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Publications | The Banin Research Group

Publications

2023
David Stone, Li, Xiang , Naor, Tom , Dai, Jiekai , Remennik, Sergei , and Banin, Uri . 12/7/2023. Size And Emission Control Of Wurtzite Inp Nanocrystals Synthesized From Cu3&Ndash;Xp By Cation Exchange. Chemistry Of Materials, In press. . Publisher's Version Abstract
Phosphide-based nanocrystals (NCs), including InP and Cu3–xP, are relevant for applications in light-emitting devices and catalysis,David_2023 yet their synthetic design is limited in terms of size range and homogeneity. We report the synthesis of uniform and size-controlled emissive wurtzite-phase InP NCs formed via cation exchange from Cu3–xP. First, size-controlled Cu3–xP NCs are synthesized by the formation of metallic Cu0 NCs and their phosphidation to Cu3–xP. By changing the ligands and precursor concentrations, the NC size is varied between 5 and 13 nm. Using cation exchange, InP NCs are then generated. As the surface of InP NCs is prone to oxidation and defects that decrease their emission, we performed a reaction with NOBF4. This yields InP NCs with resolved absorption features and efficient band-gap emission as a result of impurity removal and surface passivation. The effect of water, acid, and halides on the balance of NC etching and surface passivation is studied. With this approach, high-quality wurtzite InP NCs are obtained while the emission is tuned between 810 and 600 nm. The obtained NCs are potential building blocks for catalytic and optoelectronic applications.
Adar Levi, Hou, Bokang , Alon, Omer , Ossia, Yonatan , Verbitsky, Lior , Remennik, Sergei , Rabani, Eran , and Banin, Uri . 12/4/2023. The Effect Of Monomer Size On Fusion And Coupling In Colloidal Quantum Dot Molecules. Nano Letters, 23, 23, Pp. 11307-11313. . Publisher's Version Abstract
The fusion step in the formation of colloidal quantum dot molecules, constructed from two core/shell quantum dots,Adar 2023 dictates the coupling strength and hence their properties and enriched functionalities compared to monomers. Herein, studying the monomer size effect on fusion and coupling, we observe a linear relation of the fusion temperature with the inverse nanocrystal radius. This trend, similar to that in nanocrystal melting, emphasizes the role of the surface energy. The suggested fusion mechanism involves intraparticle ripening where atoms diffuse to the reactive connecting neck region. Moreover, the effect of monomer size and neck filling on the degree of electronic coupling is studied by combined atomistic-pseudopotential calculations and optical measurements, uncovering strong coupling effects in small QD dimers, leading to significant optical changes. Understanding and controlling the fusion and hence coupling effect allows tailoring the optical properties of these nanoscale structures, with potential applications in photonic and quantum technologies.
Tom Naor, Gigi, Shira , Waiskopf, Nir , Jacobi, Gila , Shoshani, Sivan , Kam, Doron , Magdassi, Shlomo , Banin, Ehud , and Banin, Uri . 10/3/2023. Zno Quantum Photoinitiators As An All-In-One Solution For Multifunctional Photopolymer Nanocomposites. Acs Nano, 17, 20, Pp. 20366 - 20375. . Publisher's Version Abstract
Nanocomposites are constructed from a matrix material combined with dispersed nanosized filler particles. Tom 2023Such a combination yields a powerful ability to tailor the desired mechanical, optical, electrical, thermodynamic, and antimicrobial material properties. Colloidal semiconductor nanocrystals (SCNCs) are exciting potential fillers, as they display size-, shape-, and composition-controlled properties and are easily embedded in diverse matrices. Here we present their role as quantum photoinitiators (QPIs) in acrylate-based polymer, where they act as a catalytic radical initiator and endow the system with mechanical, photocatalytic, and antimicrobial properties. By utilizing ZnO nanorods (NRs) as QPIs, we were able to increase the tensile strength and elongation at break of poly(ethylene glycol) diacrylate (PEGDA) hydrogels by up to 85%, unlike the use of the same ZnO NRs acting merely as fillers. Simultaneously, we endowed the PEGDA hydrogels with post-polymerization photocatalytic and antimicrobial activities and showed their ability to decompose methylene blue and significantly eradicate antibiotic-resistant bacteria and viral pathogens. Moreover, we demonstrate two fabrication showcase methods, traditional molding and digital light processing printing, that can yield hydrogels with complex architectures. These results position SCNC-based systems as promising candidates to act as all-in-one photoinitiators and fillers in nanocomposites for diverse biomedical applications, where specific and purpose-oriented characteristics are required.
Yonatan Ossia, Levi, Adar , Panfil, Yossi E, Koley, Somnath , Scharf, Einav , Chefetz, Nadav , Remennik, Sergei , Vakahi, Atzmon , and Banin, Uri . 8/3/2023. Electric-Field-Induced Colour Switching In Colloidal Quantum Dot Molecules At Room Temperature. Nature Materials, 22, Pp. 1210-1217. . Publisher's Version Abstract

