Phosphorescent Cationic Au4Ag2 Alkynyl Cluster Complexes for Efficient Solution‐Processed Organic Light‐Emitting Diodes

Cationic Au₄Ag₂ heterohexanuclear aromatic acetylides cluster complexes supported by bis(2‐diphenylphosphinoethyl)phenylphosphine (dpep) are prepared. The Au₄Ag₂ cluster structure originating from the combination of one anionic [Au(C≡CR)₂]^? with one cationic [Au₃Ag₂(dpep)₂(C≡CR)₂]³⁺ through the formation of Ag?acetylide η²‐bonds is highly stabilized by Au–Ag and Au–Au contacts. The Au₄Ag₂ alkynyl cluster complexes are moderately phosphorescent in the fluid CH₂Cl₂ solution, but exhibit highly intense phosphorescent emission in solid state and film. As revealed by theoretical computational studies, the phosphorescence is ascribable to significant ³[π (aromatic acetylide) → s/p (Au)] ³LMCT parentage with a noticeable Au₄Ag₂ cluster centered ³[d → s/p] triplet state. Taking advantage of mCP and OXD‐7 as a mixed host with 20 wt% dopant of phosphorescent Au₄Ag₂ cluster complex in the emitting layer, solution‐processed organic light‐emitting diodes (OLEDs) exhibit highly efficient electrophosphorescence with the maximum current, power, and external quantum efficiencies of 24.1 cd A^?1, 11.6 lm W^?1, and 7.0%, respectively. Introducing copper(I) thiocyanate (CuSCN) as a hole‐transporting layer onto the PEDOT:PSS hole‐injecting layer through the orthogonal solution process induces an obvious improvement of the device performance with lower turn‐on voltage and higher electroluminescent efficiency.     

Large Upconversion Enhancement in the “Islands” Au–Ag Alloy/NaYF4: Yb3+, Tm3+/Er3+ Composite Films,and Fingerprint Identification

The surface plasmon (SP) modulation is a promised way to highly improve the strength of upconversion luminescence (UCL) and expand its applications. In this work, the “islands” Au–Ag alloy film is prepared by an organic removal template method and explored to improve the UCL of NaYF₄: Yb3+, Tm³⁺/Er³⁺. After the optimization of Au–Ag molar ratio (Au_1.25–Ag_0.625) and the size of NaYF₄ nanoparticles (NPs, ≈7 nm), an optimum enhancement as high as 180 folds is obtained (by reflection measurement) for the overall UCL intensity of Tm³⁺. Systematic studies indicate that the UCL enhancement factor (EF) increases with the increased size of metal NPs and the increase of diffuse reflection, with the decreased size of NaYF₄ NPs, with the decreased power density of excitation light and with improving order of multiphoton populating. The total decay rate varies only ranging of about 20% while EF changes significantly. All the facts above indicate that the UCL enhancement mainly originates from coupling of SP with the excitation electromagnetic field. Furthermore, the fingerprint identification based on SP‐enhanced UCL is realized in the metal/UC system, which provides a novel insight for the application of the metal/UC device.     

AuPt Alloy Nanoparticles for CO‐Tolerant Hydrogen Activation: Architectural Effects in Au‐Pt Bimetallic Nanocatalysts

Colloidal suspensions of AuPt alloy nanoparticles (NPs) were prepared by using a rapid butyllithium reduction of Au³⁺ and Pt⁴⁺ precursors in oleylamine. The resulting 2.5 nm (av) particles were characterized by TEM with EDX, XRD, XPS and UV‐vis spectroscopy. With less butyllithium, nanowires are formed from fused NPs and grow to 100 nm in length. The activities of three different AuPt NP architectures (alloy, contact aggregate and monometallic NPs) were evaluated for catalytic hydrogen oxidation in CO‐contaminated fuel streams (1.0 % Pt loadings in Al₂O₃ supports). The alloy catalyst showed superior H₂ and CO oxidation activity, was unaffected by iron promoters and appears to operate by a different mechanism. The heteroaggregate showed a marked improvement in activity with iron promoters and is more selective for CO oxidation.     

