Showing papers in "Materials horizons in 2018"

Photocatalytic fixation of nitrogen to ammonia: state-of-the-art advancements and future prospects

Abstract: The burgeoning development of ammonia (NH3) synthesis technology addresses the urgency of food intake required to sustain the population growth of the last 100 years. To date, NH3 has mostly been synthesized by the Haber–Bosch process in industry. Under the ever-increasing pressure of the fossil fuel depletion crisis and anthropogenic global climate change with continuous CO2 emission in the 21st century, research targeting the synthesis of NH3 under mild conditions in a sustainable and environment friendly manner is vigorous and thriving. Therefore, the focus of this review is the state-of-the-art engineering of efficient photocatalysts for dinitrogen (N2) fixation toward NH3 synthesis. Strenuous efforts have been devoted to modifying the intrinsic properties of semiconductors (i.e. poor electron transport, rapid electron–hole recombination and sluggish reaction kinetics), including nanoarchitecture design, crystal facet engineering, doping and heterostructuring. Herein, this review provides insights into the most recent advancements in understanding the charge carrier kinetics of photocatalysts with respect to charge transfer, migration and separation, which are of fundamental significance to photocatalytic N2 fixation. Subsequently, the challenges, outlooks and future prospects at the forefront of this research platform are presented. As such, it is anticipated that this review will shed new light on photocatalytic N2 fixation and NH3 synthesis and will also provide a blueprint for further investigations and momentous breakthroughs in next-generation catalyst design.

Solar-driven photothermal nanostructured materials designs and prerequisites for evaporation and catalysis applications

Abstract: Solar energy is a major source of renewable energy with the potential to meet the energy demand and to support the sustainable development of the world. The efficient harvesting and conversion of solar energy is one of the key factors to maximize the utilization of solar energy. In general, solar energy can be harnessed and converted into various kinds of energy, including electricity, fuels and thermal energy, through photovoltaic, photochemical and photothermal processes, respectively. Among these technologies, photothermal conversion is a direct conversion process that has attained the highest achievable conversion efficiency. The photothermal effect has been used as a novel strategy to augment vaporization and catalysis performance. In this review, we look into the basis of the photothermal conversion process, the design of efficient photothermal conversion materials in terms of both light harvesting and thermal management, a fundamental understanding of various system schemes, and the recent progress in photothermal evaporation and catalysis applications. This review aims to afford researchers with a better understanding of the photothermal effect and provide a guide for the rational design and development of highly efficient photothermal materials in energy and environmental fields.

Metal–organic framework-derived one-dimensional porous or hollow carbon-based nanofibers for energy storage and conversion

Abstract: Metal organic framework (MOF)-derived nanoporous carbons (NPCs) have been proposed as promising electrode materials for energy storage and conversion devices. However, MOF-derived NPCs typically suffer from poor electrical conductivity due to the lack of connectivity between these particles and a micropore-dominated storage mechanism, which hinder mass and electron transfer, thereby leading to poor electrochemical performance. In recent years, one-dimensional (1D) MOF-derived carbon nanostructures obtained using an electrospinning method have emerged as promising materials for both electrochemical energy storage (EES) and energy conversion applications. In this mini review, the recent progress in the development of MOF-derived 1D porous or hollow carbon nanofibers using the electrospinning method and their application in energy storage (e.g., supercapacitors and rechargeable batteries) and conversion devices (e.g., fuel cells) is presented. The synthetic method, formation mechanism and the structure–activity relationship of such porous or hollow carbon nanofibers are also discussed in detail. Finally, future perspectives on the development of electrospun MOF-derived carbon nanomaterials for energy storage and conversion applications are provided. This review will provide some guidance for future derivations of 1D hollow carbon nanomaterials from MOFs using electrospinning technology.

Bioinspired hierarchical composite design using machine learning: simulation, additive manufacturing, and experiment

Abstract: Biomimicry, adapting and implementing nature's designs provides an adequate first-order solution to achieving superior mechanical properties. However, the design space is too vast even using biomimetic designs as prototypes for optimization. Here, we propose a new approach to design hierarchical materials using machine learning, trained with a database of hundreds of thousands of structures from finite element analysis, together with a self-learning algorithm for discovering high-performing materials where inferior designs are phased out for superior candidates. Results show that our approach can create microstructural patterns that lead to tougher and stronger materials, which are validated through additive manufacturing and testing. We further show that machine learning can be used as an alternative method of coarse-graining – analyzing and designing materials without the use of full microstructural data. This novel paradigm of smart additive manufacturing can aid in the discovery and fabrication of new material designs boasting orders of magnitude increase in computational efficacy over conventional methods.

