Semiconductor nanocrystals can be synthesized using inexpensive, scalable, solution-based techniques, and their utility as tunable light emitters has been demonstrated in various applications, including biolabeling light-emitting devices. By contrast, the use of colloidal for optical amplification lasing limited by high input power densities that have required. In this work, we show nanoplatelets (NPLs) produce amplified spontaneous emission (ASE) with pump-fluence thresholds low 6 uJ/cm2...

There have been multiple demonstrations of amplified spontaneous emission (ASE) and lasing using colloidal semiconductor nanocrystals. However, it has proven difficult to achieve low thresholds suitable for practical use nanocrystals as gain media. Low-threshold blue ASE from is an even more challenging task. Here, we show that nanoplatelets (NPLs) with electronic structure quantum wells can produce in the red, yellow, green, regions visible spectrum high gains. In particular, blue-emitting...

Soldering semiconductor nanoparticles The optical and electronic properties of can be tuned through changes in their size composition. However, poor contact between interfaces degrade nanoparticle performance devices. Dolzhnikov et al. report the synthesis a gel-like “solder” for metal chalcogenide nanoparticles, such as cadmium selenide lead telluride, by cross-linking molecular wires these materials. Science , this issue p. 425

Colloidal semiconductor nanocrystals (NCs) provide convenient "building blocks" for solution-processed solar cells, light-emitting devices, photocatalytic systems, etc. The use of inorganic ligands colloidal NCs dramatically improved inter-NC charge transport, enabling fast progress in NC-based devices. Typical (e.g., Sn(2)S(6)(4-), S(2-)) are represented by negatively charged ions that bind covalently to electrophilic metal surface sites. binding species the NC provides electrostatic...

Photosensitization of molecular catalysts to reduce CO2 CO is a sustainable route storable solar fuels. Crucial the sensitization process highly efficient transfer redox equivalents from sensitizer catalyst; in systems with sensitizers, this often slow because it gated by diffusion-limited collisions between and catalyst. This article describes photosensitization meso-tetraphenylporphyrin iron(III) chloride (FeTPP) catalyst colloidal, heavy metal-free CuInS2/ZnS quantum dots (QDs) using 450...

It has recently become possible to chemically synthesize atomically flat semiconductor nanoplatelets with monolayer-precision control over the platelet thickness. been suggested that these platelets are quantum wells; is, carriers in confined one dimension but free move other two dimensions. Here, we report time-resolved photoluminescence and transient-absorption measurements of carrier relaxation confirm quantum-well nature nanomaterials. Excitation by an intense laser pulse results...

Tin-halide perovskite nanocrystals are a viable precursor for lead-free, high-efficiency active layers photovoltaic cells. We describe new synthetic procedure quantum-confined Cs2SnI6 with size-dependent band gaps in the long-visible to near-infrared (1.38–1.47 eV). Hot injection synthesis produces particles no organic capping ligands, average diameters that increase from 12 ± 2.8 nm 38 4.1 increasing reaction temperature. The gap, energies of first excitonic peak, ground-state bleach peak...

In this work, we study the functionalization of nanocrystal (NC) surface with inorganic oxo ligands, which bring a new set functionalities to all-inorganic colloidal nanomaterials. We show that simple oxoanions, such as PO43– and MoO42–, exhibit strong binding affinity various II–VI III–V semiconductor metal oxide NCs. ζ-Potential titration offered useful tool differentiate affinities ligands toward different Direct comparison chalcogenidometallate revealed former form stronger bond NCs...

Crystalline silicon-based complementary metal-oxide–semiconductor transistors have become a dominant platform for today's electronics. For such devices, expensive and complicated vacuum processes are used in the preparation of active layers. This increases cost restricts scope applications. Here, we demonstrate high-performance solution-processed CdSe nanocrystal (NC) field-effect (FETs) that exhibit very high carrier mobilities (over 400 cm2/(V s)). is comparable to crystalline transistors....

The creation and manipulation of quantum superpositions is a fundamental goal for the development materials with novel optoelectronic properties. In this Letter, we report persistent (∼80 fs lifetime) coherence between 1S 1P excitonic states in zinc-blende colloidal CdSe dots at room temperature, measured using two-dimensional electronic spectroscopy. We demonstrate that manifests as an intradot phenomenon, frequency which depends on size dot excited within ensemble QDs. model lifetime...

Nanoparticles have been proposed as a promising material for creating devices that harvest, transport, and manipulate energy electrons. Ultrafast charge carrier dynamics represent critical design aspect are dependent on both size shape of the nanoparticle. Spectroscopic investigation electronic structure these systems is complicated by sample inhomogeneity, which broadens peaks leads to ambiguity in interpretation spectra dynamics. Here, we use two-dimensional spectroscopy remove...

Development of optoelectronic technologies based on quantum dots depends measuring, optimizing, and ultimately predicting charge carrier dynamics in the nanocrystal. In such systems, size inhomogeneity photoexcited population distribution among various excitonic states have distinct effects electron hole relaxation, which are difficult to distinguish spectroscopically. Two-dimensional electronic spectroscopy can help untangle these by resolving excitation energy subsequent nonlinear response...

