This work presents a portable system developed to perform biochemical analyses requiring both temperature sensing for the thermal sample treatment and optical sensing to detect the analyte. To achieve this goal, we coupled a system-on-glass, hosting on a single glass substrate a thin film transparent heater and two temperature sensors, with interface electronics able to drive the heating source and control the temperature. The system-on-glass has been optimized to ensure temperature uniformity better than ±1.4 °C over a large-area (6 cm 2 ) and sensor resolution better than 0.01 °C. Moreover, the presented device operates at a remarkably low power of only 2.4 W/cm 2 to achieve a temperature of 100 °C, significantly below the power requirements of most comparable devices available on the market. The electronics has been designed to minimize electromagnetic interferences between the heater and the biological samples. The temperature-controlled platform has been enclosed in a 3D-printed black resin-made box whose dimensions are 11 cm · 10 cm · 2.4 cm, while the electronics is enclosed in a metallic box (12.55 cm · 8.05 cm · 4.32 cm), connected with the 3D-printed box by an Ethernet cable. The compactness and low weight (below 0.5 kg) of the two boxes ensures the system portability while the easy coupling of the system-on-glass with different kinds of microfluidic networks allows its employment for a large variety of biosensing applications.

In this work, a pixeled plasmonic metasurface has been employed as a Surface Enhanced InfraRed Absorption (SEIRA) spectroscopy platform to detect small amounts of compounds containing a peculiar IR signature. In particular, the N3 bonds vibrational feature (placed around 2100 cm−1) has been chosen due to its location far from the fingerprint region. The proposed platform has demonstrated its capability to detect and amplify the selected IR signature with a compound containing the abovementioned vibrational feature. In particular, the K molecule (Ac-Lys(N3)-Cys-NH2) has been considered as a proof of principle molecule, showing both a strong absorption peak corresponding to the detection of the N3 bonds and a maximum redshift of 65 cm−1 as compared to the naked sensors.

Spectrochemical analysis of trace elements in complex matrices is crucial across various fields of science, industry, and technology. However, this analysis is often hindered by background interference and the challenge of detecting ultralow analyte concentrations. Surface Enhanced Infrared Absorption (SEIRA) spectroscopy is emerging as a viable technique to address these challenges as it can successfully reveal soluble and unmodified analytes in a label-free manner through their interactions with a bioreceptor following site-specific labeling with small infrared-active probes. In this study, we present and demonstrate an advanced method for mid-infrared spectroscopy utilizing a pixeled SEIRA substrate coupled with a peculiar infrared-active vibrational probe. We select a small azide moiety as the vibrational tag since its signature around 2100 cm-1 is in the cell- and protein-silent window and its small size preserves the structure and biological function of the protein it integrates into. As model bioreceptor, we utilize an antigen-binding fragment (Fab') derived from the therapeutic antibody trastuzumab, modified with azidoacetic acid, and its Her2 antigen as the soluble analyte. Employing mid-infrared SEIRA spectroscopy, we are able to monitor the immobilization of the azide-modified Fab', and demonstrate the detection of analyte quantities as low as 83 amol within an area of 100 μm2.

The need for miniaturized biological sensors which can be easily integrated into medical needles and catheters for in vivo liquid biopsies with ever-increasing performances has stimulated the interest of researchers in Lab-on-Fiber (LOF) technology. In this framework, the integration of Metasurfaces (MSs) on the tip of the optical fiber (Optical Fiber Meta- Tip, OFMT) has represented a major breakthrough. Indeed, we showed that a suitably designed plasmonic OFMT biosensor significantly outperforms standard plasmonic ones due to the advanced light wave manipulation of MSs. Here, to further improve the sensing performances, we propose a novel class of LOF optrodes for labelled biosensing based on dielectric fluorescence enhancing OFMT. We envision a single fiber probe with integrated a Silicon MS on its tip as a light coupled substrate that illuminates the sample and simultaneously collects the enhanced emission from the dye molecules labeling the biological target. We present a numerical environment to compute the fluorescence enhancement factor collected by a multi-mode-fiber, when on its tip a Silicon MS is laid, consisting of an array of cylindrical nanoantennas. According to the numerical results, a suitable design of the dielectric MS allows for a fluorescence enhancement up to three orders of magnitudes. Moreover, a feasibility study is carried out to verify the possibility to fabricate the designed MSs on the termination of multimode optical fibers using electron beam lithography followed by reactive ion etching. This work provides the main guidelines for the development of advanced LOF devices based on the fluorescence enhancement for labeled biosensing.

