86,652 research outputs found
Electrochemical Preparation of Micro and Nano Structures and Systems in Silicon for (Bio) Sensing and Nano (Medicine) Applications
No full textWhen dealing with biosensing and nanomedicine applications the length scale of targets may vary over more than 5 orders of magnitude moving from the molecular level (0.1-1 nm) up to the cell level (1-10 μm). A number of micro and nanostructuring technologies have been developed over the years to enable the preparation of both structures and systems with length scales suitable to match specific biological targets.
In this talk, electrochemical preparation of nano and micro structures and systems in silicon with length scales spanning over 5 order of magnitudes, able to target different applications both in (nano)medicine (e.g. sinusoid-like liver on a chip, nanopillars for cell transfection, 3D microincubators for tumor cell screening) and (bio)sensing (e.g. microneedles for transdermal biosensing, optical biosensors for point-of-care clinical diagnostics, chemitransitor sensors for environmental monitoring), is presented and discussed.
1. S.Mariani, V. Robbiano, L. M. Strambini, A. Debrassi, G. Egri, L. Dähne, G. Barillaro, Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing, Nature Communications, 9, 5256, 1-13 (2018)
2. B. Delalat, C. Cozzi, S. R. Ghaemi, G. Polito, F. E. Kriel, T. D. Michl, F. J. Harding, C. Priest, G. Barillaro, N. H. Voelcker, Microengineered Bioartificial Liver Chip for Drug Toxicity Screening, Advanced Functional Materials 1801825 (2018).
3. Robbiano, G. M. Paterno, A. A. La Mattina, S. G. Motti, G. Lanzani, F. Scotognella, G. Barillaro, Room-Temperature Low-Threshold Lasing From Monolithically Integrated Nanostructured Porous Silicon Hybrid Microcavities, ACS Nano12, 4536−4544 (2018).
4. J. Harding, S. Surdo, B. Delalat, C. Cozzi, R. Elnathan, S. Gronthos, N. H. Voelcker, G. Barillaro, Ordered Silicon Pillar Arrays Prepared by Electrochemical Micromachining: Substrates for High-Efficiency Cell Transfection, ACS Applied Materials and Interfaces, 8 (43), 29197-29202 (2016).
5. Mariani, L. M. Strambini, G. Barillaro, Femtomole Detection Of Proteins Using A Label-Free Nanostructured Porous Silicon Interferometer For Perspective Ultra-Sensitive Biosensing, ACS Analytical Chemistry, 88 (17), 8502-8509 (2016).
6. Mariani, L. Pino, L. M. Strambini, L. Tedeschi, G. Barillaro, 10000-Fold Improvement in Protein Detection Using Nanostructured Porous Silicon Interferometric Aptasensors, ACS Sensors, 1, 1471-1479(2016).
7. M. Sainato, L.M. Strambini, S. Rella, E. Mazzotta, G. Barillaro, Sub-Parts Per Million NO2 Chemi-Transistor Sensors Based on Composite Porous Silicon/Gold Nanostructures Prepared by Metal-Assisted Etching, ACS Applied Materials and Interfaces 7, 7136 (2015).
8. M. Strambini, A. Longo, S. Scarano, T. Prescimone, I. Palchetti, M. Minunni, D. Giannessi, G. Barillaro, Self-Powered Microneedle-Based Biosensors for Pain-Free High-Accuracy Measurement of Glycaemia in Interstitial Fluid, Biosensors and Bioelectronics,66, 162 (2015)
In-situ label-free optical detection of cells cultured in 3D microincubators
No full textIn this work, we show that high aspect-ratio silicon microstructures can play, at the same time, the roles of a cell-selective three-dimensional microincubator for cell culture and optical label-free transducer of cell morphology mapping. Silicon microincubators, integrating a periodic array of narrow (5-μm-wide), deeply etched (50-μm-deep) gaps separated by 3-μm-thick silicon walls, are fabricated by electrochemical micromachining (ECM) technology [1], and used for culturing several both epithelial and mesenchymal cell lines. Fluorescence microscopy analyses highlight that the microincubator shows cell-selective capabilities, being mostly cells with mesenchymal phenotype able to actively colonize the deeply etched gaps and grow attached to the vertical silicon walls [2]. The microincubator also features reflectivity spectral properties typical of one-dimensional (1D) photonic crystals (PhCs) structures in the near infrared range, with high reflectivity regions separated by deep reflectivity notches. According to 1DPhC optical properties, the presence of cells inside the gaps of the microincubator strongly affects the reflectivity signal, which can be measured in-situ with a fiber-optic setup orthogonally to the silicon wall surface (x-y plane). By spatially mapping the reflected power spectrum in the vertical x-y plane, it is thus possible to infer on the extension of cells growing into the microincubator attached to silicon walls. In particular, the intensity ratio between reflectivity maximum and minimum at two different wavelengths around 1.55 μm is closely related to the cell spreading on the silicon wall inside the deeply etched gaps of the microincubator. These results clearly envisage future in-situ label-free analyses of cellular activities involving changes in cell morphology and/or adhesion (e.g. apoptosis), in a three-dimensional environment.