Triplex Au–Ag–C Core–Shell Nanoparticles as a Novel Raman Label

Monodispersed, readily‐grafted, and biocompatible surface‐enhanced Raman spectroscopic (SERS) tagging materials are developed; they are composed of bimetallic Au@Ag nanoparticles (NPs) for optical enhancement, a reporter molecule for spectroscopic signature, and a carbon shell for protection and bioconjugation. A controllable and convenient hydrothermal synthetic route is presented to synthesize the layer‐by‐layer triplex Au–Ag–C core–shell NPs, which can incorporate the Raman‐active label 4‐mercapto benzoic acid (4‐MBA). The obtained gold seed–silver coated particles can be coated further with a thickness‐controlled carbon shell to form colloidal carbon‐encapsulated Au_core/Ag_shell spheres with a monodisperse size distribution. Furthermore, these SERS‐active spheres demonstrated interesting properties as a novel Raman tag for quantitative immunoassays. The results suggest such SERS tags can be used for multiplex and ultrasensitive detection of biomolecules as well as nontoxic, in vivo molecular imaging of animal or plant tissues.     

Functionalization of Graphene Oxide Films with Au and MoOx Nanoparticles as Efficient p‐Contact Electrodes for Inverted Planar Perovskite Solar Cells

A graphene oxide (GO) film is functionalized with metal (Au) and metal‐oxide (MoO_x) nanoparticles (NPs) as a hole‐extraction layer for high‐performance inverted planar‐heterojunction perovskite solar cells (PSCs). These NPs can increase the work function of GO, which is confirmed with X‐ray photoelectron spectra, Kelvin probe force microscopy, and ultraviolet photoelectron spectra measurements. The down‐shifts of work functions lead to a decreased level of potential energy and hence increased V_oc of the PSC devices. Although the GO‐AuNP film shows rapid hole extraction and increased V_oc, a J_sc improvement is not observed because of localization of the extracted holes inside the AuNP that leads to rapid charge recombination, which is confirmed with transient photoelectric measurements. The power conversion efficiency (PCE) of the GO‐AuNP device attains 14.6%, which is comparable with that of the GO‐based device (14.4%). In contrast, the rapid hole extraction from perovskite to the GO‐MoO_x layer does not cause trapping of holes and delocalization of holes in the GO film accelerates rapid charge transfer to the indium tin oxide substrate; charge recombination in the perovskite/GO‐MoO_x interface is hence significantly retarded. The GO‐MoO_x device consequently shows significantly enhanced V_oc and J_sc, for which its device performance attains PCE of 16.7% with great reproducibility and enduring stability.     

Engineering Solar Cell Absorbers by Exploring the Band Alignment and Defect Disparity: The Case of Cu‐ and Ag‐Based Kesterite Compounds

The development of kesterite Cu₂ZnSn(S,Se)₄ thin‐film solar cells is currently hindered by the large deficit of open‐circuit voltage (V_oc), which results from the easy formation of Cu_Zn antisite acceptor defects. Suppressing the formation of Cu_Zn defects, especially near the absorber/buffer interface, is thus critical for the further improvement of kesterite solar cells. In this paper, it is shown that there is a large disparity between the defects in Cu‐ and Ag‐based kesterite semiconductors, i.e., the Cu_Zn or Cu_Cd acceptor defects have high concentration and are the dominant defects in Cu₂ZnSn(S,Se)₄ or Cu₂CdSnS₄, but the Ag_Zn acceptor has only a low concentration and the dominant defects are donors in Ag₂ZnSnS₄. Therefore, the Cu‐based kesterites always show p‐type conductivity, while the Ag‐based kesterites show either intrinsic or weak n‐type conductivity. Based on this defect disparity and calculated band alignment, it is proposed that the V_oc limit of the kesterite solar cells can be overcome by alloying Cu₂ZnSn(S,Se)₄ with Ag₂ZnSn(S,Se)₄, and the composition‐graded (Cu,Ag)₂ZnSn(S,Se)₄ alloys should be ideal light‐absorber materials for achieving higher efficiency kesterite solar cells.     

