Super-resolution imaging has been advantageous in studying biological and chemical systems, but the required equipment and platforms are expensive and unable to observe single-molecules at the high (μM) fluorophore concentrations required to study protein interaction and enzymatic activity. Here, a plasmonic platform was designed that utilized an inexpensively fabricated plasmonic grating in combination with a scalable glancing angle deposition (GLAD) technique using physical vapor deposition. The GLAD creates an abundance of plasmonic nano-protrusion probes that combine the surface plasmon resonance (SPR) from the periodic gratings with the localized SPR of these nano-protrusions. The resulting platform enables simultaneous imaging of a large area without point-by-point scanning or bulk averaging for the detection of single Cyanine-5 molecules in dye concentrations ranging from 50 pM to 10 μM using epifluorescence microscopy. Combining the near-field plasmonic nano-protrusion probes and super-resolution technique using localization microscopy, we demonstrate the ability to resolve grain sizes down to 65 nm. This plasmonic GLAD grating is a cost-effective super-resolution imaging substrate with potential applications in high-speed biomedical imaging over a wide range of fluorescent concentrations.

We present a new approach for fabricating robust, regenerable antimicrobial coatings containing an ionic liquid (IL) phase incorporating silver nanoparticles (AgNPs) as a reservoir for Ag(0)/Ag(+) species within sol-gel-derived nanocomposite films integrating organosilicate nanoparticles. The IL serves as an ultralow volatility (vacuum-compatible) liquid target, allowing for the direct deposition and dispersion of a high-density AgNP "ionosol" following conventional sputtering techniques. Two like-anion ILs were investigated in this work: methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, [N(8881)][Tf(2)N], and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][Tf(2)N]. Silver ionosols derived from these two ILs were incorporated into silica-based sol-gel films and the resultant antimicrobial activity evaluated against Pseudomonas aeruginosa bacteria. Imaging of the surface morphologies of the as-prepared films established a link between an open macroporous film architecture and the observation of high activity. Nanocomposites based on [N(8881)][Tf(2)N] displayed excellent antimicrobial activity against P. aeruginosa over multiple cycles, reducing cell viability by 6 log units within 4 h of contact. Surprisingly, similar films prepared from [emim][Tf(2)N] presented negligible antimicrobial activity, an observation we attribute to the differing abilities of these IL cations to infiltrate the cell wall, regulating the influx of silver ions to the bacterium's interior.

This paper presents a detailed electrochemical impedance spectroscopy and cyclic voltammetry (CV) investigation into the electrocatalytic activity of ultrafine (i.e., smaller than 2 nm) platinum (Pt) nanoparticles generated on a fluorine-doped tin oxide (FTO) surface via room temperature tilted target sputter deposition. In particular, the Pt-decorated FTO electrode surfaces were tested as counter electrode candidates for triiodide (I3(-)) reduction in dye-sensitized solar cells (DSSCs). We observed a direct correlation between size-dependent Pt nanoparticle crystallinity and the I3(-) reduction activity underlying DSSC performance. CV analysis confirmed the higher electrocatalytic activities of sputter-deposited crystalline Pt nanoparticles (1-2 nm) compared with either sub-nanometre Pt clusters or a continuous Pt thin film. While the low catalytic activity and DSSC performance of Pt clusters smaller in size than 1 nm is believed to arise from their non-crystalline nature and charge-trapping attributes, we attribute the high catalytic performance of larger Pt nanoparticles in the 1-2 nm regime to their well-defined crystallinity and fast electron transfer kinetics. For DSSC applications, the optimized Pt loading was calculated to be ~2.54 × 10(-7) g cm(-2), which corresponds to surface coverage by ~1.6 nm sized Pt nanoparticles.

