Integration of cancer diagnosis and treatment, namely theranostics, is an important issue in the biomedical field. Benefiting from an excellent photothermal effect, ROS generation ability, and the desired mesoporous structure of the TiO2–x matrix, we strategically designed and fabricated a TiO2–x based theranostic system for realizing fluorescence/photoacoustic tomography (PAT) bimodal imaging guided triple therapy for photothemal/photodynamic/chemotherapy in this work. Nonstoichiometric TiO2–x nanospheres are excellent near-infrared absorptive material, which takes on both photosensitizer and photothermal agent roles in implementing PDT/PTT combination therapy and PAT imaging. Moreover, the mesoporous structure of TiO2–x also allowed drug loading, and the polydopamine sealing layer enabled it to induce NIR/pH-triggered drug controlled release. Resultantly, both the in vitro and in vivo experiment manifested the remarkable tumor inhibition and tumor imaging effects by the TiO2–x based theranostic system. The antitumor mechanism was attributable to a synergistic therapeutic effect (combination index = 0.318) of DOX-induced DNA damage, and PDT/PTT caused mitochondrial dysfunction and a change in the cell membrane permeability. Innovatively, the B-mode ultrasonography was adopted to monitor the rehabilitation process at the solid tumor site after treatment, which observed a liquefaction necrosis process.

•pH-responsive amphiphilic block copolymers were coupled with a pH oscillator.•Non-equilibrium self-assembly of the copolymers was realized and investigated.•The self-assembly of copolymers bring an additional influence on the pH oscillator.Realizing and investigating artificial an non-equilibrium self-assembly is one of the challenging but attractive fields in supramolecular chemistry, because most molecular self-assembly in living organisms are out of thermodynamic equilibrium. In this article, we achieved the non-equilibrium self-assembly of amphiphilic block copolymers that contained polyethylene glycol segment and polyacrylic acid segment (PEG-PAAs) by coupling them with a pH oscillator. The self-assembly of PEG-PAAs varied dynamically and periodically in the pH oscillator. Furthermore, we found that the self-assembly of PEG-PAAs can bring additional influence on the dynamics of the pH oscillator. This line of work not only demonstrates the interrelationship between chemical oscillators and self-assembly of amphiphilic copolymers, but also contributes to develop chemical oscillators into a general driving force to realize and investigate non-equilibrium self-assembly of stimuli-responsive building blocks, and promotes the study of molecular self-assembly one step forward from static self-assembly under thermodynamic equilibrium to a dissipative system like living organisms.Download high-res image (93KB)Download full-size image

We describe a sensitive approach for visual and point-of-care detection of E. coli O157:H7 and its toxic gene by combining carbon nanotube (CNT) multilayer biosensors and microfluidic chip-based loop-mediated isothermal amplification (LAMP). The anti-E. coli O157:H7 functionalized CNT multilayer biosensor can selectively capture the target bacterium E. coli O157:H7 in complex samples. After culturing, the captured bacteria can be released on demand by cleavage of the anti-E. coli O157:H7 antibody–bacteria interaction. The DNA concentration of the released bacteria was subsequently analyzed with microfluidic chip-based LAMP. After systematic optimization of capturing and detecting conditions, the proposed sensing platform was capable of detecting concentrations as low as 1 CFU mL−1 without complicated instrumentation, this is much more sensitive than previous reported methods. The distinct advantages of the proposed sensing platform, such as high specificity, low cost, good reproducibility and the ability of regenerating, make it a potential platform for detecting E. coli O157:H7 in related food safety and clinical diagnosis.