Electronic dynamics span broad energy scales with ultrafast time constants in the condensed phase. Two-dimensional (2D) electronic spectroscopy permits study of these simultaneous resolution both frequency and time. In practice, this technique is sensitive to changes nonlinear dispersion laser pulses as delays are varied during experiment. We have developed a 2D spectrometer that uses broadband continuum generated argon light source. Using visible phase-sensitive optical experiments presents...

Recently, solution-processing became a viable route for depositing CdTe use in photovoltaics. Ultrathin (∼500 nm) solar cells have been made using colloidal nanocrystals with efficiencies exceeding 12% power conversion efficiency (PCE) demonstrated by very simple device stacks. Further progress requires an effective method extracting charge carriers generated during light harvesting. Here, we explored solution-based methods creating transparent Ohmic contacts to the solution-deposited...

Growing interest in molten salts as effective high-temperature heat-transfer fluids for sustainable energy systems drives a critical need to fundamentally understand the interactions between metals and salts. This work utilizes multimodal microscopy methods of synchrotron X-ray nanotomography electron investigate 3D morphological chemical evolution two-model systems, pure nickel metal Ni-20Cr binary alloy, representative salt (KCl-MgCl2 50–50 mol %, 800 °C). In both unexpected shell-like...

The previously ill-characterized [H(x)Rh(22)(CO)(35)](4-/5-) carbonyl cluster has been obtained as a byproduct of the synthesis [H(3)Rh(13)(CO)(24)](2-) and effectively separated by metathesis their sodium salts with [NEt(4)]Cl. Although yields are modest never exceed 10-15% (based on Rh), this procedure affords spectroscopically pure [H(3)Rh(22)(CO)(35)](5-) anion. Formation latter in mixture other Rh clusters was also observed electrospray ionization-mass spectrometry (ESI-MS) oxidation...

We report on photoconductivity of films CdTe nanocrystals (NCs) using time-resolved microwave (TRMC). Spherical and tetrapodal NCs with tunable size-dependent properties are studied as a function surface ligand (including inorganic molecular chalcogenide species) annealing temperature. Relatively high carrier mobility is measured for sintered tetrapod (4 cm2/(V s)). Our TRMC findings show that Te2– capped marked improvement in (11 s)), indicating NC termination can be altered to play crucial...

Heterogeneous Re/SiO2 catalysts prepared using a one pot sol–gel synthesis were found to display high activity in the direct, selective methanol conversion methylal, which is correlated an unprecedented rhenium oxide structure.

This work investigates the structure and properties of soluble chalcogenidocadmates, a molecular form cadmium chalcogenides with unprecedented one-dimensional bonding motifs. The single crystal X-ray reveals that sodium selenocadmate consists infinite wires (Cd2Se3)n2n- charge balanced by Na+ stabilized coordinating solvent molecules. Exchanging cation tetraethylammonium or didodecyldimethylammonium expands versatility improving its solubility in variety polar nonpolar solvents without...

Here we report the syntheses of largely unexplored lead and bismuth chalcogenidometallates in solution phase. Using N2H4 as solvent, new compounds such K6Pb3Te6·7N2H4 were obtained. These soluble molecular underwent cation exchange processes using resin chemistry, replacing Na+ or K+ by decomposable N2H5+ tetraethylammonium cations. They also transformed into stoichiometric chalcogenide nanomaterials with addition metal salts. Such a versatile chemistry led to variety composition-matched...

A reinvestigation of the synthesis [H(5-n)Rh(13)(CO)(24)](n-) (n = 2, 3) led to isolation a series Rh(19), Rh(26), and Rh(33) high-nuclearity carbonyl carbonyl-substituted rhodium clusters. The [Rh(19)(CO)(31)](5-) (1) is electronically equivalent with [Pt(19)(CO)(22)](4-), but poor crystal diffraction data all salts obtained date have prevented its geometrical analysis. structures Rh(26)(CO)(29)(CH(3)CN)(11) (2) as 2·2CH(3)CN [Rh(33)(CO)(47)](5-) (3) [NEt(4)](5)[3]·Me(2)CO were determined...

The local structure of dilute CrCl 3 in a molten MgCl 2 :KCl salt was investigated by situ x-ray absorption spectroscopy (XAS) at temperatures from room temperature to 800 o C. This constitutes the first experiment where Cr speciation is explored chloride salt, ostensibly due compounding challenges arising low concentration matrix heavy absorbers extreme temperatures. confirmed be stable species between 200 and 500 C, while mobility metal ions higher (>700 C) prevented confirmation structure.

The local structure of dilute CrCl<sub>3</sub> in a molten MgCl<sub>2</sub>:KCl salt was investigated by <i>in situ</i> x-ray absorption spectroscopy (XAS) at temperatures from room temperature to 800<sup>o</sup>C. This constitutes the first experiment where Cr speciation is explored chloride salt, ostensibly due compounding challenges arising low concentration matrix heavy absorbers extreme temperatures. confirmed be stable species between 200...

Abstract Colloidal semiconductor nanocrystals, also known as “quantum dots” (QDs), represent an example of a disruptive technology for display and lighting applications. Their high luminescence efficiency tunable, narrow emission are nearly ideal achieving saturated colors enriching the or TV color gamut. Our contribution will discuss next generation inorganic nanostructures with electronic structure optimized characteristics beyond traditional near‐spherical QDs. For example,...