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Showing papers in "Nanoscale in 2017"


Journal ArticleDOI
TL;DR: This review addresses the recent progress in the production methodologies of cellulose nanocrystals, covering principal cellulose resources and the main processes used for its isolation.
Abstract: Cellulose nanocrystals, a class of fascinating bio-based nanoscale materials, have received a tremendous amount of interest both in industry and academia owing to its unique structural features and impressive physicochemical properties such as biocompatibility, biodegradability, renewability, low density, adaptable surface chemistry, optical transparency, and improved mechanical properties. This nanomaterial is a promising candidate for applications in fields such as biomedical, pharmaceuticals, electronics, barrier films, nanocomposites, membranes, supercapacitors, etc. New resources, new extraction procedures, and new treatments are currently under development to satisfy the increasing demand of manufacturing new types of cellulose nanocrystals-based materials on an industrial scale. Therefore, this review addresses the recent progress in the production methodologies of cellulose nanocrystals, covering principal cellulose resources and the main processes used for its isolation. A critical and analytical examination of the shortcomings of various approaches employed so far is made. Additionally, structural organization of cellulose and nomenclature of cellulose nanomaterials have also been discussed for beginners in this field.

691 citations


Journal ArticleDOI
Xu Qiu1, Lixi Wang1, Hongli Zhu, Guan Yongkang1, Zhang Qitu1 
TL;DR: P porous biomass carbon has great potential to become lightweight microwave absorbers because KOH is an efficient activation agent in the fabrication of carbonaceous materials and the microwave absorption properties have been investigated.
Abstract: Lightweight microwave absorbing materials have drawn tremendous attention. Herein, nano-porous biomass carbon materials have been prepared by carbonization with a subsequent potassium hydroxide activation of walnut shells and the microwave absorption properties have also been investigated. The obtained samples have large specific surface areas with numerous micropores and nanopores. The sample activated at 600 °C with a specific surface area of 736.2 m2 g-1 exhibits the most enhanced microwave absorption performance. It has the maximum reflection loss of -42.4 dB at 8.88 GHz and the effective absorption bandwidth (reflection loss below -10 dB) is 1.76 GHz (from 8.08 GHz to 9.84 GHz), corresponding to a thickness of 2 mm. Additionally, the effective absorption bandwidth can reach 2.24 GHz (from 10.48 GHz to 12.72 GHz) when the absorber thickness is 1.5 mm. Three-dimensional porous architecture, interfacial polarization relaxation loss, and the dipolar relaxation loss make a great contribution to the excellent microwave absorption performance. In contrast, the non-activated sample with lower specific surface area (435.3 m2 g-1) has poor microwave absorption performance due to a poor dielectric loss capacity. This comparison highlights the role of micropores and nanopores in improving the dielectric loss property of porous carbon materials. To sum up, porous biomass carbon has great potential to become lightweight microwave absorbers. Moreover, KOH is an efficient activation agent in the fabrication of carbonaceous materials.

407 citations


Journal ArticleDOI
Wei Wu1
TL;DR: This review presents a summary of work to date on the utilization of inorganic nanomaterials-based inks in the successful preparation of printed conductive patterns, electrodes, sensors, thin film transistors (TFTs) and other micro-/nanoscale devices.
Abstract: Owing to their capability of bypassing conventional high-priced and inflexible silicon based electronics to manufacture a variety of devices on flexible substrates by using large-scale and high-volume printing techniques, printed electronics (PE) have attracted increasing attention in the field of manufacturing industry for electronic devices This simple and cost-effective approach could enhance current methods of constructing a patterned surface for nanomaterials and offer opportunities for developing fully-printed functional devices, especially offering the possibility of ubiquitous low-cost and flexible devices This review presents a summary of work to date on the inorganic nanomaterials involved in PE applications, focused on the utilization of inorganic nanomaterials-based inks in the successful preparation of printed conductive patterns, electrodes, sensors, thin film transistors (TFTs) and other micro-/nanoscale devices The printing techniques, sintering methods and printability of functional inks with their associated challenges are discussed, and we look forward so you can glimpse the future of PE applications

394 citations


Journal ArticleDOI
TL;DR: The most recent developments in nanostructured materials directly synthesized on 3D nickel foam as potential electrode candidates for electrochemical water electrolysis, namely, the oxygen evolution reaction (OER) and the hydrogen evolution Reaction (HER).
Abstract: Highly efficient and low-cost electrocatalysts are essential for water spitting via electrolysis in an economically viable fashion. However, the best catalytic performance is found with noble metal-based electrocatalysts, which presents a formidable obstacle for the commercial success of electrolytic water splitting-based H2 production due to their relatively high cost and scarcity. Therefore, the development of alternative inexpensive earth-abundant electrode materials with excellent electrocatalytic properties is of great urgency. In general, efficient electrocatalysts must possess several key characteristics such as low overpotential, good electrocatalytic activity, high stability, and low production costs. Direct synthesis of nanostructured catalysts on a conducting substrate may potentially improve the performance of the resultant electrocatalysts because of their high catalytic surface areas and the synergistic effect between the electrocatalyst and the conductive substrate. In this regard, three dimensional (3D) nickel foams have been advantageously utilized as electrode substrates as they offer a large active surface area and a highly conductive continuous porous 3D network. In this review, we discuss the most recent developments in nanostructured materials directly synthesized on 3D nickel foam as potential electrode candidates for electrochemical water electrolysis, namely, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). We also provide perspectives and outlooks for catalysts grown directly on 3D conducting substrates for future sustainable energy technologies.