AbstractSelf-assembly of inorganic nanoparticles into ordered structures is of interest in both science and technology because it is expected to generate new properties through collective behavior; however, such nanoparticle assemblies with characteristics distinct from those of individual building blocks are rare. Herein we use atomically precise Au clusters to make ordered assemblies with emerging optical activity. Chiral Au clusters with strong circular dichroism (CD) but free of circularly polarized luminescence (CPL) are synthesized and organized into uniform body-centered cubic (BCC) packing nanocubes. Once the ordered structure is formed, the CD intensity is significantly enhanced and a remarkable CPL response appears. Both experiment and theory calculation disclose that the CPL originates from restricted intramolecular rotation and the ordered stacking of the chiral stabilizers, which are fastened in the crystalline lattices.

AbstractSelf-assembly of inorganic nanoparticles into ordered structures is of interest in both science and technology because it is expected to generate new properties through collective behavior; however, such nanoparticle assemblies with characteristics distinct from those of individual building blocks are rare. Herein we use atomically precise Au clusters to make ordered assemblies with emerging optical activity. Chiral Au clusters with strong circular dichroism (CD) but free of circularly polarized luminescence (CPL) are synthesized and organized into uniform body-centered cubic (BCC) packing nanocubes. Once the ordered structure is formed, the CD intensity is significantly enhanced and a remarkable CPL response appears. Both experiment and theory calculation disclose that the CPL originates from restricted intramolecular rotation and the ordered stacking of the chiral stabilizers, which are fastened in the crystalline lattices.

In the present study, needle-like tungsten suboxide W18O49 nanocrystals were fabricated as the optical active substance to realize the aim of optical control of near-infrared light. The W18O49 nanocrystals were selected in this regard due to their unique optical performance. As revealed by the powder absorption result, the needle-like W18O49 nanocrystals show strong and wide photoabsorption in the entire near infrared region of 780–2500 nm, from which thin films with the W18O49 nanocrystal coating thus benefits and can strongly shield off almost all near infrared irradiation, whereas transmitting the majority of visible light. To make it more tunable, the W18O49 nanocrystals were finally assembled onto an ITO glass via the layer-by-layer strategy for later electrochromic investigation. The nanostructured architectures of the W18O49 nanocrystal electrochromic films exhibit high contrast, faster switching response, higher coloration efficiencies (150 cm2 C−1 at 650 nm and 255 cm2 C−1 at 1300 nm), better long-term redox switching stability (reversibility of 98% after 500 cycles) and wide electrochromic spectrum coverage of both the visible and infrared regions.

•The large scale microarrays of CdTe QDs and AChE were fabricated by facile inkjet-assisted LbL printing technique.•The QDs/AChE microscopic dot arrays could be used quantitatively and rapidly for the sensitively visual detection of OPs.•A detection limit of 10 μg L−1 was achieved, much lower than levels specified by standard tests and other colorimetric detection methods.•The low cost, short processing time, sufficient sensitivity, good stability and ease of use make it for a facile platform for on-site screening.We present a facile fabrication of layer-by-layer (LbL) microarrays of quantum dots (QDs) and acetylcholinesterase enzyme (AChE). The resulting arrays had several unique properties, such as low cost, high integration and excellent flexibility and time–saving. The presence of organophosphorous pesticides (OPs) can inhibit the AChE activity and thus changes the fluorescent intensity of QDs/AChE microscopic dot arrays. Therefore, the QDs/AChE microscopic dot arrays were used for the sensitive visual detection of OPs. Linear calibration for parathion and paraoxon was obtained in the range of 5–100 μg L−1 under the optimized conditions with the limit of detection (LOD) of 10 μg L−1. The arrays have been successfully used for detection of OPs in fruits and water real samples. The new array was validated by comparison with conventional high performance liquid chromatography-mass spectrometry (HPLC-MS).A fluorimetric assay for high-throughput screening of organophosphorous pesticides was developed based on the CdTe QDs/AChE microarrays via inkjet-assisted LbL printing techniques.

