Research Article Issue
A waterproof and breathable Cotton/rGO/CNT composite for constructing a layer-by-layer structured multifunctional flexible sensor
Nano Research 2022, 15 (10): 9341-9351
Published: 31 May 2022
Abstract PDF (22 MB) Collect

Developing a cotton fabric sensing layer with good waterproofness and breathability via a low-cost and eco-friendly method is increasingly important for the construction of comfortable and wearable electronic devices. Herein, a waterproof and breathable cotton fabric composite decorated by reduced graphene oxide (rGO) and carbon nanotube (CNT), Cotton/rGO/CNT, is reported by a facile solution infiltration method, and we adopt such Cotton/rGO/CNT composite to develop a layer-by-layer structured multifunctional flexible sensor, enabling the high-sensitivity detection of pressure and temperature stimulus. Particularly, the multifunctional flexible sensor exhibits a high response toward tiny pressure, demonstrating salient superiority in the continuous and reliable monitoring of human physiological information. Concerning temperature sensing, a good linear response for the temperatures ranging from 28 to 40 °C is achieved by the multifunctional flexible sensor and gives rise to be successfully applied to the non-contact real-time monitoring of human respiration signal. Finally, an array consisting of multifunctional flexible sensors further demonstrates its feasibility in perceiving and mapping the pressure and temperature information of contact objects. This work provides a feasible strategy for designing cotton-based sensing layers that can effectively resist liquid water penetration and allow water vapor transmission, and offers reasonable insight for constructing comfort and multifunctional wearable electronics.

Research Article Issue
MXene quantum dot within natural 3D watermelon peel matrix for biocompatible flexible sensing platform
Nano Research 2022, 15 (4): 3653-3659
Published: 25 November 2021
Abstract PDF (7.5 MB) Collect

Environmentally friendly biomimetic materials with good deformability, high pressure-sensitive performance, and excellent biocompatibility are highly attractive for health monitoring, but to simultaneously meet these requirements is a formidable challenge. In this study, biocompatible MXene quantum dot (MQD)/watermelon peel (WMP) aerogels were obtained by immersing freeze-dried fresh watermelon peel into the quantum dot dispersion. The resulting bio-aerogels with a three-dimensional (3D) porous network structure exhibited a low in elasticity modulus (0.03 MPa) and limit of detection (0.4 Pa) and it showed biocompatibility. With a maximum pressure-sensitive response of 323 kPa-1, the 3D porous MQD/WMP aerogels exhibited good stability. In addition, the sensing signals could be displayed on mobile phones through a Bluetooth module to monitor human motion (pulse, sound, and walking) in real time. More importantly, the MQD/WMP aerogels exhibited excellent biocompatibility in a cytotoxicity test, thus decreasing the safety risk when they are applied to human skin. The finding in this study will facilitate the fabrication of high-performance biomimetic MXene active matrices, which are derived from natural biological materials, for flexible electronics.

Research Article Issue
High-performance flexible self-powered strain sensor based on carbon nanotube/ZnSe/CoSe2 nanocomposite film electrodes
Nano Research 2022, 15 (1): 170-178
Published: 17 April 2021
Abstract PDF (36.6 MB) Collect

High-performance energy storage and sensing devices have been undergoing rapid development to meet the demand for portable and wearable electronic products, which require flexibility, extensibility, small volume and lightweight. In this study, we construct a lightweight and flexible self-powered sensing system by integrating a highly stretchable strain sensor with a high-performance asymmetric supercapacitor based on ZnSe/CoSe2//ECNT (ECNT: electrochemically activated carbon nanotube film). The ZnSe/CoSe2 two-dimentional nanosheets on carbon nanotube (CNT) films are synthesized through a simple and efficient strategy derived from ZnCo-based metal-organic frameworks (MOFs). The density functional theory (DFT) simulations show the higher conductivity of the ZnSe/CoSe2/CNT electrode than the CoSe2/CNT electrode. Due to the synergistic properties of self-supported two-dimentional ZnSe/CoSe2 nanosheets with high specific surface area and the high pathway of one-dimention CNTs, the nanocomposite electrode provides efficient transmission and short paths for electron/ion diffusion. The asymmetric supercapacitor provides a stable output power supply to the sensors that can precisely respond to strain and pressure changes. The sensor can also be attached to a garment for measuring a variety of joint movements.

