Monodisperse cadmium sulphide (CdS) quantum dots (QDs) with a tunable size from 1.4 to 4.3 nm were synthesized by a non-injection method, and their surface states were characterized by ...photoluminescence spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The steady state photoluminescence study identified that the proportion of the trap state emission increased with the QD size decrease, while from the photoluminescence decay study, it appeared that the trap state emission results from the emission via a surface deep trap state. The XPS measurements revealed the existence of surface Cd with sulfur vacancy sites which act as electron trap sites, and the population of these sites increases with the QD size decrease. These results are consistent to conclude that the trap state emission mainly originates from the surface deep trapped electrons at the surface Cd with sulfur vacancy sites.
A spontaneous patterning technique via parallel vacuum ultraviolet is developed for fabricating large‐scale, complex electronic circuits with 1 μm resolution. The prepared organic thin‐film ...transistors exhibit a low contact resistance of 1.5 kΩ cm, and high mobilities of 0.3 and 1.5 cm2 V−1 s−1 in the devices with channel lengths of 1 and 5 μm, respectively.
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In harmony: Nanoparticles of Mn3O4 and core/shell‐structured Rh/Cr2O3 as cocatalysts on the surface of a solid solution of GaN and ZnO as catalyst promote O2 and H2 evolution, respectively, under ...visible light (λ>420 nm), thereby achieving enhanced water‐splitting activity compared to analogues modified with either Mn3O4 or Rh/Cr2O3.
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Size matters: The core‐etching reaction by free glutathione is studied for glutathionate (SG)‐protected Aun(SG)m clusters with n=10–39 and m=10–24 (see picture). Only the Au25(SG)18 clusters remain ...unetched, whereas the Aun(SG)m clusters with n<25 and n>25 are transformed into a AuI:SG complex and stable Au25:SG, respectively. The selective synthesis of thiolate (SR)‐protected Au25:SR on a large scale may be possible.
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•Mainstream strategies for avoiding oxidation of Cu inks are reviewed.•Cu precursor inks are elaborated as an effective strategy.•Efficient sintering methods and related sintering ...mechanisms are summarized.•Strategies for the improvement of the reliability of Cu patterns are summarized.•Challenges and future prospects for Cu inks are provided.
Conductive inks have gathered increasing attention in the fabrication of next-generation electronic devices because of their prominent compatibility and producibility. Recently, copper (Cu) inks as the new darling of conductive inks are studied extensively because Cu possesses an intrinsic high conductivity (comparable to the highest conductive metal, silver (Ag)) but an ultralow cost (about 1% the cost of Ag) with abundant reserves. However, the low resistance of Cu towards oxidation results in three issues, in aspects of the synthesis of stable Cu inks, the fabrication of highly conductive Cu patterns, and the long-term reliability of Cu-based electronic performances, which hinders the application prospect of Cu inks in the next-generation electronic devices. Herein, this review summaries the advanced developments of Cu inks in term of formulations, sintering methods, and long-term reliability. The mainstream strategies for avoiding oxidation and improving the stability of Cu inks and Cu patterns are described, while the efficient sintering methods and related sintering mechanisms are analyzed. The effect of ink formulations and sintering methods on the conductivity of Cu patterns on various substrates are also discussed. In addition, the strategies for the improvement of long-term reliability of Cu patterns and their application in various devices are summarized and forecasted. Finally, the challenges and future prospects for Cu inks are involved as well.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Cost-effective copper conductive inks are considered as the most promising alternative to expensive silver conductive inks for use in printed electronics. However, the low stability and high ...sintering temperature of copper inks hinder their practical application. Herein, we develop rapidly customizable and stable copper–nickel complex inks that can be transformed in situ into uniform copper@nickel core–shell nanostructures by a self-organized process during low-temperature annealing and immediately sintered under photon irradiation to form copper–nickel alloy patterns on flexible substrates. The complex inks are synthesized within 15 min via a simple mixing process and are particle-free, air-stable, and compatible with large-area screen printing. The manufactured patterns exhibit a high conductivity of 19–67 μΩ·cm, with the value depending on the nickel content, and can maintain high oxidation resistance at 180 °C even when the nickel content is as low as 6 wt %. In addition, the printed copper–nickel alloy patterns exhibit high flexibility as a consequence of the local softening and mechanical anchoring effect between the metal pattern and the flexible substrate, showing strong potential in the additive manufacturing of highly reliable flexible electronics, such as flexible radio-frequency identification (RFID) tags and various wearable sensors.
