Direct Creation of Biopatterns via a Combination of Laser-Based Techniques and Click Chemistry.

In this paper, we present the immobilization of thiol-modified aptamers on alkyne- or alkene-terminated silicon nitride surfaces by laser-induced click chemistry reactions. The aptamers are printed onto the surface by laser-induced forward transfer (LIFT), which also induces the covalent bonding of the aptamers by thiol-ene or thiol-yne reactions that occur upon UV irradiation of the thiol-modified aptamers with ns laser pulses. This combination of LIFT and laser-induced click chemistry allows the creation of high-resolution patterns without the need for masks. Whereas the click chemistry already takes place during the printing process (single-step process) by the laser pulse used for the printing process, further irradiation of the LIFT-printed aptamers by laser pulses (two-step process) leads to a further increase in the immobilization efficiency.

Optically implemented broadband blueshift switch in the terahertz regime.

We experimentally demonstrate, for the first time, an optically implemented blueshift tunable metamaterial in the terahertz (THz) regime. The design implies two potential resonance states, and the photoconductive semiconductor (silicon) settled in the critical region plays the role of intermediary for switching the resonator from mode 1 to mode 2. The observed tuning range of the fabricated device is as high as 26% (from 0.76 THz to 0.96 THz) through optical control to silicon. The realization of broadband blueshift tunable metamaterial offers opportunities for achieving switchable metamaterials with simultaneous redshift and blueshift tunability and cascade tunable devices. Our experimental approach is compatible with semiconductor technologies and can be used for other applications in the THz regime.

Coherent control of THz pulses polarization from femtosecond laser filaments in gases.

We demonstrate the possibility to rotate the polarization of linearly polarized THz pulses via the accurate control of the 2-color filament surrounding gas pressure. We also show ways to produce elliptically and circularly polarized THz pulses.

Probing the electronic stability of multiply charged anions: sulfonated pyrene tri- and tetraanions.

The strong intramolecular Coulomb repulsion in multiply charged anions (MCAs) creates a potential barrier that provides dynamic stability to MCAs and allows electronically metastable species to be observed. The 1-hydroxy-3,6,8-pyrene-trisulfonate {[Py(OH)(SO(3))(3)](3-) or HPTS(3-)} was recently observed as a long-lived metastable MCA with a large negative electron binding energy of -0.66 eV. Here we use Penning trap mass spectrometry to monitor the spontaneous decay of HPTS(3-) --> HPTS(*2-) + e(-) and have determined the half-life of HPTS(3-) to be 0.1 s. To explore the limit of electronic metastability, we tried to make the related quadruply charged pyrene-1,3,6,8-tetrasulfonate {[Py(SO(3))(4)](4-)}. However, only its decay product, the triply charged radical anion [Py(SO(3))(4)](*3-), as well as the triply charged ion-pairs [Py(SO(3))(4)H](3-) and [Py(SO(3))(4)Na](3-), was observed, suggesting that the tremendous intramolecular Coulomb repulsion makes the [Py(SO(3))(4)](4-) anion extremely short-lived. Photoelectron spectroscopy data showed that [Py(SO(3))(4)](*3-) is an electronically stable species with electron binding energies of +0.5 eV, whereas [Py(SO(3))(4)H](3-) and [Py(SO(3))(4)Na](3-) possess electron binding energies of 0.0 and -0.1 eV, respectively. Ab initio calculations confirmed the stability of these triply charged species and further predicted a large negative electron binding energy (-2.78 eV) for [Py(SO(3))(4)](4-), consistent with its short lifetime.

Laser Induced Forward Transfer: a study on the enhancement of sensitivity for multianalyte sensing.

In this article novel approaches for the improvement of the recorded signal coupled with the feasibility of multiple analyte detection, irrespective of the biosensor platform are being presented. The techniques that have been developed address commonly encountered issues that have traditionally hindered the commercialization of biosensors, such as cost, reproducibility and sensitivity and most importantly multianalyte detection. The fluorescence-based detection of copper is being described as an example of the use of Laser Induced Forward Transfer technique (LIFT) for the immobilization of biomolecules with high spatial resolution, in addition to a technique that involves the displacement of a short complementary strand to the immobilized probe molecule for the quantification of analyte binding and the enhancement of the recorded signal.

Detection of harmful residues in honey using terahertz time-domain spectroscopy.

Terahertz time-domain spectroscopy (THz-TDS) has been applied for the detection and discrimination of harmful chemical residues in honey. Three antibiotics (sulfapyridine, sulfathiazole, and tetracycline) and two acaricides (coumaphos and amitraz) were characterized in the THz frequency regime between 0.5 THz and 6.0 THz. All chemical substances present distinct absorption peaks. THz transmission measurements of honey mixtures with antibiotics have been performed, revealing that antibiotic residues are traceable in highly absorptive food products, such as honey, at concentrations down to 1% weight percentage, thanks to their THz fingerprints. Moreover, multiple antibiotics were identified in their mixture with honey, pointing out the potential of the technique to be used in the near future as a fast, real-time technique for detecting and discriminating multi-residues strictly related to food safety issues.

Vibrational constants and binding energies for the low-lying electronic states of Sr+ CO2 from photodissociation spectroscopy.

By use of photodissociation spectroscopy of mass-selected ions, vibrationally resolved electronic spectra of the Sr+ CO2 complex are recorded in two energy regions, 20,780-22,990 and 16,210-17,550 cm(-1), correlating to the Sr+ 5(2)P <-- 5(2)S and 4(2)D <-- 5(2)S transitions, respectively. The spectra are analyzed to obtain the vibrational constants and dissociation energies of the molecular states. The observed spin-orbit splitting indicates a linear complex in agreement with theoretical calculations. The results are compared with similar systems and explained in the framework of electrostatic interactions.