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The employment of an intrinsic quinoidal building block, benzodipyrrolidone (BDP), on constructing conjugated polymers (PBDP-2F and PBDP-2CN) with high electron mobility and unipolar transport characteristic in polyethylenimine ethoxylated (PEIE) modified organic field-effect transistors (OFETs) is reported. The intrinsic quinoidal characteristic and excellent co-planarity of BDP can lower the lowest unoccupied molecular orbital (LUMO) levels and improve ordered interchain packing of the resulting polymers in solid states, which are favorable for electron-injection and transport. By using PEIE as the interlayer to block the hole injection, unipolar n-type transport characteristics with high electron mobility of 0.58 and 1.01 cm2 V−1 s−1 were achieved by the OFETs based on PBDP-2F and PBDP-2CN, respectively. More importantly, the extracted mobilities are highly reliable with the reliability factor of above 80%. To the best of our knowledge, PBDP-2CN is the very first quinoid-based conjugated polymer with reliable electron mobility exceeding 1 cm2 V−1 s−1. This work represents a significant step in exploring intrinsic quinoidal CPs for application in n channel OFETs and logic complementary circuits.

Stochastic collision electrochemistry is a hot topic in single molecule/particle research, which provides an opportunity to investigate the details of the single molecule/particle reaction mechanism that is always masked in ensemble-averaged measurements. In this work, we develop an electrochemical amplification strategy to monitor the electrocatalytic behavior of single G-quadruplex/hemin (GQH) for the reaction between hydrogen peroxide and hydroquinone (HQ) through the collision upon a gold nanoelectrode. The intrinsic peroxidase activities of single GQH were investigated by stochastic collision electrochemical measurements, giving further insights into understanding biocatalytic processes. Based on the unique catalytic activity of GQH, we have also designed a hybridization chain reaction strategy to detect miRNA-15 with good selectivity and sensitivity. This work provided a meaningful strategy to investigate the electrochemical amplification and the broad application for nucleic acid sensing at the single molecule/particle level.

The nucleation of single hydrogen (H2) nanobubbles is explored in Ag nanoelectrodes (NEs, radius is 5–65 nm), where H2 is produced through proton electroreduction in H2SO4 solution. Moreover, Ag NE...

In this study, a series of large-bandgap polymer donors comprising dithieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2-c][1,2,5]thiadiazole (fDTBT) and benzo[1,2-b:4,5-b′]dithiophene units with or without sulfur/fluorine substitution in the side-chains are designed. It is found that the energy levels of these polymer donors can be linearly tuned due to the π-accepting properties of the sulfur atom and strong electron-withdrawing ability of the fluorine atom, while the absorption spectra keep nearly unchanged, which offers us the opportunity to balance the open-circuit voltage and charge separation driving force in all-polymer solar cells (all-PSCs). The device performances of these polymer donors are validated by combining them with the polymer acceptor PJ1. The device results indicate that as the energy-level offsets are increased, these systems exhibit a more efficient charge transfer and lesser charge recombination, which afford remarkably improved short-circuit current density, fill factors, and power conversion efficiency (PCE). Eventually, high-efficiency binary all-PSCs with a maximum efficiency of 15.8% are obtained, which is the highest value reported so far for all-PSCs. Moreover, this system demonstrates superior performance for 1 cm2 all-PSC devices with a PCE of 14.4% and semitransparent all-PSC devices with a PCE of 10.3% (with average visible-light transmittance of 21.5%). Our study manifests that these fDTBT-based polymers are promising donor candidates for high-performance all-PSCs toward practical applications.