357 citations


Journal ArticleDOI
TL;DR: It was found that one type of CDs synthesized from p-phenylenediamine could emit various long wavelength lights independent of the excitation wavelength when dispersed in different solvents.
Abstract: Carbon dots (CDs) usually emit a strong blue light and excitation wavelength dependent long wavelength lights. This significantly limits their applications because one has to use a series of different excitation light sources to get different colors and the long wavelength emissions are usually very weak. We found that one type of CDs synthesized from p-phenylenediamine could emit various long wavelength lights (green to red) independent of the excitation wavelength when dispersed in different solvents. The photoluminescence quantum yields of the same CDs were 10–35% in different solvents for different color emissions. Based on this solvent-color effect, we further mixed the same CDs with different polymers to form solid CD films for various color emissions, and these film emissions were also excitation wavelength independent. Multicolor LEDs were demonstrated with the same CDs in solution and solid film states for color displays.

354 citations


Journal ArticleDOI
TL;DR: The reduction protocol in this study allowed to achieve the highest conductivity values reported so far for the aqueous reduction of graphene oxide mediated by sodium borohydride, reflected in the dramatic change in the structural stability of the rGO nanofoams produced by freeze-drying.
Abstract: The electrical conductivity of reduced graphene oxide (rGO) obtained from graphene oxide (GO) using sodium borohydride (NaBH4) as a reducing agent has been investigated as a function of time (2 min to 24 h) and temperature (20 °C to 80 °C). Using a 300 mM aqueous NaBH4 solution at 80 °C, reduction of GO occurred to a large extent during the first 10 min, which yielded a conductivity increase of 5 orders of magnitude to 10 S m-1. During the residual 1400 min of reaction, the reduction rate decreased significantly, eventually resulting in a rGO conductivity of 1500 S m-1. High resolution XPS measurements showed that C/O increased from 2.2 for the GO to 6.9 for the rGO at the longest reaction times, due to the elimination of oxygen. The steep increase in conductivity recorded during the first 8-12 min of reaction was mainly due to the reduction of C-O (e.g., hydroxyl and epoxy) groups, suggesting the preferential attack of the reducing agent on C-O rather than C[double bond, length as m-dash]O groups. In addition, the specular variation of the percentage content of C-O bond functionalities with the sum of Csp2 and Csp3 indicated that the reduction of epoxy or hydroxyl groups had a greater impact on the restoration of the conductive nature of the graphite structure in rGO. These findings were reflected in the dramatic change in the structural stability of the rGO nanofoams produced by freeze-drying. The reduction protocol in this study allowed to achieve the highest conductivity values reported so far for the aqueous reduction of graphene oxide mediated by sodium borohydride. The 4-probe sheet resistivity approach used to measure the electrical conductivity is also, for the first time, presented in detail for filtrate sheet assemblies' of stacked GO/rGO sheets.

331 citations


Journal ArticleDOI
TL;DR: A photoinduced imine crosslinking hydrogel glue is exploited as an exosome scaffold to prepare an acellular tissue patch (EHG) for cartilage regeneration and it was found that EHG can retain SC-Exos and positively regulate both chondrocytes and hBMSCs in vitro.
Abstract: The regeneration of articular cartilage, which scarcely shows innate self-healing ability, is a great challenge in clinical treatment. Stem cell-derived exosomes (SC-Exos), an important type of extracellular nanovesicle, exhibit great potential for cartilage regeneration to replace stem cell-based therapy. Cartilage regeneration often takes a relatively long time and there is currently no effective administration method to durably retain exosomes at cartilage defect sites to effectively exert their reparative effect. Therefore, in this study, we exploited a photoinduced imine crosslinking hydrogel glue, which presents excellent operation ability, biocompatibility and most importantly, cartilage-integration, as an exosome scaffold to prepare an acellular tissue patch (EHG) for cartilage regeneration. It was found that EHG can retain SC-Exos and positively regulate both chondrocytes and hBMSCs in vitro. Furthermore, EHG can integrate with native cartilage matrix and promote cell deposition at cartilage defect sites, finally resulting in the promotion of cartilage defect repair. The EHG tissue patch therefore provides a novel, cell-free scaffold material for wound repair.

