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12 pags., 8 figs., 2 tabs., app., Silver nanostars (AgNS) have promising applications in spectroscopic, theranostic and sensing applications. In this work we have tuned the morphology of AgNS by the modification of the experimental fabrication conditions. Silver nanostars were fabricated by following a two-step process that involves the use of two different chemical reducers: neutral hydroxylamine (HA), employed as primary chemical reducer, and citrate (CIT), in a second reduction step. The key experimental parameters which were modified in this work were the [HA]/[Ag] ratio (R), the [HA]/[CIT] ratio (R) and the time between reductions or elapsed time (T), which also determines a factor of the highest importance: the ratio between the Ag concentrations existing at the beginning of each reduction process (R). The growth mechanisms followed by Ag nanostars to reach their final size and shape determined different growth pathways which were identified in this work as well, as deduced by the analysis derived from the transmission electron micoroscopic (TEM) images and the extinction spectra from the resulting plasmons. The SERS effectiveness of the resulting substrates was analyzed by using thiophenol (TP) as molecular probe, and a correlation between morphology and SERS intensification factor was deduced. The experimental parameters leading to the highest SERS enhancement were identified. Finally, these Ag nanostars were probed in the sensitive detection of Congo Red, an amyloid marker dye usually employed in the detection of amyloid fibrils related to Alzheimer diseases., Ministerio de Economía y Competitividad (MINECO, grant FIS2014-52212-R).

12 pags., 12 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0, Periodic structures of alternating amorphous-crystalline fringes have been fabricated in silicon using repetitive femtosecond laser exposure (800 nm wavelength and 120 fs duration). The method is based on the interference of the incident laser light with far- and near-field scattered light, leading to local melting at the interference maxima, as demonstrated by femtosecond microscopy. Exploiting this strategy, lines of highly regular amorphous fringes can be written. The fringes have been characterized in detail using optical microscopy combined modelling, which enables a determination of the three-dimensional shape of individual fringes. 2D micro-Raman spectroscopy reveals that the space between amorphous fringes remains crystalline. We demonstrate that the fringe period can be tuned over a range of 410 nm - 13 μm by changing the angle of incidence and inverting the beam scan direction. Fine control over the lateral dimensions, thickness, surface depression and optical contrast of the fringes is obtained via adjustment of pulse number, fluence and spot size. Large-area, highly homogeneous gratings composed of amorphous fringes with micrometer width and millimeter length can readily be fabricated. The here presented fabrication technique is expected to have applications in the fields of optics, nanoelectronics, and mechatronics and should be applicable to other materials., M.G.-L. thanks the Spanish Ministry of Education for a FPU fellowship. This work was supported by the LiNaBioFluid project (H2020-FETOPEN-2014-2015RIA, grant 665337) of the European Commission; and the research grant (TEC2014-52642-C2-1-R) from the Spanish Ministry of Economy and Competitiveness.

12 pags., 8 figs., 1 tab., Substance P (SP) is one of the most studied peptide hormones and knowing the relationship between its structure and function may have important therapeutic applications in the treatment of a variety of stress-related illnesses. In order to obtain a deeper insight into its folding, the effects of different factors, such as pH changes, the presence of Ca ions, and the substitution of the Met-NH moiety in the SP structure, was studied by Raman and infrared spectroscopies. SP has a pH-dependent structure. Under acidic–neutral conditions, SP possesses a prevalent β-sheet structure although also other secondary structure elements are present. By increasing pH, a higher orderliness in the SP secondary structure is induced, as well as the formation of strongly bound intermolecular β-strands with a parallel alignment, which favour the self-assembly of SP in β-aggregates. The substitution of the Met-NH moiety with the acidic functional group in the SP sequence, giving rise to a not biologically active SP analogue, results in a more disordered folding, where the predominant contribution comes from a random coil. Conversely, the presence of Ca ions affects slightly but sensitively the folding of the polypeptide chain, by favouring the α-helical content and a different alignment of β-strands; these are structural elements, which may favour the SP biological activity. In addition, the capability of SERS spectroscopy to detect SP in its biologically active form was also tested by using different metal nanoparticles. Thanks to the use of silver NPs prepared by reduction of silver nitrate with hydroxylamine hydrochloride, SP can be detected at very low peptide concentration (~ 90 nM). However, the SERS spectra cannot be obtained under alkaline conditions since both the formation of SP aggregates and the lack of ion pairs do not allow a strong enough interaction of SP with silver NPs. [Figure not available: see fulltext.]., This work was supported by the Scientific Grant Agency of the Ministry of the Education of Slovak Republic (APVV-15- 0485) and the Ministerio de Economía y Competitividad from Spain under the grant FIS2017-84314-R.