Colloidal semiconductor quantum dots are robust emitters implemented in numerous prototype and commercial optoelectronic devices. Yonatan_2023However, active fluorescence colour tuning, achieved so far by electric-field-induced Stark effect, has been limited to a small spectral range, and accompanied by intensity reduction due to the electron–hole charge separation effect. Utilizing quantum dot molecules that manifest two coupled emission centres, we present a unique electric-field-induced instantaneous colour-switching effect. Reversible emission colour switching without intensity loss is achieved on a single-particle level, as corroborated by correlated electron microscopy imaging. Simulations establish that this is due to the electron wavefunction toggling between the two centres, induced by the electric field, and affected by the coupling strength. Quantum dot molecules manifesting two coupled emission centres may be tailored to emit distinct colours, opening the path for sensitive field sensing and colour-switchable devices such as a novel pixel design for displays or an electric-field-induced colour-tunable single-photon source.

Nadav Frenkel, Scharf, Einav , Lubin, Gur , Levi, Adar , Panfil, Yossef E, Ossia, Yonatan , Planelles, Josep , Climente, Juan I, Banin, Uri , and Oron, Dan . 7/17/2023. Two Biexciton Types Coexisting In Coupled Quantum Dot Molecules. Acs Nano, 17, 15, Pp. 14990-15000. . Publisher's Version Abstract

Coupled colloidal quantum dot molecules (CQDMs) are an emerging class of nanomaterials, manifesting two coupled emission centers and thus introducing additional degrEinav_2023ees of freedom for designing quantum-dot-based technologies. The properties of multiply excited states in these CQDMs are crucial to their performance as quantum light emitters, but they cannot be fully resolved by existing spectroscopic techniques. Here we study the characteristics of biexcitonic species, which represent a rich landscape of different configurations essentially categorized as either segregated or localized biexciton states. To this end, we introduce an extension of Heralded Spectroscopy to resolve the different biexciton species in the prototypical CdSe/CdS CQDM system. By comparing CQDMs with single quantum dots and with nonfused quantum dot pairs, we uncover the coexistence and interplay of two distinct biexciton species: A fast-decaying, strongly interacting biexciton species, analogous to biexcitons in single quantum dots, and a long-lived, weakly interacting species corresponding to two nearly independent excitons. The two biexciton types are consistent with numerical simulations, assigning the strongly interacting species to two excitons localized at one side of the quantum dot molecule and the weakly interacting species to excitons segregated to the two quantum dot molecule sides. This deeper understanding of multiply excited states in coupled quantum dot molecules can support the rational design of tunable single- or multiple-photon quantum emitters.

Shalaka Varshney, Oded, Meirav , Remennik, Sergei , Gutkin, Vitaly , and Banin, Uri . 7/7/2023. Controlling The Surface Of Aluminum Nanocrystals: From Aluminum Oxide To Aluminum Fluoride. Small, In press. . Publisher's Version Abstract

Aluminum nanocrystals are emerging as a promising alternative to silver and gold for various applications ranging from plasmonic functionalities to photocatalysis avarshney_2023nd as energetic materials. Such nanocrystals often exhibit an inherent surface oxidation layer, as aluminum is highly reactive. Its controlled removal is challenging but required, as it can hinder the properties of the encaged metal. Herein, two wet-chemical colloidal approaches toward the surface coating of Al nanocrystals, which afford control over the surface chemistry of the nanocrystals and the oxide thickness, are presented. The first approach utilizes oleic acid as a surface ligand by its addition toward the end of the Al nanocrystals synthesis, and the second approach is the post-synthesis treatment of Al nanocrystals with NOBF4, in a "wet" colloidal-based approach, which is found to etch and fluorinate the surface oxides. As surface chemistry is an important handle for controlling materials' properties, this research paves a path for manipulating Al nanocrystals while promoting their utilization in diverse applications.