The nanopore-based technique is a useful tool for single-molecule sensing and characterization. In this work, we have developed a new DNA-functionalized gold-modified nanopore, and analytes can induce the conformational switch of i-motif DNA formed on the inner surface of the nanopore. i-Motif DNA structure can be formed in the presence of silver ions (Ag+), which will result in the change in surface charge and structure of the nanopore tip and ion current rectification (ICR) ratio. The i-motif DNA structure on nanopore surface will be destroyed after the addition of glutathione (GSH) due to the strong interaction of Ag-S bond, which results in the recovery of surface charge, steric hindrance, and ICR ratio. This analyte-triggered conformational switch of i-motif DNA can help us deeply understand the DNA technology inside single nanopore and will benefit the possible applications in an ultrasensitive detection and biological/chemical analysis.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is one of the most widely used hole transporting materials in organic solar cells (OSCs). Multiple strategies have been adopted to improve the conductivity of PEDOT:PSS, however, effective strategy that can optimize the conductivity, work function, and surface energy simultaneously to reach a better energy alignment and interface contact is rare. Here, we demonstrate that oxoammonium salts (TEMPO+X−) with different counterions can act as facile and novel dopants to realize secondary doping of PEDOT:PSS. The effective charge transfer process achieved between TEMPO+X− and PEDOT:PSS results in enhanced carrier density and improved conductivity of PEDOT:PSS. Moreover, different counterions of TEMPO+X− can tune the work function and surface energy of PEDOT:PSS, enabling improved device performances. The resulting device with PM6:Y6 as the active layer shows a high power conversion efficiency (PCE) over 16%. Moreover, this doping strategy can also be applied to other conjugated polymers such as poly(3-hexylthiophene). This work provides a promising strategy to tune the properties of conjugated polymers through doping, thus effectively boosting the performance of organic solar cells.

Nanopores have become one of the most important tools for single-molecule sensing, but the challenge for selective detection of specific biomolecules still exists. In this contribution, we develop a new technique for sensing carcinoembryonic antigen (CEA), one of the important cancer biomarkers, using solid-state nanopores as a tool. The method is based on the specific affinity between aptamer (Apt) modified magnetic Fe

Enzymes encapsulated in metal-organic frameworks (enzyme@MOFs), as a promising immobilized enzyme, were investigated for intrinsic catalytic activities at the single entity level via a stochastic collision electrochemical technique. Zeolitic imidazolate frameworks with amorphous (aZIF-8) and crystalline (ZIF-8) structures were chosen as model MOFs to encapsulate glucose oxidase (GOx). We carried out single enzyme@MOF nanoparticle (NP) collision experiments using the carbon ultramicroelectrode (CUME), which demonstrated that the catalytic activity of GOx@ZIF-8 NPs was much less than GOx@aZIF-8 NPs. Meanwhile, the kcat and TON per GOx in aZIF-8 NPs were obtained, revealing the intrinsic catalytic activity of GOx in aZIF-8 NPs at the single entity level. This strategy is the first approach for investigating enzyme@MOFs at a single entity level, which can not only broaden the horizons of single entity electrochemistry (SEE) but also provide further insights into research on electrochemistry, catalysis, and nanocomposites.

Nano-structured thin films have a variety of applications from waveguides, gaseous sensors to piezoelectric devices. Grazing Incidence Small Angle x-ray Scattering images enable classification of such materials. One challenge is to determine structure information from scattering patterns alone. This paper highlights the design of multiple Convolutional Neural Networks (CNN) to classify nanoparticle orientation in a thin film by learning scattering patterns. The network was trained on several thin films with a success rate of 94%. We demonstrate CNN robustness under different noises as well as demonstrate the potential of our proposed approach as a strategy to decrease scattering pattern analysis time.

Solid-state nanopores have been employed as useful tools for single molecule analysis due to their advantages of easy fabrication and controllable diameter, but selectivity is always a big concern for complicated samples. In this work, functionalized magnetic core-shell Fe3O4-Au nanoparticles, which acted as a molecular carrier, were introduced into nanopore electrochemical system for microRNA sensing in complicated samples with high sensitivity, selectivity and signal-to-noise ratio (SNR). This strategy is based on the specific affinity between neutral peptide nucleic acids (PNA)-modified Fe3O4-Au nanoparticles and negative miRNA, and the formation of negative Fe3O4-Au-PNA-miRNA complex, which can pass through the nanopore by application of a positive potential and eliminate neutral Fe3O4-Au-PNA complex. To detect miRNA in complicated samples, a magnet has been used to separate Fe3O4-Au-PNA-miRNA complex with good selectivity. We think this is a facile and effective method for the detection of different targets at single molecular level, including nucleic acids, proteins, and other small molecules, which will open up a new approach in the nanopore sensing field.