Water‐Soluble Polyfluorenes as an Interfacial Layer Leading to Cathode‐Independent High Performance of Organic Solar Cells

Novel poly[(9,9‐bis((6′‐(N,N,N‐trimethylammonium)hexyl)‐2,7‐fluorene)‐alt‐(9,9‐bis(2‐(2‐(2‐methoxyethoxy)ethoxy)ethyl)‐9‐fluorene)) dibromide (WPF‐6‐oxy‐F) and poly[(9,9‐bis((6′‐(N,N,N‐trimethylammonium)hexyl)‐2,7‐fluorene)‐alt‐(9,9‐bis(2‐(2‐methoxyethoxy)ethyl)‐fluorene)] dibromide (WPF‐oxy‐F) compounds are developed and the use of these water‐soluble polymers as an interfacial layer for low‐cost poly(3‐hexylthiophene):phenyl‐C₆₁ butyric acid methyl ester (P3HT:PCBM) organic solar cells (OSCs) is investigated. When WPF‐oxy‐F or WPF‐6‐oxy‐F is simply inserted between the active layer and the cathode as an interfacial dipole layer by spin‐coating water‐soluble polyfluorenes, the open‐circuit voltage (V_oc), fill factor (FF), and power‐conversion efficiency (PCE) of photovoltaic cells with high work‐function metal cathodes, such as Al, Ag, Au, and Cu, dramatically increases. For example, when WPF‐6‐oxy‐F is used with Al, Ag, Au, or Cu, regardless of the work‐function of the metal cathode, the V_oc is 0.64, 0.64, 0.58, and 0.63 V, respectively, approaching the original value of the P3HT:PCBM system because of the formation of large interfacial dipoles through a reduction of the metal work‐function. In particular, introducing WPF‐6‐oxy‐F into a low‐cost Cu cathode dramatically enhanced the device efficiency from 0.8% to 3.36%.     

Printed,Flexible, Organic Nano‐Floating‐Gate Memory: Effects of Metal Nanoparticles and Blocking Dielectrics on Memory Characteristics

The effects of using a blocking dielectric layer and metal nanoparticles (NPs) as charge‐trapping sites on the characteristics of organic nano‐floating‐gate memory (NFGM) devices are investigated. High‐performance NFGM devices are fabricated using the n‐type polymer semiconductor, poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)), and various metal NPs. These NPs are embedded within bilayers of various polymer dielectrics (polystyrene (PS)/poly(4‐vinyl phenol) (PVP) and PS/poly(methyl methacrylate) (PMMA)). The P(NDI2OD‐T2) organic field‐effect transistor (OFET)‐based NFGM devices exhibit high electron mobilities (0.4–0.5 cm² V^?1 s^?1) and reliable non‐volatile memory characteristics, which include a wide memory window (≈52 V), a high on/off‐current ratio (I_on/I_off ≈ 10⁵), and a long extrapolated retention time (>10⁷ s), depending on the choice of the blocking dielectric (PVP or PMMA) and the metal (Au, Ag, Cu, or Al) NPs. The best memory characteristics are achieved in the ones fabricated using PMMA and Au or Ag NPs. The NFGM devices with PMMA and spatially well‐distributed Cu NPs show quasi‐permanent retention characteristics. An inkjet‐printed flexible P(NDI2OD‐T2) 256‐bit transistor memory array (16 × 16 transistors) with Au‐NPs on a polyethylene naphthalate substrate is also fabricated. These memory devices in array exhibit a high I_on/I_off (≈10^{4 ± 0.85}), wide memory window (≈43.5 V ± 8.3 V), and a high degree of reliability.     

High‐Performance Colorful Semitransparent Polymer Solar Cells with Ultrathin Hybrid‐Metal Electrodes and Fine‐Tuned Dielectric Mirrors