288 citations


Journal ArticleDOI
Kai Yin1, Dongkai Chu1, Xinran Dong1, Cong Wang1, Ji’an Duan1, Jun He1 
TL;DR: This study presents a simple, efficient method to fabricate superhydrophilic and underwater superoleophobic stainless steel mesh surfaces with one-step femtosecond laser induced periodic nanoripple structures that can be applied in the cleanup of large-scale oil spills in the near future.
Abstract: Marine oil spills have induced severe water pollution and threatened sea ecosystems, which also result in a loss of energy resources. To deal with this problem, much work has been done for using superhydrophobic or superhydrophilic mesh for oil–water separation. Nevertheless, there are still great challenges in the rapid fabrication of extremely durable mesh with superwetting properties, particularly considering the highly efficient oil–water separation. In this study, we present a simple, efficient method to fabricate superhydrophilic and underwater superoleophobic stainless steel mesh surfaces with one-step femtosecond laser induced periodic nanoripple structures. The as-prepared mesh shows high separation efficiency, which is higher than 99% for various oil–water mixtures. More importantly, the wettability and the separation efficiency of the fabricated mesh show no obvious change after the abrasion tests and corrosion tests, indicating that the as-prepared samples possess robust stability. This study provides an efficient route for constructing durable and highly efficient separation mesh, which can be applied in the cleanup of large-scale oil spills in the near future.

278 citations


Journal ArticleDOI
TL;DR: The first experimental demonstrations of the complete complex-amplitude holograms with subwavelength definition at visible wavelengths were achieved, and excellent performances with a remarkable signal-to-noise ratio as compared to those of traditional phase-only holograms were obtained.
Abstract: Reconstruction of light profiles with amplitude and phase information, called holography, is an attractive optical technology with various significant applications such as three-dimensional imaging and optical data storage. Subwavelength spatial control of both amplitude and phase of light is an essential requirement for an ideal hologram. However, traditional holographic devices suffer from their restricted capabilities of incomplete modulation in both amplitude and phase of visible light; this results in sacrifice of optical information and undesirable occurrences of critical noises in holographic images. Herein, we have proposed a novel metasurface that is capable of completely controlling both the amplitude and phase profiles of visible light independently with subwavelength spatial resolution. The full, continuous, and broadband control of both amplitude and phase was achieved using X-shaped meta-atoms based on the expanded concept of the Pancharatnam-Berry phase. The first experimental demonstrations of the complete complex-amplitude holograms with subwavelength definition at visible wavelengths were achieved, and excellent performances with a remarkable signal-to-noise ratio as compared to those of traditional phase-only holograms were obtained. Extraordinary control capability with versatile advantages of our metasurface paves a way to an ideal holography, which is expected to be a significant advancement in the field of optical holography and metasurfaces.

271 citations


Journal ArticleDOI
TL;DR: It is shown that a large-area WS2 film synthesized by sulfurization of a tungsten film exhibits high humidity sensing performance both in natural flat and high mechanical flexible states, indicating a potential mask-free breath monitoring for healthcare application.
Abstract: Skin-mountable chemical sensors using flexible chemically sensitive nanomaterials are of great interest for electronic skin (e-skin) application. To build these sensors, the emerging atomically thin two-dimensional (2D) layered semiconductors could be a good material candidate. Herein, we show that a large-area WS2 film synthesized by sulfurization of a tungsten film exhibits high humidity sensing performance both in natural flat and high mechanical flexible states (bending curvature down to 5 mm). The conductivity of as-synthesized WS2 increases sensitively over a wide relative humidity range (up to 90%) with fast response and recovery times in a few seconds. By using graphene as electrodes and thin polydimethylsiloxane (PDMS) as substrate, a transparent, flexible, and stretchable humidity sensor was fabricated. This senor can be well laminated onto skin and shows stable water moisture sensing behaviors in the undeformed relaxed state as well as under compressive and tensile loadings. Furthermore, its high sensing performance enables real-time monitoring of human breath, indicating a potential mask-free breath monitoring for healthcare application. We believe that such a skin-activity compatible WS2 humidity sensor may shed light on developing low power consumption wearable chemical sensors based on 2D semiconductors.

268 citations


Journal ArticleDOI
TL;DR: In the present work, the mechanism of THz metamaterial sensing and dry sample and microfluidic sensing applications based on meetamaterials are introduced and new directions of THZ metamMaterial sensing advancement and introduction of two-dimensional materials and nanoparticles for future THz applications are summarized and discussed.
Abstract: Terahertz (THz) technology has attracted great worldwide interest and novel high-intensity THz sources and plasmonics are two of the most active fields of recent research. Being situated between infrared light and microwave radiation, the absorption of THz rays in molecular and biomolecular systems is dominated by the excitation of intramolecular and intermolecular vibrations. This indicates that THz technology is an effective tool for sensing applications. However, the low sensitivity of free-space THz detection limits the sensing applications, which gives a great opportunity to metamaterials. Metamaterials are periodic artificial electromagnetic media structured with a size scale smaller than the wavelength of external stimuli. They present localized electric field enhancement and large values of quality factor (Q factor) and show high sensitivity to minor environment changes. In the present work, the mechanism of THz metamaterial sensing and dry sample and microfluidic sensing applications based on metamaterials are introduced. Moreover, new directions of THz metamaterial sensing advancement and introduction of two-dimensional materials and nanoparticles for future THz applications are summarized and discussed.