[1] M. Bassu, S. Surdo, L. M. Strambini, G. Barillaro, Adv. Funct. Mat., 22 (2012), 1222-1228;
[2] F. Carpignano, G. Silva, S. Surdo, V. Leva, A. Montecucco, F Aredia, A. Scovassi, S. Merlo, G. Barillaro, G. Mazzini, Plos ONE 7 (2012) DOI: 10.1371/journal.pone.0048556
Colorful Light-Emitting-Diodes via Modulation of the Concentration of Red-Emitting Silicon Nanocrystal Phosphors
No full textThe research activity into the development of luminescent forms of silicon has now spanned two decades, driven by scientific interest, commercial potential, and technological advancement [1]. It is now well established that silicon crystallites of reduced dimensions, typically below 5 nm, emit light with high efficiency due to quantum confinement effect, with respect to inefficient light emission of bulk crystalline silicon [2]. Canham [2] was the first to demonstrate in 1990 room- temperature photoluminescence from nanocrystallites of silicon (i.e. porous silicon) that were obtained by electrochemical erosion of crystalline silicon in acidic electrolytes. Many other methods were subsequently developed for the synthesis of luminescent nanostructured forms of silicon, including annealing of SiOx powder followed by etching in HF, plasma synthesis, solution reduction of SiCl4, plasma etching of silicon and subsequent thermal oxidation [3-6].
Very recently silicon nanocrystals (SiNs) with high PL quantum yield (about 17%), obtained by low-cost electrochemical erosion of crystalline silicon substrate, has been proposed as non-toxic phosphors for wavelength conversion in ultraviolet/blue LEDs. [7, 8].
Here we show that SiN phosphors with strong and broad photoluminescence in the red portion of the spectrum, obtained by electrochemical erosion of silicon, can be used as non-toxic phosphors for effectively tuning the color of commercial blue-LEDs from blue to violet, magenta, and red via wavelength conversion, by coating the LED with polydimethylsiloxane (PDMS) encapsulating different SiN concentrations [16]. Good reliability of the tuning process, with respect to SiN fabrication and concentration, and excellent stability of the tuning color, with respect to LED operation current, is demonstrated through simultaneous electrical/optical characterization of a number of SiN-modified commercial LEDs.
In spite of the huge research effort that has been paid so far on the use of SiNs for LED applications, the possibility of efficiently tuning the color of LEDs via wavelength-conversion by modultating the concentration of red-emitting SiN phosphors has never been reported.New exciting perspectives in the field of light-emitting applications of SiNs are envisaged by building on these results.
[1] L. Mangolini, Journal of Vacuum Science and TechnologyB 31, 020801 (2013).
[2] L. T. Canham, Applied Physics Letters 57, 1046 (1990).
[3] Shu-Man Liu, Yang Yang, Seiichi Sato, and Keisaku Kimura, Chemistry of Materials 18, 637
(2006).
[4] X. D. Pi, R. W. Liptak, J. Deneen Nowak, N. P. Wells, C. B. Carter, S. A. Campbell, and U.
Kortshagen, Nanotechnology 19, 245601 (2008).
