2021 New's Items

Anomalous nanoparticle surface diffusion in LCTEM is revealed by deep learning-assisted analysis

Jamali V
Hargus C
Ben-Moshe A
Aghazadeh A
Ha HD
Mandadapu KK
Alivisatos AP
2021

The motion of nanoparticles near surfaces is of fundamental importance in physics, biology, and chemistry. Liquid cell transmission electron microscopy (LCTEM) is a promising technique for studying motion of nanoparticles with high spatial resolution. Yet, the lack of understanding of how the electron beam of the microscope affects the particle motion has held back advancement in using LCTEM for in situ single nanoparticle and macromolecule tracking at interfaces. Here, we experimentally studied the motion of a model system of gold nanoparticles dispersed in water and moving adjacent...

Dynamic lattice distortions driven by surface trapping in semiconductor nanocrystals

Guzelturk B
Cotts BL
Alivisatos AP
Salleo A
Rabani E
Lindenberg AM
2021

Nonradiative processes limit optoelectronic functionality of nanocrystals and curb their device performance. Nevertheless, the dynamic structural origins of nonradiative relaxations in such materials are not understood. Here, femtosecond electron diffraction measurements corroborated by atomistic simulations uncover transient lattice deformations accompanying radiationless electronic processes in colloidal semiconductor nanocrystals. Investigation of the excitation energy dependence in a core/shell system shows that hot carriers created by a photon energy considerably larger than the...

Observation of ordered organic capping ligands on semiconducting quantum dots via powder X-ray diffraction

Calvin JJ
Kaufman TM
Sedlak AB
Crook MF
Alivisatos AP
2021

Powder X-ray diffraction is one of the key techniques used to characterize the inorganic structure of colloidal nanocrystals. The comparatively low scattering factor of nuclei of the organic capping ligands and their propensity to be disordered has led investigators to typically consider them effectively invisible to this technique. In this report, we demonstrate that a commonly observed powder X-ray diffraction peak around q=1.4Å...

The chain of chirality transfer in tellurium nanocrystals

Ben-Moshe A
Silva Ad
Müller A
Abu-Odeh A
Harrison P
Waelder J
Niroui F
Ophus C
Minor AM
Asta M
Theis W
Ercius P
Alivisatos AP
2021

Despite persistent and extensive observations of crystals with chiral shapes, the mechanisms underlying their formation are not well understood. Although past studies suggest that chiral shapes can form because of crystallization in the presence of chiral additives, or because of an intrinsic tendency that stems from the crystal structure, there are many cases in which these explanations are not suitable or have not been tested. Here, an investigation of model tellurium nanocrystals provides insights into the chain of chirality transfer between crystal structure and shape. We show...

Characterization of Carrier Cooling Bottleneck in Silicon Nanoparticles by Extreme Ultraviolet (XUV) Transient Absorption Spectroscopy

Porter IJ
Lee A
Cushing SK
Chang HT
Ondry JC
Alivisatos AP
Leone SR
2021

Silicon nanoparticles have the promise to surpass the theoretical efficiency limit of single-junction silicon photovoltaics by the creation of a “phonon bottleneck,” a theorized slowing of the cooling rate of hot optical phonons that in turn reduces the cooling rate of hot carriers in the material. Verifying the presence of a phonon bottleneck in silicon nanoparticles requires simultaneous resolution of electronic and structural changes at short timescales. Here, extreme ultraviolet transient absorption spectroscopy is used to observe the excited-state electronic and lattice dynamics...

Elucidating the Role of Halides and Iron during Radiolysis-Driven Oxidative Etching of Gold Nanocrystals Using Liquid Cell Transmission Electron Microscopy and Pulse Radiolysis

Crook MF
Laube C
Moreno-Hernandez IA
Kahnt A
Zahn S
Ondry JC
Liu A
Alivisatos AP
2021

Graphene liquid cell transmission electron microscopy (TEM) has enabled the observation of a variety of nanoscale transformations. Yet understanding the chemistry of the liquid cell solution and its impact on the observed transformations remains an important step toward translating insights from liquid cell TEM to benchtop chemistry. Gold nanocrystal etching can be used as a model system to probe the reactivity of the solution. FeCl3 has been widely used to promote gold oxidation in bulk and liquid cell TEM studies, but the roles of the halide and iron...

Redox Mediated Control of Electrochemical Potential in Liquid Cell Electron Microscopy

Moreno-Hernandez IA
Crook MF
Ondry JC
Alivisatos AP
2021

Liquid cell electron microscopy enables the study of nanoscale transformations in solvents with high spatial and temporal resolution, but for the technique to achieve its potential requires a new level of control over the reactivity caused by radical generation under electron beam irradiation. An understanding of how to control electron–solvent interactions is needed to further advance the study of structural dynamics for complex materials at the nanoscale. We developed an approach that scavenges radicals with redox species that form well-defined redox couples and control the...

Outdoor performance of a tandem InGaP/Si photovoltaic luminescent solar concentrator

Phelana M
Needell DR
Bauser H
Su H
Deceglie M
Theingi S
Koscher B
Nett Z
Bukowsky CR
Ilic O
Stradins P
Geisz J
Nuzzo R
Alivisatos AP
Atwater HA
2021

We report the design, fabrication and outdoor characterization of a tandem luminescent solar concentrator/Si multi-junction photovoltaic module. Our tandem LSC/Si device consists of an InGaP LSC functioning as a top cell and a passivated contact Si bottom cell. The LSC comprises of an InGaP microcell array coupled to a polymer waveguide, loaded with CdSe/CdS core-shell quantum dot luminophores. The light trapping efficiency of the LSC waveguide is enhanced by encapsulation with photoluminescence trapping mirrors consisting of dielectric multilayer thin films. We demonstrate the...

Unraveling excitation energy transfer assisted by collective behaviors of vibrations

Li Z
Ko L
Yang Z
Sarovar M
Whaley KB
2021

Abstract We investigate how collective behaviors of vibrations such as cooperativity and interference can enhance energy transfer in a nontrivial way, focusing on an example of a donor–bridge–acceptor trimeric chromophore system coupled to two vibrational degrees of freedom. Employing parameters selected to provide an overall uphill energy transfer from donor to acceptor, we use numerical calculations of dynamics in a coupled exciton–vibration basis, together with perturbation-based analytics and calculation of vibronic spectra, to identify clear spectral features of single- and...

Engineering high-coherence superconducting qubits

Siddiqi I
2021

Advances in materials science and engineering have played a central role in the development of classical computers and will undoubtedly be critical in propelling the maturation of quantum information technologies. In approaches to quantum computation based on superconducting circuits, as one goes from bulk materials to functional devices, amorphous films and non-equilibrium excitations — electronic and phononic — are introduced, leading to dissipation and fluctuations that limit the computational power of state-of-the-art qubits and processors. In this Review, the major sources of...