MicroRNAs (miRNAs) have been applied as biomarkers and better detection of their expression profiles plays important roles in early diagnosis of cancers. In this work, a simple dual-signal amplification strategy has been used to construct a novel nanosensor on single Au nanowire electrodes (SAuNWEs) for miRNA-16 detection based on the “signal-on” and “signal-off” features during hybridization/de-hybridization process. The ferrocene-labeled aptamer capture probe (Fc-CP-16) is designed to hybridize with thiolated methylene blue-labeled DNA probe (MB-CP) on SAuNWE to form duplex DNA, and the addition of miRNA-16 can lead to the dissociation of duplex structure due to the highly matched sequences between miRNA-16 and Fc-CP-16. The remaining MB-CP can thus tend to recover its hairpin structure at the presence of Mg2+ through the hybridization of its complementary sequences. During this hybridization/de-hybridization process, the changes of Fc and MB oxidation peaks can be recorded, and there has a linear relationship between the sum of dual-signal changes ( Δ I = Δ I M B + | Δ I F c | ) and the logarithm of miRNA-16 concentrations, which can be used to detect miRNA-16. Including miRNA extraction, the dual-signal amplification strategy for miRNA sensing assay was carried out about 2 h for the detection in real samples. This novel nanosensor has small dimension, good selectivity, rapid response and regeneration ability, which can satisfy the need for early cancer marker detection in cells/organelles.

In this paper, single Hg nanoelectrodes were prepared by single nucleation/growth of mercury on the surface of single gold nanodisk electrodes, which were fabricated by improved laser-assisted pulling method. The nucleation/growth process was characterized by scanning electron microscopy (SEM), transition electron microscopy (TEM) and electrochemical method. Pb2+ and Cu2+ could be accumulated and melted with single Hg nanoelectrodes (amalgam formed) through preconcentration step, and then two typical anodic waves would be obtained through square-wave anodic stripping voltammetry (SWASV) method. The peak currents were corresponded to the concentration of Pb2+ and Cu2+, and thus the single Hg nanoelectrodes could be used as a kind of novel nanosensor for simultaneous detection of lead and copper with high sensitivity and selectivity.

Conjugated polymers are emerging as promising organic photocatalysts for photocatalytic hydrogen evolution; however, they are suffering from poor water dispersabilities. Herein, this problem is addressed in an easy and green way with the assistance of a biomass-derived material. An amphipathic xylan derivative that can be self-assembled into nanomicelles was employed as carriers to encapsulate a series of conjugated polymers to form uniform composite micelles in water. By this way, the hydrophobic conjugated polymers and their blends were successfully dispersed into water and thus enabling efficient hydrogen evolution. Moreover, the energy level offsets of these conjugated polymers enable the formation of photoinduced charge transfer (PCT) process and fluorescence resonance energy transfer (FRET) process in their composite micelles. The photocatalytic experimental results showed that in these composite micelles, conjugated polymer blends with PCT characteristic delivered much higher photocatalytic hydroge...

In this work, a label-free electrochemical apta-nanosensor was fabricated on a single gold nanodisk electrode (AuNDE) for thrombin sensing with high sensitivity via a novel signal amplification strategy. This recognition platform was fabricated via self-assembly of helper DNA (HP-DNA), thrombin-binding aptamer (TBA) and gold nanoparticle (AuNP)-DNA complexes to form a sandwich structure on the AuNDE surface. A novel signal amplification strategy via designed AuNP-DNA complexes was introduced using Ru(NH3)63+ as the signal reporter based on the electrostatic interaction. In the presence of thrombin, the strong interaction between the TBA and target led to the dissociation of sandwich DNA complexes from the AuNDE, which resulted in the reduction current of Ru(NH3)63+. This proposed sensing platform showed a wide detection range of 0.1 pM-5 nM and a low detection limit of 0.02 pM. Considering the small overall dimensions and high sensitivity, this nanosensor can be potentially applied for bioanalysis in living biosystems.

