152 research outputs found
Enhanced power-conversion efficiency in organic solar cells incorporating polymeric compatibilizers
No full textEnhanced power-conversion efficiency in organic solar cells incorporating copolymeric phase-separation modulators
No full textA new class of copolymers containing oligothiophene moieties with different lengths and fullerene units have been designed and prepared by an easy and inexpensive one-step synthetic approach. The incorporation of small quantities of these copolymers into bulk heterojunction (BHJ) solar cells with donor regioregular polythiophene (P3HT) and an acceptor fullerene derivate (PCBM) results in good control of the phase separation process without further affecting the BHJ optoelectronic properties. Indeed, under thermal annealing these copolymers allow the modulation of the growth of domains whose size depends on the length of the copolymer repetitive units. Domain size on the same length scale as the P3HT exciton diffusion length with a good continuity between the electrodes gives efficient exciton dissociation and charge mobility. Thus by employing copolymers containing oligothiophenic chains with a size of about 8 nm, the power conversion efficiency (PCE) (4.46%) and short current density (JSC) (16.15 mA cm−2) values are the highest reported so far for P3HT:PCBM solar cells on plastic substrates
ELECTROCHROMIC PERFORMANCE OF A NOVEL POLY(NAPHTHALENEDIIMIDEQUATERTHIOPHENE)
No full textConjugated polymers (CP) display several interesting properties which enable them their application in different fields such as solar cells, light emitting diodes, field effect transistors, electrochromic devices to cite a few. One of the most interesting properties of this class of materials is their ability of switching from a conductive to an insulating state and vice versa by changing their redox state. The possibility to switch from an oxidized to a neutral or reduced state induces variations of the optical spectrum due to changes in the electron excitation energy configuration resulting in electrochromism. Nowadays, electrochromic conjugated polymers are stimulating the development of transmissive and reflective technologies such as transmissive and reflective displays, smart windows, e-papers, optical memories, and optical shutters. In this work we prepared and investigated the electrochromic properties of a new, air stable polythiophene derivative, namely poly-naphthalenediimidequaterthiophene (PNDIT4). PNDIT4 thin films have been obtained by the electrochemical oxidation of the chemically synthesized monomer on transparent ITO electrodes supported on PET in two solvents mixtures having different volume ratios. The morphological and chemical investigation of the thin film have been performed by a number of surface tools including microscopy and spectroscopy techniques allowing to correlate their structure with the electrochromic performances. Spectroelectrochemical experiments have been performed in a two electrodes electrochemical cell endowed with quartz windows. Both absorbance spectra under different polarization potentials and transmittance vs time plots under different excitation wavelengths have been recorded.
Figure 1 shows a typical optical contrast of a PNDIT4 film on ITO, obtained by applying a square wave potential of ±0.8V (anode vs cathode) at 900 nm. The polymer displayed a colour variation from green to beige when switched from the doped to the undoped states, respectively, along with a good optical memory in the explored time interval
Piezoresistive semi-transparent flexible sensors by bithiophene fulleropyrrolidine thin films
No full textPiezoresistive sensors are considered among the fundamental components of the future wearable electronic devices, given their potential applications in artificial skin, motion capture and personalized medicine.[1-5] Here, we present a cost-effective, viable fabrication approach to realize piezoresistive sensors using a novel polymeric biotiophene fulleropyrrolidine system (bis-C60Bi) synthesized on flexible ITO/PET supports by electrochemical chronoamperometry. By applying an anodic potential (1.5 V) to a solution containing the monomer, it is possible to obtain a homogeneous semi-transparent thin film on the ITO/PET surface (see Figure). AFM,
XPS, UV-vis have been employed to characterize the morphology and chemical composition of the new synthesized polymeric thin films, confirming the chemical structure and showing a nanoscale surface roughness of about 25 nm. The resulting polymer-based device shows good resistance variation on bending in the semi-static regime, outperforming current ITO/PET resistive sensors [6] and well matching commercial devices based on opaque amorphous carbon materials.[7] The durability of the sensor has been validated over almost one hundred cycles. This new class of polymeric piezoresistive sensors may open new applications in the field of kinematic acquisition or of sensor monitoring, with several potential applications as well as in medicine, robotics and physiotherapy.
