Integrating an electrically active colloidal quantum dot photodiode with a graphene phototransistor.

The realization of low-cost photodetectors with high sensitivity, high quantum efficiency, high gain and fast photoresponse in the visible and short-wave infrared remains one of the challenges in optoelectronics. Two classes of photodetectors that have been developed are photodiodes and phototransistors, each of them with specific drawbacks. Here we merge both types into a hybrid photodetector device by integrating a colloidal quantum dot photodiode atop a graphene phototransistor.

Synthesis of the molecular amalgam [{AuHg₂(o-C₆F₄)₃}{Hg₃(o-C₆F₄)₃}]⁻: a rare example of a heterometallic homoleptic metallacycle.

The preparation of homoleptic heterometallic complexes still remains a challenge. Herein, we report the synthesis and characterization of [Au(PMe3)2][{AuHg2(o-C6F4)3}{Hg3(o-C6F4)3}] (), a gold-mercury homoleptic metallacycle. The crystal structure of displays two [Hg2M(o-C6F4)3] (M = Au(I), Hg(II)) units linked through a short AuHg contact of 3.

Understanding light trapping by resonant coupling to guided modes and the importance of the mode profile.

We present a simple conceptual model describing the absorption enhancement provided by diffraction gratings due to resonant coupling to guided modes in a multi-layered structure. In doing so, we provide insight into why certain guided modes are more strongly excited than others and demonstrate that the spatial overlap of the mode profile with the grating is important. The model is verified by comparison to optical simulations and experimental measurements.

Tailoring the Electronic Properties of Colloidal Quantum Dots in Metal-Semiconductor Nanocomposites for High Performance Photodetectors.

Metallic nanoparticles tailor the electronic properties of PbS colloidal quantum dots in a post-synthetic, all solution-processable approach. The Fermi level of the resulting nanocomposites can be tuned from p- to n-type due to remote charge transfer and electron trap state passivation. This concurrently reduces dark current, improves time response, and increases sensitivity in PbS photoconductors, yielding an over-two-fold increase in detectivity.

Hybrid 2D-0D MoS2 -PbS quantum dot photodetectors.

A hybrid phototransistor consisting of colloidal PbS quantum dots and few layers of MoS2 (≥2 layers) is demonstrated. The hybrid benefits from tailored light absorption in the quantum dots throughout the visible/near infrared region, efficient charge-carrier separation at the p-n interface, and fast carrier transport through the MoS2 channel. It shows responsivity of up to 10(6) A W(-1) and backgate-dependent sensitivity.

Ultrasmall NHC-coated gold nanoparticles obtained through solvent free thermolysis of organometallic Au(i) complexes.

Ultrasmall gold nanoparticles (Au UNPs) represent a unique class of nanomaterials making them very attractive for certain applications. Herein, we developed an organometallic approach to the synthesis of Au UNPs stabilized with the C18H37-NHC ligand by the solvent free thermolysis of [RMIM][Au(C6F5)2] () or [Au(C6F5)(RNHC)] () (with R = C18H37-), by controlling the reactivity of pentafluorophenyl ligands as deprotonating or reductive elimination agents; Au UNPs can be achieved by solvent free thermolysis. Pentafluorophenyl Au(i) complexes and are synthesized from the corresponding ionic and neutral precursors.

Remote trap passivation in colloidal quantum dot bulk nano-heterojunctions and its effect in solution-processed solar cells.

More-efficient charge collection and suppressed trap recombination in colloidal quantum dot (CQD) solar cells is achieved by means of a bulk nano-heterojunction (BNH) structure, in which p-type and n-type materials are blended on the nanometer scale. The improved performance of the BNH devices, compared with that of bilayer devices, is displayed in higher photocurrents and higher open-circuit voltages (resulting from a trap passivation mechanism).

Imprinted electrodes for enhanced light trapping in solution processed solar cells.

A simple approach is demonstrated to combine a light trapping scheme and a conductive substrate for solution processed solar cells. By means of soft lithography, a new light-trapping architecture can be integrated as the bottom electrode for emerging thin-film solar-cell technologies without added costs, fully compatible with low-temperature processes, and yielding an enhancement in the photocurrent without altering the rest of the electrical performance of the device.

Heterometallic gold(I)-thallium(I) compounds with crown thioethers.