We develop a rapid and facile method to fabricate tubular scaffolds by a single-step rolling operation. With the aid of fibrin medical glue and a smooth expanded polytetrafluoroethylene (ePTFE) mandrel, we can wrap a piece of flat thin film into a three-dimensional (3D), multi-layered tubular structure with well-controlled diameter, wall thickness, and mechanical strength within 10 min. By patterning different cells in a pre-designed area on the film, after rolling, we can obtain blood vessel-mimicking tissues with well-arranged, multilayered 3D architectures within 70 min. Our strategy provides an excellent platform to rapidly fabricate tubular scaffolds essentially with no equipment and straightforward manipulations.

In this work, the highly oriented CdS-coated-ZnO nanorod arrays have been fabricated. The CdS-coated-ZnO nanorod arrays show high electrochemiluminescence intensity, fast response and good stability. All of the desirable properties spur the development of an ECL immunosensor for the detection of the liver cancer cell line (HepG2 cells). Two successive modification steps of 3-aminopropyltriethoxysilane and gold nanoparticles onto the CdS-coated-ZnO nanorod arrays not only offer the substrates for conjugation of antibody, but also effectively enhance the ECL signal, resulting in production of the high performance ECL immunosensor. The ECL immunosensor exhibits a sensitive response to HepG2 cells in a linear range of 300–10000 cells mL−1 with a detection limit of 256 cells mL−1. The proposed sensor characteristics of high specificity, good reproducibility and remarkable stability will provide a sensitive, selective, and convenient approach for the clinical detection of cancer cells.

Enantioselective analysis of biological thiols, including cysteine (Cys) and glutathione (GSH), is extremely important because of their unique role in bioentities. Here we demonstrated that the end-to-end assemblies of plasmonic gold nanorods with chiral Cys or GSH can be used as a distinctive chiroptical sensor for reliable determination of the absolute configuration of Cys and GSH at the visible light region. The end-to-end assemblies of Au nanorods induced by Cys or GSH exhibit strong circular dichroism (CD) signals in the region of 500–850 nm, which is attributed to chiral current inside Au nanorods induced by the mixed biothiols. The CD intensity of the assemblies shows good linearity with the amount of Cys and GSH. The limit of detection for Cys and GSH using end-to-end assemblies is at micromolar concentrations. In addition, the sensing system exhibits good selectively toward Cys and GSH in the presence of other amino acids.

Nanoparticles of a sparingly soluble silver salt of AgBr with an appropriate solubility product and high photocatalytic response ought to be promising candidates with superior and multifunctional antibacterial effects, but they have received relatively little scientific attention until now. In the present study, the antibacterial activities of AgBr nanocubes and their derivative Ag@AgBr against E. coli were investigated both in the dark and under visible light irradiation. Benefiting from the “dual-punch” of eluted Ag+-induced disturbance of bio-function and nanocube-induced contact damage to cellular membranes, the 100 nm well-defined AgBr nanocubes realized outstanding antibacterial properties, with MIC (minimal inhibition concentration) and MBC (minimum bactericidal concentration) values as low as 0.1 μg ml−1 and 0.4 μg ml−1, respectively. Ag decoration on the surface of AgBr seems to deteriorate the antibacterial properties, as the MIC and MBC values increased to 0.75 μg ml−1 and 1 μg ml−1 in the dark for the sample of Ag@AgBr, but it exhibits better photocatalytic inhibition of E. coli growth than pure AgBr by virtue of the enhanced light-harvesting by the LSPR effect from the Ag component. Thus, the encouraging results shown in this study indicate the great potential of AgBr nanomaterial to serve as an antibacterial candidate with high antibacterial activity.