[5] J. Zou, P. Sanelle, K. A. Pettigrew, and S. M. Kauzlarich, Journal of Cluster Science 17, 565
(2006).
[6] S. S. Walavalkar, C. E. Hofmann, A. P. Homyk, M. D. Henry, H. A. Atwate, and A. Scherer,
Nano Letters 10, 4423 (2010).
[14] C.-C. Tu, Q. Zhang, L. Y. Lin, and G. Cao, Optics Express 20, A69 (2011).
[15] C.-C. Tu, J. H. Hoo, K. F. Bohringer, L. Y. Lin, and G. Cao, Optics Letters 37, 4771 (2012). [16] G. Barillaro, L. M. Strambini, Applied Physics Letters 104, 091102 (2014
Electrochemical silicon micromachining: A new technique
No full textIn this paper the electrochemical silicon etching in HF-based solution is demonstrated as a new technique for silicon micromachining, alternative to commonly used methods. Electrochemical etching of silicon in HF-based electrolyte, a well known technique for regular macropore formation, is here exploited to produce a multitude of different regular silicon microstructures (microtubes, microtips, microchannels, microspirals, micropillars, microwalls, etc.). The electrochemical micromachining technique is here detailed and discussed
Boosting Static and Dynamic Performance of Integrated Solid-State Diodes By Peripheral Integration of Nanostructured Porous Silicon
No full textOver the past two decades, different nanomaterials have been proposed for the design of novel silicon-based electronic devices or to push the performance of existing ones, leveraging the unique properties of charge carriers traveling in meso-to-nano scale structures.
Porous silicon (PSi) is the nano- (n-PSi) to micro- (m-Psi) structured form of silicon achieved by anodic etching of a silicon wafer in acidic HF-based electrolytes. However, the low mobility and reduced lifetime of charge carriers traveling in n-PSi have been mainly perceived such as a deterioration the bulk silicon properties, thus hampering the use of n-PSi in micro and nano electronics to date.
Here, we show that the integration of n-PSi in specific regions of a solid-state diode significantly improves both static and dynamic electrical performance of the diode, with respect to the unmodified device. Specifically, leveraging the unique mobility and lifetime of charge carriers traveling in the n-PSi layer, we achieve a significant increase of the breakdown voltage (>2x) and reduction of the turn-off time (about 30%). This improvement is shown to be robust with respect to n-PSi preparation conditions and diode typologies. Two dimensional (2D) TCAD simulations further corroborate that the improvement of the electrical performance of n-PSi modified diodes is related to the strong mobility and lifetime reduction of carriers in the nanostructured porous silicon layer. Remarkably, no significant drawbacks are observed after the peripheral integration of n-PSi in solid-state diodes, thus confirming the beneficial effect of n-PSi when employed for the modification of micro and nano electronic devices.
A. Paghi, L. M. Strambini, F. F. Toia, M. Sambi, M. Marchesi, R. Depetro, M. Morelli, G. Barillaro, Peripheral Nanostructured Porous Silicon Boosts Static and Dynamic Performance Of Integrated Electronic Devices, Advanced Electronic Materials 6, 2000615 (2020)
The surgical treatment of colorectal cancer in patients over seventy-five years old. Risk factor analysis in patients operated in election and in emergency
No full text
Photoluminescence and radiative-rate modifications in 1D silicon photonic crystals infiltrated with luminescent conjugated polymers
No full textWe report the modification of the photoluminescence (PL) of one-dimensional (1D) porous silicon photonic crystals (PS-PhCs) infiltrated with luminescent conjugated polymers.
First, we used an aqueous HF-based electrochemical etch of p++-silicon substrates to prepare rugate filters, a special case of 1D PS-PhCs [1]. These are nanostructured systems featuring quasi-cylindrical vertical cavities whose diameter (a few hundreds nanometres) along the direction perpendicular to the substrate surface (“z-direction”) is modulated by varying the sinusoidal etching current. Structures with sinusoidally-shaped periodic porosity (between 55.3% and 62.3%) and, in turn, with sinusoidally-shaped refractive index (maximum contrast of about 0.25) are produced. We then infiltrated PS-PhCs prepared with different period repetitions (25 to 100), with either F8BT (poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt- (benzo[2,1,3]thiadiazol-4,8-diyl)]) or MDMO-PPV (poly[2-methoxy-5-(3′,7′- dimethyloctyloxy)-1,4-phenylenevinylene]).