The polymeric Au/Tl compounds [{Au(C6X5)2}Tl]n (X = Cl, F) react with the crown thioethers 1,4,7-trithiacyclononane ([9]aneS3), 1,5,8,11-tetrathiacyclotetradecane ([14]aneS4), and 1,4,7,10,13,16,19,22-octathiacyclotetracosane ([24]aneS8) in an appropriate molar ratio to afford [{Au(C6X5)2}Tl(L)]2 [L = [9]aneS3, X = Cl (1), F (4); L = [14]aneS4, X = Cl (2), F (5)], [{Au(C6Cl5)2}2Tl2([24]aneS8)]n (3) or [{Au(C6F5)2}2Tl2([24]aneS8)] (6). X-ray diffraction studies of 3, 4 and 6 reveal polymeric (3) or tetranuclear (4, 6) structures formed via Tl-S bonds and AuTl or AuTl and AuAu contacts. All the complexes are luminescent in the solid state, but not in solution, where the metal-metal interactions, which are responsible for the luminescence, are no longer present.

Experimental and theoretical evidence of the existence of gold(I)···mercury(II) interactions in solution through fluorescence-quenching measurements.

Heteronuclear complexes {[Hg(R)2][Au(R')(PMe3)]2}n (R=R'=C6Cl2F3 (3); R=R'=C6F5 (4); R=C6Cl2F3, R'=C6F5 (5); R=C6F5, R'=C6Cl2F3 (6)) were prepared by the treatment of the corresponding organomercury compounds, [Hg(C6X5)2], with two equivalents of [Au(C6X5)(PMe3)]. Their crystal structures, as determined by using X-ray diffraction methods, display Au···Hg interactions. Although only compound 4 and 5 show luminescence in the solid state, all of these compounds quench the fluorescence of naphthalene in solution.

Luminescent gold-silver complexes derived from neutral bis(perfluoroaryl)diphosphine gold(I) precursors.

Complex [Au{4-C(6)F(4)(4-C(6)BrF(4))}(tht)] reacts with diphosphines (L-L) such as bis(diphenylphosphino)methane (dppm) or 1,2-bis(diphenylphosphino)benzene (dppb) in a 2 : 1 molar ratio in dichloromethane, leading to neutral products of stoichiometry [(Au{4-C(6)F(4)(4-C(6)BrF(4))})(2)(μ-L-L)] (L-L = dppm (1), dppb (2)). In the crystal structure of complex 2 short Au···Au interactions of 2.9367(5) and 2.

Making the golden connection: reversible mechanochemical and vapochemical switching of luminescence from bimetallic gold-silver clusters associated through aurophilic interactions.

Aiming at the development of new architectures within the context of the quest for strongly luminescent materials with tunable emission, we utilized the propensity of the robust bimetallic clusters [Au₂Ag₂(R(I)/R(II))₄] (R(I) = 4-C₆F₄I, R(II) = 2-C₆F₄I) for self-assembly through aurophilic interactions. With a de novo approach that combines the coordination and halogen-bonding potential of aromatic heteroperhalogenated ligands, we have generated a family of remarkably luminescent bimetallic materials that provide grounds to address the relevance, relative effects, and synergistic action of the two interactions in the underlying photophysics. By polymerizing the green-emitting (λ(max)(em) = 540 nm) monomer [Au₂Ag₂R(II)₄(tfa)₂]²⁻ (tfa = trifluoroacetate) to a red-emitting (λ(max)(em) = 660 nm) polymer [Au₂Ag₂R(II)₄(MeCN)₂](n), we demonstrate herein that the degree of cluster association in these materials can be effectively and reversibly switched simply by applying mechanochemical and/or vapochemical stimuli in the solid state as well as by solvatochemistry in solution, the reactions being coincident with a dramatic switching of the intense, readily perceptible photoluminescence.

Amalgamating at the molecular level. A study of the strong closed-shell Au(I)···Hg(II) interaction.

Complex {[Hg(C(6)F(5))(2)][Au(C(6)F(5))(PMe(3))](2)}(n)2 displays unsupported Au(I)···Hg(II) and Au(I)···Au(I) interactions. Its crystal structure displays a polymeric -(Au-Hg-Au-Au-Hg-Au)(n)- disposition. Ab initio calculations show very strong Au(I)···Hg(II) and Au(I)···Au(I) closed-shell interactions of -73.

Combining aurophilic interactions and halogen bonding to control the luminescence from bimetallic gold-silver clusters.

The luminescence in a series of new bimetallic gold-silver vapochromic structures can be efficiently switched among different colors simply by exposure to solvent vapors. The emission color in these systems is controlled by both aurophilic interactions and halogen bonding, which affect the emission energy through different orbitals.