Bibliography
1 M. Ricci, G. Di Lazzaro, A. Pisani, N. B. Mercuri, F. Giannini, G. Saggio, IEEE Journal of Biomedical and Health Informatics, 2019,
doi: 10.1109/JBHI.2019.2903627
2 G. Arrabito, V. Errico, Z. Zhang, W. Han, C. Falconi, Nano Energy, 2018, 46, 54. doi: 10.1016/j.nanoen.2018.01.029
3 G. Saggio, G. Orengo, A. Pallotti, V. Errico, M. Ricci, IEEE International Symposium on Medical Measurements and Applications
(MeMeA), 2018, doi: 10.1109/MeMeA.2018.8438767
4 N. Jasoon, M.D. Ho, W. Cheng, J. Mater. Chem. C, 2017, 5, 5845.
5 G. Saggio ; G. Orengo ; A. Pallotti ; V. Errico ; M. Ricci, International Symposium on Networks, Computers and Communications
(ISNCC) 2018 doi: 10.1109/ISNCC.2018.8531054
6 T. Lee, Y. W. Choi, G. Lee, P. V. Pikhita, D. Kang, S.M. Kim and M. Choi, J. Mater. Chem. C, 2016, 4, 9947.
7 G. Saggio, G. Orengo, Sensors and Actuators A, 2018, 273, 221
Notch-1 decreased expression contributes to leptin receptor downregulation in nasal epithelium from allergic turbinates.
No full textAbstract
BACKGROUND:
Allergic rhinitis is characterized by a remodeling of nasal epithelium. Since the Notch and TGF-β signaling pathways are known to be involved in cell differentiation and remodeling processes and leptin adipokine has already been identified as a marker for homeostasis in human bronchial and nasal epithelial cells of asthmatics, roles played by these pathways have been investigated for chronic allergic rhinitis.
METHODS:
The leptin/leptin receptor expression has been investigated in a study with 40 biopsies from allergic (AR, n = 18) and non-allergic (C, n = 22) inferior turbinates, using immunohistochemistry, immunofluorescence staining and RT-PCR. In addition, extracts from in vitro samples prepared from primary cells of inferior turbinates as well as in vitro cultured human nasal epithelial RPMI 2650 cells (ATCC-CCL-30) were also tested for leptin expression and activation of the Notch-1 pathway.
RESULTS:
With regards to AR, in vivo expression levels of both leptin and its receptor significantly decreased in comparison to C. Furthermore, leptin receptor mRNA was significantly reduced in AR as compared to C. Immunofluorescence showed an apparent co-expression of leptin receptor with Notch-1, which was not seen with TGF-β. In vitro, in primary turbinate epithelial cells, the expression of leptin receptor and Notch-1 significantly decreased in AR as compared to C. Moreover, in RPMI 2650 cells, leptin receptor expression was shown to be induced by Notch-1 ligand signaling.
CONCLUSION:
Thus, both the leptin and Notch-1 pathways appear to represent markers for epithelial homeostasis in allergic rhinitis.
Copyright © 2019 Elsevier B.V. All rights reserved.
KEYWORDS:
Allergic rhinitis; Epithelium; Leptin; Notc
Notch-1 signaling activation sustains overexpression of interleukin 33 in the epithelium of nasal polyps
No full textBackground: Alterations in the nasal epithelial barrier homeostasis and increased interleukin 33 (IL-33) expression contribute to the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP). Aims: As Notch-1 signaling is crucial in repair processes of mucosa, the current study assessed Notch-1/Jagged-1 signaling and IL-33 in the epithelium of nasal polyps biopsies from allergic (A-CRSwNP; n = 9) and not allergic (NA-CRSwNP; n = 9) subjects by immunohistochemistry. We also assessed, in a model of nasal epithelial cells, the effects of stimulation of Notch-1 with Jagged-1 on the expression of IL-33 (by flow cytometry, immunofluorescence, and immunocytochemistry), Jagged-1 (by flow cytometry), and p-CREB transcription factor (by western blot analysis). Results: Ex vivo (a) in normal epithelium, the expression of Notch-1 and IL-33 were higher in NA-CRSwNP than in A-CRSwNP; (b) in metaplastic epithelium, the expression of Notch-1, Jagged-1, and IL-33 were higher in NA-CRSwNP than in A-CRSwNP; (c) in hyperplastic epithelium, the expression of Notch-1, Jagged-1, and IL-33 were higher in A-CRSwNP than in NA-CRSwNP; and (d) in basal epithelial cells, no differences were observed in the expression of Jagged-1, IL-33, and Notch-1. The expression of Notch-1 significantly correlated with the expression of IL-33. In vitro, stimulation of Notch-1 with Jagged-1 induced the expression of (a) Jagged-1; (b) IL-33; and (c) p-CREB transcription factor. The inhibitor of Notch-1, DAPT, reduced all the effects of Jagged-1 on nasal epithelial cells. Conclusions: The data herein provided support, for the first time, a putative role of Notch-1/Jagged-1 signaling in the overexpression of IL-33 in the epithelium of nasal polyps from patients with CRSwNP