Hardly any other compound has realized better optical absorption of near-infrared (NIR) rays (780–2500 nm) than tungsten bronze nanoparticles in terms of absorption coefficient, widths of the working spectrum, photothermal transformation efficiency and their own physicochemical stability. However, efforts concerning the development of tungsten bronze nanoparticles for serving as a NIR absorbent are very limited due to the shortage of effective approaches to obtain these nanoparticles, especially for tungsten bronzes with insertion of bigger cations, such as CsxWO3 and (NH4)xWO3. In this work, we describe how to fabricate (NH4)xWO3 using a high-temperature but short-time solvothermal process, which involves employing oleic acid–oleylamine as the solvent and WCl6 as the W resource, together with the inspection of its NIR-absorption related properties. The nanocubes of 100 nm have been characterized by XRD, TG-MS, XPS and TEM to examine the crystal phase and nanostructures. Moreover, the dispersion of the nanocubes in the form of a thin film was used to investigate the NIR absorption properties. As determined by the optical test, the thin film consisting of the nanocubes exhibits extraordinary features as a solar control window, which can transmit the majority of visible light while absorbing nearly all of the NIR rays from 780 nm to 2500 nm. Meanwhile, the (NH4)xWO3 thin film can maintain its high shielding effect for the 1064 nm NIR light up to 35.3 kW m−2 radiation and has excellent cyclic stability for 100 cycles without obvious optical changes. Finally, it has been found that the (NH4)xWO3 nanocubes show a remarkable photothermal conversion phenomenon even when dispersed in a thin film.

•The nanocomposite of CdSe@ZnS QDs and graphene was deposited on ITO coated glass electrode.•The QD/graphene hybrid exhibits enhanced photocurrent responses upon visible light irradiation.•The integration of QD/graphene hybrid with AChE yields a highly sensitive PEC assays for OPs.•The LOD is as low as 2.5×10−12 M for dichlorvos and 6.055×10−14 M for paraoxon, respectively.A sensitive photoelectrochemical (PEC) biosensor for detection of organophosphorus pesticides (OPs) using the nanocomposite of CdSe@ZnS quantum dots (QDs) and graphene deposited on the ITO coated glass electrode as a photoactive electrode is presented. The integration of CdSe@ZnS/graphene nanocomposite with biomolecules acetylcholinesterase (AChE) as a biorecognition element yields a novel biosensing platform. Under visible light irradiation, the AChE–CdSe@ZnS/graphene nanocomposite can generate a stable photocurrent and the photocurrent is found to be inversely dependent on the concentration of OPs. Under the optimal experimental conditions, the photocurrents were proportional to the logarithm of paraoxon and dichlorvos within the concentration range of 10−12–10−6 M. The detection limits (LOD) of the proposed biosensor for paraoxon and dichlorvos are as low as 10−14 M and 10−12 M. The photoelectrochemical biosensor shows good sensitivity, reproducibility, stability, and could be successfully applied to detection of OPs in real fruit samples.

A three-dimensional (3D) N-doped graphene aerogel with porous structures and uniformly distributed PtRu NPs (N-GA/PtRu) is constructed by a simple, rapid and eco-friendly method. The N-GA/PtRu exhibits an unprecedented performance towards the methanol electrochemical oxidation reaction. Notably, N-GA/PtRu can be directly used as the anode of direct methanol fuel cells by simple physical pressing without the need for any binders or additives.

Electrochemiluminescence resonance energy transfer (ECL-RET) based on dye–quantum dot (QD) hybrids, is a very powerful tool for chemical sensing and probing many important biological processes. In this work, we have investigated both electrochemiluminescence (ECL) and photoluminescence (PL) properties of the hybrid system, in which tris(2,2′-bipyridyl)ruthenium(II) ([Ru(bpy)3]2+)/2-(dibutylamino)ethanol (DBAE) and QD are employed as the ECL donor and acceptor, respectively. Unexpectedly, we find that ECL of the [Ru(bpy)3]2+/DBAE system can be efficiently quenched by various types of QDs. In addition, ECL quenching in the [Ru(bpy)3]2+/DBAE system is independent of the core size and the surface charge of QDs, indicating that the quenching effect does not originate from resonance energy transfer between the [Ru(bpy)3]2+/DBAE system and QDs. Photoluminescence properties of the hybrid system under electrochemical control and electron spin resonance (ESR) measurements further reveal that a charge transfer between QDs and the radical-state DBAE is responsible for ECL quenching in the [Ru(bpy)3]2+/DBAE system. Contrary to previously published information, we propose that electron transfer, rather than energy transfer, dominates in the hybrid system under electrochemical control. We further demonstrate that such electron transfer could be switched to energy transfer by controlling the distance between [Ru(bpy)3]2+/DBAE ECL and QDs. The energy/electron transfer process between [Ru(bpy)3]2+/DBAE ECL and QDs is implemented to develop a novel platform for immune sensing.