A general salt-resistant hydrophilic/hydrophobic nanoporous double layer design for efficient and stable solar water evaporation distillation

Abstract: A novel and elegant hydrophilic/hydrophobic nanoporous double layer structure was designed and developed for efficient long-term water desalination. It contained a hydrophobic salt-resistant hierarchical layer of well-defined Cu2SnSe3 (or Cu2ZnSnSe4) nanosphere arrays for broad solar harvesting and water vapor evaporation, and a hydrophilic filter membrane for continuous water supply and vapor generation. The as-fabricated self-floatable devices achieve remarkable solar water evaporation performances (average evaporation rate: 1.657 kg m−2 h−1 and solar thermal conversion efficiency: 86.6% under one sun) with super stability for water distillation from seawater and wastewater containing organic dyes, heavy metals and bacteria.

Rationally designed meta-implants: a combination of auxetic and conventional meta-biomaterials

Abstract: Rationally designed meta-biomaterials present unprecedented combinations of mechanical, mass transport, and biological properties favorable for tissue regeneration. Here we introduce hybrid meta-biomaterials with rationally-distributed values of negative (auxetic) and positive Poisson's ratios, and use them to design meta-implants that unlike conventional implants do not retract from the bone under biomechanical loading. We rationally design and additively manufacture six different types of meta-biomaterials (three auxetic and three conventional), which then serve as the parent materials to six hybrid meta-biomaterials (with or without transitional regions). Both single and hybrid meta-biomaterials are mechanically tested to reveal their full-field strain distribution by digital image correlation. The best-performing hybrid meta-biomaterials are then selected for the design of meta-implants (hip stems), which are tested under simulated-implantation conditions. Full-field strain measurements clearly show that, under biomechanical loading, hybrid meta-implants press onto the bone on both the medial and lateral sides, thereby improving implant–bone contact and potentially implant longevity.

Co/CoP embedded in a hairy nitrogen-doped carbon polyhedron as an advanced tri-functional electrocatalyst

Abstract: The design and synthesis of a multi-functional electrocatalyst with low cost and high efficiency is still a great challenge. Herein, we report the rational design and realization of a tri-functional electrocatalyst featuring Co/CoP embedded in a hairy nitrogen-doped carbon polyhedral (Co/CoP–HNC) derived from common metal organic frameworks (MOFs). The components of Co, CoP, and hairy nitrogen-doped carbon in the catalyst respectively render catalytic activity, high electrochemical surface area, and electronic conductivity. The synergy of the tailored Co/CoP–HNC catalyst provides high activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The catalytic performance and assembly feasibility are further demonstrated in overall water splitting and Zn–air battery tests, and both revealed high efficiency and long durability of the proposed electrocatalyst.

Band engineering in Mg3Sb2 by alloying with Mg3Bi2 for enhanced thermoelectric performance

Abstract: Mg3Sb2–Mg3Bi2 alloys show excellent thermoelectric properties. The benefit of alloying has been attributed to the reduction in lattice thermal conductivity. However, Mg3Bi2-alloying may also be expected to significantly change the electronic structure. By comparatively modeling the transport properties of n- and p-type Mg3Sb2–Mg3Bi2 and also Mg3Bi2-alloyed and non-alloyed samples, we elucidate the origin of the highest zT composition where electronic properties account for about 50% of the improvement. We find that Mg3Bi2 alloying increases the weighted mobility while reducing the band gap. The reduced band gap is found not to compromise the thermoelectric performance for a small amount of Mg3Bi2 because the peak zT in unalloyed Mg3Sb2 is at a temperature higher than the stable range for the material. By quantifying the electronic influence of Mg3Bi2 alloying, we model the optimum Mg3Bi2 content for thermoelectrics to be in the range of 20–30%, consistent with the most commonly reported composition Mg3Sb1.5Bi0.5.

Additive manufacturing of complex micro-architected graphene aerogels

Abstract: 3D graphene foams exhibit immense degradation of mechanical properties. Micro-architecture can alleviate this problem, but no current technique meets the manufacturing requirements. Herein we developed a light-based 3D printing process to create hierarchical graphene structures with arbitrary complexity and order-of-magnitude finer features, showing enhanced mechanical properties at decreasing density.

