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The lattice geometry of natural materials and the structural geometry of artificial materials are crucial factors determining their physical properties. Most materials have predetermined geometries that lead to fixed physical characteristics. Here, the demonstration of a carbon nanotube network serves as an example of a system with controllable orientation achieving on-demand optical properties. Such a network allows programming their optical response depending on the orientation of the constituent carbon nanotubes and leads to the switching of its dielectric tensor from isotropic to anisotropic. Furthermore, it also allows for the achievement of wavelength-dispersion for their principal optical axes - a recently discovered phenomenon in van der Waals triclinic crystals. The results originate from two unique carbon nanotubes features: uniaxial anisotropy from the well-defined cylindrical geometry and the intersection interaction among individual carbon nanotubes. The findings demonstrate that shaping the relative orientations of carbon nanotubes or other quasi-one-dimensional materials of cylindrical symmetry within a network paves the way to a universal method for the creation of systems with desired optical properties.

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Single-walled carbon nanotubes (SWCNTs) are considered to be promising material platforms for various photodetectors (including phototransistors) due to their unique optoelectrical properties (e.g., high mobility and a wide variety of bandgap values). Herein, we present highly sensitive phototransistors which utilised sparse networks of SWCNTs on a silicon/silica substrate and operated by means of the photogating effect. The response of SWCNTs to photo-induced electrostatic charges (photogating effect) was highly dependent on the conductivity type of the channel, which was "metallic" or "semiconducting", depending on the SWCNT density. We determined the performance of these transistors depending on the characteristics of the substrate and conductivity type of the SWCNT channel. The optimized configuration of phototransistors with a channel comprising a sparse network of SWCNTs permitted improvement in the specific detectivity and relative response compared with previously reported photodetectors based on graphene and carbon nanotubes. We demonstrated an absolute responsivity of ∼60 A W-1 at an incident light power of ∼2 nW, specific detectivity of 7.8 × 1011 cm·Hz1/2 W-1, and response time of 300 µs. These data revealed the high potential of photogating-based SWCNTs detectors for extremely weak signals with a high signal-to-noise ratio.

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The films of single-walled carbon nanotubes (SWCNTs) are a promising material for flexible transparent electrodes, which performance depends not only on the properties of individual nanotubes but also, foremost, on bundling of individual nanotubes. This work investigates the impact of densification on optical and electronic properties of SWCNT bundles and fabricated films. Our ab initio analysis shows that the optimally densified bundles, consisting of a mixture of quasi-metallic and semiconducting SWCNTs, demonstrate quasi-metallic behavior and can be considered as an effective conducting medium. Our density functional theory calculations indicate the band curving and bandgap narrowing with the reduction of the distance between nanotubes inside bundles. Simulation results are consistent with the observed conductivity improvement and shift of the absorption peaks in SWCNT films densified in isopropyl alcohol. Therefore, not only individual nanotubes but also the bundles should be considered as building blocks for high-performance transparent conductive SWCNT-based films.

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A sensor array based on heterojunctions between semiconducting organic layers and single walled carbon nanotube (SWCNT) films is produced to explore applications in breathomics, the molecular analysis of exhaled breath. The array is exposed to gas/volatiles relevant to specific diseases (ammonia, ethanol, acetone, 2-propanol, sodium hypochlorite, benzene, hydrogen sulfide, and nitrogen dioxide). Then, to evaluate its capability to operate with real relevant biological samples the array is exposed to human breath exhaled from healthy subjects. Finally, to provide a proof of concept of its diagnostic potential, the array is exposed to exhaled breath samples collected from subjects with chronic obstructive pulmonary disease (COPD), an airway chronic inflammatory disease not yet investigated with CNT-based sensor arrays, and breathprints are compared with those obtained from of healthy subjects. Principal component analysis shows that the sensor array is able to detect various target gas/volatiles with a clear fingerprint on a 2D subspace, is suitable for breath profiling in exhaled human breath, and is able to distinguish subjects with COPD from healthy subjects based on their breathprints. This classification ability is further improved by selecting the most responsive sensors to nitrogen dioxide, a potential biomarker of COPD.