Research Article Issue
Modify Cd3As2 nanowires with sulfur to fabricate self-powered NIR photodetectors with enhanced performance
Nano Research 2021, 14 (10): 3379-3385
Published: 03 March 2021
Abstract PDF (21.2 MB) Collect

Cd3As2 nanowires (NWs) have great potential in the near-infrared (NIR) photodetection field due to their excellent optoelectronic properties as a typical Dirac semimetal. However, the existence of surface oxidization limits their photoresponse performance for practical applications. Here, we modified the surface of Cd3As2 NWs with sulfur to prevent surface oxidizing and optimize the bandgap structure to improve the photoresponse performance. The S-modified Cd3As2 samples existed as core/shell Cd3As2/CdS NWs and the corresponding single NW device showed a responsivity of 0.95 A/W in the NIR band at a 0 V bias, which is three orders of magnitude higher than that of an unmodified NW. This study provides an efficient and universally applicable way to prevent semimetals nanostructures from oxidizing and promote their optoelectronic properties.

Research Article Issue
Reliable sensors based on graphene textile with negative resistance variation in three dimensions
Nano Research 2021, 14 (8): 2810-2818
Published: 25 February 2021
Abstract PDF (11.6 MB) Collect

The weft-knitted reduced graphene oxide (r-GO) textile that is made up of many conductive r-GO coated fibers was successfully prepared dependent on the electrospray deposition technique. Interestingly, the r-GO textile presents negative resistance variation not only in axial direction as the pressure increases but also in transverse direction as the lateral stretch increases which makes it has the advantage to fabricate the reliable sensors based on strain-resistance effect. The transverse-strain and pressure sensors based on the r-GO textiles all show the excellent sensing characteristics such as high sensitivity, reliability, and good durability, etc. The maximum gauge factors (GF) of the transverse-sensor are 27.1 and 153.5 in the x- and y-direction, respectively. And the practical detection range can up to 40% in the x-direction and 35% in the y-direction, respectively. The r-GO textile pressure sensor also shows high sensitivity for a broad pressure range that with a GF up to 716.8 kPa-1 for less than 4.5 kPa region and still has more sensitive pressure sensing characteristics even the pressure goes up to 14 kPa. Based on those good performances of r-GO textile sensors, its potential applications in human body states monitoring have been studied.

Research Article Issue
Highly sensitive hybrid nanofiber-based room-temperature CO sensors: Experiments and density functional theory simulations
Nano Research 2018, 11 (2): 1029-1037
Published: 11 August 2017
Abstract PDF (1.8 MB) Collect

Chemical sensors (CSs) are an emerging area in nanoscience research, which focuses on the highly sensitive detection of toxic and hazardous gases and disease-related volatile organics. While the field has advanced rapidly in recent years, it lacks the theoretical support required for the rational design of innovative materials with tunable measurement responses. Herein, we present a one-dimensional (1D) hybrid nanofiber decorated with ultrafine NiO nanoparticles (NiO NPs) as an efficient active component for CSs. Highly dispersed (110)-facet NiO NPs with a high percentage of Ni2+ active sites with unsaturated coordination were confined in a TiO2 nanofiber (TiO2 NF) matrix that is favorable for surface catalytic reactions. The CSs constructed using the 1D heterostructure NiO/TiO2 nanofibers (NiO/TiO2 HNFs) exhibited a highly selective response to trace CO gas molecules (1 ppm) with high sensitivity (ΔR/R0 = 1.02), ultrafast response/recovery time (Tres/Trecov < 20 s), and remarkable reproducibility at room temperature. The density functional theory (DFT) simulations and experimental results confirmed that the selective response could be attributed to the high molecular adsorption energy of the NiO nanoparticles with (110) facets and abundant interfaces, which act synergistically to promote CO adsorption and facilitate charge transfer.

