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A vertically aligned hierarchical WO3 nanosheet array on a transparent conducting substrate is produced via a template-free and capping-agent-free hydrothermal method. Due to its high porosity among the nanosheets and good contact with the conductive substrate, the WO3 nanosheet film exhibits advantageous electrochemical abilities. For example, fast switching speed (5.2 and 2.2 s for coloration and bleaching, respectively), significant optical modulation (62% at 633 nm and 67% at 2000 nm), high coloration efficiency of 55.6 cm2 C−1 at 700 nm and excellent cycling stability (95.4% after 3000 cycles) are achieved for the WO3 nanosheet array film in electrochromic application. In addition, the nanosheet film also shows outstanding electrocatalytic ability for chemical reduction of H2O2.

Co-doped NiO electrochromic nanoflake array films grown on FTO with antireflection ability have been synthesized by low temperature chemical bath deposition. Co doping has an influence on the growth and electrochromic properties of NiO nanoflake arrays. Noticeably, all the films show a very high transmittance at the bleached state in the region of visible light. Compared to the undoped NiO, the 1% Co-doped NiO nanoflake array film exhibits outstanding electrochromism, including large transmittance modulation (88.3%), high coloration efficiency (47.7 cm2 C−1), fast switching speed (3.4 s and 5.4 s), excellent reversibility and cycling durability at a wavelength of 550 nm. The enhanced electrochromic performances can be attributed to the synergetic effect contribution from low crystallization, oblique nanoflake array configuration and improved p-type conductivity by appropriate Co doping.

One-dimension MnCo 2 O 4 nanowire arrays are synthesized on nickel foam by a facile hydrothermal method. The MnCo 2 O 4 nanowires are highly crystalline with an average diameter of 70 nm and exhibit excellent properties for electrochemical energy storage. Impressively, the MnCo 2 O 4 nanowire array exhibits noticeable pseudocapacitive performance with a high capacitance of 349.8 F g −1 at 1 A g −1 and 328.9 F g −1 at 20 A g −1 as well as excellent cycling stability. As an anode material for Li-ion batteries, the MnCo 2 O 4 nanowire array delivers an initial specific discharge capacity of 1288.6 mAh g −1 at 100 mA g −1 , with reversible capacity retention of 92.7% after 50 cycles. The outstanding electrochemical performances are mainly attributed to its nanowire array architecture which provides large reaction surface area, fast ion and electron transfer and good structure stability.

The TiO2@PANI core/shell nanorod array is prepared by the combination of hydrothermal and electro-polymerization methods. A significant optical modulation (57.6% at 700 nm), high coloration efficiency (37.1 cm2 C–1), and good cycling performance (62.1% after 1000 cycles) are achieved for the TiO2@PANI core/shell nanorod array. The improved electrochromic properties are mainly attributed to the core/shell structure, formation of the donor–acceptor system, and the porous space among the nanorods, which can reduce the oxidation potential, make the ion diffusion easier and provide larger surface area for charge-transfer reactions. The data indicate great promise for the TiO2@PANI core/shell nanorod array as a potential multicolor electrochromic material.

Ultra-thin WO3 nanorods (NRs) embedded polyaniline (PANI) composite thin films were synthesized by embedding WO3 NRs into polyaniline using a surface-initiated-polymerization method, followed by spin-coating deposition. The ultra-thin WO3 NRs with length of 60 nm and diameter of 4 nm were prepared by a solvothermal method. The nanofillers were well-dispersed in the polymer matrix. The nanocomposites were finally deposited onto ITO-coated glass via spin-coating technology. The electrochromic contrast, switching speed, and durability of the composite films were investigated in details. The composite film, being a dual electrochromic material, varied from purple to green, light yellow and finally dark blue. The switching speed (0.9 s) is much faster than the films only composed of WO3 NRs. The durability of the hybrid film was enhanced compared with neat WO3 NRs film.