High-efficiency organic solar cells (OSCs) largely rely on polymer donors. Herein, we report a new building block BNT and a relevant polymer PBNT-BDD featuring B-N covalent bond for application in OSCs. The BNT unit is synthesized in only 3 steps, leading to the facile synthesis of PBNT-BDD. When blended with a nonfullerene acceptor Y6-BO, PBNT-BDD afforded a power conversion efficiency (PCE) of 16.1 % in an OSC, comparable to the benzo[1,2-b:4,5-b']dithiophene (BDT)-based counterpart. The nonradiative recombination energy loss of 0.19 eV was afforded by PBNT-BDD. PBNT-BDD also exhibited weak crystallinity and appropriate miscibility with Y6-BO, benefitting of morphological stability. The singlet-triplet gap (ΔEST ) of PBNT-BDD is as low as 0.15 eV, which is much lower than those of common organic semiconductors (≥0.6 eV). As a result, the triplet state of PBNT-BDD is higher than the charge transfer (CT) state, which would suppress the recombination via triplet state effectively.

Nonfullerene acceptors (NFAs) have contributed significantly to the progress of organic solar cells (OSCs). However, most NFAs feature a large fused-ring backbone, which usually requires a tedious multiple-step synthesis, and are not applicable to commercial applications. An alternative strategy is to develop nonfused NFAs, which possess synthetic simplicity and facile tunability in optoelectronic properties and solid-state microstructures. In this work, we report two nonfused NFAs, BTCIC and BTCIC-4Cl, based on an A-D-A'-D-A architecture, which possess the same electron-deficient benzothiadiazole central core but different electron-withdrawing terminal groups. The optical properties, energy levels, and molecular crystallinities were finely tuned by changing the terminal groups. Moreover, a decent power conversion efficiency of 9.3 and 10.5% has been achieved by BTCIC and BTCIC-4Cl, respectively, by blending them with an appropriate polymer donor. These results demonstrate the potential of A-D-A'-D-A type nonfused NFAs for high-performance OSCs. Further development of nonfused NFAs will be very fruitful by employing appropriate building blocks and via side-chain optimizations.

Three energetic copper (II) complexes, [Cu(1-MAT)2(HDNBA)2](DNBA)2 (1), [Cu(1-MAT)2](PA)2 (2) and [Cu(1-MAT)4(H2O)2](ClO4)2 (3) [1-MAT: 1-methyl-5-aminotetrazole; HDNBA: 3,5-dinitrobenzoic acid; PA: picric acid] were synthesized and characterized. The X-ray single-crystal diffraction results illustrate that the structure of the coordination compounds 1, 2 and 3 belong to the P21/c, P21212 and C2/m space group, respectively. The central copper ion forms a hexacoordinated octahedral structure with N and O atoms. All of them possess good thermal stability, with the thermal decomposition temperatures of 254°C (1), 272°C (2) and 322°C (3), respectively, due to their plenty of coordination bonds, intramolecular and intermolecular H-bonds. According to the results of impact sensitivity and friction sensitivity, these compounds are insensitive to impact (>40 J) and friction (>360 N), except the impact sensitivity of 3 is 2.7 J. The measured constant volume combustion energies of 1, 2 and 3 are 13480, 3537 and 7442 kJ mol−1, respectively.