High-yield production of 2D crystals by wet-jet milling

Abstract: Efficient and scalable production of two-dimensional (2D) materials is required to overcome technological hurdles towards the creation of a 2D-material-based industry. Here, we present a novel approach developed for the exfoliation of layered crystals, i.e., graphite, hexagonal-boron nitride and transition metal dichalcogenides. The process is based on high-pressure wet-jet-milling (WJM), resulting in a 2 L h−1 production of 10 g L−1 of single- and few-layer 2D crystal flakes in dispersion making the scaling-up more affordable. The WJM process enables the production of defect-free and high quality 2D-crystal dispersions on a large scale, opening the way for their full exploitation in different commercial applications, e.g., as anode active material in lithium ion batteries, as reinforcement in polymer–graphene composites, and as conductive inks, as we demonstrate in this report.

The progress and prospects of non-fullerene acceptors in ternary blend organic solar cells

Abstract: The rapid development of organic solar cells (OSCs) based on non-fullerene acceptors has attracted increasing attention during the past few years, with a record power conversion efficiency of over 13% in a binary bulk heterojunction architecture This exciting development also enables new possibilities for ternary OSCs to further enhance their efficiency and stability This review summarizes very recent developments of ternary OSCs, with a focus on blends involving non-fullerene acceptors We also highlight the challenges and perspectives for further development of ternary blend organic solar cells

A three-dimensional multilayer graphene web for polymer nanocomposites with exceptional transport properties and fracture resistance

Abstract: Small amounts of two-dimensional (2D) graphene sheets are usually added into a polymer matrix to fabricate nanocomposites with improved mechanical and functional properties. Further enhancements of these properties beyond those of ordinary nanocomposites require much higher loadings of well-dispersed fillers, preferably in the form of an interconnected network with the preferential orientation along the direction of interest. However, the assembly of 2D fillers to form such a three-dimensional (3D) network remains a formidable task. Herein, a totally new approach is developed to fabricate a high-density 3D multilayer graphene web with interconnected, in-plane oriented graphene struts based on the versatile chemical vapor deposition technique. The continuous high-quality graphene network within the epoxy composites leads to exceptional electrical and thermal conductivities of 50 S cm−1 and 8.8 Wm−1 K−1, respectively. The high filler loading of 8.3 wt% also gives rise to a remarkable fracture toughness of 2.18 MPa m1/2, well over 100% enhancement over the neat epoxy. The simultaneous achievements of both remarkable transport properties and fracture toughness at these levels by an identical nanocomposite are unprecedented and have never been reported previously. The combination of unrivalled electrical and thermal conductivities with extraordinary fracture resistance offers the composites unique opportunities for multi-functional applications.

Pseudocapacitance contribution in boron-doped graphite sheets for anion storage enables high-performance sodium-ion capacitors

Abstract: Research on metal-ion hybrid capacitors is emerging as one of the hottest topics in energy storage fields because of their combination of high power and energy densities. To improve the sluggish faradaic reaction in traditional electrode materials for metal-ion hybrid capacitors, intercalation pseudocapacitive materials have been developed as attractive candidates. However, all the previously reported pseudocapacitances in intercalation/deintercalation reactions are based on cations (Li+, Na+, Zn2+etc.). In this work, we demonstrated the high pseudocapacitance contribution in boron-doped graphite (BG) sheets by taking advantage of anion storage. The BG electrode can reversibly store anions (PF6−) through both a surface-controlled pseudocapacitive reaction and a diffusion-limited intercalation/deintercalation reaction. The fabricated Na-ion hybrid capacitor with a BG cathode exhibits superior electrochemical performance. Density functional theory (DFT) calculation reveals that B-doping can significantly reduce the PF6− diffusion energy barrier in the graphite layers.

Multifunctional hydrogel enables extremely simplified electrochromic devices for smart windows and ionic writing boards

Abstract: A much simplified electrochromic structure is designed based on a multifunctional ionic hydrogel. The three-layered structure exhibits significant color change with large transmittance modulation and high coloration efficiency. Moreover, an ionic writing board is developed with the hydrogel to realize the first rewritable electrochromic display.