Periodical bowl-like macroporous WO3 array film was electrodeposited on ITO glasses using self-assembled monolayer polystyrene (PS) spheres as template. The film showed a connected network of close-packed hemisphere pores (microbowl arrays) with average size of 600 nm after the template was removed. The structure of the film revealed by XRD and TEM was that nanocrystals embedded into an amorphous matrix. The electrochromic property of the WO3 microbowl array film was examined in 0.5 M H2SO4 solution. Compared with dense film prepared without PS template, the WO3 microbowl array film showed superior electrochromic property with coloration efficiency of 68 cm2 C−1, response times of 3.6 s (coloration) and 1.0 s (bleaching), and without significant change in cyclic stability.

Nanostructured nickel oxide (NiO) thin films were prepared by a simple electrodeposition in choline chloride-based ionic liquid followed by an oxidation in air. Uniform granules and some voids opened between these granules were presented in the polycrystalline NiO films deposited for 10 and 30 s, but the film became compact as the deposition time increased to 60 s. The optical transmittance of the film decreased with the increase of the film thickness. All the NiO films exhibit high coloration efficiency, fast electrochromic switching and good cycling durability. The ultra fast switching time (0.74 s and 0.88 s) and maximum coloration efficiency of 250 cm2 C−1 were observed for the film deposited for 10 s.

A novel spectrum sensing approach based on distribution discontinuity estimation facilitated by change-point (CP) detection algorithm has been presented in this work. Specifically, a Markov Chain Monte Carlo (MCMC) based CP detection algorithm to estimate the variations in the distribution over the received signal is developed. Primary User (PU) activity, autonomous classification of modulation and detection of PU emulation attempts are detected using the CP- Maximum Likelihood Estimation (MLE) framework. Specifically, the CP based approach facilitates PU activity detection and initiates the MLE based mechanism to discern or reveal the underlying modulation scheme within the received signal. Thus, the proposed joint CP-MLE framework not only aims at detecting the discontinuity or the variations in the underlying distribution over the sensed signal, but also helps in attributing those variations to distinct modulation schemes, in an effort to identify PU emulation attempts. This CP- MLE framework has been extensively validated using the Universal Software Radio Peripheral (USRP) devices for various types of scenarios involving real-time modulation classification and identification of PU emulation type attacks.

An extremely stretchable electroluminescent device is fabricated by P. S. Lee and co-workers, as described on page 4490. The stretchable alternating-current electroluminescent (ACEL) device possesses extremely high stretchability, and can be linearly stretched to 700% with the luminance being maintained at 70% of the initial value before stretching. The device can be repeatedly stretched to 400% with stable emission behavior. The presented device will provide new opportunities in stretchable lighting, volumetric 3D displays, interactive readout systems, and other unprecedented applications.

The sheet-like nano TiO2 particles were prepared by using hydrothermal method, and were characterized by X-ray diffraction(XRD), infrared spectroscopy(IR), and transmission electron microscopy (TEM). It is found that the nanoparticle sizes and crystallinity increase with the increase of hydrothermal temperature from 150 °C to 160 °C, and then to 180 °C. With the increase of particle sizes, the absorption capacities and photocatalytic abilities of as-prepared TiO2 particles for crystal violet become better and better. The nano TiO2 with big particles is more stable than that with small particles, although its initial photocatalytic activity is relatively lower compared with that of the small particle samples.

Porous WO

Porous WO3 films with ultra-high transmittance modulation were successfully fabricated on different substrates by a novel, facile and economical pulsed electrochemical deposited method with 1.1 s interval time between each pulse. The near ideal optical modulation (97.7% at 633 nm), fast switching speed (6 and 2.7 s), high coloration efficiency (118.3 cm2 C−1), and excellent cycling stability are achieved by the porous WO3 on ITO-coated glass. The outstanding electrochromic performances of the porous WO3 film were mainly attributed to the porous structure, which facilitates the charge-transfer, promotes the electrolyte infiltration and alleviates the expansion of the WO3 during H+ insertion compared to that of the compact structure. In addition, the relationships between the structural and electrochemical activity of the electrochromic WO3 films were further explored by the scanning electrochemical microscopy. These results testify that the porous structure can promote the infiltration of electrolyte and reduce the diffusion path, which consequently enhance the electrochemical activity. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Fenestration, such as windows, plays a key role in modern architecture as it has enormous impact on the energy efficiency and comfort to the occupants of the building. Herein, current state‐of‐art strategies of nanostructured electrochromic materials, the fabrication of large scale smart windows, rational design of multifunctional smart chromogenic devices, and their performance are highlighted. Moreover, the current challenges from material selection to smart window performance are discussed and feasible solutions are provided. Development of a novel, simple, and economical synthesis of electrochromic materials is the first step in realizing high‐performance smart window. In addition, electrolyte, packaging materials, and judicious design of the fabrication process also play critical roles in the development of multifunctional and energy‐efficient smart windows. Finally, the concept of energy‐efficient multifunctional smart windows is addressed in which the smart windows are powered by sustainable energy in daytime, while the windows dynamically control the solar radiation into the building through transmittance modulation, enabling adjustable occupant's privacy. Sustainable energy can be stored in the smart windows during daytime and can be discharged to power other electronic devices at night. It is envisioned that this review shall promote a rapid development on electrochromic materials and novel multifunctional smart windows. NRF (Natl Research Foundation, S’pore) Accepted version