Polymer solar cells (PSCs) possess the unique features of semitransparency and coloration, which make them potential candidates for applications in aesthetic windows. Here, the authors fabricate inverted semitransparent PSCs with high‐quality hybrid Au/Ag transparent top electrodes and fine‐tuned dielectric mirrors (DMs). It is demonstrated that the device color can be tailored and the light harvesting in the PSCs can be enhanced by matching the bandgap of the polymer donors in the active layer with the specifically designed maximum‐reflection‐center‐wavelengths of the DMs. A detailed chromaticity analysis of the semitransparent PSCs from both bottom and top (mirror) views is also carried out. Furthermore, the inverted semitransparent PSCs based on PTB7‐Th:PC₇₁BM with six pairs of DMs demonstrate a maximum power conversion efficiency (PCE) of 7.0% with an average visible transmittance (AVT) of 12.2%. This efficiency is one of the highest reported for semitransparent PSCs, corresponding to 81.4% of the PCE from opaque counterpart devices. The device design and processing method are also successfully adapted to a flexible substrate, resulting in a device with a competitive PCE of 6.4% with an AVT of 11.5%. To the best of our knowledge, this PCE value is the highest value reported for a flexible semitransparent PSC.     

Zn(II)‐Protoporphyrin IX‐Based Photosensitizer‐Imprinted Au‐Nanoparticle‐Modified Electrodes for Photoelectrochemical Applications

The electropolymerization of thioaniline‐modified Au nanoparticles (NPs) on thioaniline monolayer‐functionalized electrodes in the presence of Zn(II)‐protoporphyrin IX yields bis aniline‐crosslinked Au NPs matrices that include molecular imprinted sites for binding the Zn(II)‐protoporphyrin IX photosensitizer. The binding of the photosensitizer yields photoelectrochemically active electrodes that produce anodic photocurrents in the presence of the electron donor benzohydroquinone. The efficient photocurrents formed in the presence of the imprinted electrode are attributed to the high‐affinity binding of the photosensitizer to the imprinted sites, K_a = 3.2 × 10⁶ m ^?1, and to the effective transport of the photoejected electrons to the bulk electrode via the bridged Au NPs matrix. Similarly, a N,N′‐dialkyl‐4,4′‐bipyridinium‐modified Zn(II)‐protoporphyrin IX photosensitizer‐electron acceptor dyad is imprinted in the bis aniline‐crosslinked Au NPs matrix. The photocurrent generated by the imprinted matrix is approximately twofold higher as compared to the photocurrent generated by the Zn(II)‐protoporphyrin IX‐imprinted Au NPs matrix. The efficient photocurrents generated in the presence of the bipyridinium‐modified Zn(II)‐protoporphyrin IX‐imprinted matrix are attributed to the effective primary charge separation of the electron–hole species in the dyad structure, followed by the effective transport of the photoejected electrons to the electrode via the bis aniline‐crosslinked Au NPs matrix.     

Transparent Ultrathin Oxygen‐Doped Silver Electrodes for Flexible Organic Solar Cells

An effective method for depositing highly transparent and conductive ultrathin silver (Ag) electrodes using minimal oxidation is reported. The minimal oxidation of Ag layers significantly improves the intrinsic optical and structural properties of Ag without any degradation of its electrical conductivity. Oxygen‐doped Ag (AgO_x) layers of thicknesses as low as 6 nm exhibit completely 2D and continuous morphologies on ZnO films, smaller optical reflections and absorbances, and smaller sheet resistances compared with those of discontinuous and granular‐type Ag layers of the same thickness. A ZnO/AgO_x/ZnO (ZAOZ) electrode using an AgO_x (O/Ag = 3.4 at%) layer deposited on polyethylene terephthalate substrates at room temperature shows an average transmittance of 91%, with a maximum transmittance of 95%, over spectral range 400?1000 nm and a sheet resistance of 20 Ω sq^?1. The average transmittance value is increased by about 18% on replacing a conventional ZnO/Ag/ZnO (ZAZ) electrode with the ZAOZ electrode. The ZAOZ electrode is a promising bottom transparent conducting electrode for highly flexible inverted organic solar cells (IOSCs), and it achieves a power conversion efficiency (PCE) of 6.34%, whereas an IOSC using the ZAZ electrode exhibits a much lower PCE of 5.65%.     