Journal ArticleDOI
TL;DR: This study shows how gas treatment synthesis such as ammoniation can transform carbide MXenes into 2D nitrides with higher electrical conductivities and metallic behavior, opening a new avenue in 2D materials synthesis.
Abstract: MXenes are a rapidly growing class of 2D transition metal carbides and nitrides, finding applications in fields ranging from energy storage to electromagnetic interference shielding and transparent conductive coatings. However, while more than 20 carbide MXenes have already been synthesized, Ti4N3 and Ti2N are the only nitride MXenes reported so far. Here by ammoniation of Mo2CTx and V2CTx MXenes at 600 °C, we report on their transformation to 2D metal nitrides. Carbon atoms in the precursor MXenes are replaced with N atoms, resulting from the decomposition of ammonia molecules. The crystal structures of the resulting Mo2N and V2N were determined with transmission electron microscopy and X-ray pair distribution function analysis. Our results indicate that Mo2N retains the MXene structure and V2C transforms to a mixed layered structure of trigonal V2N and cubic VN. Temperature-dependent resistivity measurements of the nitrides reveal that they exhibit metallic conductivity, as opposed to semiconductor-like behavior of their parent carbides. As important, room-temperature electrical conductivity values of Mo2N and V2N are three and one order of magnitude larger than those of the Mo2CTx and V2CTx precursors, respectively. This study shows how gas treatment synthesis such as ammoniation can transform carbide MXenes into 2D nitrides with higher electrical conductivities and metallic behavior, opening a new avenue in 2D materials synthesis.

Journal ArticleDOI
TL;DR: A variety of promising applications of semiconductor-enhanced Raman scattering in photoelectric characterization, redox biochemistry, sensing, and the catalytic degradation of organic pollutants are introduced.
Abstract: Surface-enhanced Raman scattering (SERS)-active nanomaterials have extended from noble metals and transition metals to semiconductor materials, since the first discovery of SERS in the mid-1970s. In comparison with metal substrates and transition metals, semiconductor materials have additional optical and electrical properties besides SERS enhancement ability, which enable them to display remarkable charge-transfer enhancement and catalytic ability. Moreover, their superior biocompatibility allows these nanomaterials to have great potential applications in bioscience. Herein we highlight the fast growing research field focusing on SERS-active semiconductor nanomaterials and semiconductor-other material heterostructures developed in our group as well as in other related research studies. The material size, morphology and assembly-dependent SERS enhancement have been discussed in detail. Furthermore, a variety of promising applications of semiconductor-enhanced Raman scattering in photoelectric characterization, redox biochemistry, sensing, and the catalytic degradation of organic pollutants are introduced.

Journal ArticleDOI
TL;DR: The as-prepared MXene QDs achieved simultaneous photoacoustic imaging and the remarkable PTT effect of tumors and showed great biocompatibility without causing noticeable toxicity in vitro and in vivo, indicating their high potential for clinical applications.
Abstract: Titanium carbide MXene quantum dots (QDs) were synthesized using an effective fluorine-free method as a biocompatible and highly efficient nanoagent for photothermal therapy (PTT) applications. In contrast to the traditional, hazardous and time-consuming process of HF pretreatment, our fluorine-free method is safe and simple. More importantly, abundant Al oxoanions were found to be modified on the MXene QD surface by the fluorine-free method, which endowed the QDs with strong and broad absorption in the NIR region. As a result, the as-prepared MXene QDs exhibited an extinction coefficient as large as 52.8 Lg-1 cm-1 at 808 nm and a photothermal conversion efficiency as high as 52.2%. Both the values are among the best reported so far. The as-prepared MXene QDs achieved simultaneous photoacoustic (PA) imaging and the remarkable PTT effect of tumors. Moreover, MXene QDs showed great biocompatibility without causing noticeable toxicity in vitro and in vivo, indicating their high potential for clinical applications.

Journal ArticleDOI
TL;DR: Density functional theory calculations reveal that Al-CoP has a more thermo-neutral hydrogen adsorption free energy than CoP, and this work offers an attractive cost-effective catalyst electrode in water-splitting devices for large-scale production of hydrogen fuels.
Abstract: The scalable production of hydrogen fuel through electrochemical water reduction needs efficient Earth-abundant electrocatalysts to make the whole water-splitting process more energy efficient. In this Article, we report that an Al-doped CoP nanoarray on carbon cloth (Al-CoP/CC) behaves as a durable hydrogen evolution electrocatalyst with superhigh activity in 0.5 M H2SO4. It demands a pretty low overpotential of 23 mV to drive a geometrical catalytic current density of 10 mA cm−2, outperforming all reported non-precious metal catalysts. Density functional theory calculations reveal that Al-CoP has a more thermo-neutral hydrogen adsorption free energy than CoP. Notably, this Al-CoP/CC is also superior in activity and durability as a bifunctional catalyst for alkaline water electrolysis, and its two-electrode water electrolyser delivers 10 mA cm−2 water-splitting current at a cell voltage of 1.56 V in 1.0 M KOH. This work offers us an attractive cost-effective catalyst electrode in water-splitting devices for large-scale production of hydrogen fuels.