Bokang Hou, Thoss, Michael , Banin, Uri , and Rabani, Eran . 5/27/2023. Incoherent Nonadiabatic To Coherent Adiabatic Transition Of Electron Transfer In Colloidal Quantum Dot Molecules. Nature Communications, 14, 1, Pp. 3073. . Publisher's Version Abstract
Electron transfer is a fundamental process in chemistry, biology, and physics. One of the most intriguing questions concerns the realization of the transitions between nonadiabatic and adiabatic regimes of electron transfer. Using colloidal quantum dot molecules, we computationally demonstrate how the hybridization energy (electronic coupling) can be tuned by changing the neck dimensions and/or the quantum dot sizes. This provides a handle to tune the electron transfer from the incoherent nonadiabatic regime to the coherent adiabatic regime in a single system. We develop an atomistic model to account for several states and couplings to the lattice vibrations and utilize the mean-field mixed quantum-classical method to describe the charge transfer dynamics. Here, we show that charge transfer rates increase by several orders of magnitude as the system is driven to the coherent, adiabatic limit, even at elevated temperatures, and delineate the inter-dot and torsional acoustic modes that couple most strongly to the charge transfer dynamics.
Orian Elimelech, Oded, Meirav , Harries, Daniel , and Banin, Uri . 3/9/2023. Spontaneous Patterning Of Binary Ligand Mixtures On Cdse Nanocrystals: From Random To Janus Packing. Acs Nano, 17, 6, Pp. 5852-5860. . Publisher's Version Abstract
Binary compositions of surface ligands are known to improve the colloidal stability and fluorescence quantum yield of nanocrystals (NCs), due to ligand–ligand interactions and surface organization. Orian_2023Herein, we follow the thermodynamics of a ligand exchange reaction of CdSe NCs with alkylthiol mixtures. The effects of ligand polarity and length difference on ligand packing were investigated using isothermal titration calorimetry (ITC). The thermodynamic signature of the formation of mixed ligand shells was observed. Correlating the experimental results with thermodynamic mixing models has allowed us to calculate the interchain interactions and to infer the final ligand shell configuration. Our findings demonstrate that, in contrast to macroscopic surfaces, the small dimensions of the NCs and the subsequent increased interfacial region between dissimilar ligands allow the formation of a myriad of clustering patterns, controlled by the interligand interactions. This work provides a fundamental understanding of the parameters determining the ligand shell structure and should help guide smart surface design toward NC-based applications.
Nanochemistry provides powerful synthetic tools allowing one to combine different materials on a single nanostructure, thus unfolding numerous possibilities to tailor their properties toward diverse functionalities. yuval_david_2023Herein, we review the progress in the field of semiconductor–metal hybrid nanoparticles (HNPs) focusing on metal–chalcogenides–metal combined systems. The fundamental principles of their synthesis are discussed, leading to a myriad of possible hybrid architectures including Janus zero-dimensional quantum dot-based systems and anisotropic quasi 1D nanorods and quasi-2D platelets. The properties of HNPs are described with particular focus on emergent synergetic characteristics. Of these, the light-induced charge-separation effect across the semiconductor–metal nanojunction is of particular interest as a basis for the utilization of HNPs in photocatalytic applications. The extensive studies on the charge-separation behavior and its dependence on the HNPs structural characteristics, environmental and chemical conditions, and light excitation regime are surveyed. Combining the advanced synthetic control with the charge-separation effect has led to demonstration of various applications of HNPs in different fields. A particular promise lies in their functionality as photocatalysts for a variety of uses, including solar-to-fuel conversion, as a new type of photoinitiator for photopolymerization and 3D printing, and in novel chemical and biomedical uses.
2022
Lior Asor, Liu, Jing , Xiang, Shuting , Tessler, Nir , Frenkel, Anatoly I. , and Banin, Uri . 11/17/2022. Zn-Doped P-Type Inas Nanocrystal Quantum Dots. Advanced Materials, 35, 5. . Publisher's Version Abstract