Few-layered phosphorene is exfoliated through a liquid phase exfoliation in ethanol, acting as an additive to mix with tempo-oxidized cellulose nanofibrils (CNF), forming a transparent, flexible nanogenerator paper. The gas barrier property of CNF protects phosphorene against oxidation in ambient condition. The phosphorene in the hybrid paper is stable over six months even with exposure to ambient condition (23 °C, 70% RH) in air. The hybrid paper is used as an active layer to construct a triboelectric energy nanogenerator (TENG). This hybrid paper shows an open-circuit voltage of 5.2 V with a current density of 1.8 µA cm−2, which is five and nine times higher than that of the pure CNF paper device, respectively. This work reveals the role of phosphorene in acting as a charge carrier in the hybrid paper and demonstrates a new way to attain stable functional phosphorene hybrids in ambient condition. The resultant phosphorene hybrid paper could be used as a building block for TENG with enhanced output performance.

Electrochromic smart windows that are able to dynamically control the light and heat transmission into a building have attracted intense interests in the field of green building. However, currently external energy consumption is required for electrochromic smart windows to change their optical properties such as transmittance, reflectance and absorption. How to recycle the energy expended and finely integrate the multifunctional smart window are still challenging at present. With our earlier established work on the various of electrochromic nanomaterials such as NiO, WO3 on transparent conductors such as ITO, FTO, silver grid/PEDOT substrates, the importance and progresses of multifunctional smart window have been highlighted.1-4 We extended our efforts on large size multifunctional smart windows (more than 300 cm2) fabricated by inkjet printing technique which is one of the low cost and solution processible methods. The assembled electrochromic windows exhibit outstanding performance including large optical modulation, high coloration efficiency, fast switching and excellent bistability. The designed multifunctional smart window can be used as typical electrochromic window as well as energy-storage device. The smart window is able to change its color to dynamically control the light and heat into a building and store the energy in the day time, and then releases the stored energy to power other electronic devices at night. Moreover, we can monitor the level of stored energy in the window via the visually detectable reversible color variation. The reported multifunctional smart window represents a leap towards the realization of fascinating and energy-efficient smart green building. References (1) Cai, G.; Wang, X.; Cui, M.; Darmawan, P.; Wang, J.; Eh, A. L.-S.; Lee, P. S. Nano Energy 2015, 12, 258. (2) Cai, G.; Wang, J.; Lee, P. S. Acc. Chem. Res. 2016, 49, 1469. (3) Cai, G.; Darmawan, P.; Cui, M.; Chen, J.; Wang, X.; Eh, A. L.-S.; Magdassi, S.; Lee, P. S. Nanoscale 2016, 8, 348. (4) Cai, G.; Darmawan, P.; Cui, M.; Wang, J.; Chen, J.; Magdassi, S.; Lee, P. S. Adv. Energy Mater. 2016, 6, 1501882.

In this article, an iterative demodulation and decoding receiver for M-ary differential chaos shift keying (DSCK) modulation is proposed over Additive White Gaussian Noise (AWGN) channel. The Log-Likelihood Ratios (LLRs) of coherent DCSK demodulator and decoder are derived assuming that its perfect carrier synchronization happened. The simulation results show that the performance of our proposed iterative receiver outperform that of the noniterative receiver over AWGN channel due to extrinsic information exchanged between demodulator and decoder. Further-more, Extrinsic Information Transfer chart is used to investigate the convergence behavior of our proposed receiver.