A single-component hydrogel bioink for bioprinting of bioengineered 3D constructs for dermal tissue engineering

Abstract: Bioprinting is attractive to create cellularized constructs for skin repair. However, the vast majority of bioinks present limitations in the printing of chemically defined 3D constructs with controllable biophysical and biochemical properties. To address this challenge, a single-component hydrogel bioink with a controlled density of cell-adhesive ligands, tuneable mechanical properties and adjustable rheological behaviour is developed for extrusion bioprinting and applied for the biofabrication of 3D dermal constructs. A methacrylate modified pectin bioink is designed to allow the tethering of integrin-binding motifs and the formation of hydrogels by UV photopolymerization and ionic gelation. The rheological behaviour of a low polymer concentration (1.5 wt%) solution is adjusted by ionic crosslinking, yielding a printable bioink that holds the predesigned shape upon deposition for postprinting photocrosslinking. Printed constructs provide a suitable microenvironment that supports the deposition of endogenous extracellular matrix, rich in collagen and fibronectin, by entrapped dermal fibroblasts. This approach enables the design of chemically defined and cell-responsive bioinks for tissue engineering applications and particularly for the generation of biomimetic skin constructs.

Pyroelectric nanoplatform for NIR-II-triggered photothermal therapy with simultaneous pyroelectric dynamic therapy

Abstract: Photothermal therapy (PTT) has been attracting much attention because of its high efficiency and ease of use. Currently deployed PTT, however, shows two main deficiencies: limited penetration depth and interference from heat shock proteins (HSPs). Here we describe a specific application of a pyroelectric material, specifically SnSe-polyvinylpyrrolidone (SnSe-PVP) nanorods, for tumor photoacoustic imaging and PTT, accompanied by pyroelectric dynamic therapy (PEDT), utilizing near-infrared-II (NIR-II) light as the excitation trigger. Moreover, we used PEDT to generate reactive oxygen species (ROS) from SnSe-PVP nanorods and to have the ROS attack HSPs and cancer cells during heating and cooling. This work revealed a high potential for the application of pyroelectric materials in biomedicine, especially for PTT with PEDT via NIR-II light stimulation.

Vitamin metal–organic framework-laden microfibers from microfluidics for wound healing

Abstract: Vitamin MOF-laden microfibers with alginate shells and copper- or zinc-vitamin framework cores are controllably generated by using a coaxial capillary microfluidic spinning approach The practical value of these MOF-laden hydrogel microfibers in improving tissue wound healing has also been explored based on the antibiosis and antioxidation of the controllably released vitamins, copper ions and zinc ions of the compound materials

Two-dimensional ferroelectricity and switchable spin-textures in ultra-thin elemental Te multilayers

Abstract: New ferroelectric materials with satisfactory performance at the nanoscale are critical for the ever-developing microelectronics industry. Here, we report two-dimensional (2D) ferroelectricity in elemental tellurium multilayers, which exhibit spontaneous in-plane polarization due to the interlayer interaction between lone pairs. The magnitude of the polarization reaches about 1.02 × 10−10 C m−1 per layer, which can be detected by current experimental technology as recently done for the 2D FE compound SnTe. The spontaneous ferroelectric polarization can be preserved for the bilayer Te film even above room temperature. Also, we show that due to the strong spin–orbit coupling of Te, there appear nontrivial valley-dependent spin-textures for the hole carriers, and the textures are coupled with the direction of FE polarization, which is tunable by an external electric field. Our findings not only introduce the concept of ferroelectricity in elemental systems, but also broaden the family of the 2D ferroelectric materials and offer a promising platform for novel electronic and spintronic applications.

Monoclinic oxygen-deficient tungsten oxide nanowires for dynamic and independent control of near-infrared and visible light transmittance

Abstract: The transmittance of near-infrared (NIR) and visible (VIS) light spectral regions can be dynamically and independently controlled using a single-component material – monoclinic oxygen-deficient tungsten oxide nanowires, without the need for compositing with other electrochromic materials. A localized surface plasmon resonance and phase-transition assisted mechanism and bandgap transition electrochromism are individually responsible for the modulation of the NIR and VIS light transmissions.