An innovative pixeled plasmonic metasurface (MS) has been developed for surface-enhanced infrared absorption (SEIRA) spectroscopy. The MS is comprised of different pixels, each designed to monitor a specific region of the electromagnetic spectrum. These pixels are engineered with plasmonic resonances that match the Amide I and Amide II vibrational bands in the range of 1500-2000 cm-1. The proposed MS allowed a label-free spectroscopic characterization of a solution of biofibers isolated from cultured fibroblasts treated with an oligothiophene based oligomer. The reflection spectra acquired on areas containing a biofiber show the presence of the typical Amide I and Amide II vibrational bands, while reflection spectra acquired outside the fibers show no signal. Additionally, the evaluated enhancement factor (up to 1.4·103) enables the detection of very small amounts of material bound on the proposed platform, as in the case of a biofiber placed on the nanoantennas composing the MS pixels.

Next generation High Energy Physics (HEP) accelerators will require new devices and technologies capable of operating in extreme environments characterized by ultra-high radiation doses up to the MGy levels. To this aim, we report on an innovative Lab-On-Fiber (LOF) probe for the real-time dose monitoring. The proposed platform is based on a metallo-dielectric nanostructured grating made of gold and poly(methyl methacrylate) (PMMA) patterned on the termination of single mode fibers. The nanostructure has been judiciously designed to support a plasmonic resonance in the reflection spectrum occurring at near infrared wavelengths. Electron beam lithog-raphy was used for the fabrication of two LOF prototypes, which in turn, were exposed to X-rays with a total dose of 2.02 MGy and a dose rate of 88 kGy/h. Reflection spectra acquired during the irradiation revealed a clear dependence of the LOF resonance wavelength and depth on the absorbed dose, confirming the outcomes of our previous proton campaign. Morphological characterization of the irradiated samples showed that the main ra-diation induced effect is the reduction of the PMMA thickness (ranging between 26 % and 40 %), which in turn strongly affects the resonance behavior. Quantitative morphological measurements have been used to achieve a fair and objective correlation with our numerical modelling. Moreover, we investigated the effect of ultra-high doses of several radiation types, including X-rays, electrons and protons, on the thickness of PMMA nanolayers deposited on planar substrates. Experimental results revealed that the amount of absorbed dose (1.9-16.06 MGy) is the main parameter affecting the PMMA relative compaction (9.5-59.1 %), while the influence of the radiation type, dose rate and initial PMMA thickness can be considered negligible. Overall, these results pave the way to the development of radiation type independent PMMA assisted LOF dosimeters operating at MGy doses for the radiation monitoring in future HEP experiments.

In this work, we present a low-noise tunable DC-DC converter designed for driving high-resistance thin film heaters (in the order of a few of k ). The converter features a two-stage design comprising a voltage-boosting initial stage and a subsequent voltage-regulating stage where carefully selected LC and RC filters are employed to achieve low output ripple and minimize electromagnetic interference. In particular, the first stage elevates the input voltage to 120 V, while the second stage enables precise voltage control using a PWM-controlled synchronous buck converter. Experimental results demonstrate linearity within 2–120 V, with sub-millivolt ripples and minimal high-frequency noise (below 10 mV). This converter offers a reliable power supply solution for precise temperature control, improving thermal management and performance of high-resistance thin film heaters for several applications.

