No abstract

The development of low-cost, flexible electronic devices is subordinated to the advancement in solution-based and low-temperature-processable semiconducting materials, such as colloidal quantum dots (QDs) and single-walled carbon nanotubes (SWCNTs). Here, excellent compatibility of QDs and SWCNTs as a complementary pair of semiconducting materials for fabrication of high-performance complementary metal-oxide-semiconductor (CMOS)-like inverters is demonstrated. The n-type field effect transistors (FETs) based on I capped PbS QDs (V = 0.2 V, on/off = 10 , S = 114 mV dec , µ = 0.22 cm V s ) and the p-type FETs with tailored parameters based on low-density random network of SWCNTs (V = -0.2 V, on/off > 10 , S = 63 mV dec , µ = 0.04 cm V s ) are integrated on the same substrate in order to obtain high-performance hybrid inverters. The inverters operate in the sub-1 V range (0.9 V) and have high gain (76 V/V), large maximum-equal-criteria noise margins (80%), and peak power consumption of 3 nW, in combination with low hysteresis (10 mV).

Cell-based biosensors constitute a fundamental tool in biotechnology, and their relevance has greatly increased in recent years as a result of a surging demand for reduced animal testing and for high-throughput and cost-effective in vitro screening platforms dedicated to environmental and biomedical diagnostics, drug development and toxicology. In this context, electrochemical/electronic cell-based biosensors represent a promising class of devices that enable long-term and real-time monitoring of cell physiology in a non-invasive and label-free fashion, with a remarkable potential for process automation and parallelization. Common limitations of this class of devices at large include the need for substrate surface modification strategies to ensure cell adhesion and immobilization, limited compatibility with complementary optical cell-probing techniques, and need for frequency-dependent measurements, which rely on elaborated equivalent electrical circuit models for data analysis and interpretation. We hereby demonstrate the monitoring of cell adhesion and detachment through the time-dependent variations in the quasi-static characteristic current curves of a highly stable electrolyte-gated transistor, based on an optically transparent network of printable polymer-wrapped semiconducting carbon-nanotubes. MAIN TEXTOptical cell viability assay and immunofluorescence staining: The proliferation was evaluated after 1, 2, 3, and 4 d in vitro. For each time point the medium was removed and replaced with RPMI without phenol red containing 0.5 mg mL −1 of MTT reagent (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Sigma-Aldrich). Cells were reincubated at 37 °C for 3 h. Formazan salt produced by cells through reduction of MTT was then solubilized with 200 mL of ethanol and the absorbance was read at 560 and 690 nm (using a microplate reader TECAN Spark10M). The proliferation cell rate was calculated as the difference in absorbed intensity at 560 and 690 nm. Cells grown on glass coverslips coated with SWCNT networks were washed twice with PBS and fixed for 15 min at RT in 4 % paraformaldehyde and 4 % sucrose in 0.12 M sodium phosphate buffer, pH 7.4. Fixed cells were pre-incubated for 20 min in gelatin dilution buffer (GDB: 0.02 M sodium phosphate buffer, pH 7.4, 0.45 M NaCl, 0.2% (w/v) gelatin) containing 0.3% (v/v)

In this paper, the fabrication of carbon nanotubes field effect transistors by chemical self-assembly of semiconducting single walled carbon nanotubes (s-SWNTs) on prepatterned substrates is demonstrated. Polyfluorenes derivatives have been demonstrated to be effective in selecting s-SWNTs from raw mixtures. In this work the authors functionalized the polymer with side chains containing thiols, to obtain chemical self-assembly of the selected s-SWNTs on substrates with prepatterned gold electrodes. The authors show that the full side functionalization of the conjugated polymer with thiol groups partially disrupts the s-SWNTs selection, with the presence of metallic tubes in the dispersion. However, the authors determine that the selectivity can be recovered either by tuning the number of thiol groups in the polymer, or by modulating the polymer/SWNTs proportions. As demonstrated by optical and electrical measurements, the polymer containing 2.5% of thiol groups gives the best s-SWNT purity. Field-effect transistors with various channel lengths, using networks of SWNTs and individual tubes, are fabricated by direct chemical self-assembly of the SWNTs/thiolated-polyfluorenes on substrates with lithographically defined electrodes. The network devices show superior performance (mobility up to 24 cm V s ), while SWNTs devices based on individual tubes show an unprecedented (100%) yield for working devices. Importantly, the SWNTs assembled by mean of the thiol groups are stably anchored to the substrate and are resistant to external perturbation as sonication in organic solvents.

Noncovalent functionalization of carbon nanotubes by wrapping them using π‐conjugated polymers is one of the most promising techniques to sort, separate, and purify semiconducting nanotube species for applications in optoelectronic devices. However, wide energy bandgap polymers commonly used in this technique reduce charge transport through the nanotube network. To avoid the formation of insulating barriers between the tubes, challenging procedures for the removal of the polymer from the nanotube walls are necessary. Here, the use of two narrow bandgap polymers based on naphthalene‐bis(dicarboximide) (NDI), namely, poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,59‐(2,29‐bithiophene)}, (P(NDI2OD‐T2 or ActivInk N2200) and its molecular cousin, poly{[(N,N′‐bis(2‐octyldodecyl)‐1,4,5,8‐naphthalenedicarboximide‐2,6‐diyl)‐alt‐5,5′‐(2,2′‐bithiophene)]‐co‐[(N,N′‐bis(2‐octyldodecyl)‐1,4,5,8‐naphthalenedicarboximide‐2,6‐diyl)‐alt‐5,5′‐(2,2′‐(4,4′‐dimethoxybithiophene))]}(ActivInk PE‐N‐73), for selecting semiconducting single‐walled carbon nanotubes (s‐SWNTs) is demonstrated. The influence of the chemical structure of these polymers on the nanotube selectivity, as well as the effect of residual excess polymer and their band‐gaps, are investigated through optical spectroscopy and charge transport measurements. While the electron transport of the devices fabricated with PE‐N‐73 and N2200 wrapped SWNTs is comparable, a substantial difference is observed in the hole transport. The better alignment of the HOMO level of PE‐N‐73 with that of the nanotubes allows achieving improved p‐type characteristics even with a large amount of residual polymer in the network.