Janus DNA orthogonal adsorption of graphene oxide and metal oxide nanoparticles enabling stable sensing in serum

Abstract: While DNA/graphene oxide (GO) conjugates have been widely used for DNA detection, they suffer from non-specific DNA displacement by proteins, making their application in biological samples difficult. To find new materials tightly adsorbing DNA but not proteins, we screened seven metal oxide nanoparticles, all interacting with the phosphate backbone of DNA, while DNA uses its nucleobases to interact with GO. In this regard, DNA is a Janus polymer orthogonally adsorbing GO and metal oxides. The DNA adsorption affinity ranks CoO > NiO > Cr2O3 > Fe2O3 > Fe3O4 > TiO2 > CeO2 based on a phosphate displacement assay. Among them, CoO is nearly fully resistant to protein displacement, while NiO has the best limit of detection of 0.24 nM DNA. This study provides fundamental insights into the biointerface chemistry of DNA, and reveals new materials useful for bioanalytical chemistry, DNA separation, and DNA-directed assembly.

Toward non-volatile photonic memory: concept, material and design

Abstract: Digital technology is one of the greatest modern breakthroughs, allowing sounds, words and images to be stored in binary form. However, there is a huge gap between the amount of data created daily and the capacities of existing storage media. Developing multibit memory in which 2n levels, typically represented by distinguishable current levels, can be achieved in a single cell is a critical specification for achieving high-density memory devices. Compared with electrically operated memory, photonic memory—in which electrical read-out is orthogonal to the photo-programming operation—promises high differentiation among different data levels. From another aspect, benefiting from its high density, multifunctionality, low power consumption, and multilevel data storage, photonic memory devices hold future promise for built-in, non-volatile memory and reconstructed logic operation and are expected to bridge this capacity gap. Thus, we present a review on the development of photonic memory, with a view towards inspiring more intriguing ideas on the elegant selection of materials and design of novel device structures that may finally induce major progress in the manufacture and application of photonic memory.

Polymorphism controls the degree of charge transfer in a molecularly doped semiconducting polymer

Abstract: When an organic semiconductor (OSC) is blended with an electron acceptor molecule that can act as a p-type dopant, there should ideally be complete (integer) transfer of charge from the OSC to the dopant. However, some dopant–OSC blends instead form charge transfer complexes (CTCs), characterized by fractional charge transfer (CT) and strong orbital hybridization between the two molecules. Fractional CT doping does not efficiently generate free charge carriers, but it is unclear what conditions lead to incomplete charge transfer. Here we show that by modifying film processing conditions in the semiconductor–dopant couple poly(3-hexylthiophene):2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (P3HT:F4TCNQ), we can selectively obtain nearly pure integer or fractional CT phases. Fractional CT films show electrical conductivities approximately 2 orders of magnitude lower than corresponding integer CT films, and remarkably different optical absorption spectra. Grazing incidence wide-angle X-ray diffraction (GIXD) reveals that fractional CT films display an unusually dense and well-ordered crystal structure. These films show lower paracrystallinity and shorter lamellar and π-stacking distances than undoped films processed under similar conditions. Using plane-wave DFT we obtain a structure with unit cell parameters closely matching those observed by GIXD. This first-ever observation of both fractional and integer CT in a single OSC–dopant system demonstrates the importance of structural effects on OSC doping and opens the door to further studies.

Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission heterojunction devices

Abstract: Singlet exciton fission is an exciton multiplication process that occurs in certain organic materials, converting the energy of single highly-energetic photons into pairs of triplet excitons. This could be used to boost the conversion efficiency of crystalline silicon solar cells by creating photocurrent from energy that is usually lost to thermalisation. An appealing method of implementing singlet fission with crystalline silicon is to incorporate singlet fission media directly into a crystalline silicon device. To this end, we developed a solar cell that pairs the electron-selective contact of a high-efficiency silicon heterojunction cell with an organic singlet fission material, tetracene, and a PEDOT:PSS hole extraction layer. Tetracene and n-type crystalline silicon meet in a direct organic–inorganic heterojunction. In this concept the tetracene layer selectively absorbs blue-green light, generating triplet pairs that can dissociate or resonantly transfer at the organo-silicon interface, while lower-energy light is transmitted to the silicon absorber. UV photoemission measurements of the organic–inorganic interface showed an energy level alignment conducive to selective hole extraction from silicon by the organic layer. This was borne out by current–voltage measurements of devices subsequently produced. In these devices, the silicon substrate remained well-passivated beneath the tetracene thin film. Light absorption in the tetracene layer created a net reduction in current for the solar cell, but optical modelling of the external quantum efficiency spectrum suggested a small photocurrent contribution from the layer. This is a promising first result for the direct heterojunction approach to singlet fission on crystalline silicon.