A pixeled plasmonic metasurface (MS) has been developed as a surface-enhanced infrared absorption (SEIRA) spectroscopy substrate to monitor the denaturation process of a protein A (PA) monolayer. The different pixels of the MS have been properly engineered to monitor different regions of the electromagnetic spectrum. Specifically, these pixels have their plasmonic resonances placed in the range 1500–2000 cm−1, well matched with Amide I and Amide II vibrational bands. In particular, the SEIRA reflectance spectra of the native PA and the denatured PA have been compared, observing a redshift of about 10 cm−1 for both Amide I and Amide II groups. Moreover, the evaluated enhancement factor (up to 7 × 104) allows to reveal both the presence and the denaturation process occurring to a very low amount of PA molecules (about 3 fmoles).

The need for miniaturized biological sensors which can be easily integrated into medical needles and catheters for in vivo liquid biopsies with ever-increasing performances has stimulated the interest of researchers in lab-on-fiber (LOF) technology. LOF devices arise from the integration of functional materials at the nanoscale on the tip of optical fibers, thus endowing a simple optical fiber with advanced functionalities and enabling the realization of high-performance LOF biological sensors. Consequently, in 2017, we demonstrated the first optical fiber meta-tip (OFMT), consisting of the integration of plasmonic metasurfaces (MSs) on the optical fiber end-face which represented a major breakthrough along the LOF technology roadmap. Successively, we demonstrated that label-free biological sensors based on the plasmonic OFMT are able to largely overwhelm the performance of a standard plasmonic LOF sensor, in view of the extraordinary light manipulation capabilities of plasmonic array exploiting phase gradients. To further improve the overall sensitivity, a labelled sensing strategy is here suggested. To this end, we envision the possibility to realize a novel class of labelled LOF optrodes based on OFMT, where an all-dielectric MS, designed to enhance the fluorescence emission by a labelled target molecule, is integrated on the end-face of a multimode fiber (MMF). We present a numerical environment to compute the fluorescence enhancement factor collected by the MMF, when on its tip a Silicon MS is laid, consisting of an array of cylindrical nanoantennas, or of dimers or trimers of cylindrical nanoantennas. According to the numerical results, a suitable design of the dielectric MS allows for a fluorescence enhancement up to three orders of magnitudes. Moreover, a feasibility study is carried out to verify the possibility to fabricate the designed MSs on the termination of multimode optical fibers using electron beam lithography followed by reactive ion etching. Finally, we analyze a real application scenario in the field of biosensing and evaluate the degradation in the fluorescence enhancement performances, taking into account the experimental conditions. The present work, thus, provides the main guidelines for the design and development of advanced LOF devices based on the fluorescence enhancement for labelled biosensing applications.

We apply surface-enhanced infrared absorption (SEIRA) spectroscopy to monitor the denaturation process of a surface-bound protein A monolayer. Our proposed platform relies on a plasmonic metasurface comprising different spatial subregions ("pixels") that are engineered to exhibit different resonances covering the infrared region of the electromagnetic spectrum that is matched to the vibrational modes of the Amide groups. Specifically, we are able to determine changes in the Amide I and Amide II vibration coupled modes, by comparing the SEIRA reflectance spectra pertaining to the native state and a denatured state induced by a pH variation. In particular, we observe some evident red-shifts in the principal Amide I mode and the Amide II vibration coupled modes (attributable to the breaking of hydrogen bonds), which result in insurmountable barriers for refolding. Thanks to the strong field localization, and consequent enhancement of the light-matter interactions, our proposed sensing platform can operate with extremely small amounts of an analyte, with an estimated detection limit of about 3 femtomoles of molecules.