In this paper, an adaptive retransmission mechanism of single-input frequency-modulated differential chaos shift keying Ultra-wideband (SIMO FM-DCSK UWB) system with automatic repeat request (ARQ) protocol has been investigated, in which scheme adaptive unit delay (Td) is used to control transmission. Unlike the previous work based on optimal assignment of number of pulses per symbol or frame duration, the adaptive unit delay (Td) will not change the data rate or bandwidth, only can change the position of the pulses. Through simulation it is shown that bit error rate (BER) and throughput performances of the proposed scheme are better than normal retransmission mechanism when it is applied to two-user or multi-user systems over indoor channel, it reflects that our proposed scheme can enhance performance of chaotic UWB systems.

In this article the capacity expression is derived for M-ary Differential Chaos Shift Keying (M-DCSK) modulation over additive white Gaussian noise (AWGN) channel. Then the capacity bound curves of M-DCSK are provided by Monte Carlo method. Theoretical analysis and simulation results show that the high dimension DCSK modulation has more obvious capacity advantage than the conventional modulations. So they are appropriate for the power-limited communication systems.

Lithium-ion capacitors (LICs) are promising electrical energy storage systems for mid-to-large-scale applications due to the high energy and large power output without sacrificing long cycle stability. However, due to the different energy storage mechanisms between anode and cathode, the energy densities of LICs often degrade noticeably at high power density, because of the sluggish kinetics limitation at the battery-type anode side. Herein, a high-performance LIC by well-defined ZnMn2 O4 -graphene hybrid nanosheets anode and N-doped carbon nanosheets cathode is presented. The 2D nanomaterials offer high specific surface areas in favor of a fast ion transport and storage with shortened ion diffusion length, enabling fast charge and discharge. The fabricated LIC delivers a high specific energy of 202.8 Wh kg-1 at specific power of 180 W kg-1 , and the specific energy remains 98 Wh kg-1 even when the specific power achieves as high as 21 kW kg-1 . National Research Foundation (NRF) This work was financially supported by the National Research Foundation Competitive Research Programme, Award No. NRF-CRP-13-2014-02, and the NRF Investigatorship (NRFI), Award No. NRF-NRFI2016-05.

This paper studies the channel capacity with respect to Cosinusoid Gaussian serial pulses of MPPM-TH-UWB communication systems under additive white Gaussian noise (AWGN) channel. It mainly makes comparison between optimum combined cosinusoid gaussian pulse and 2nd devative Gaussian pulse conforming to the FCC regulations. The simulation results demonstrate that the capacity is influenced by variance of various pulses autocorrelation function. This conclusion is helpful for the pulse analysis and selection for UWB systems.

V-doped TiO(2)nanoparticles were synthesized at low temperature and characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, and photoluminescence (PL) spectroscopy, respectively. It is found the nanoparticle shape changed from needle, to short stick and then to cubic with the increase of doped V concentration, which was also accompanied by the improvement of crystallinity. The specific surface area (S(BET)) decreased with increasing V content. It is confirmed that V ions can be doped in TiO(2) by substituting Ti(4+) ions, which suppressed the CB --> VB and surface recombination of photoinduced electrons and holes, and a relation was found between the PL spectra and the UV photocatalytic activity. There was an optimum V content for the V-doped TiO(2) to present the best UV-light induced photoactivity, but they were visible-inactive. At last, the effect of the doping V as trapping centers on photocatalysis was investigated in detail, and used to explain the difference between the photocatalysis under the illumination of UV light and visible light.