Hydrophobic Nanoreactor Soft‐Templating: A Supramolecular Approach to Yolk@Shell Materials

Due to their unique morphology‐related properties, yolk@shell materials are promising materials for catalysis, drug delivery, energy conversion, and storage. Despite their proven potential, large‐scale applications are however limited due to demanding synthesis protocols. Overcoming these limitations, a simple soft‐templated approach for the one‐pot synthesis of yolk@shell nanocomposites and in particular of multicore metal nanoparticle@metal oxide nanostructures (M_NP@MO_x) is introduced. The approach here, as demonstrated for Au_NP@ITO_TR (ITO_TR standing for tin‐rich ITO), relies on polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) inverse micelles as two compartment nanoreactor templates. While the hydrophilic P4VP core incorporates the hydrophilic metal precursor, the hydrophobic PS corona takes up the hydrophobic metal oxide precursor. As a result, interfacial reactions between the precursors can take place, leading to the formation of yolk@shell structures in solution. Once calcined these micelles yield Au_NP@ITO_TR nanostructures, composed of multiple 6 nm sized Au NPs strongly anchored onto the inner surface of porous 35 nm sized ITO_TR hollow spheres. Although of multicore nature, only limited sintering of the metal nanoparticles is observed at high temperatures (700 °C). In addition, the as‐synthesized yolk@shell structures exhibit high and stable activity toward CO electrooxidation, thus demonstrating the applicability of our approach for the design of functional yolk@shell nanocatalysts.     

Lending Triarylphosphine Oxide to Phenanthroline: a Facile Approach to High‐Performance Organic Small‐Molecule Cathode Interfacial Material for Organic Photovoltaics utilizing Air‐Stable Cathodes

Cathode interfacial material (CIM) is critical to improving the power conversion efficiency (PCE) and long‐term stability of an organic photovoltaic cell that utilizes a high work function cathode. In this contribution, a novel CIM is reported through an effective and yet simple combination of triarylphosphine oxide with a 1,10‐phenanthrolinyl unit. The resulting CIM possesses easy synthesis and purification, a high T _g of 116 °C and attractive electron‐transport properties. The characterization of photovoltaic devices involving Ag or Al cathodes shows that this thermally deposited interlayer can considerably improve the PCE, due largely to a simultaneous increase in V _oc and FF relative to the reference devices without a CIM. Notably, a PCE of 7.51% is obtained for the CIM/Ag device utilizing the active layer PTB7:PC₇₁BM, which far exceeds that of the reference Ag device and compares well to that of the Ca/Al device. The PCE is further increased to 8.56% for the CIM/Al device (with J _sc = 16.81 mA cm^?2, V _oc = 0.75 V, FF = 0.68). Ultraviolet photoemission spectroscopy studies reveal that this promising CIM can significantly lower the work function of the Ag metal as well as ITO and HOPG, and facilitate electron extraction in OPV devices.     

Cooperative plasmon enhanced organic solar cells with thermal coevaporated Au and Ag nanoparticles

Cooperative plasmon enhanced small molecule organic solar cells are demonstrated based on thermal coevaporated Au and Ag nanoparticles (NPs). The optimized device with an appropriate molar ratio of Au:Ag NPs shows a power conversion efficiency of 3.32%, which is 22.5% higher than that of the reference device without any NPs. The improvement is mainly contributed to the increased short-circuit current which resulted from the enhanced light harvesting due to localized surface plasmon resonance of Au:Ag NPs and the increased conductivity of the device. Besides, factors that determining the performance of the Au:Ag NPs cooperative plasmon enhance organic solar cells are investigated, and it finds that the thickness of MoO₃ buffer layer plays a crucial role. Owing to the different diameter of the thermal evaporated Au and Ag NPs, a suitable MoO₃ buffer layer is required to afford a large electromagnetic enhancement and to avoid significant exciton quenching by the NPs.     