Semiconducting single‐walled carbon nanotubes (s‐SWNTs) are used as a protective interlayer between the lead sulfide colloidal quantum dot (PbS CQD) active layer and the anode of the solar cells (SCs). The introduction of the carbon nanotubes leads to increased device stability, with 85% of the initial performance retained after 100 h exposure to simulated solar light in ambient condition. This is in sharp contrast with the behavior of the device without s‐SWNTs, for which the photoconversion efficiency, the open circuit voltage, the short‐circuit current, and the fill factor all experiencing a sharp decrease. Therefore, the inclusion of s‐SWNT as interlayer in CQD SCs, give rise to SCs of identical efficiency (above 8.5%) and prevents their performance degradation.

Noncovalent functionalization of single‐walled carbon nanotubes (SWNTs) using π‐conjugated polymers has become one of the most effective techniques to select semiconducting SWNTs (s‐SWNTs). Several conjugated polymers are used, but their ability to sort metallic and semiconducting species, as well as the dispersions yields, varies as a function of their chemical structure. Here, three polymers are compared, namely, poly[2,6‐(4,4‐bis‐(2‐dodecyl)‐4H‐cyclopenta[2,1‐b;3,4b′]dithiophene)‐alt‐4,7(2,1,3‐benzothiadiazole)] (P12CPDTBT), poly(9,9‐di‐n‐dodecylfluorenyl‐2,7‐diyl) (PF12), and poly(3‐dodecylthiophene‐2,5‐diyl) (P3DDT) in their ability to select two types of carbon nanotubes comprising small (≈1 nm) and large (≈1.5 nm) diameters. P12CPDTBT is a better dispersant than PF12 for small diameter nanotubes, while both polymers are good dispersants of large diameter nanotubes. However, these dispersions contain metallic species. P3DDT, instead presents the best overall performance regarding the selectivity toward semiconducting species, with a dispersion yield for s‐SWNTs of 15% for small and 21% for large diameter nanotubes. These results are rationalized in terms of electronic and chemical structure showing that: (i) the binding energy is stronger when more alkyl lateral chains adsorb on the nanotube surface; (ii) the binding energy is stronger when the polymer backbone is more flexible; (iii) the purity of the dispersions seems to depend on a strong polymer–nanotube interaction.

production of low-cost network field-effect transistors (FETs), [1] logic circuits, [2,3] and other electronic devices. [4][5][6][7][8] The polymerwrapping selection of semiconducting SWCNT was introduced by Nish et al. in 2007, [9] and improved and expanded by many authors in the last years. [10][11][12][13][14][15][16][17][18][19][20] Polyfluorene, [18,21,22] poly thiophene [23][24][25][26] derivatives, and many other polymers [27][28][29][30][31][32] are used to interact with the SWCNT walls. [33][34][35][36] However, the interaction of the polymer chains with the SWCNT is rather weak, resulting in the main advantage of this sorting method, namely the polymer wrapping does not greatly alter the electronic properties of the nanotubes. [37][38][39] In the last years, this technique has become very popular as compared with other solution-based selection processes such as density gradient ultracentrifugation and gel chromatography, in particular because of its simplicity, scalability, and high dispersion yield. [36,40,41] The mechanism of the selection process of s-SWCNT, even if still under debate, can be described as following. First, the π-π interaction is driving the polymer backbone to the SWCNT walls, and the alkyl side chains wrap around the tube limiting its interaction with the solvent. Second, the selection mechanism, as it has been speculated, arises from the screening of the s-SWCNT polarizability by wrapped poly mers. [12] The metallic-SWCNT (m-SWCNT) species have roughly three orders of magnitude larger polarizability as compared with the s-SWCNT. [42,43] It is, therefore, the large polarizability and the insufficient screening that lead to the rebundling of the m-SWCNT. [23] The significant weight difference between bundles and individualized tubes is the last ingredient, which allows for the separation of the two species by means of ultracentrifugation.Not only the polymer structure but also the chain conformation in the solvent is an important factor to obtain high selectivity and high dispersion yield. Wang et al. investigated different organic solvents for the selection process bringing forward the idea that a poor solvent for the polymer is necessary to reduce the polymer-solvent interaction and favor the interaction with the SWCNT walls. [20] Toluene has been the most used solvent as it allows to obtain a good selection yield for semiconducting tubes with many different polymers. [11,13,18,24,44,45] Unfortunately, though, the shelf lifetime of s-SWCNT inks in toluene is severely limited by nanotube aggregation and In the past years, high-quality semiconducting single-walled carbon nanotube (s-SWCNT) inks obtained by conjugated polymer wrapping using toluene as solvent have been used for the fabrication of high-performance field-effect transistors. Charge-carrier mobilities up to 50 cm 2 V −1 s −1 and on/off ratios above 10 8 have been reported for devices based on networks of s-SWCNT. However, devices fabricated from inks that are only a few weeks old generally show a marked decrease in perf...