ELECTRODEPOSITION OF NOVEL POLY(NAPHTHALENEDIIMIDE-QUATERTHIOPHENE) THIN FILMS AND APPLICATIONS IN PLASTIC OPTOELECTRONICS DEVICES
No full textA novel symmetric naphthalenediimide-quaterthiophene derivative (NDIT4d) has been polymerized on different substrates including glassy carbon and ITO/PET electrodes by means of electrochemical methods. XPS and UV-VIS spectroscopy as well as cyclic voltammetry have been employed for characterizing the thin film chemical features, the band gap and the HOMO and LUMO levels. DFT computational studies were in close agreement with the experimental observables also showing intriguing geometrical effects on the band gap energy values.
The comparison of the energy levels locations of the electrodeposited poly(naphthalenediimide-quaterthiophene) derivative (e-PNDIT4) and P3HT thin films transferred by the Inverse Langmuir-Schaefer (ILS) technique, demonstrates that e-PNDIT4 behaves as acceptor at the interface with P3HT. Steady state fluorescence studies have been performed in order to study the electron transfer in both planar (double layer) and bulk heterojunctions made of e-PNDIT4 and P3HT. The bulk heterojunction – obtained by thermal annealing of the double layer system – has shown a fluorescence quenching of about 97%, indicating an efficient electron transfer from the excited P3HT to e-PNDIT4.
Furthermore, electrochromic properties of e-PNDIT4 thin films have been studied by means of spectroelectrochemical measurements. Transmittance versus time plots, recorded under an applied square wave potential, showed an optical contrast of about 20%.
These studies open new possibilities in terms of all-polymer devices including the employment of a new class of symmetric push-pull derivatives and the development of fabrication processes exploiting the synergetic use of electrochemical and layer-by-layer deposition methods
Low Angle Bending Detection Semi-transparent Piezoresistive Sensor
No full textWe designed, fabricated, and validated a piezoresistive bending sensor, a fundamental component of wearable electronic devices for monitoring human motion. The most diffused opaque carbon-based resistance flex sensors suffer from low detection for small bending angles. The sensor we here present is based on a semi-transparent active material (fulleropyrrolidine bisadducts polymer) and has the remarkable advantage of good electrical properties for low bending angles. The fabrication steps are effective since a pre-patterned ITO/PET surface is functionalized by chronoamperometric deposition, and the silver electrical contacts are inkjet printed. We propose a fitting function of the measured thin film resistance curve vs. the bending angle, showing promising properties as a complimentary bending sensor to the most diffused flex sensors. The results pave the way to new applications and more performant wearables
Bending Sensors Based on Thin Films of Semitransparent Bithiophene-Fulleropyrrolidine Bisadducts
No full textA novel bithiophene-fulleropyrrolidine bisadducts system (bis-Th2PC60) was synthesized and electropolymerized by chronoamperometry onto flexible ITO/PET substrates. The resulting semitransparent thin film was characterized by XPS, FT-IR, cyclic voltammetry and optical techniques, confirming the good outcome of the electropolymerization process. AFM investigations permitted to highlight an inherent disordered granular morphology, in which the grain-to-grain separation depends upon the application of bending. The electrical resistance of the thin film was characterized as a function of bending (in the range 0°–90°), showing promising responsivity to low bending angles (10°–30°). The ΔR/R0 variations turn out to be 8 %,16 % and 20 % for bending angles equal to 10°, 20° and 30°, respectively. This study represents a first step towards the understanding of piezoresistive properties in electropolymerized fullerenes-based thin films, opening up applications as bending sensor
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