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•Surface-activation-localized electroless plating enables high resolution electronics.•1 µm resolution multi-metal patterns are realized on various flexible substrates.•Multilayer ...flexible 3D interconnections are fabricated with tailored functions.•Large-area transistor arrays are fabricated with high performance and flexibility.
Patterning high-resolution multi-metal layers without using subtractive lithography poses a substantial challenge but is indispensable for the development of the modern electronics industry, especially flexible electronics. Herein, the general and feasible additive manufacturing approach is reported to selectively deposit high-resolution multi-metal patterns via surface-activation-localized electroless plating (SALEP) and enable the fabrication of 3-dimensional (3D) interconnections and high-performance organic thin-film transistor (OTFT) arrays for flexible electronics. The SALEP approach comprises the direct layer-by-layer deposition of multi-metal patterns interconnected by via holes, which are defined by the selective adsorption of palladium catalysts and a metallization process. The localized adsorption of the catalyst is guided by the difference in surface wettability and adsorbability caused by vacuum ultraviolet (VUV)-induced photochemical modification. The low-temperature and 3D approach enables miniaturization of flexible electrical circuits down to 1 µm in width; it also enables integration of an OTFT array on a flexible substrate. The fabricated OTFT array with multi-metal Cu/Ni/Au as contact electrodes exhibits a high hole mobility exceeding 10 cm2 V−1 s−1, demonstrating the adaptability of the SALEP approach for the low-cost, high-efficiency, and scalable fabrication of high-performance flexible electronic devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The directed self‐assembly of electronic circuits using functional metallic inks has attracted intensive attention because of its high compatibility with extensive applications ranging from soft ...printed circuits to wearable devices. However, the typical resolution of conventional self‐assembly technologies is not sufficient for practical applications in the rapidly evolving additively manufactured electronics (AMEs) market. Herein, an ultrahigh‐resolution self‐assembly strategy is reported based on a dual‐surface‐architectonics (DSA) process. Inspired by the Tokay gecko, the approach is to endow submicrometer‐scale surface regions with strong adhesion force toward metallic inks via a series of photoirradiation and chemical polarization treatments. The prepared DSA surface enables the directed self‐assembly of electronic circuits with unprecedented 600 nm resolution, suppresses the coffee‐ring effect, and results in a reliable conductivity of 14.1 ± 0.6 µΩ cm. Furthermore, the DSA process enables the layer‐by‐layer fabrication of fully printed organic thin‐film transistors with a short channel length of 1 µm, which results in a large on–off ratio of 106 and a high field‐effect mobility of 0.5 cm2 V−1 s−1.
The dual surface architectonics is developed as an ultrahigh‐resolution directed self‐assembly technology for high‐performance soft electronics. The strong adsorbing and pinning effect enables patterning of metal nanoparticle inks with 600 nm resolution. This technology further allows the fabrication of short‐channel organic thin‐film transistors with a high field‐effect mobility of 0.5 cm2 V−1 s−1 and a large on/off ratio of 106.
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In the present work, we studied a unique and facile method for the drastic structural transformation of hydrophobic small CdE (E = S, Se, Te) nanoparticles into large, high-quality pencil-shaped ...nanoparticles through an Ostwald ripening process induced by Cl− and surfactants (oleic acid and oleylamine). This study revealed that Cl− is the effective anion for the controlled structural transformation of CdE nanoparticles. This transformation reaction can be readily extended to the formation of various functional materials.
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We apply a nanomanipulation technique to assemble pairs of monodispersed octahedral gold nanocrystals (side length, 150 nm) along their major axes with a varying tip-to-tip separation (25−125 nm). ...These pairs are immobilized onto indium tin oxide coated silica substrates and studied as plasmonic dimers by polarization-selective total internal reflection (TIR) microscopy and spectroscopy. We confirm that the plasmon coupling modes with the scattering polarization along the incident light direction result from the transverse-magnetic-polarized incident light, which induces two near-field-coupled dipole moments oriented normal to the air−substrate interface. In such cases, both in-phase (antibonding) and antiphase (bonding) plasmon coupling modes can be directly observed with the incident light wave vector perpendicular and parallel to the dimer axis, respectively. The observation of antiphase plasmon coupling modes (“dark” plasmons) is made possible by the unique polarization nature of the TIR-generated evanescent field. Furthermore, with decreasing nanocrystal separation, the plasmon coupling modes shift to shorter wavelengths for the incident light perpendicular to the dimer axis, whereas relatively large red shifts of the plasmonic coupling modes are found for the parallel incident light.
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