Journal ArticleDOI
TL;DR: The experimental observations on polymorphism in nanoscale HfO2-ZrO2 solid solution thin films of a wide range of film compositions and thicknesses are comprehensively related to the theoretical predictions based on a thermodynamic surface energy model, which can semi-quantitatively explain the experimental results on the phase-evolution.
Abstract: The unexpected ferroelectric properties of nanoscale hafnia-zirconia are considered to be promising for a wealth of applications including ferroelectric memory, field effect transistors, and energy-related applications. However, the reason why the unexpected ferroelectric Pca21 phase can be stabilized has not been clearly understood although numerous extensive theoretical and experimental results have been reported recently. The ferroelectric orthorhombic phase is not a stable phase under processing conditions from the viewpoint of bulk free energy. Although the possibility of stabilization of the ferroelectric phase due to the surface energy effect has been theoretically suggested, such a theoretical model has not been systematically compared with actual experimental results. In this study, the experimental observations on polymorphism in nanoscale HfO2–ZrO2 solid solution thin films of a wide range of film compositions and thicknesses are comprehensively related to the theoretical predictions based on a thermodynamic surface energy model. The theoretical model can semi-quantitatively explain the experimental results on the phase-evolution, but there were non-negligible discrepancies between the two results. To understand these discrepancies, various factors such as the film stress, the role of a TiN capping layer, and the kinetics of crystallization are systematically studied. This work also reports on the evolution of electrical properties of the film, i.e. dielectric, ferroelectric, anti-ferroelectric, and morphotropic phase changes, as a function of the film composition and thickness. The in-depth analyses of the phase change are expected to provide an important guideline for subsequent studies.

Journal ArticleDOI
Kai Yin1, Haifeng Du1, Xinran Dong1, Cong Wang1, Ji-An Duan1, Jun He1 
TL;DR: This work presents a simple, low-cost method to prepare a hybrid superhydrophobic-hydrophilic surface that exhibits enhanced fog collection efficiency and shows excellent anti-corrosion ability after immersing in 1 M HCl, 1 M NaOH, and 10 wt% NaCl solutions for 2 hours.
Abstract: Fog collection is receiving increasing attention for providing water in semi-arid deserts and inland areas. Inspired by the fog harvesting ability of the hydrophobic-hydrophilic surface of Namib desert beetles, we present a simple, low-cost method to prepare a hybrid superhydrophobic-hydrophilic surface. The surface contains micro/nanopatterns, and is prepared by incorporating femtosecond-laser fabricated polytetrafluoroethylene nanoparticles deposited on superhydrophobic copper mesh with a pristine hydrophilic copper sheet. The as-prepared surface exhibits enhanced fog collection efficiency compared with uniform (super)hydrophobic or (super)hydrophilic surfaces. This enhancement can be tuned by controlling the mesh number, inclination angle, and fabrication structure. Moreover, the surface shows excellent anti-corrosion ability after immersing in 1 M HCl, 1 M NaOH, and 10 wt% NaCl solutions for 2 hours. This work may provide insight into fabricating hybrid superhydrophobic-hydrophilic surfaces for efficient atmospheric water collection.

Journal ArticleDOI
TL;DR: This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces and the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superHydrophobic polymers and their applications.
Abstract: Numerous research studies have contributed to the development of mature superhydrophobic systems. The fabrication and applications of polymeric superhydrophobic surfaces have been discussed and these have attracted tremendous attention over the past few years due to their excellent properties. In general, roughness and chemical composition, the two most crucial factors with respect to surface wetting, provide the basic criteria for yielding polymeric superhydrophobic materials. Furthermore, with their unique properties and flexible configurations, polymers have been one of the most efficient materials for fabricating superhydrophobic materials. This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces. Significantly, the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superhydrophobic polymers and their applications. The principles of these methods can be divided into two categories: the first involves adding nanoparticles to a low surface energy polymer, and the other involves combining a low surface energy material with a textured surface, followed by chemical modification. Notably, surface-initiated radical polymerization is a versatile method for a variety of vinyl monomers, resulting in controlled molecular weights and low polydispersities. The surfaces produced by these methods not only possess superhydrophobicity but also have many applications, such as self-cleaning, self-healing, anti-icing, anti-bioadhesion, oil–water separation, and even superamphiphobic surfaces. Interestingly, the combination of responsive materials and roughness enhances the responsiveness, which allows the achievement of intelligent transformation between superhydrophobicity and superhydrophilicity. Nevertheless, surfaces with poor physical and chemical properties are generally unable to withstand the severe conditions of the outside world; thus, it is necessary to optimize the performances of such materials to yield durable superhydrophobic surfaces. To sum up, some challenges and perspectives regarding the future research and development of polymeric superhydrophobic surfaces are presented.