Doped heavy metal-free III-V semiconductor nanocrystal quantum dots are of great interest both from the fundamental aspects of doping in highly confined structures, and from the applicative side of utilizing such lior_a_2022building blocks in the fabrication of p-n homojunction devices. InAs nanocrystals, that are of particular relevance for short wave IR detection and emission applications, manifest heavy n-type character poising a challenge for their transition to p-type behavior. We present p-type doping of InAs nanocrystals with Zn - enabling control over the charge carrier type in InAs QDs field effect transistors. The post-synthesis doping reaction mechanism is studied for Zn precursors with varying reactivity. Successful p-type doping was achieved by the more reactive precursor, diethylzinc. Substitutional doping by Zn2+ replacing In3+ is established by X-ray absorption spectroscopy analysis. Furthermore, enhanced near IR photoluminescence is observed due to surface passivation by Zn as indicated from elemental mapping utilizing high resolution electron microscopy corroborated by X-ray photoelectron spectroscopy study. The demonstrated ability to control the carrier type, along with the improved emission characteristics, paves the way towards fabrication of optoelectronic devices active in the short wave IR region utilizing heavy-metal free nanocrystal building blocks.

Shira Gigi, Naor, Tom , Waiskopf, Nir , Stone, David , Natan, Michal , Jacobi, Gila , Levi, Adar , Remennik, Sergei , Levi-Kalisman, Yael , Banin, Ehud , and Banin, Uri . 11/1/2022. Photoactive Antimicrobial Cuzno Nanocrystals . The Journal Of Physical Chemistry C, 126, 44, Pp. 18683-18691. . Publisher's Version Abstract
Semiconductor nanocrystals (NCs) are promising photocatalysts due to their high surface area to volume ratio and tunable physicochemical properties. Of particular interest are earth-abundant metal oxides, such as ZnO and CuO, which are stableShira G CuZnO under ambient conditions and in aqueous media and are environmentally and biologically compatible. While CuO NCs are efficient catalytic and antimicrobial materials featuring strong and broad absorption in the visible region, their challenging surface chemistry and low colloidal stability so far limited their wide implementation as photocatalysts. On the other hand, colloidal ZnO NCs function as excellent photocatalysts in various media, but their absorption is limited to the UV region. Herein, colloidal antimicrobial Cu1–xZnxO NCs are synthesized via a facile and cost-effective method, forming a unique spatial dependent structure and composition, with higher zinc concentration on the surface. The doped NCs show enhanced antimicrobial activity increasing with higher amount of dopant. Furthermore, the NCs exhibit superior antimicrobial activity upon visible light illumination effectively eradicating even multidrug resistant bacteria, due to increased ion migration and photocatalytic formation of reactive oxygen species. Such Cu1–xZnxO NCs, therefore, show promise as biocompatible antimicrobial materials that can be utilized under ambient conditions in diverse scenarios enabled by wet chemical processing.
Oren Elishav, Stone, David , Tsyganok, Anton , Jayanthi, Swetha , Ellis, David S. , Yeshurun, Tamir , Maor, Itzhak I. , Levi, Adar , Beilin, Vadim , Shter, Gennady E. , Yerushalmi, Roie , Rothschild, Avner , Banin, Uri , and Grader, Gideon S. . 9/12/2022. Composite Indium Tin Oxide Nanofibers With Embedded Hematite Nanoparticles For Photoelectrochemical Water Splitting. Acs Applied Materials & Interfaces, 14, 37, Pp. 41851-41860. . Publisher's Version Abstract

Hematite is a classical photoanode material for photoelectrochemical water splitting due to its stability, performance, and low cost. However, the effect of particle size is still a question due to the charge transfer to the electrodes.Oren Elishav In this work, we addressed this subject by the fabrication of a photoelectrode with hematite nanoparticles embedded in close contact with the electrode substrate. The nanoparticles were synthesized by a solvothermal method and colloidal stabilization with charged hydroxide molecules, and we were able to further use them to prepare electrodes for water photo-oxidation. Hematite nanoparticles were embedded within electrospun tin-doped indium oxide nanofibers. The fibrous layer acted as a current collector scaffold for the nanoparticles, supporting the effective transport of charge carriers. This method allows better contact of the nanoparticles with the substrate, and also, the fibrous scaffold increases the optical density of the photoelectrode. Electrodes based on nanofibers with embedded nanoparticles display significantly enhanced photoelectrochemical performance compared to their flat nanoparticle-based layer counterparts. This nanofiber architecture increases the photocurrent density and photon-to-current internal conversion efficiency by factors of 2 and 10, respectively.