A carbon nanotube (CNT) based nanoarchitecture is developed for rapid, sensitive and specific detection of cancer cells by using real time electrical impedance sensing. The sensor is constructed with carbon nanotube (CNT) multilayers and EpCAM (epithelial cell adhesion molecule) antibodies, which are assembled on an indium tin oxide (ITO) electrode surface. The binding of tumor cells to EpCAM antibodies causes increase of the electron-transfer resistance. The electrochemical impedance of the prepared biosensors is linear with the logarithm of concentration of the liver cancer cell line (HepG2) within the concentration range of 10 to 105 cells per mL. The detection limit for HepG2 cells is 5 cells per mL. The proposed impedimetric sensing devices allow for sensitive and specific detection of cancer cells in whole-blood samples without any sample pretreatment steps.

The oxygen reduction reaction (ORR) is one of the key steps in clean and efficient energy conversion techniques such as in fuel cells and metal–air batteries; however, several disadvantages of current ORRs including the kinetically sluggish process and expensive catalysts hinder mass production of these devices. Herein, we develop carbonized nanoparticles, which are derived from monodisperse nanoscale metal organic frameworks (MIL-88B-NH3), as the high performance ORR catalysts. The onset potential and the half-wave potential for the ORR at these carbonized nanoparticles is up to 1.03 and 0.92 V (vs RHE) in 0.1 M KOH solution, respectively, which represents the best ORR activity of all the non-noble metal catalysts reported so far. Furthermore, when used as the cathode of the alkaline direct fuel cell, the power density obtained with the carbonized nanoparticles reaches 22.7 mW/cm2, 1.7 times higher than the commercial Pt/C catalysts.Keywords: carbonization; direct methanol fuel cell; metal organic framework; oxygen reduction reaction;

Reversibly fluorescent switchable materials have important applications in the fields of ultrahigh-density optical data storage, molecular switches, logic gates, molecular wires, optical/electronic devices, sensors, bioimaging and so on. Some systems have been developed based on smart luminescent polymers and organic photoswitchable molecules. However, the use of such materials for practical applications is dramatically restricted by their intrinsic drawbacks such as low ON/OFF ratios, irreversibility and poor environmental resistance. An imperative challenge toward real applications is to design and fabricate photoluminescence switching devices with high on/off contrast and fast response time, and especially to obtain multicolored systems, in which the photoluminescence wavelength can be easily tuned in the visible region. Here we report the first inorganic example of a multicolored photoluminescence switching system by controlling the organization of crown-type polyoxometalates (POMs) and CdSe@CdS core–shell quantum dots (QDs) into the layer-by-layer (LBL) nanostructures. The photoluminescence of this system can be switched on and off reversibly upon application of step potentials for different redox states, owing to the energy transfer between reduced POMs and QDs. This system displays a quick response (off 17 s, on 38 s), high on/off contrast (∼91%), good cycling performance (the modulation ratio is only decreased by 19% after 200 cycles) and also has the advantage of low power consumption. Furthermore, reversible four-state fluorescence switching is realized by integrating different-sized QDs in one multifunctional system.