The ability to control light at the nanoscale is at the basis of contemporary photonics and plasmonics. In particular, properly engineered periodic nanostructures not only allow the inhibition of propagation of light at specific spectral ranges or its confinement in nanocavities or waveguides, but make also possible field enhancement effects in vibrational, Raman, infrared and fluorescence spectroscopies, paving the way to the development of novel high-performance optical sensors. All these devices find an impressive analogy in nearly-periodic photonic nanostructures present in several plants, animals and algae, which can represent a source of inspiration in the development and optimization of new artificial nano-optical systems. Here we present the main properties and applications of cutting-edge nanostructures starting from several examples of natural photonic architectures, up to the most recent technologies based on metallic and dielectric metasurfaces.

In this paper we present a device integrating on a single glass substrate a transparent heater and two resistive temperature sensors. Both heater and sensors are constituted by ITO/Au/ITO stacked film, whose thicknesses have been optimized in order to achieve at the same time good electrical conductivity (about 106 S/m) and high transparency degree (higher than 80%) in the visible region of the spectrum. A double-spiral design has been chosen for the heater in order to achieve a uniform temperature distribution on a large area. Indeed, this geometry ensures a temperature variation of ±1.4 °C in a 2.8 cm diameter circle. For the resistive temperature sensors, a distributed meander-shaped geometry ensures temperature sensitivity as high as 0.12 $\text{k}\pmb \Omega / ^{\circ }\text{C}$ . The proposed device shows therefore the capability to work as a large-area transparent heater introducing the possibility to perform a precise control of the substrate temperature.

We propose and demonstrate a sensing platform based on plasmonic metasurfaces for the detection of very low concentrations of deoxyribo-nucleic acid (DNA) fragments. The platform relies on surface-enhanced infrared absorption spectroscopy, implemented via a multispectral metasurface. Specifically, different regions (“pixels”) are engineered so as to separately cover the medium-infrared range of the electromagnetic spectrum extending from the functional-groups to the fingerprint region of a single analyte. In conjunction with a suitable bio-functionalization, this enables univocal and label-free recognition of specific molecules. For experimental validation, we fabricate a large-area gold metasurface on a silicon chip, and functionalize it with a recognition layer of peptide nucleic acid (PNA). Our experimental results indicate the possibility to detect complementary DNA fragments in concentrations as low as 50 fM, i.e., well below the value attained by standard methods, with additional advantages in terms of processing time, versatility and ease of implementation/operation.

The valorization of sugar beet pulp (SBP) from sugar industry as a source of valuable substances has been taken in consideration in this work. In particular, the eco-friendly extraction of pectins with citric acid has been adopted as a preliminary step in a simplified biorefinery concept where the pectin-free solid is subsequently subjected to a torrefaction treatment for its upgrading into a commodity solid biofuel. An extensive physicochemical characterization of the raw feedstock and the isolated pectins has also been performed, which may be useful to identify suitable application routes. Results show that the extraction conditions [1.5 pH, 90 °C, 4 h contact time and SBP-to-solvent ratio of 1:30 (g/mL)] selected in this work allow obtaining a relatively high yield (25% wt, db) of high methoxyl pectins (with some impurities), which exhibit the same colorimetric characteristics of commercial citrus pectins and are not conducive to microbial growth. A further purification step of isolated pectins is required to improve the emulsifying properties.

The steadily increasing demand for accurate analysis of vitamin D level, via measurement of its best general marker, 25-hydroxyvitamin D (25(OH)D), pushes for the development of novel automated assays capable of working at very low concentrations. Here, we propose a plasmonic biosensor of 25(OH)D3 (calcifediol) based on surface-enhanced infrared absorption spectroscopy, which exploits the resonant coupling between plasmonic nanoantennas and vibrational excitation of small molecules. Specifically, our proposed platform features a large-area (several mm 2 ) metasurface made of gold nanoantennas fabricated on a silicon substrate, comprising different macroregions (“pixels”) of area 500 × 500 µm 2 . In each pixel, the nanoantenna geometrical parameters are tuned so as to support localized surface plasmon resonances (and hence large field enhancements at the nanoscale) within different regions of the infrared spectrum. As a result, a single chip is capable of performing analysis from the region of functional groups to that of fingerprint. Two different designs are fabricated via electron beam lithography, functionalized with a correlated antibody for the detection of 25(OH)D3, and characterized via Fourier-transform infrared spectroscopy. Our experiments demonstrate the capability to detect a concentration as low as 86 pmol/L, and an amount of immobilized small molecules of 25(OH)D3 monohydrate (molecular weight: 418.65 g/mol) as low as 4.31 amol over an area of 100 × 100 µm 2 .