Lior Verbitsky, Jasrasaria, Dipti , Banin, Uri , and Rabani, Eran . 9/12/2022. Hybridization And Deconfinement In Colloidal Quantum Dot Molecules. The Journal Of Chemical Physics, 157, 134502. . Publisher's Version Abstract

The structural, electronic, and optical properties of CdSe/CdS core-shell colloidal quantum dot molecules, a new class of coupled quantum dot dimers, are explored using atomistic approaches. Unlike the case of dimers grown by molecular bealior_v_hyb_vs_decm epitaxy, simulated strain profile maps of free-standing colloidal dimers show negligible additional strain resulting from the attachment. The electronic properties of the relaxed dimers are described within a semiempirical pseudopotential model combined with the Bethe-Salpeter equation within the static screening approximation to account for electron-hole correlations. The interplay of strain, hybridization (tunneling splitting), quantum confinement, and electron-hole binding energies on the optical properties is analyzed and discussed. The effects of the dimensions of the neck connecting the two quantum dot building blocks, as well as the shell thickness, are studied.

Somnath Koley, Cui, Jiabin , Panfil, Yossef E, Ossia, Yonatan , Levi, Adar , Scharf, Einav , Verbitsky, Lior , and Banin, Uri . 8/2022. Photon Correlations In Colloidal Quantum Dot Molecules Controlled By The Neck Barrier. Matter, 5, Pp. 1-18. . Publisher's Version Abstract

The charge redistribution upon optical excitation of various necked homodimer colloidal quantum dot molecules (CQDMs) is investigated using single-particle emission spectroscopy. By tuning the hybridization of the electron wavefunctions at a fixed center-to-center distance through controlling the neck girth, we reveal two coupling limits: matter_2022on one hand, a ‘‘connected-but-confined’’ situation where neighboring CQDs are weakly fused to each other, manifesting a weak-coupling regime, and on the other hand, a ‘‘connected-anddelocalized’’ situation where the neck is filled beyond the facet size, leading to a rod-like architecture manifesting strong coupling. The interplay between the radiative and non-radiative Auger decays of these states turns emitted photons from the CQDMs in the weakcoupling regime highly bunched unlike CQD monomers, while the antibunching is regained at the strong-coupling regime. This work sets an analogy for the artificial molecule CQDMs with regular molecules, where the two distinct regimes of weak and strong coupling correspond to ionic- or covalent-type bonding, respectively.

Einav Scharf, Krieg, Franziska , Elimelech, Orian , Oded, Meirav , Levi, Adar , Dirin, Dmitry N. , Kovalenko, Maksym V. , and Banin, Uri . 5/23/2022. Ligands Mediate Anion Exchange Between Colloidal Lead-Halide Perovskite Nanocrystals. Nano Letters, 22, 11, Pp. 4340 - 4346. . Publisher's Version Abstract

The soft lattice of lead-halide perovskite nanocrystals (NCs) allows tuning their optoelectronic characteristics via anion exchange by introducing halide salts to a solution of perovskite NCEinav2022s. Similarly, cross-anion exchange can occur upon mixing NCs of different perovskite halides. This process, though, is detrimental for applications requiring perovskite NCs with different halides in close proximity. We study the effects of various stabilizing surface ligands on the kinetics of the cross-anion exchange reaction, comparing zwitterionic and ionic ligands. The kinetic analysis, inspired by the “cage effect” for solution reactions, showcases a mechanism where the surface capping ligands act as anion carriers that diffuse to the NC surface, forming an encounter pair enclosed by the surrounding ligands that initiates the anion exchange process. The zwitterionic ligands considerably slow down the cross-anion exchange process, and while they do not fully inhibit it, they confer improved stability alongside enhanced solubility relevant for various applications.