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Materials with electrically tunable optical properties offer a wide range of opportunities for photonic applications. The optical properties of the single-walled carbon nanotubes (SWCNTs) can be significantly altered in the near-infrared region by means of electrochemical doping. The states' filling, which is responsible for the optical absorption suppression under doping, also alters the nonlinear optical response of the material. Here, for the first time we report that the electrochemical doping can tailor the nonlinear optical absorption of SWCNT films and demonstrate its application to control pulsed fiber laser generation. With a pump-probe technique, we show that under an applied voltage below 2 V the photobleaching of the material can be gradually reduced and even turned to photoinduced absorption. Furthermore, we integrated a carbon nanotube electrochemical cell on a side-polished fiber to tune the absorption saturation and implemented it into the fully polarization-maintaining fiber laser. We show that the pulse generation regime can be reversibly switched between femtosecond mode-locking and microsecond Q-switching using different gate voltages. This approach paves the road toward carbon nanotube optical devices with tunable nonlinearity.

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Soft, flexible, and stretchable electronic devices provide novel integration opportunities for wearable and implantable technologies. Despite the existing efforts to endow electronics with the capability of large deformation, the main technological challenge is still in the absence of suitable materials for the manufacturing of stretchable electronic circuits and devices with active (sensitive) and passive (stable) components. Here, we present a universal material, based on single-walled carbon nanotube (SWCNT) films deposited on a polydimethylsiloxane (PDMS) substrate, which can act as a material being both sensitive and insensitive to strain. The diverse performance of SWCNT/PDMS structures was achieved by two simple dry-transfer fabrication approaches: SWCNT film deposition onto the as-prepared PDMS and on the prestretched PDMS surface. The correlation between applied strain, microstructural evolution, and electro-optical properties is discussed on the basis of both experimental and computational results. The SWCNT/PDMS material with the mechanically tunable performance has a small relative resistance change from 0.05 to 0.07, while being stretched from 10 to 40% (stable electrode applications). A high sensitivity of 20.1 of the SWCNT/PDMS structures at a 100% strain was achieved (strain sensing applications). Our SWCNT/PDMS structures have superior transparency and conductivity compared to the ones reported previously, including the SWCNT/PDMS structures, obtained by wet processes.

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Although carbon nanotubes have already been demonstrated to be a promising material for bolometric photodetectors, enhancing sensitivity while maintaining the speed of operation remains a great challenge. Here, we present a holey carbon nanotube network, designed to improve the temperature coefficient of resistance for highly sensitive ultra-fast broadband bolometers. Treatment of carbon nanotube films with low-frequency oxygen plasma allows fine tuning of the electronic properties of the material. The temperature coefficient of resistance of our films is much greater than the reported values for pristine carbon nanotubes, up to -2.8% K-1 at liquid nitrogen temperature. The bolometer prototypes made from the treated films demonstrate high sensitivity over a wide IR range, a short response time, smooth spectral characteristics and a low noise level.

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Electrically conductive hydrogels (ECHs) are attracting much interest in the field of biomaterials science because of their unique properties. However, effective incorporation and dispersion of conductive materials in the matrices of polymeric hydrogels for improved conductivity remains a great challenge. Here, we demonstrate highly transparent, electrically conductive, stretchable tough hydrogels modified by single-walled carbon nanotubes (SWCNTs). Two different approaches for the fabrication of SWCNT/hydrogel structures are examined: a simple SWCNT film transfer onto the as-prepared hydrogel and the film deposition onto the pre-stretched hydrogel. Functionality of our method is confirmed by scanning electron microscopy along with optical and electrical measurements of our structures while subjecting them to different strains. Since the hydrogel-based structures are intrinsically soft, stretchable, wet, and sticky, they conform well to a human skin. We demonstrate applications of our material as skin-like passive electrodes and active finger-mounted joint motion sensors. Our technique shows promise to accelerate the development of biointegrated wearable electronics.

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We present a method for reduced graphene oxide (GO) patterning on the surface of GO film by a 445 nm solid-state laser with the adjustable fluence from 0.2-20 kJ cm-2. We demonstrate that the optimal argon concentration in air to obtain good quality reduced GO films is 90%. Varying the laser irradiation energy density allows controlling the resistance and I G /I D and I G /I 2D ratios of Raman peak intensities. As a result, we demonstrate the possibility of forming of conductive patterns with a sheet resistance of 189 Ohm/□ and ∼1 µm film thickness by a local reduction of the GO. The fabricated structures reveal excellent bolometric response with a high speed and sensitivity to the radiation in the visible wavelength region.

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The optoacoustic method has been shown to be an accurate technique for the measurement of the properties of submicron metal coatings deposited on a dielectric substrate, i.e., mirrors. The method has been previously theoretically described in terms of a linear model of optoacoustic transformation in a system substrate/coating/liquid. The goal of the present work was to determine the limits at which the linear model is still applicable. The modification of the laser induced acoustic signal profiles and transfer functions of optoacoustic transformation versus the laser fluence was studied for two liquids: ethanol and water.

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