Facile functionalization of a fully fluorescent perfluorophenyl BODIPY: photostable thiol and amine conjugates

Selective nucleophilic substitution on a perfluorophenyl unit comprising a BODIPY fluorophore using an alkanethiol or a primary amine offers a quantitative fluorophore labelling strategy, while retaining high photostability and emission quantum yields approaching unity.     

Patterning of indium-tin oxide on glass with picosecond lasers

The results of patterning of the indium-tin oxide (ITO) film on the glass substrate with high repetition rate picosecond lasers at various wavelengths are presented. Laser radiation initiated the ablation of the material, forming grooves in ITO. Profile of the grooves was analyzed with a phase contrast optical microscope, a stylus type profiler, scanning electron microscope (SEM) and atomic force microscope (AFM). Clean removal of the ITO film was achieved with the 266 nm radiation when laser fluence was above the threshold at 0.20 J/cm², while for the 355 nm radiation, the threshold was higher, above 0.46 J/cm². The glass substrate was damaged in the area where the fluence was higher than 1.55 J/cm². The 532 nm radiation allowed getting well defined grooves, but a lot of residues in the form of dust were generated on the surface. UV radiation with the 266 nm wavelength provided the widest working window for ITO ablation without damage of the substrate. Use of UV laser radiation with fluences close to the ablation threshold made it possible to minimize surface contamination and the recast ridge formation during the process.     

Influence of applied potential on bradykinin adsorption onto Ag,Au, and Cu electrodes

Surface‐enhanced Raman scattering, electrochemistry, and generalized two‐dimensional correlation analysis (G2DCA) methods were used to characterize bradykinin (BK), a hormone which is known to be involved in small‐cell and non‐small‐cell lung carcinoma and prostate cancer. BK was deposited onto Ag, Au, and Cu electrode surfaces under different applied electrode potentials (−1.000 V to 0.200 V) in aqueous solutions. Based on the analysis of the enhancement, the broadening, and the shifts in the wavenumbers of individual bands, specific conclusions were drawn regarding the peptide geometry and changes in this geometry that occurred when the electrode type and applied electrode potential were varied. Briefly, BK deposited onto the Ag, Au, and Cu electrode surfaces showed bands that were due to the vibrations of moieties in contact with or in close proximity to the electrode surfaces and were thus located on the same side of the polypeptide backbone. These moieties included the Phe, Arg, and Pro residues. The findings for adsorbed BK were fully supported by G2DCA, which also allowed us to determine the order in which changes occurred when the electrode potential was changed. In addition, it was found that at negative electrode potentials, the Phe rings and methylene groups interact with Ag electrode surface. No such interaction was observed for Au and Cu electrodes. Copyright © 2013 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering sensing on black silicon

Reactive ion etching was used to fabricate black‐Si over the entire surface area of 4‐inch Si wafers. After 20 min of the plasma treatment, surface reflection well below 2% was achieved over the 300–1000 nm spectral range. The spikes of the black‐Si substrates were coated by gold, resulting in an island film for surface‐enhanced Raman scattering (SERS) sensing. A detection limit of 1 × 10^?6 M (at count rate > 10² s^?1 . mW^?1) was achieved for rhodamine 6G in aqueous solution when drop cast onto a ～ 100‐nm‐thick Au coating. The sensitivity increases for thicker coatings. A mixed mobile‐on‐immobile platform for SERS sensing is introduced by using dog‐bone Au nanoparticles on the Au/black‐Si substrate. The SERS intensity shows a non‐linear dependence on the solid angle (numerical aperture of excitation/collection optics) for a thick gold coating that exhibits a 10 times higher enhancement. This shows promise for augmented sensitivity in SERS applications.     

Pulsed-laser generation of gold nanoparticles with on-line surface plasmon resonance detection

Size of nanoparticles is an important parameter for their applications. The real-time monitoring is required for reliable and reproducible production of nanoparticles with controllable size. We present results of our research on development of the system for the online nanoparticle characterization during their production by a laser. The laser ablation chamber which allows measurements of surface plasmon resonance spectra during the nanoparticle generation process has been designed and fabricated. The online characterization system was tested by producing and modification of gold nanoparticles. Nanoparticles were generated by nanosecond-laser (wavelength 1064 nm) ablation of gold target in deionized water, and optimal conditions for the highest nanoparticle productivity were estimated. The mean diameter of nanoparticles was determined using their absorption spectra measured in the real-time during the ablation experiments and from the TEM images analysis, and it varied from 20 to 45 nm. The mismatch between nanoparticle diameters, estimated using these two methods, is due to the polydispersity of the generated nanoparticles. The further experiments of laser-induced modification of colloidal gold nanoparticles were carried out using second harmonic (wavelength 532 nm) of nanosecond Nd:YAG laser and alteration in nanoparticle size were acquired by the online measurement system.     

Control of surface charge for high‐fidelity nanostructuring of materials

The universal problem of surface charging during focused ion milling has been fully resolved using a flood‐gun approach based on simultaneous co‐illumination with a UV light‐emitting diode (LED). Non‐distorted as‐designed nano‐patterns were milled using Ga⁺ ions on dielectric materials which charge up strongly. Deep‐UV (250–280 nm) LED co‐illumination during the ion beam milling fully discharges optically the surface under standard Ga⁺ ion‐milling conditions. Photo‐ionization of electrons trapped at the sub‐surface defects to the free vacuum state is a key to the phenomenon ( nm corresponds to a photon energy  eV). The method is applicable as a solution to other charging problems where electrons (primary or secondary) and their spatial redistribution affect nanofabrication or imaging.     

Development of Functionalized Cyclotriveratrylene Analogues: Introduction of Withdrawing and π-Conjugated Groups

Cyclotriveratrylene analogues (CTVs) are supramolecular bowl-shaped molecules known for their ability to complex organic and organometallic guests, to form liquid crystals, polymers, or nanostructures. In this Article, we report the synthesis of new cyclotriveratrylene analogues with fluorescence properties in which various electron-withdrawing or π-extended conjugated groups are appended to the wide rim ortho to the methoxy-donating groups. Synthetically, these functionalized CTVs cannot be obtained as CTVs with electron-rich functions by the typical method (i.e., the trimerization of the corresponding benzyl alcohol) but are prepared from a common key intermediate, the C(3)-triiodocyclotriveratrylene (CTV-I(3)), in good yields. Despite the synthetic difficulties encountered due to the presence of three reactive centers, we have demonstrated the possibility of performing Sonogashira coupling and Huisgen cycloaddition reactions directly to the CTV core for the first time. CTVs with π-extended conjugated groups reveal interesting fluorescence profiles. More broadly, this study utilizes CTV-I(3) to introduce novel functionalities into CTVs to keep exploring their potential applications.     

C3-triiodocyclotriveratrylene as a key intermediate to fluorescent probes: application to selective choline recognition

A new strategy to obtain fluorescent cyclotriveratrylene (CTV) probes is proposed. The key intermediate, a triiodo CTV, is prepared in 3 steps with 47% overall yield. The whole synthesis requires only one purification step. The potential of this triiodo CTV as an intermediate is illustrated through the synthesis of a fluorescent phosphorylated probe that is able to bind choline and acetylcholine in pseudo-physiological conditions, with selectivity towards choline. As a consequence, this intermediate should allow us to rapidly form a library of probes in order to highlight the most promising ones.