We study both experimentally and theoretically the driven motion of domain walls in extended amorphous magnetic films patterned with a periodic array of asymmetric holes. We find two crossed-ratchet effects of opposite sign that change the preferred sense for domain wall propagation, depending on whether a flat or a kinked wall is moving. By solving numerically a simple phi(4) model we show that the essential physical ingredients for this effect are quite generic and could be realized in other experimental systems involving elastic interfaces moving in multidimensional ratchet potentials.

Surface enhanced Raman scattering (SERS) is a powerful technique based on the intensification of the Raman signal because of the interaction of a molecule with a nanostructured metal surface. Electrochemically roughened silver has been widely used as SERS substrate in the qualitative detection of analytes at the ultra-trace level. However, its potential for quantitative analysis has not been widely exploited yet. In this work, the combination of time-resolved Raman spectroelectrochemistry with silver screen-printed electrodes (SPE) is proposed as a novel methodology for the preparation of SERS substrates. The in situ activation of a SERS substrate is performed simultaneously with the analytical detection of a probe molecule, controlling the process related to the preparation of the substrate and performing the analytical measurement in real time. The results show the good performance of silver SPE as electrochemically-induced surface-enhanced Raman scattering substrates. Raman spectra were recorded at fairly low integration times (250 ms), obtaining useful spectroelectrochemical information of the processes occurring at the SPE surface with excellent time-resolution. By recording the microscopic surface images at different times during the experiment, we correlated the different data obtained: structural, optical and electrochemical. Finally, the in situ activation process was used to obtain a suitable in situ SERS signal for ferricyanide and tris(bipyridine)ruthenium(II) quantification. The detection of the analytes at concentrations of a few tens of nM was possible with a low integration time (2 s) and good precision, demonstrating the exceptional performance of the Raman spectroelectrochemical method and the possibility to use cost-effective screen-printed electrodes for applications where a high sensitivity is needed.

Nowadays,a nalytical methods with portable characteristics for on-site and in-situ measurements continue to attract significant attention. In this context,t he use of miniaturizede lectrochemical systems has been proposed because they have severalo ft he requirements of portable methods [1,2].H owever, in manyc ases,m iniaturized systems are characterized by low robustness and reduced range of applications for each system or device. In 1991, Wang and Taha [3] introduced at echnique named batch injection analysis (BIA). In BIA systems with electrochemical detection, as ample plug is injected from am icropipette tip directly on the electrodes urface that is immersed in al arge-volume blank electrolyte solution. Ther esults obtained with aB IA system are conceptionally similar to FIA or SIA, however, withoutu sing additional components such as pumping systems,i njection valves,a nd tubes (possibility of problemsw ith air bubbles and leaks) [4].I nB IA systems, all of these components were replaced by ab attery powered electronic micropipette and, therefore,t he set consisting by BIA cell, electronic micropipette,m ini-potentiostat, and tablet or laptop computerc an be used as ap ortable electrochemical system.R ecently,o ur research group has developed BIA cells specially designed to work with screen-printed electrodes (SPEs) [5,6].S imilar to BIA systems, SPEs also presented some desirable features useful in portable analytical systems,s uch as low cost (large-scale production), disposability,r apid responses,s implicity and robustness (working, countera nd pseudo-reference electrodes are printed on achemically inert substrate).Considering the characteristics of BIA cells and SPEs, one can conclude that the system that combinesb oth de-vices has great potential to be used as ap ortable electrochemical system. Recently,w ei ntroduced ac ompact system composed by aB IA cell specially designed for SPEs( BIASPE cell).F igure 1s howsi mages of the detailed schematic design of the cell (Fig. 1A), photographs of the complete BIASPE cell ( Fig. 1B) and the innovative open-close system (no screws needed) for easy SPE replacement (Fig.1C).When the BIASPE cell is combinedw ith battery-powered accessories( electronic micropipette,p otentiostat and at ablet or al aptop computer), the generateds et can be considered as ar obust portable electrochemical system (Fig.1D). Further details on the proposed BIASPE cell can be found in multiplei mages availablei n supporting information. In addition, specific details on the operation of the BIASPE system (cella ssembly,p ositioning of the SPE in the cell, electronic micropipette operation,a mperometric and voltammetric experiments and visualization of the phenomena that occur on the working electrode surface during injection procedures) can be ac-Abstract:H erein, ac ompact batch injection analysisc ell for screen printed electrodes (BIASPE cell) is reported. Thep roposed system shows several requirements of ap ortable system that include easy-to-operate ("userfriendly"),h igh-speed qu...

The magnetization reversal process has been studied in amorphous magnetic films patterned with ordered arrays of antidots in the diluted limit (i.e., with small enough antidot density so that the original film anisotropy is maintained and the flux closure structures around each dot are independent from each other). The role of the material parameters in the final behavior has been analyzed comparing the results on films made of two different Co-based amorphous alloys, CoxSi1−x and CoyZr1−y, that present a similar intrinsic uniaxial anisotropy but have a different saturation magnetization. The patterned holes are found to act as weak pinning centers for the motion of the Néel walls involved in the reversal process which results in an enhancement of coercivity in certain angular ranges. However, they are only effective in the material with the lower saturation magnetization (CoxSi1−x) which can be related with the different relative sizes of the patterned holes and the Néel walls in each case.

Herein, a new miniaturized analytical instrumentation for electrochemiluminescence (ECL) assays is presented. A photodiode integrated in an ECL cell combined with a potentiostat/galvanostat, all integrated in a one-piece instrument (μSTAT ECL), was developed. In addition, a complementary micro-spectrometer integrated in a similar ECL cell for luminescence spectra recording is also proposed. Both cells are intended to be used with screen-printed electrodes and all the devices are portable and small sized. Their performance was corroborated with two innovative proofs-of-concept that centered on the luminol transduction chemistry: a first time reported ECL assay based on the enzymatic reaction between an indoxyl substrate and the enzyme alkaline phosphatase, and the electrochemiluminescence resonance energy transfer (ECL-RET) process triggered by the electro-oxidized luminol to the acceptor fluorescein. The photodiode system revealed to be more sensitive than the spectrometer device in collecting the light; however, with the latter, it is possible to discriminate different luminescent species according to their maximum wavelength emission, which is extremely useful for carrying out simple and simultaneous ECL multiplex analyzes. The spectrometer device works as an excellent accessory to couple with the μSTAT ECL instrument, complementing the experiments. Graphical abstract Schematic representation of the ECL-RET: from luminol-H2O2 system to fluorescein, the micro-spectrometer for the light collection and the 3D representation of the ECL-RET reaction.