Yossef E. Panfil, Cui, Jiabin , Koley, Somnath , and Banin, Uri . 3/15/2022. Complete Mapping Of Interacting Charging States In Single Coupled Colloidal Quantum Dot Molecules. Acs Nano, 16, 4, Pp. 5566 - 5576. . Publisher's Version Abstract

Colloidal quantum dots (CQDs), major building blocks in modern optoelectronic devices, have so far been synthesized with only one emission center where the exciton resides. Recent development of coupled colloidal quantum dots molecules (CQDM), where two core–shell CQDs are fused to form two emission centers in close proximity, allows exploration of how charge carriers in one CQD affect the charge carriers in the other CQD. Yossi_2022Cryogenic single particle spectroscopy reveals that while CQD monomers manifest a simple emission spectrum comprising a main emission peak with well-defined phonon sidebands, CQDMs exhibit a complex spectrum with multiple peaks that are not all spaced according to the known phonon frequencies. Based on complementary emission polarization and time-resolved analysis, this is assigned to fluorescence of the two coupled emission centers. Moreover, the complex peak structure shows correlated spectral diffusion indicative of the coupling between the two emission centers. Utilizing Schrödinger-Poisson self-consistent calculations, we directly map the spectral behavior, alternating between neutral and charged states of the CQDM. Spectral shifts related to electrostatic interaction between a charged emission center and the second emission center are thus fully mapped. Furthermore, effects of moving surface charges are identified, whereby the emission center proximal to the charge shows larger shifts. Instances where the two emission centers are negatively charged simultaneously are also identified. Such detailed mapping of charging states is enabled by the coupling within the CQDM and its anisotropic structure. This understanding of the coupling interactions is progress toward quantum technology and sensing applications based on CQDMs.

Orian Elimelech, Aviv, Omer , Oded, Meirav , Peng, Xiaogang , Harries, Daniel , and Banin, Uri . 2/14/2022. Entropy Of Branching Out: Linear Versus Branched Alkylthiols Ligands On Cdse Nanocrystals. Acs Nano, 16, Pp. 4308–4321. . Publisher's Version Abstract

Surface ligands of semiconductor nanocrystals (NCs) play key roles in determining their colloidal stability and physicochemical properties and are thus enablers also for the NCs flexible manipulation toward numerous applications. Orian_2022Attention is usually paid to the ligand binding group, while the impact of the ligand chain backbone structure is less discussed. Using isothermal titration calorimetry (ITC), we studied the effect of structural changes in the ligand chain on the thermodynamics of the exchange reaction for oleate coated CdSe NCs, comparing linear and branched alkylthiols. The investigated alkylthiol ligands differed in their backbone length, branching position, and branching group length. Compared to linear ligands, lower exothermicity and entropy loss were observed for an exchange with branched ligands, due to steric hindrance in ligand packing, thereby justifying their previous classification as “entropic ligands”. Mean-field calculations for ligand binding demonstrate the contribution to the overall entropy originating from ligand conformational entropy, which is diminished upon binding mainly by packing of NC-bound ligands. Model calculations and the experimental ITC data both point to an interplay between the branching position and the backbone length in determining the entropic nature of the branched ligand. Our findings suggest that the most entropic ligand should be a short, branched ligand with short branching group located toward the middle of the ligand chain. The insights provided by this work also contribute to a future smarter NC surface design, which is an essential tool for their implementation in diverse applications.

Tal Cohen, Waiskopf, Nir , Levi, Adar , Stone, David , Remennik, Sergei , and Banin, Uri . 1/17/2022. Flow Synthesis Of Photocatalytic Semiconductor&Ndash;Metal Hybrid Nanocrystals. Nanoscale, 14, 5, Pp. 1944 - 1953. . Publisher's Version Abstract

Semiconductor–metal hybrid nanostructures are promising materials for photocatalytic applications, providing high efficiencies compared to their composing counterparts. So far, the synthesis of such hybrid nanoparticles was limited to batch reactors, achieving tunability while demonstrating how each of the nanocrystals’ characteristics affects photocatalytic performances. Flow synthesis of photocatalytic semiconductor–metal hybrid nanocrystals Yet, new methodologies should be established to increase the synthetic yield while maintaining high control over the resulting structures. Herein, scalable advanced flow techniques are introduced, yielding ZnSe–metal hybrid nanoparticles either in a thermal growth or photo-induced growth regime. Firstly, thermal gold growth in the flow reactor is achieved with good control over the metal tip size and the nanoparticle morphology. We address the dependence of the reaction on temperature, the precursor to nanorod molar ratios, and additional parameters. Additionally, light-induced growth by the flow reactor is demonstrated for platinum clusters. The quality of the resulting hybrids is directly demonstrated by their functionality in photocatalytic hydrogen generation by water reduction, displaying enhanced activity compared to bare ZnSe nanorods. The fairly straightforward adaptation of such powerful flow-reaction techniques to scale-up photocatalytic hybrid nanoparticle syntheses takes them one step forwards towards the realization of their potential in real-life application scenarios.