We measured reflectance, photoluminescence (PL), and time-resolved PL of both bare and infiltrated PS-PhCs. We found that the photonic stop-band is red-shifted upon polymer infiltration, as expected due to reduced refractive index contrast of the polymer-infiltrated nanostructured system [2]. We also observed both suppression (in the stop-band) and enhancement (at the band-edge) of the photoluminescence. Remarkably, time-resolved measurements reveal a modification of the emission lifetime, which is enhanced at the band- edge and suppressed within the stop-band, and clearly point to a variation of the radiative decay rate of excitations in such hybrid organic-inorganic photonic nanostructures.
Keywords
[1] A. M. Ruminski, et al., Adv. Funct. Mat., 18, 3418-3426 (2008) [2] G. Barillaro, et al., Opt. Lett., 34, 1912-1914 (2009)
[3] L. Berti, et al., J. Phys. Chem. C., 114, 2403-2413, (2010
Chemi-Transistor Sensors based on Composite Silicon/Gold Nanostructures Prepared by Metal Assisted Etching
No full textThe ability to fabricate micro [1] and nanostructures [2] on silicon (Si) with the possibility to dope the final porous structures with noble metal NPs (e.g. gold, silver), using Metal-Assisted Etching (MAE)[3] is a unique advantage of MAE as to sensing applications. Over the standard fabrication technique such as anodic etching [4], MAE represents a low-cost room-temperature method for the synthesis of Si-based nanomaterials with peculiar sensing features, in terms of sensitivity and selectivity, towards specific gases, by bringing the catalytic properties and distinctive selectivity of the metals nanoparticles[5] and the widely tunable bandgap of the porous silicon into play.
Here the prospect of using composite silicon/gold nanostructures (cSiAuN) prepared by MAE, gold-assisted, as highly sensitive material for adsorption of Nitrogen Dioxide (NO2) is proposed, examining the controllable high-yield integration of the material into solid-state devices.
The controllable fabrication of the final nanostructures achieved by MAE approach leads to the fabrication of cSiAuN with high degree of control in terms of morphology of the pores and depth of the matrix, with enhanced sensing capabilities, which justifies their successful application in the preparation of chemi-transistor sensors, such as field-effect transistors, FETs, to be employed for gas sensing applications. As a case-of-study, we investigate the effective method for controllable integration of composite cSiAuN between electrodes of junction-field-effect transistors (JFET), aimed at the detection of NO2 down to 100 parts-per-billion (ppb). The resulting chemi-transistor sensor, cSiAuJFET (Composite Silicon Gold JFET), consists of a p-channel JFET in which the cSiAuN material is placed on top of the p-channel and acts as an extra floating gate and are responsible for the sensing capability of the JFET device. The cSiAuJFET sensors operate at room temperature and shows fast and reliable response to NO2 in the range 100-500 ppb without significant aging effects, in terms of baseline drift, response times, and sensitivity value, up to two days of continuous operation. The achieved approach presented in this work represent a guide for the possibility of employing MAE for gas sensing applications.
[1] A. G. F. Owen J. Hildreth, Ching Ping Wong, ACSNano 2012, 6, 9.
[2] L. Boarino, D. Imbraguglio, E. Enrico, N. De Leo, F. Celegato, P. Tiberto, N. Pugno, G. Amato, physica status solidi (a) 2011, 208, 1412.
[3] Peng K. Q. et al. Advanced Materials 2002, 14, 1164.
[4] G. M. Lazzerini, L. M. Strambini, G. Barillaro, Sci Rep 2013, 3, 1161.
[5] L. C. Nicola Cioffi, Eliana Ieva, Rosa Pilolli, Nicoletta Ditaranto, Maria Daniela Angione, Serafina Cotrone, Kristina Buchholt, Anita Lloyd Spetz, Luigia Sabbatini, Luisa Torsi, Electrochimica Acta 2011, 56
Fabrication of self-aligned gated silicon microtip array using electrochemical silicon etching
No full text- …
