₃) included in this study, as measured by cell proliferation and metabolism. Notably, the observed cytotoxic effects correlated to the primary size, rather than the hydrodynamic size. Similarly, NP cytotoxicity was found to be correlated with the NP surface area. These findings highlight the importance of including primary size and surface area information in NP characterisation in cytotoxicity studies.     

Quantification of Protein‐Induced Membrane Remodeling Kinetics In Vitro with Lipid Multilayer Gratings

The dynamic self‐organization of lipids in biological systems is a highly regulated process that enables the compartmentalization of living systems at micro‐ and nanoscopic scales. Consequently, quantitative methods for assaying the kinetics of supramolecular remodeling such as vesicle formation from planar lipid bilayers or multilayers are needed to understand cellular self‐organization. Here, a new nanotechnology‐based method for quantitative measurements of lipid–protein interactions is presented and its suitability for quantifying the membrane binding, inflation, and budding activity of the membrane‐remodeling protein Sar1 is demonstrated. Lipid multilayer gratings are printed onto surfaces using nanointaglio and exposed to Sar1, resulting in the inflation of lipid multilayers into unilamellar structures, which can be observed in a label‐free manner by monitoring the diffracted light. Local variations in lipid multilayer volume on the surface is used to vary substrate availability in a microarray format. A quantitative model is developed that allows quantification of binding affinity (K _D) and kinetics (k_on and k_off). Importantly, this assay is uniquely capable of quantifying membrane remodeling. Upon Sar1‐induced inflation of single bilayers from surface supported multilayers, the semicylindrical grating lines are observed to remodel into semispherical buds when a critical radius of curvature is reached.