CLEO: Applications and Technology 2017 San Jose, California United States 14–19 May 2017, We demonstrate an innovative way to fabricate different types of amorphous-crystalline surface structures in silicon using ultrashort laser pulses. Fluence-dependent solidification dynamics and interference of incident and scattered laser light are identified as underlying mechanisms.

In this work, a novel methodology based on hyperspectral imagery with enhanced Darkfield microscopy for probing and characterizing changes in blood cell components was tested. Two main categories of blood cells were analyzed, red and white blood cells. Unique spectral signatures of ordinary and most common deformed morphologies of red blood cells were identified. Moreover, examination of white blood cells allowed to characterize and differentiate active from inactive cells. The findings indicate the ability of this technique to detect changes in light scattering property of blood cells due to their morphological properties Since pathological states can alterate the discocyte shape, this preliminary, but promising application of the hyperspectral analysis to blood cells can be useful to evaluate significant correlations of blood cell spectral features in healthy and pathological conditions. The combination of the quali- and quantitative spectral signatures of hyperspectral imaging microscopy with the information of the subject health conditions may provide a new tool for clinical applications.

We report in this work the fabrication, for the first time, of silver nanostars (AgNS) by a simple new method consisting of the chemical reduction of Ag+ by neutral hydroxylamine, followed by a capping–reduction process induced by citrate. TEM and SEM were employed to study the morphology of the resulting nanoparticles, which exhibit a star-shaped morphology with a central particle provided with several arms or protuberances with low sharpness in the vertices. Dark field microscopy was employed to study the scattering emission of individual nanostars indicating the increasing presence of nanoparticles with scattering emission toward the red region. AgNS displayed a high performance in surface-enhanced Raman scattering (SERS) applications. The effectiveness of these nanoparticles was probed by using the drug probenecid, leading to intense SERS spectra without the addition of aggregation agents.

10 págs.; 5 figs.; 1 scheme, ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) is a compound extensively employed to evaluate the free radical trapping capacity of antioxidant agents and complex mixtures such as biological fluids or foods. This evaluation is usually performed by using a colourimetric experiment, where preformed ABTS radical cation (ABTS˙+) molecules are reduced in the presence of an antioxidant causing an intensity decrease of the specific ABTS˙+ UV-visible absorption bands. In this work we report a strong effect of silver plasmonic nanoparticles (Ag NPs) on ABTS leading to the formation of ABTS˙+. The reaction of ABTS with Ag NPs has been found to be dependent on the interfacial and plasmonic properties of NPs. Specifically, this reaction is pronounced in the presence of spherical nanoparticles prepared by the reduction of silver nitrate with hydroxylamine (AgH) and in the case of star-shaped silver nanoparticles (AgNS). On the other hand, spherical nanoparticles prepared by the reduction of silver nitrate with citrate apparently do not react with ABTS. Additionally, the formation of ABTS˙+ is investigated by surface-enhanced Raman scattering (SERS) and the assignment of the most intense vibrational bands of this compound is performed. The SERS technique enables us to detect this radical cation at very low concentrations of ABTS (∼2 μM). Altogether, these findings allow us to suggest the use of ABTS/Ag NPs-systems as reliable and easy going substrates to test the antioxidant capacity of various compounds, even at concentrations much lower than those usually used in the spectrophotometric assays. Moreover, we have suggested that ABTS could be employed as a suitable agent to investigate the interfacial and plasmonic properties of the metal nanoparticles and, thus, to characterize the nanoparticle metal systems employed for various purposes. This journal is©the Owner Societies 2016, This work was supported by the Scientific Grant Agencies of the Ministry of the Education of Slovak Republic (APVV-15-0485 and VEGA 1/0929/16) and the 7FP EU project CELIM 316310. This work has also been financially supported by MINECO (Project FIS2014-52212-R). A. G.-L. acknowledges CSIC and FSE for a JAE-Pre PhD fellowship.