Silver grids are attractive for replacing indium tin oxide as flexible transparent conductors. This work aims to improve the electrochemical stability of silver-based transparent conductors. A silver grid/PEDOT:PSS hybrid film with high conductivity and excellent stability is successfully fabricated. Its functionality for flexible electrochromic applications is demonstrated by coating one layer of WO3 nanoparticles on the silver grid/PEDOT:PSS hybrid film. This hybrid structure presents a large optical modulation of 81.9% at 633 nm, fast switching, and high coloration efficiency (124.5 cm2 C−1). More importantly, an excellent electrochemical cycling stability (sustaining 79.1% of their initial transmittance modulation after 1000 cycles) and remarkable mechanical flexibility (optical modulation decay of only 7.5% after 1200 compressive bending cycles) is achieved. A novel smart supercapacitor is presented that functions as a regular energy-storage device and simultaneously monitors the level of stored energy by a rapid and reversible color variation even at high current charge/discharge conditions. The film sustains an optical modulation of 87.7% and a specific capacitance of 67.2% at 10 A g−1 compared to their initial value at a current density of 1 A g−1. The high-performance silver grid/PEDOT:PSS hybrid transparent films exhibit promising features for various emerging flexible electronics and optoelectronic devices. NRF (Natl Research Foundation, S’pore) Accepted version

Hierarchical structure Ti-doped WO3 thin films are prepared by a template-free hydrothermal method. The influence of Ti doping on the electrochromic properties of WO3 thin films is investigated in the visible-infrared region. Ti doping can lead to significant surface morphology change and lower the crystallization, which plays an important role in the electrochromic properties of WO3 films. The large transmittance modulation (49.1% at 750 nm, 64.6% at 2000 nm and 59.3% at 10 μm), fast switching speed (1.7 s and 1.6 s) and high coloration efficiency (68 cm2 C−1 at 750 nm) are achieved for the low Ti-doped WO3 film. The enhancement in the electrochromic performance of the low Ti-doped WO3 films is attributed to their low crystallization, a star-like structure which has low charge transfer and ion diffusion resistance, leading to superior electrical conductivity and reaction kinetics.

Nanostructured NiO thin films were directly prepared by simple and efficient electrodeposition in a choline chloride-based ionic liquid. Uniform granules and some open voids between these granules are observed in the film deposited at 70 °C, while the film becomes compact and the NiO particles are 2–6 nm in size when the electrodeposition temperature is 90 °C. The optical transmittance of the film increased with the increase of the electrodeposition temperature. Although the electrochromic switching and reaction kinetics of the NiO film deposited at low temperature are fast due to the presence of metallic Ni and some voids, little transmittance modulation occurs in the wavelength range of 300–900 nm. In contrast, the NiO film deposited at high temperature exhibits high optical modulation of 67% at 550 nm, high coloration efficiency (98 cm2 C−1 at 400 nm, 92 cm2 C−1 at 550 nm and 51 cm2 C−1 at 750 nm), good memory effect and cycling durability.

A porous NiO/RGO hybrid film is prepared by the combination of electrophoretic deposition and chemical-bath deposition. The porous hybrid film exhibits a noticeable electrochromism with reversible color changes from transparent to dark brown, and shows high coloration efficiency (76 cm(2) C(-1)), fast switching speed (7.2 s and 6.7 s) and better cycling performance compared with the porous NiO thin film. The enhancement of electrochromic performances are attributed to the reinforcement of the electrochemical activity of the RGO sheets and the greater amount of open space in the porous hybrid film which allows the electrolyte to penetrate and shorten the proton diffusion paths within the bulk of NiO.

A new multi-carrier $M$ -ary differential chaos shift keying system with code index modulation, referred to as CIM-MC- $M$ -DCSK , is proposed in this paper. In the proposed CIM-MC- $M$ -DCSK system, the reference and information-bearing signals for each subcarrier can be transmitted simultaneously by using the orthogonal sinusoidal carriers, where the information-bearing signal adopts the $M$ -DCSK modulation to further increase the data rate. With an aim to making full use of the system energy resources, the reference signals in all subcarriers are coded by a Walsh code to carry additional information bits. The analytical bit-error-rate (BER) expressions of the proposed CIM-MC- $M$ -DCSK system are derived over additive white Gaussian noise as well as multipath Rayleigh fading channels. Furthermore, a noise-reduction scheme and a hierarchical-modulation scheme are designed for the proposed system. In particular, the former scheme can significantly improve the BER performance while the latter scheme can provide different quality of service for the transmitted bits according to their different levels of importance. Simulation results verify the accuracy of the analytical expressions and the superiority of the proposed systems.