Journal ArticleDOI
TL;DR: This work developed a simple strategy to synthesize alkyl phosphate (TDPA) coated CsPbBr3 QDs by using 1-tetradecylphosphonic acid both as the ligand for the CspbBr 3 QDs and as the precursor for the formation of alkyL phosphate.
Abstract: Inorganic halide perovskite quantum dots (QDs) suffer from problems related to poor water stability and poor thermal stability. Here we developed a simple strategy to synthesize alkyl phosphate (TDPA) coated CsPbBr3 QDs by using 1-tetradecylphosphonic acid both as the ligand for the CsPbBr3 QDs and as the precursor for the formation of alkyl phosphate. These QDs not only retain a high photoluminescence quantum yield (PLQY, 68%) and narrow band emission (FHWM ∼ 22 nm) but also exhibit high stability against water and heat. The relative PL intensity of the QDs was maintained at 75% or 59% after being dispersed in water for 5 h or heated to 375 K (100 °C), respectively. Finally, white light-emitting diodes (WLEDs) with a high luminous efficiency of 63 lm W−1 and a wide color gamut (122% of NTSC) were fabricated by using green-emitting CsPbBr3/TDPA QDs and red-emitting K2SiF6:Mn4+ phosphors as color converters. The luminous efficiency of the WLEDs remained at 90% after working under a relative humidity (RH) of 60% for 15 h, thereby showing promise for use as backlight devices in LCDs.

Journal ArticleDOI
TL;DR: GO/BPNF aerogels with promising bio-related applications, such as photothermal therapy for cancer treatment, are reported, based on graphene oxide and black phosphorus nanoflakes for the first time.
Abstract: Here we report a new kind of three-dimensional (3D) hybrid aerogels, based on graphene oxide (GO) and black phosphorus nanoflakes (BPNFs), for the first time. Our results demonstrate that the as-prepared GO/BPNF hybrid aerogels exhibited significantly enhanced photothermal as well as electrical properties of GO aerogels due to the addition of BP. Moreover, they also possessed excellent photothermal stability under ambient conditions without any protection, which can be ascribed to the coverage of BPNFs with GO nanosheets in these aerogels. This exceptional photothermal property along with robust stability renders GO/BPNF aerogels with promising bio-related applications, such as photothermal therapy for cancer treatment.

Journal ArticleDOI
TL;DR: The preparation and electrochemical properties of black phosphorus, recent advances, potential challenges, and relevant perspectives in electrochemical energy storage, and the potential of BP are discussed in this work.
Abstract: Recently, a new two-dimensional material, single- or few-layered black phosphorus (BP), has attracted considerable attention for applications in electronics, optoelectronics, and batteries due to its unique properties, including large specific surface area, anisotropy, and tunable and direct band gaps. In particular, contributions to electrochemical energy storage devices, such as lithium and sodium ion batteries and supercapacitors, have emerged. However, critical issues remain to be explored before scaled-up commercial production of BP, such as preparation, stability, and performance. Herein, we present the first review of recent progress in BP-based electrochemical energy storage device. The preparation and electrochemical properties of black phosphorus, recent advances, potential challenges, and relevant perspectives in electrochemical energy storage, and the potential of BP are discussed in this work.

Journal ArticleDOI
TL;DR: Results indicate that fiber-taper WS2 SAs with smaller waist diameter and longer fused zone are promising photonic devices for ultrashort pulse generation in all-fiber lasers.
Abstract: Tungsten disulphide (WS2), which exhibits excellent saturable absorption properties, has attracted much attention in the applications of photonic devices. In this paper, WS2 is applied for the preparation of a saturable absorber (SA). Using the pulsed laser deposition (PLD) method, WS2 is deposited on the side surface of the tapered fiber. In order to obtain larger non-linearity of the SAs with evanescent wave interaction, the tapered fiber had a smaller waist diameter and longer fused zone. Gold film was deposited on the fiber-taper WS2 SAs to improve their reliability and avoid oxidation and corrosion. Employing the balanced twin-detector method, the modulation depth of the fiber-taper WS2 SAs was measured to be 17.2%. With the fiber-taper WS2 SA, a generated pulse with 246 fs duration and a 57 nm bandwidth was obtained at 1561 nm. The electrical signal to noise ratio was better than 92 dB. To our knowledge, the pulse duration was the shortest among the reported all-fiber lasers with transition metal dichalcogenide (TMD) SAs. These results indicate that fiber-taper WS2 SAs with smaller waist diameter and longer fused zone are promising photonic devices for ultrashort pulse generation in all-fiber lasers.