Unidirectional water delivery on a superhydrophilic surface with two-dimensional asymmetrical wettability barriers

Abstract: A superhydrophilic surface decorated with 2D hydrophobic water barriers is proven to be a potential platform for unidirectional liquid transport Differing from the existing systems based on 3D micro-structures, this functional surface features a simplified structure and high adaptiveness that provide more possibilities for the development of fluid manipulating materials

Accelerated atomic-scale exploration of phase evolution in compositionally complex materials

Abstract: Combining nanoscale-tip arrays with combinatorial thin film deposition and processing as well as direct atomic-scale characterization (APT and TEM) enables accelerated exploration of the temperature- and environment-dependent phase evolution in multinary materials systems. Results from nanocrystalline CrMnFeCoNi show that this alloy is unstable and already decomposes after 1 h at low temperatures of around 300 °C. The combinatorial processing platform approach is extendible to explore oxidation and corrosion in complex structural and functional materials on the atomic scale.

Stable and sensitive stimuli-responsive anisotropic hydrogels for sensing ionic strength and pressure

Abstract: Anisotropic hydrogels with a large mono-domain, nematic organization of cellulose nanocrystals (CNCs) were prepared. External stimuli such as ionic strength and pressure allow the hydrogels to change their shapes anisotropically through swelling/shrinking and expansion/contraction, respectively. These stimuli cause changes in a phase difference for the light passing through them while retaining the monodomain structure, leading to large color changes when the hydrogels are viewed between crossed polarizers.

Electrochemically enabled manipulation of gallium-based liquid metals within porous copper

Abstract: A novel phenomenon of electrochemically enabled reactive wetting, coating and spreading of gallium-based liquid metals within porous copper (Cu) was observed, and its mechanism was demonstrated. Its extensive applications including in the fabrication of large-area conductive film patterns, transfer-printing technology and the preparation of thermal interface materials with superhigh heat conductivity are presented.

An all-solid-state biocompatible ion-to-electron transducer for bioelectronics

Abstract: Reported here is an all-solid-state organic electrochemical transistor based on the biopolymer melanin. The underlying mechanism is demonstrated using a unique hydration dependence protocol and explained using an adapted double capacitor model. The demonstration of an all-solid-state bioelectronic prototype is critical for the development of miniaturised bioelectronic logic.

Biofabrication of multifunctional nanocellulosic 3D structures: A facile and customizable route

Abstract: Biomass-based nanomaterials such as bacterial cellulose (BC) are one of the most promising building blocks for the development of sustainable materials with the potential to outperform their conventional, synthetic, counterparts. The formation of BC occurs at the air–water interface, which has been exploited to engineer materials with finely controlled microtopographical features or simple three-dimensional morphologies for a wide range of applications. However, a high degree of control over the 3D morphology of BC films across several length scales (micro to macro) has not yet been achieved. Herein, we describe a simple yet customizable process to finely engineer the morphology of BC in all (x, y, z) directions, enabling new advanced functionalities, by using hydrophobic particles and superhydrophobized surfaces. This results in hollow, seamless, cellulose-based objects of given shapes and with sizes from ca. 200 μm to several centimeters. We demonstrate some of the unique properties of the process and the resulting objects via post-fabrication merging (biowelding), by in situ encapsulation of active cargo and by multi-compartmentalization for near limitless combinations, thus extending current and new applications for example in advanced carbon materials or regenerative medicine.

Size-dependent modulation of fluorescence and light scattering: a new strategy for development of ratiometric sensing

Abstract: Simultaneous response of fluorescence and light scattering can be obtained by using nanomaterials with size- and shape-dependent physiochemical properties. On the basis of this principle, we report a new strategy to design ratiometric sensors by combining fluorescence and light scattering, two different and independent signals. To obtain fluorescence and scattering signals simultaneously under the same excitation, two signal collection strategies are proposed based on the principles of fluorescence, light scattering and diffraction. One is to collect normal (down-conversion) fluorescence and second-order scattering (SOS) signals, and the other is to record the fluorescence excited by the second-order diffraction light of excitation wavelength λ/2 (SODL-fluorescence) and first-order scattering (FOS) or frequency doubling scattering (FDS) signals. A proof of concept study has been performed by using a carbon dots (CDs) and cobalt oxyhydroxide (CoOOH) nanoflakes system for ascorbic acid (AA) sensing. Apart from construction of ratiometric sensors, the combined fluorescence and scattering can also act as a useful technique to monitor aggregation-induced fluorescence quenching or enhancement.