Mesoporous anatase TiO2 spheres with tunable sizes ranging from 400 nm to 3 μm were synthesized using an original so-called “water-controlled solvothemal release process”. In this method, the well-known esterification reaction between ethanol and acetic acid was creatively employed to generate water gradually during a solvothermal process. Thereafter, the slowly released water molecules functioned as nucleation centers for completing the hydrolysis of titanium tetraisopropoxide to produce homogenous mesoporous TiO2 spheres. In reality, these samples consisted of densely packed nanoparticles that formed spherical secondary particles with interparticle pores. Research has demonstrated that the diameter of the TiO2 spheres can be easily tuned by controlling the concentration of the Ti source in the starting solution. Regardless of their diameter, all of these TiO2 spheres exhibited a high specific surface area (above 150 m2 g−1) originating largely from the contribution of mesopores. On the merits of their porous structure and related high specific surface area, the mesoporous TiO2 spheres showed a higher photocatalytic activity than P25 for the oxidative photo-destruction of NOx gas.

Public concern over pesticide residues has been increasing dramatically owing to the high toxicity and bioaccumulation effects of pesticides and the serious risks that they pose to the environment and human health. It is therefore crucial to monitor pesticide residues by using various analytical methods and techniques, especially highly sensitive, highly selective, simple, rapid, cost-effective, and portable ones. Biosensor strategies have become research hotspots and ideal candidates for pesticide detection, having such features as high sensitivity, fast response, robustness, low cost and miniaturization, as well as in situ and real-time monitoring. This review covers advances in the design and fabrication of biosensors for pesticide detection since 2005. Special emphasis is placed on the state-of-art selection of receptors, the use of different transduction techniques and fast screening strategies, and the application of various biosensors developed in food and environmental safety. Both advantages and drawbacks of these techniques are then summarized. Finally, challenges, strategies, and perspectives in further developing pesticide biosensors are also discussed.

Vertically aligned CdTe–ZnO composite nanorods are constructed on the indium tin oxide substrates by layer-by-layer deposition of CdTe quantum dots on ZnO nanorod arrays. The CdTe shell forms an intact interface with the wurtzite ZnO nanorod, and its thickness can be accurately tuned by changing the deposition cycles. Photoluminescent measurements further disclose the band alignment between the CdTe shell and the ZnO core, which makes CdTe–ZnO composite nanorods exhibiting good photoelectron-chemical properties and being a prospective material for removal of phenol from wastewater under visible light irradiation. Impressively, about 75% degradation of 100 mg/L phenol solution and up to 53.2% removal of the total organic carbon are achieved within 150 min using the optimized CdTe–ZnO composite nanorods as photoelectrocatalysts under visible light.

The electrogenerated chemiluminescence (ECL) of semiconductor quantum dots (QDs) is generally believed to be independent of particle sizes or the capping agents used. Herein, we demonstrate that CdTe QDs with different sizes and stabilizers evidently exhibit different ECL behavior in aqueous solution. The ECL of CdTe QDs stabilized by 3-mercaptopropionic acid (MPA) displays two waves at potentials of about +1.17 V and +1.74 V vs. Ag/AgCl, respectively. ECL spectra confirm that the ECL of QDs is attributed to their band gap luminescence, in which the peak positions are changed with QD sizes. The ECL mechanism of CdTe QDs involves superoxide radical generation by reduction of dissolved oxygen at lower potential or water splitting at higher potential. Direct evidence for superoxide radicals in this medium was obtained via electron spin resonance (ESR) experiments. In comparison, the 2-mercaptoethylamine (MEA)-capped CdTe QDs did not exhibit any ECL in air-saturated pH 7.4 PBS. Both ESR and X-ray photon spectroscopy (XPS) experiments revealed that amine groups in MEA-capped QDs were responsible for the absence of ECL. The reaction of an amine group with a superoxide radical leads to the quenching of ECL. The ECL quenching of MPA-capped CdTe QDs was further used to detect melamine. Under the optimum conditions, the inhibited ECL was linear with the logarithm of concentration of melamine within the concentration range of 10−9 to 10−5 M and the detection limit was found to be 6.74 × 10−10 M, which was 100–100000 times lower than that of the most previous methods.