Aptamer‐Conjugated Nanoparticles Efficiently Control the Activity of Thrombin

Thrombin‐binding aptamer‐conjugated gold nanoparticles (TBA‐Au NPs) for highly effective control of thrombin activity towards fibrinogen are demonstrated. While a 29‐base long oligonucleotide (TBA₂₉) has known no enzymatic inhibitory functions for thrombin‐mediated coagulation, the ultrahigh anticoagulant potency of TBA₂₉‐Au NPs can be demonstrated via the steric blocking effect, at two orders of magnitude higher than that of free TBA₂₉. The surface aptamer density on the Au NPs is important in determining their enzymatic inhibition of thrombin and their stability in the presence of nuclease. The practicality of 100TBA₂₉‐Au NPs (100 TBA₂₉ molecules per Au NP) for controlling thrombin‐mediated coagulation in plasma is found, and the 100TBA₂₉‐Au NPs has an ultra binding affinity towards thrombin (K_d = 2.7 × 10^?11M ) due to their high ligand density. The anticoagulant activity of TBA₂₉‐Au NPs is found to be suppressed by TBA₂₉ complementary sequence (cTBA₂₉) modified Au NPs (cTBA₂₉‐Au NPs), with a suppression rate 4.6‐fold higher than that of cTBA₂₉. The easily prepared and low‐cost TBA₂₉‐Au NPs and cTBA₂₉‐Au NPs show their potential in biomedical applications for treating various diseases related to blood clotting disorders. In principle, this study opens the possibility of regulation of molecule binding, protein recognizing, and enzyme activity by using aptamer‐functionalized nanomaterials.     

Performance Enhancement of Tri‐Cation and Dual‐Anion Mixed Perovskite Solar Cells by Au@SiO2 Nanoparticles

Tri‐cation and dual‐anion mixed perovskites have been widely utilized in perovskite solar cell (PSC) applications due to their novel properties such as high absorption, high stability, and low cost. To commercialize the PSCs, further improving the device performance without detrimentally changing the device configuration is important at present. Herein, Au@SiO₂ nanoparticles (NPs) are introduced to modify the interface between mesoporous TiO₂ (mp‐TiO₂) and mixed perovskite with increased main photovoltaic parameters of the device, resulting in a ≈29% enhancement of power conversion efficiency (PCE) from 15.8% to 20.3%. The origins of the enhancement have been studied by exploring the optical absorption, optical power distribution, and charge carrier behaviors within the system. The small perturbation transient photovoltage measurement exhibits prolonged charge carrier lifetimes after the Au@SiO₂ NPs incorporation, and time of flight photoconductivity measurement shows that charge carrier mobilities of this system are also enhanced. These characteristics make metallic nanostructures a promising functional material in facile tuning of the charge carriers transport and further boosting the PCE of the PSCs.     

High‐Throughput Fabrication of Au–Cu Nanoparticle Libraries by Combinatorial Sputtering in Ionic Liquids

Materials libraries of binary alloy nanoparticles (NPs) are synthesized by combinatorial co‐sputter deposition of Cu and Au into the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₁C₄im][Tf₂N]), which is contained in a micromachined cavity array substrate. The resulting NPs and NP‐suspensions are investigated by transmission electron microscopy (TEM), X‐ray diffraction (XRD), UV‐Vis measurements (UV‐Vis), and attenuated total reflection Fourier transformed infrared (ATR‐FTIR) spectroscopy. Whereas the NPs can be directly observed in the IL using TEM, for XRD measurements the NP concentration is too low to lead to satisfactory results. Thus, a new NP isolation process involving capping agents is developed which enables separation of NPs from the IL without changing their size, morphology, composition, and state of aggregation. The results of the NP characterization show that next to the unary Cu and Au NPs, both stoichiometric and non‐stoichiometric Cu–Au NPs smaller than 7 nm can be readily obtained. Whereas the size and shape of the alloy NPs change with alloy composition, for a fixed composition the NPs have a small size distribution. The measured lattice constants of all capped NPs show unexpected increased values, which could be related to the NP/surfactant interactions.     