Research Article Issue
Fabrication of rigid and flexible SrGe4O9 nanotube-based sensors for room-temperature ammonia detection
Nano Research 2018, 11 (1): 431-439
Published: 10 August 2017
Abstract PDF (2.2 MB) Collect

Ammonia (NH3) detection at room temperature has attracted considerable attention because of the increasing demand for health monitoring, personal safety protection, and industrial manufacturing. Herein, we report the synthesis of polycrystalline SrGe4O9 nanotubes (NTs) via an electrospinning process. These NTs are a new sensing material for the detection of ammonia at room temperature. The SrGe4O9 NTs exhibited a maximum sensing response of 2.49 for 100 ppm NH3, which was increased to 7.08 by decorating the NTs with Pt nanoparticles. Flexible gas sensors were fabricated, which exhibited comparable performance to the rigid device. Additionally, the flexible devices showed excellent flexibility, mechanical stability, and sensing stability under different bending states, manifesting their potential applications in flexible and wearable electronics.

Research Article Issue
Fiber gas sensor-integrated smart face mask for room-temperature distinguishing of target gases
Nano Research 2018, 11 (1): 511-519
Published: 27 June 2017
Abstract PDF (2 MB) Collect

Wearable gas sensors that are lightweight, portable, and inexpensive have great potential application in the real-time detection of human health and environmental monitoring. In this work, we fabricated flexible fiber gas sensors with single-walled carbon nanotube (SWCNT), multi-walled carbon nanotube (MWCNT), and ZnO quantum dot-decorated SWCNT (SWCNTs@ZnO) sensing elements. These flexible fiber gas sensors could be operated at room temperature to detect target gases with good sensitivity and recovery time. They also exhibited superior long-term stability, as well as good device mechanical bending ability and robustness. Integrating these flexible gas sensors into face masks, the fabricated wearable smart face masks could be used to selectively detect C2H5OH, HCHO, and NH3 by reading the corresponding LEDs with different colors. Such face masks have great potential application in the Internet of Things and wearable electronics.

Research Article Issue
Fabrication of flexible reduced graphene oxide/Fe2O3 hollow nanospheres based on-chip micro-supercapacitors for integrated photodetecting applications
Nano Research 2016, 9 (2): 424-434
Published: 28 December 2015
Abstract PDF (1.3 MB) Collect

Micro-supercapacitors (MSCs) as important on-chip micropower sources have attracted considerable attention because of their unique and advantageous design for optimized maximum functionality within a minimized sized chip and excellent mechanical flexibility/stability in miniaturized portable electronic device applications. In this work, we report a novel, high-performance flexible integrated on-chip MSC based on hybrid nanostructures of reduced graphene oxide/Fe2O3 hollow nanospheres using a microelectronic photo-lithography technology combined with plasma etching technique. The unique structural design for on-chip MSCs enables high-performance enhancements compared with graphene-only devices, exhibiting high specific capacitances of 11.57 F·cm-3 at a scan rate of 200 mV·s-1 and excellent rate capability and robust cycling stability with capacitance retention of 92.08% after 32, 000 charge/discharge cycles. Moreover, the on-chip MSCs exhibit superior flexibility and outstanding stability even after repetition of charge/discharge cycles under different bending states. As-fabricated highly flexible on-chip MSCs can be easily integrated with CdS nanowire-based photodetectors to form a highly compacted photodetecting system, exhibiting comparable performance to devices driven by conventional external energy storage units.

Research Article Issue
Two-dimensional Ni(OH)2 nanoplates for flexible on-chip microsupercapacitors
Nano Research 2015, 8 (11): 3544-3552
Published: 14 September 2015
Abstract PDF (2.1 MB) Collect

On-chip microsupercapacitors (MSCs) compatible with on-chip geometries of integrated circuits can be used either as a separate power supply in microelectronic devices or as an energy storage or energy receptor accessory unit. In this work, we report the fabrication of flexible two-dimensional Ni(OH)2 nanoplates-based MSCs, which achieved a specific capacitance of 8.80 F/cm3 at the scan rates of 100 mV/s, losing only 0.20% of its original value after 10, 000 charge/discharge cycles. Besides, the MSCs reached an energy density of 0.59 mWh/cm3 and a power density up to 1.80 W/cm3, which is comparable to traditional carbon-based devices. The flexible MSCs exhibited good electrochemical stability when subjected to bending at various conditions, illustrating the promising application as electrodes for wearable energy storage.

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