‘Annurca’ apple, a southern Italian cultivar, is known for its reddening, taste and flavour among the other types of apples, and also for health promoting effects. The aim of this study is to evaluate the effect of a novel pre-treatment, by dipping in a solution containing trehalose, sodium chloride, sucrose, and of drying process conditions (temperature and time) on drying kinetics and quality attributes of dried apple slabs. Drying experiments were carried out by convective drying at temperatures of 50, 55, 60 and 65°C at a constant air velocity of 2.3m/s. Pre-treatment provided an increment of moisture loss, and a reduction of drying time and shrinkage at all temperatures. The combination of pre-treatment and drying at 65°C assured the lowest colour changes, the best preservation of structure, as well as the less shrinkage, the higher rehydration capacity and the highest score for sensorial overall acceptability. On the contrary, the used pre-treatment combined with lower drying temperatures (50 and 55°C) better preserve the antioxidant activity of apple slabs. In conclusion, the proposed solution enabled to reduce the processing time and better retain the quality attributes (i.e. physical, chemical, nutritional, sensorial) of dried apples slabs for their commercialization as snacks.

Infrared spectroscopy is an effective technique extensively used in research and industry for the label-free and unambiguous identification of molecular species. However, the sensitivity of this technique is severely limited as a result of Beer's law and, the small infrared absorption cross-section that make prohibitively weak the absorption signals, of minute amounts of analyte as those present in monolayers. This limitation can be overcome by enhancing the infrared vibration of molecules through the enhancement of the electromagnetic (EM) field. Surface Enhanced InfraRed Absorption (SEIRA) using resonant metal Nano-scale Antennas (NAs) can provide huge electromagnetic fields on the nanometer scale featuring localized collective oscillations of electrons, an effect named Localized Surface Plasmonic Resonances (LSPRsWe here report on a series of 2D arrays of cross-shaped NAs having several mm(2) area coverage (metasurface) as SEIRA optimized antennas, which can be used in practical applications such as the vibrational sensing of chemical and biological analytes. Cross-shape designed NAs are insensitive to the polarization of the electromagnetic radiation impinging the active area. Due to the random orientation of the dipole moments of molecules they are particularly suitable for the construction of bio-molecular sensors. At the same time, the 2D-array configuration ensures a good near-field signal enhancement arising from the coupling between neighbour NAs Moreover, SEIRA NAs can be easily integrated with micrometre-sized channels and be suitable for the high sensitivity, real time analysis of IR emitting samples, in matrices where IR spectroscopy is severely limited due to absorption bands of liquid water. We present the design, fabrication and experimental characterization of large-area metasurfaces based on cross-shaped plasmonic NAs for the spectroscopic characterization of various types of compounds and for sensing applications in the mid-infrared range. The cross-shaped NAs we have designed exhibit SEIRA phenomena which are very sensitive to both refractive index changes in the surrounding medium and to the specific molecular vibration band emerging from surface adsorbed molecules. To test this effect on our device, we have used as model compounds small molecules (molecular weight (MW) < 500 g/mol) containing triple bond groups resonating at about 2100 cm(-1) and a large polymer (MW (similar to) 950,000 g/mol) containing carbonyl groups resonating at wavenumbers of about 1700 cm-1. We show a sensitivity of 600 nm/RIU at different wavelengths at a maximum amount of immobilized small molecule of 0.7 fmoles and a SEIRA enhancement factor of 48,000. We also show the device potential to reveal chemical reactions, occurring on the sensor surface at the same scale, where the nitrile group is converted to a triazole ring.