A simple procedure for constructing the photoelectrochemical biosensor based on TiO2/CdSe@CdS QD nanocomposite modified electrode was developed. The TiO2/CdSe@CdS QD nanocomposite modified electrode was obtained by alternately depositing water-soluble CdSe@CdS QD and a mixture of [cobalt(o-phen)3]2+/3+ and poly(ethyleneimine) (PEI) over mesoscopic TiO2 films. The obtained TiO2/CdSe@CdS QD nanocomposite modified electrode exhibits much higher and stable photocurrent intensity than that of the photoelectrochemical biosensors reported so far. After the TiO2/CdSe@CdS QD nanocomposite modified electrode was coated with glucose oxidase, the photocurrent intensity was enhanced towards the addition of glucose. Thus, a photoelectrochemical biosensor for the detection of glucose was developed by monitoring the changes in the photocurrent intensity. Moreover, the proposed biosensor possessed good reproducibility and storage stability. Combining TiO2/CdSe@CdS nanocomposite and other biomolecules could be extended readily for sensing other biorecognition events.

The optical transducer of CdTe semiconductor quantum dots (QDs) has been integrated with acetylcholinesterase enzyme (AChE) by the layer-by-layer (LbL) assembly technique, resulting in a highly sensitive biosensor for detection of organophosphorus pesticides (OPs) in vegetables and fruits based on enzyme inhibition mechanism. The detection limits of the proposed biosensors are as low as 1.05 × 10−11 M for paraoxon and 4.47 × 10−12 M for parathion, which are significantly better than those of the conventional GC/MS methods or amperometric biosensors (0.5 nM). These biosensors are used for quick determination of low concentrations of OPs in real vegetable and fruit samples and exhibit satisfactory reproducibility and accuracy. Moreover, the stock stability of the biosensors are very good due to the stabilizing environment for the enzyme in the nanostructures made by LbL technique. Many advantages provided by these biosensors, like fluorescent change recognized by naked eyes and mass production with low cost, will facilitate future development of rapid and high-throughput screening of OPs.

A novel type of inorganic hybridized ultrathin film consisting of Preyssler-type polyoxometalates K14[Na(H2O)P5W30O110] (Na-POMs) and CdSe@CdS nanoparticles (NPs) was prepared on the solid substrates by a layer-by-layer assembly technique. The film exhibits reversible fluorescence switching behavior under control of irradiation with either UV light or visible light, which is ascribed to the selective occurrence of fluorescence resonance energy transfer between luminescent NPs and different states of photochromic Na-POMs.

Metal and semiconductor nanoparticles attract much attention due to their astonishing properties and numerous possibilities for applications in sensors. Significant progress has been made on the synthesis of metal and semiconductor nanoparticles with different shapes, composition, and controllable optical and electrical properties. For realizing their application in sensing, the multidimensional assembly of nanoparticles with controlled arrays is required. Nanoparticle assemblies give rise to new nanostructures and produce remarkable collective physical properties, which offer many opportunities for sensing applications. This review summarizes recent progress in the utilization of highly ordered one-, two-, and three-dimensional assemblies of nanoparticles for chemical and biological sensing, and future development in this research area is also discussed.

We briefly review the basic concepts and methodologies in designing and fabricating polyoxometalate-based nanostructured thin films, and their diverse applications.

We developed a green, low-cost, bioinspired aqueous synthesis method to fabricate one-dimensional (1D) vertically aligned ZnO nanorod arrays on zinc substrates at room temperature. Scanning electron microscopy images, transmission electron microscopy images, and energy-dispersive X-ray spectrum show densely well-aligned single-crystal ZnO nanorod arrays with a length of ∼400 nm fabricated by a simple method. Further, we reveal a growth mechanism that continuously deposits the freshly formed ZnO onto the zinc substrates, which results from the reaction between Zn2+ coordinated with cysteine and its derivatives and OH− in base solution, and leads to forming ZnO nanorod arrays. More importantly, the simple preparation can grow hierarchical structures of ZnO nanorod arrays as well as fabricating the arrays on different types of zinc-based substrates. Finally, the paper reports as-prepared ZnO nanorod arrays repeatedly photobleach Rhodamine 6G, and the results suggest the photobleach efficiency increases significantly due to the arrays.