2021
Adar Levi, Verbitsky, Lior , Waiskopf, Nir , and Banin, Uri . 12/29/2021. Sulfide Ligands In Hybrid Semiconductor&Ndash;Metal Nanocrystal Photocatalysts: Improved Hole Extraction And Altered Catalysis. Acs Applied Materials & Interfaces, 14, Pp. 647–653. . Publisher's Version Abstract

Hybrid semiconductor–metal nanocrystals manifest efficient photocatalytic activity related to the metal domain promoting charge carrier separation and providing an active catalytic site. The surface properties of such nanoparticles are also of paramount importance in determining their photocatalytic activity. Addressing the combination of surface effects in catalysis on metals, with the electronic properties of hybrid nanoparticles, we examined the effect of coating CdS–Au hybrid nanoparticles with sulfide, an anion that is expected to bind strongly to both domains, on the photocatalytic functionality.AMI2021 Upon sulfide coating, one-electron processes – namely the oxidative production of hydroxyl radicals and the reductive production of superoxide – were increased, whereas the activity for two-electron reduction processes – H2 and hydrogen peroxide generation – was hampered. These findings indicate a double-edged sword effect for sulfide coating that on one side relieves the hole extraction bottleneck from the semiconductor segment and, on the other hand, poisons the metal domain restricting its reductive capacity for the two-electron processes requiring a chemisorption step on the metal surface. The work further demonstrates the importance of surface properties for the photocatalytic action of such hybrid nanoparticle systems.

David Stone, Koley, Somnath , Remennik, Sergei , Asor, Lior , Panfil, Yossef E. , Naor, Tom , and Banin, Uri . 11/2021. Luminescent Anisotropic Wurtzite Inp Nanocrystals. Nano Letters, 21, 23, Pp. 10032–10039. . Publisher's Version Abstract

Indium phosphide (InP) nanocrystals are emerging as an alternative to heavy metal containing nanocrystals for optoelectronic applications but lag behind in terms of synthetic control. Herein, luminescent wurtzite InP nanocrystals with narrow size distribution were synthesized via a cation exchange reaction from hexagonal Cu3P nanocrystals. A comprehensive surface treatment with NOBF4 was performed, which removes excess copper while generating stoichiometric In/P nanocrystals with fluoride surface passivation. NL_2021The attained InP nanocrystals manifest a highly resolved absorption spectrum with a narrow emission line of 80 meV, and photoluminescence quantum yield of up to 40%. Optical anisotropy measurements on ensemble and single particle bases show the occurrence of polarized transitions directly mirroring the anisotropic wurtzite lattice, as also manifested from modeling of the quantum confined electronic levels. This shows a green synthesis path for achieving wurtzite InP nanocrystals with desired optoelectronic properties including color purity and light polarization with potential for diverse optoelectronic applications.Indium phosphide (InP) nanocrystals are emerging as an alternative to heavy metal containing nanocrystals for optoelectronic applications but lag behind in terms of synthetic control. Herein, luminescent wurtzite InP nanocrystals with narrow size distribution were synthesized via a cation exchange reaction from hexagonal Cu3P nanocrystals. A comprehensive surface treatment with NOBF4 was performed, which removes excess copper while generating stoichiometric In/P nanocrystals with fluoride surface passivation. The attained InP nanocrystals manifest a highly resolved absorption spectrum with a narrow emission line of 80 meV, and photoluminescence quantum yield of up to 40%. Optical anisotropy measurements on ensemble and single particle bases show the occurrence of polarized transitions directly mirroring the anisotropic wurtzite lattice, as also manifested from modeling of the quantum confined electronic levels. This shows a green synthesis path for achieving wurtzite InP nanocrystals with desired optoelectronic properties including color purity and light polarization with potential for diverse optoelectronic applications.