Solar Cells with Enhanced Photocurrent Efficiencies Using Oligoaniline‐Crosslinked Au/CdS Nanoparticles Arrays on Electrodes

Different configurations of CdS nanoparticles (NPs) are linked to Au electrodes by electropolymerization of thioaniline‐functionalized CdS NPs onto thioaniline‐functionalized Au‐electrodes. In one configuration, thioaniline‐functionalized CdS NPs are electropolymerized in the presence of thioanline‐modified Au NPs to yield an oligoaniline‐crosslinked CdS/Au NPs array. The NP‐functionalized electrode generates a photocurrent with a quantum yield that corresponds to ca. 9%. The photocurrent intensities are controlled by the potential applied on the electrode, and the redox‐state of the oligoaniline bridge. In the oxidized quinoide state of the oligoaniline units, the bridges act as electron acceptors that trap the conduction‐band electrons that are transported to the electrode and lead to high quantum yield photocurrents. The reduced π‐donor oligoaniline bridges act as π‐donor sites that associate N,N′‐dimethyl‐4,4′‐bipyridinium, MV²⁺, by donor/acceptor interactions, K_a = 5270 M^?1. The associated MV²⁺ acts as an effective trap of the conduction‐band electrons, and in the presence of triethanolamine (TEOA) as an electron donor, high photocurrent values are measured (ca. 12% quantum yield). The electropolymerization of thioaniline‐functionalized Au NPs and thioaniline‐modified CdS NPs in the presence of MV²⁺ yields a MV²⁺‐imprinted NP array. The imprinted array exhibits enhanced affinities toward the association of MV²⁺ to the oligoaniline π‐donor sites, K_a = 2.29 × 10⁴ M^?1. This results in the effective trapping of the conduction‐band electrons and an enhanced quantum yield of the photocurrent, ca. 34%. The sacrificial electron donor, TEOA, was substituted with the reversible donor I₃^?. A solar cell consisting of the imprinted CdS/Au NPs array, with MV²⁺ and I₃^?, was constructed. The cell generated a photocurrent with a quantum yield of 4.7%.     

Employing Interfaces with Metavalently Bonded Materials for Phonon Scattering and Control of the Thermal Conductivity in TAGS‐x Thermoelectric Materials

The thermoelectric compound (GeTe)_x(AgSbTe₂)_1?x, in short (TAGS‐x), is investigated with a focus on two stoichiometries, i.e., TAGS‐50 and TAGS‐85. TAGS‐85 is currently one of the most studied thermoelectric materials with great potential for thermoelectric applications. Yet, surprisingly, the lowest thermal conductivity is measured for TAGS‐50, instead of TAGS‐85. To explain this unexpected observation, atom probe tomography (APT) measurements are conducted on both samples, revealing clusters of various compositions and sizes. The most important role is attributed to Ag₂Te nanoprecipitates (NPs) found in TAGS‐50. In contrast to the Ag₂Te NPs, the matrix reveals an unconventional bond breaking mechanism. More specifically, a high probability of multiple events (PME) of ≈60% is observed for the matrix by APT. Surprisingly, the PME value decreases abruptly to ≈20–30% for the Ag₂Te NPs. These differences can be attributed to differences in chemical bonding. The precipitates' PME value is indicative of normal bonding, i.e., covalent bonding with normal optical modes, while materials with this unconventional bond breaking found in the matrix are characterized by metavalent bonding. This implies that the interface between the metavalently bonded matrix and covalently bonded Ag₂Te NP is partly responsible for the reduced thermal conductivity in TAGS‐50.     

Anisotropic Ag2S–Au Triangular Nanoprisms with Desired Configuration for Plasmonic Photocatalytic Hydrogen Generation in Visible/Near‐Infrared Region

Anisotropic Ag₂S‐edged Au‐triangular nanoprisms (TNPs) are constructed by controlling preferential overgrowth of Ag₂S as plasmonic photocatalysts for hydrogen generation. Under visible and near‐infrared light irradiation, Ag₂S‐edged Au‐TNPs exhibit almost fourfold higher efficiency (796 µmol h⁻¹ g⁻¹) than those of Ag₂S‐covered Au‐TNPs (216 µmol h⁻¹ g⁻¹) and pure Au‐TNPs in hydrogen generation. A single‐particle photoluminescence study demonstrates that the plasmon‐induced hot electrons transfer from Au‐TNPs to Ag₂S for hydrogen generation. Finite‐difference‐time‐domain simulations verify that the corners/edges of Au‐TNPs are high‐curvature sites with maximum electric field distributions facilitating hot electron generation and transfer. Therefore, Ag₂S‐edged Au‐TNPs are efficient plasmonic photocatalyst with the desired configurations for charge separation boosting hydrogen generation.