A blood glucose sensor has been developed based on the multilayer films of CdTe semiconductor quantum dots (QDs) and glucose oxidase (GOD) by using the layer-by-layer assembly technique. When the composite films were contacted with glucose solution, the photoluminescence of QDs in the films was quickly quenched because the enzyme-catalyzed reaction product (H2O2) of GOD and glucose gave rise to the formation of surface defects on QDs. The quenching rate was a function of the concentration of glucose. The linear range and sensitivity for glucose determination could be adjusted by controlling the layers of QDs and GOD. The biosensor was used to successfully determine the concentration of blood glucose in real serum samples without sample pretreatment and exhibited satisfactory reproducibility and accuracy.

Recent trends and challenges in developing nanosensors for the detection of organophosphate (OP) pesticide residues in food are reviewed. Nanosensors have superior properties over the existing techniques such as high-performance liquid chromatography or gas chromatography, because they can provide rapid, sensitive, simple and low-cost on-field detection. The measurement protocols based on nanoparticles and nanotubes are also suitable for mass fabrication of miniaturized devices. The application of nanobiosensors for detection of OP agents is introduced in detail. Future prospects toward the development of selective, sensitive biosensing systems are discussed.

Metal and semiconductor nanoparticles attract much attention due to their astonishing properties and numerous possibilities for applications in sensors. Significant progress has been made on the synthesis of metal and semiconductor nanoparticles with different shapes, composition, and controllable optical and electrical properties. For realizing their application in sensing, the multidimensional assembly of nanoparticles with controlled arrays is required. Nanoparticle assemblies give rise to new nanostructures and produce remarkable collective physical properties, which offer many opportunities for sensing applications. This review summarizes recent progress in the utilization of highly ordered one-, two-, and three-dimensional assemblies of nanoparticles for chemical and biological sensing, and future development in this research area is also discussed.

A three-dimensional (3D) N-doped graphene aerogel with porous structures and uniformly distributed PtRu NPs (N-GA/PtRu) is constructed by a simple, rapid and eco-friendly method. The N-GA/PtRu exhibits an unprecedented performance towards the methanol electrochemical oxidation reaction. Notably, N-GA/PtRu can be directly used as the anode of direct methanol fuel cells by simple physical pressing without the need for any binders or additives.

Reversibly fluorescent switchable materials have important applications in the fields of ultrahigh-density optical data storage, molecular switches, logic gates, molecular wires, optical/electronic devices, sensors, bioimaging and so on. Some systems have been developed based on smart luminescent polymers and organic photoswitchable molecules. However, the use of such materials for practical applications is dramatically restricted by their intrinsic drawbacks such as low ON/OFF ratios, irreversibility and poor environmental resistance. An imperative challenge toward real applications is to design and fabricate photoluminescence switching devices with high on/off contrast and fast response time, and especially to obtain multicolored systems, in which the photoluminescence wavelength can be easily tuned in the visible region. Here we report the first inorganic example of a multicolored photoluminescence switching system by controlling the organization of crown-type polyoxometalates (POMs) and CdSe@CdS core–shell quantum dots (QDs) into the layer-by-layer (LBL) nanostructures. The photoluminescence of this system can be switched on and off reversibly upon application of step potentials for different redox states, owing to the energy transfer between reduced POMs and QDs. This system displays a quick response (off 17 s, on 38 s), high on/off contrast (∼91%), good cycling performance (the modulation ratio is only decreased by 19% after 200 cycles) and also has the advantage of low power consumption. Furthermore, reversible four-state fluorescence switching is realized by integrating different-sized QDs in one multifunctional system.