Ionic liquids (ILs) are being widely investigated as advanced electrolytes within electric double-layer capacitors (EDLCs) due to their inherent ionic conductivity, wide electrochemical windows, essentially zero volatility, and high temperature stability. Despite being composed entirely of ions, the ionic conductivity of a typical IL is significantly hindered by its high viscosity, rendering it akin to normal electrolytes. In this light, in order to increase the applicability of IL electrolytes, it is of the utmost priority to discover approaches for improving the electrochemical properties of ILs without adversely affecting their other beneficial attributes. In this work, we make important strides toward this goal by employing low energy sputtering to generate novel electrolytes comprising gold nanoparticle dispersions within the prototypical IL 1-ethyl-3-methylimidazolium ethyl sulfate, [emim][EtSO 4 ]. This study also afforded the unique opportunity to investigate nanoscale growth mechanisms occurring within the IL. Cyclic voltammetry and electrochemical impedance spectroscopy analyses revealed that when the IL contained a substantial fraction of sub-nanometer-sized particles, the double-layer capacitance was increased by $190%, concomitant with a bulk electrolyte resistance decrease of $70% with respect to a gold-free control. An exponential rise in resistance accompanied by a proportional decrease in capacitance accompanies nanoparticle growth until a critical size is reached-typically within 10 h at room temperature-beyond which the final capacitance is typically $60% higher than the control with an electrolyte resistance similar to the control. Overall, our results reveal an anomalous capacitance increase and low internal resistance for nanoparticle-in-IL dispersions, suggesting intriguing potential as electrolytes for next-generation EDLCs, fuel cells, and sensors.

Using a solid-state diffusion technique, conducting perylene radical ion salt films have been prepared with alkali ions (Na+ and K+) and antimony hexachloride (SbCl6−) as counter ions. The successful preparation of separate radical anion salt films and cation salt films, respectively, is proved by in situ absorption spectroscopy, conductivity measurements, and electron spin resonance. In contrast to comparatively weakly doped inorganic semiconductors, the ion salts have a high concentration of charge carriers of roughly one charge per molecular unit entailing correlation of the carriers. The sandwich structures consisting of both the cation salt layer and the anion salt layer, form an electrical junction comparable to the PIN-junctions (p-doped, intrinsic, n-doped) known from inorganic diodes. The rectifying ratio amounts up to 105:1 at ±0.5 V and the breakdown voltage in the reverse sense is −20 V at 300 K.

Classical methods for enhancing the electromagnetic field from substrates for spectroscopic applications, such as surface-enhanced Raman spectroscopy (SERS), have involved the generation of hotspots through directed self-assembly of nanoparticles or by patterning nanoscale features using expensive nanolithography techniques. A novel large-area, cost-effective soft lithographic technique involving glancing angle deposition (GLAD) of silver on polymer gratings is reported here. This method produces hierarchical nanostructures with high enhancement factors capable of analyzing single-molecule SERS. The uniform ordered and patterned nanostructures provide extraordinary field enhancements that serve as excitatory hotspots and are herein interrogated by SERS. The high spatial homogeneity of the Raman signal and signal enhancement over a large area from a self-assembled monolayer (SAM) of 2-naphthalenethiol demonstrated the uniformity of the hotspots. The enhancement was shown to have a critical dependence on the underlying nanostructure via the surface energy landscape and GLAD angles for a fixed deposition thickness, as evidenced by atomic force microscopy and scanning electron microscopy surface analysis of the substrate. The nanostructured surface leads to an extremely concentrated electromagnetic field at sharp nanoscale peaks, here referred to as 'nano-protrusions', due to the coupling of surface plasmon resonance (SPR) with localized SPR. These nano-protrusions act as hotspots which provide Raman enhancement factors as high as 10 over a comparable SAM on silver. Comparison of our substrate with the commercial substrate Klarite™ shows higher signal enhancement and minimal signal variation with hotspot spatial distribution. By using the proper plasmon resonance angle corresponding to the laser source wavelength, further enhancement in signal intensity can be achieved. Single-molecule Raman spectra for rhodamine 6G are obtained from the best SERS substrate (a GLAD angle of 60°). The single-molecule spectrum is invariant over the substrate, due to the patterned ordered nanostructures (nano-protrusions).

No abstract

Thin films of 2,5-dimethyl-NN'-dicyanoquinonediimine (DMe-DCNQI) with alkaline counter ions can be used as contactless sensors for spin-carrying gases, e.g. oxygen or NO. In the title compound, the linewidth of the electron spin resonance signal is a linear function of the partial pressure of oxygen. The sensitivity is in the order of 10-10 mol. O2. The films are 100 nm thick and show typical response times which are faster than tau =100 ms, the time constant of the ESR apparatus used. Because of the sensitivity, the constants of diffusion of gases through layers of coatings can be measured even at macroscopic thicknesses.