Journal ArticleDOI
TL;DR: In this article, the authors performed density functional theory (DFT) and constrained DFT calculations for a range of hBN point defects in order to identify potential emission candidates by applying a number of criteria on the electronic structure of the ground state and the atomic structure of excited states of the considered defects, and then calculating the Huang-Rhys factor.
Abstract: Hexagonal boron nitride (hBN) has recently emerged as a fascinating platform for room-temperature quantum photonics due to the discovery of robust visible light single-photon emitters In order to utilize these emitters, it is necessary to have a clear understanding of their atomic structure and the associated excitation processes that give rise to this single photon emission Here, we performed density-functional theory (DFT) and constrained DFT calculations for a range of hBN point defects in order to identify potential emission candidates By applying a number of criteria on the electronic structure of the ground state and the atomic structure of the excited states of the considered defects, and then calculating the Huang–Rhys (HR) factor, we found that the CBVN defect, in which a carbon atom substitutes a boron atom and the opposite nitrogen atom is removed, is a potential emission source with a HR factor of 166, in good agreement with the experimental HR factor We calculated the photoluminescence (PL) line shape for this defect and found that it reproduces a number of key features in the experimental PL lineshape

Journal ArticleDOI
TL;DR: The insights obtained from this study are likely to be helpful for tuning the photo-response of these substances and their better utilization in light-based applications.
Abstract: Understanding the nature and dynamics of the photo-induced transients of all-inorganic perovskite nanocrystals (NCs) is key to their exploitation in potential applications. In order to determine the nature of charge carriers, their deactivation pathways and dynamics, the photo-induced transients of CsPbBr3, CsPbBr2I, CsPbBr1.5I1.5 and CsPbI3 NCs are spectrally and temporally characterized employing a combination of femtosecond transient absorption (TA) and photoluminescence (PL) up-conversion techniques and global analysis of the data. The results provide distinct identities of the excitons and free charge carriers and distinguish the hot charge carriers from the cold ones. The carrier trapping is attributed to the electrons and their dynamics is unaffected in mixed halide perovskites. The excitation energy dependence of the TA dynamics suggests that the trap states are shallow in nature and mainly limited near the band-edge level. In mixed halide perovskites, an increase in the iodine content leads to hole trapping in a short time scale (<5 ps). The insights obtained from this study are likely to be helpful for tuning the photo-response of these substances and their better utilization in light-based applications.

Journal ArticleDOI
Yingbo Liu1, Liang Zhou1, Yanan Li1, Ruiping Deng1, Hongjie Zhang1 
TL;DR: These nitrogen-doped carbon dots, which were prepared via the hydrothermal treatment of citric acid and tris(hydroxymethyl)methyl aminomethane, have a high QY of 75%, together with excellent thermal and photo stability and allow them to be used as invisible ink for loading important information and advanced anti-counterfeiting.
Abstract: High quantum yields (QY) and stable performances are prerequisites for implementing carbon dots in practical applications. In this study, we demonstrate that nitrogen-doped carbon dots (N-CDs), which were prepared via the hydrothermal treatment of citric acid (CA) and tris(hydroxymethyl)methyl aminomethane (Tris), have a high QY of 75%, together with excellent thermal and photo stability. These N-CDs deliver an excellent thermal stability performance over the temperature range of 25 °C to 95 °C, and even at a heating temperature of 90 °C for 360 min. Upon exposure to UV illumination with a radiant intensity of 20 mW cm-2, 96% fluorescence intensity is retained. This florescence stability performance is probably due to the chemical composition and steric effect of the nitrogen-doping agent. Furthermore, the remarkable optical properties of these N-CDs allow them to be used as invisible ink for loading important information and advanced anti-counterfeiting.

Journal ArticleDOI
TL;DR: A novel colorimetric sensing platform was constructed for quantitative detection of acetylcholinesterase (AChE) activity and its inhibitor with highly promising performance and has been used to fabricate test strips for rapid and convenient visual detection of AChE and its inhibitors.
Abstract: In the present study, a novel colorimetric sensing platform was constructed for quantitative detection of acetylcholinesterase (AChE) activity and its inhibitor. Manganese dioxide (MnO2) nanosheets as an oxidase-mimicking nanomaterial could directly oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into oxTMB without the need for horseradish peroxidase and H2O2. When AChE was introduced, acetylthiocholine could be catalytically hydrolyzed to produce thiocholine, which easily triggers the decomposition of MnO2 nanosheets, causing the decrease of solution absorbance. Owing to the inhibition effect of organophosphorus pesticides, the enzymatic activity was suppressed, preventing the decomposition of MnO2 and resulting in the increase of absorbance. Under optimal conditions, the colorimetric platform shows sensitive responses to AChE and paraoxon in the range of 0.1-15 mU mL-1 and 0.001-0.1 μg mL-1, respectively. The detection limits of AChE and paraoxon reached 35 μU mL-1 and 1.0 ng mL-1, respectively. Furthermore, the MnO2-TMB platform has been used to fabricate test strips for rapid and convenient visual detection of AChE and its inhibitor with highly promising performance.