8 págs.; 5 figs.; 1 tab., Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N ) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics., This work has been supported by the LiNaBioFluid project of the H2020 program of the European Commission (FETOPEN- 665337) as well as by the Spanish TEC2014-52642-C2- 1-R. MG-L and JH-R acknowledge the grants respectively awarded by the Spanish Ministry of Education and the Spanish Ministry of Economy and Competiveness.

1 pag. -- Correction to: Scientifc Reports https://doi.org/10.1038/s41598-017-04891-3, published online 04 July 2017

9 pas.; 7 figs.; 2 tabs., This journal is © The Royal Society of Chemistry. Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars. The size, shape, and composition of Ag as well as their optical properties were studied by extinction spectroscopy, hyperspectral dark field microscopy, transmission and scanning electron microscopy (TEM and SEM), and energy dispersive X-ray spectroscopy (EDX). Finally, the surface-enhanced Raman scattering (SERS) activity of these HNS was investigated by using thioflavin T, a biomarker of the β-amyloid fibril formation, responsible for Alzheimer's disease. Lucigenin, a molecule displaying different SERS activities on Au and Ag, was also used to explore the presence of these metals on the NP surface. Thus, a relationship between the morphology, plasmon resonance and SERS activity of these new NPs was made., This work has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO, grant FIS2014-52212- R). A. G.-L. acknowledges CSIC and FSE 2007–2013 for a JAE-CSIC predoctoral grant.

In this work, a novel methodology based on hyperspectral imagery with enhanced Darkfield microscopy for probing and characterizing changes in blood cell components was tested. Two main categories of blood cells were analyzed, red and white blood cells. Unique spectral signatures of ordinary and most common deformed morphologies of red blood cells were identified. Moreover, examination of white blood cells allowed to characterize and differentiate active from inactive cells. The findings indicate the ability of this technique to detect changes in light scattering property of blood cells due to their morphological properties Since pathological states can alterate the discocyte shape, this preliminary, but promising application of the hyperspectral analysis to blood cells can be useful to evaluate significant correlations of blood cell spectral features in healthy and pathological conditions. The combination of the quali- and quantitative spectral signatures of hyperspectral imaging microscopy with the information of the subject health conditions may provide a new tool for clinical applications.

The vibrational characterization of the dye most commonly used for detection of amyloid aggregates Thioflavin T (ThT) was carried out by means of Raman and surface-enhanced Raman scattering (SERS) at different excitation wavelengths. The vibrational spectra obtained experimentally were subsequently analyzed using DFT calculations at the B3LYP/6-31+G** level. The Raman spectrum of ThT in aqueous solution correlates very well with the calculated spectrum of ThT with the torsional angle between the benzothiazole (BT) and dimethylaminobenzene (DMB) moieties of 37°. The SERS technique was very useful for the detection of two structures of ThT molecules in the vicinity of the metal nanoparticles: (i) directly adsorbed onto the metal surface and (ii) molecules forming multilayers. The structure of ThT molecules in multilayers is similar to the structure of free ThT in aqueous solution. The molecules directly adsorbed on the metal surface actually correspond to the molecules with 90° torsional angle between the BT and DMB rings. © 2013 American Chemical Society., This work has been supported by the Spanish Ministerio de Ciencia e Innovacion (FIS2010-15405) and Comunidad de ́ Madrid through the MICROSERES II network (grant S2009/ TIC-1476), by the Agency of the Ministry of Education of the Slovak Republic for the Structural Funds of EU (project ”Development of optical nanosensors for multicomponental analysis of trace amount of environmental pollutants and drugs (NanoBioSens)” (ITMS 26220120024) (60%)), by the Slovak Research and Development Agency (contract APVV- 0242-11), and Slovak Grant Agency VEGA (projects 2/0025/12 and 2/ 0155/11). A.G.-L. acknowledges CSIC for a JAE-Pre PhD fellowship.

Silicon is one of the key-materials of nowadays technology. This is partly related to its special phase change dynamics characteristics. In particular, upon pulsed laser irradiation, silicon can re-solidify either in the crystalline (c-) or amorphous (a-) phase depending on the local supercooling achieved [1]. This feature has recently been used to produce non-ablative LIPSS (Laser Induced Periodic Surface Structures [2]) in crystalline silicon upon multiple laser pulse exposure. The induced structures consist of a-c-fringes with subwavelength period [3].