A new nanosensor for glutathione (GSH) detection by use of single nanoelectrodes has been developed through a dual-signaling ratiometric amplification strategy. Ag nanoparticles (Ag NPs) metalized DNA1 was modified on an Au nanoelectrode surface. Due to the strong affinity between Ag NP and GSH, Ag NPs could be removed by the addition of GSH. The remaining metalized DNA1 could hardly form a double strand, while the de-metalized DNA1 could hybrid with DNA2 and DNA3 to form a complex structure to adsorb methylene blue (MB), and then the electrochemical signal of differential pulse voltammetry (DPV) from MB oxidation could be observed. With the addition of GSH, the peak current of MB oxidation at about −0.27 V (IMB) increases, while the signal of Ag oxidation at about 0.1 V (IAg) decreases. It was found that there had a linear relationship between the ratio of dual-signal (IMB/IAg) and the GSH concentrations, which could be used to detect GSH. The ratiometric nanosensor is label-free, easy to operate, and can eliminate inherent system errors. Considering the advantages of nanoelectrodes, such as low IR drop, fast response, and small overall dimension, this developed nanosensor can be used for GSH detection living systems (e.g., cell lysate).

A simple nanopore modification and sensing strategy was developed for the detection of miRNAs. This preparation and sensing approach provides a quick, simple and facile tool for the detection of specific biomolecules with high sensitivity and selectivity, and may find a wide range of applications in bio-analysis.

Silver nanowires (AgNWs) have received much attention due to their excellent optical, electrical, and conductive properties. In this work, we provided a new perspective for investigating the property of AgNWs from a single nanowire level. Single Ag nanowire electrodes and single Pt@Ag nanowire electrodes were fabricated by a laser-assisted pulling technique and galvanic replacement reaction (GRR). The radius, length, and metal ratio of the nanowires are tunable as needed. The prepared nanowire exhibited excellent electrocatalytic activity toward the methanol electro-oxidation and high sensitivity for monitoring the reduction of 4-nitrothiophenol by recording SERS spectra. This work will help us deeply understand the catalytic performance at the single nanowire level and open a new perspective for nanomaterials research.

Understanding the electrocatalytic activity at single nanoparticles/nanoclusters level is extremely important. In this work, a method for the electro-deposition of single Pt-Pd nanoparticles (NPs) is described using a single nanopore electrode as a template. The electro-deposition process was investigated carefully and the results show that the process is controlled by diffusion and electro-crystallization process, simultaneously, and the glass sheath property around the nanopore has a large impact on the formation of single Pt-Pd NPs due to the "edge effect". The prepared single Pt-Pd NPs exhibit excellent electrocatalytic activity in the methanol oxidation reaction, which can be used to screen electrocatalysts with high efficiency for utility in the energy field.

Nano-sized electrodes have their special advantages for sensing applications, such as small overall dimension, fast response and low background current. In this work, single gold nanoclusters (AuNCs) were controllably prepared on single Pt nanoelectrode surface by electrodeposition method. The AuNCs covered Pt nanoelectrode (AuNCs/PtNE) had steady-state voltammetric response in redox species solution, which was similar to micro-/nano-sized electrodes. It was interesting to find isonicotinic acid hydrazide (INH, also known as isoniazid) showed good electrochemical response on AuNCs/PtNE surface, which had investigated carefully by square wave voltammetry (SWV) and chronoamperometry. Moreover, the prepared single AuNCs/PtNEs showed the capability for INH sensing with good sensitivity, reproducibility and selectivity, which was demonstrated for INH detection in human urine samples.

Carbon coated CoP hollow spheres (CoP/C) were prepared from cobalt-based MOFs via simple calcining and subsequent phosphorization process. Meanwhile, N-doped carbon shells were also synthesized by a low-cost hard-templating method. Both of the obtained CoP/C and N-doped carbon shells deliver remarkable specific capacitances and excellent capacitance retentions when used as electrodes for supercapacitor. Remarkably, the asymmetric supercapacitor device based on the CoP/C and N-doped carbon shells delivers a high energy density of 16.14 Wh kg−1 at a power density of 700 W kg−1 and outstanding cycling stability (99.5% capacitance retention after 5000 cycles at a current density of 7 A g−1). CoP/C should be a promising electrode material for next-generation supercapacitor application.