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TL;DR: A green method for fabrication of a number of transition metal phosphides (TMPs) by pyrolyzing melamine and self-assembled phytic acid (PA) cross-linked metal complexes, which exhibit relatively high activity toward HER.
Abstract: Applications of highly-efficient and durable non-precious metal electrocatalysts for hydrogen evolution reaction (HER) have great potential to relieve the energy crisis. Here, we demonstrate a green method for fabrication of a number of transition metal phosphides (TMPs) by pyrolyzing melamine and self-assembled phytic acid (PA) cross-linked metal complexes. The obtained materials consisting of TMP nanoparticles (NPs) are encapsulated in N,P-codoped carbon (NPC). Among TMPs, the resultant FeP NPs encapsulated in the NPC matrix (FeP NPs@NPC) show the highest HER activity at all pH values. At a current density of 10 mA cm−2, FeP NPs@NPC displays overpotentials of 130, 386 and 214 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution (PBS) and 1.0 M KOH, respectively. Additionally, the encapsulation by NPC effectively prevents FeP NPs from corrosion, exhibiting almost unfading catalytic activity after 10 h testing in acidic, neutral and basic electrolytes. More importantly, other TMPs wrapped in NPC (CoP NPs@NPC and Ni2P NPs@NPC) can be easily obtained by this method, which also exhibit relatively high activity toward HER. Therefore, this generic synthesis strategy opens a door for unprecedented design and fabrication of novel low-cost TMP based electrocatalysts for HER and other electrochemical applications.

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TL;DR: It is shown that a significant increase in the dielectric constant can be achieved in polyetherimide nanocomposites with nanofillers whose dielectrics can be similar to that of the matrix.
Abstract: In order to increase the dielectric constants of polymer-based dielectrics, composite approaches, in which inorganic fillers with much higher dielectric constants are added to the polar polymer matrix, have been investigated. However, high dielectric constant fillers cause high local electric fields in the polymer, resulting in a large reduction of the electric breakdown strength. We show that a significant increase in the dielectric constant can be achieved in polyetherimide nanocomposites with nanofillers whose dielectric constant can be similar to that of the matrix. The presence of nanofillers reduces the constraints on the dipole response to the applied electric field, thus enhancing the dielectric constant. Our results demonstrate that through nanostructure engineering, the dielectric constant of nanocomposites can be enhanced markedly without using high dielectric constant nanofillers.

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TL;DR: The cytotoxicity, biocompatibility and frontier applications in biomedicine of the three nanocellulose categories were the focus and are detailed in each section.
Abstract: Nanocellulose, extracted from the most abundant biomass material cellulose, has proved to be an environmentally friendly material with excellent mechanical performance owing to its unique nano-scaled structure, and has been used in a variety of applications as engineering and functional materials. The great biocompatibility and biodegradability, in particular, render nanocellulose promising in biomedical applications. In this review, the structure, treatment technology and properties of three different nanocellulose categories, i.e., nanofibrillated cellulose (NFC), nanocrystalline cellulose (NCC) and bacterial nanocellulose (BNC), are introduced and compared. The cytotoxicity, biocompatibility and frontier applications in biomedicine of the three nanocellulose categories were the focus and are detailed in each section. Future prospects concerning the cytotoxicity, applications and industrial production of nanocellulose are also discussed in the last section.

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Junjun Liu1, Si yu Lu1, Qiu ling Tang1, Kai Zhang1, Wei xian Yu1, Hongchen Sun1, Bai Yang1 
TL;DR: A green, simple hydrothermal approach to synthesize water-soluble, nontoxic, highly photoluminescent carbon nanodots (CNDs) from Metronidazole, which possess selective antibacterial activity against obligate anaerobes for the first time.
Abstract: Carbon dots (CDs) with high quantum yield (QY), low toxicity and good biocompatibility are the major quests of biomedical research. In this paper, we develop a green, simple hydrothermal approach to synthesize water-soluble, nontoxic, highly photoluminescent carbon nanodots (CNDs) from Metronidazole, which possess selective antibacterial activity against obligate anaerobes for the first time. Metronidazole was used as a sole precursor to prepare CNDs at 250 °C (CNDs-250) for 8 h. After the CNDs-250 with an average size of 2.9 nm, consisting of a highly carbon crystalline core and various surface groups were obtained, the formation and fluorescence mechanisms of CNDs were further explored by adjusting the reaction time and reaction temperatures, respectively. Biological experimental data proved that CNDs-250 can only inhibit the growth of obligate anaerobes, such as Porphyromonas gingivalis (P. gingivalis) directly, instead of further functionalization. Besides, CNDs-250 with a QY around 28.1% exhibit an obvious excitation-dependent emission, which will be conducive to multicolor bioimaging. And it may not only develop a new approach for researchers to prepare multifunctional CDs, but also provide a valuable strategy for the theranostics of some diseases as well as other fields.