In this work, we report on the first demonstration of Lab on Fiber (LOF) dosimeter for ionizing radiation monitoring at ultra-high doses. The new dosimeter consists in a metallo-dielectric resonator at sub-wavelength scale supporting localized surface plasmon resonances realized on the optical fiber (OF) tip. The resonating structure involves two gold gratings separated by a templated dielectric layer of poly(methyl methacrylate) (PMMA). Two LOF prototypes have been manufactured and exposed at the IRRAD Proton Facility at CERN in Geneva to 23 GeV protons for a total fluence of 0.67 × 10 16 protons/cm 2 , corresponding to an absorbed dose of 1.8 MGy. Experimental data demonstrated the “radiation resistance” feature of the LOF devices and a clear dependence of the reflected spectrum versus the total dose, expressed by a cumulative blue-shift of ~1.4 nm of the resonance combined with a slight increase of 0.16 dBm in the reflected spectrum. The numerical analysis carried out to correlate the experimental results with the dimensional and physical properties of the resonator, expected to be tightly connected to the absorbed dose, suggests that the main phenomenon induced by exposure to proton beam and able to explain the measured spectral behavior is the reduction of the PMMA thickness, which is also consistent with past literature in the field. Preliminary results demonstrated the potentiality of the proposed platform as dosimeter at MGy dose levels for high energy physics experiments.

The reduction of alcohol content in wines has two main objectives, the former is decreasing the wines' strength and the latter is producing new low alcohol beverages. To accomplish the latter, in this study, we focused on the dealcoholization of a white wine (cv Falanghina, 12.5 vol%) obtained from an ancient Italian grape variety that has recently aroused a renewed interest. It was dealcoholized at various alcohol content levels ranging from 9.8 to 0.3 vol% through the osmotic distillation process, and the main quality parameters of the obtained dealcoholized samples were evaluated. No significant differences (p < 0.05) in total phenols, flavonoids, organic acids and total acidity were observed among the wine samples at different alcohol content levels. On the contrary, the volatile compounds content decreased with increasing alcohol removal. Specifically, almost 50% of higher alcohols with acids and lactones were preserved in dealcoholized wine at 9.8 vol% alcohol content, but this percentage reduced to 30% in the sample at 6.8 vol%, and was even lower in the dealcoholized wine with lower alcohol content. It was argued that the transport of volatile compounds through the membrane, beside the membrane selectivity, is highly correlated with the Henry constant (R2 > 0.8021 for 9.8 vol% of dealcoholized wine). Moreover, results of the sensory evaluation indicated a significant change in terms of acidity, odour, sweetness and body taste in dealcoholized wine (0.3 vol%), giving an overall perceived imbalance and unacceptable taste with respect to the original wine. Therefore, in order to balance acid sensation and enhance body and aftertaste, an attempt was made to formulate an alcohol-free wine-based beverage with enhanced odour and sweetness, by adding some floral wine flavours, up to the amount present in the original wine.

Today, nanophotonics still lacks components for modulation that can be easily implementable in existing siliconon-insulator (SOI) technology. Chalcogenide phase change materials (PCMs) are promising candidates for tuning in the near infrared: at the nanoscale, thin layers can provide enough contrast to control the optical response of a nanostructure. Moreover, all-dielectric metamaterials allow for resonant behavior without having ohmic losses in the telecom range. Here, a novel hybridization of a SOI-based metamaterial with PCM GeTe is experimentally investigated. A metamaterial based on Si nanorods, covered by a thin layer of GeTe, is designed and fabricated. Switching GeTe from amorphous to crystalline leads to a rather high resonance-governed reflection contrast at 1.55 mu m. Additional confocal Raman imaging is done to differentiate the crystallized zones of the metamaterials' unit cell. The findings are in good agreement with numerical analysis and show good perspectives of all-dielectric tunable near-infrared nanophotonics. (C) 2019 Optical Society of America