Publications de Brennan James Walder

Iron incorporation in synthetic precipitated calcium silicate hydrates

David Lyndon Emsley, Paul Bowen, Brennan James Walder, Jirawan Siramanont

Effect of Fe3+ on the precipitation of synthetic calcium silicate hydrates (C-S-H) under controlled conditions has been evaluated. Using extremely basic either initial calcium nitrate or sodium silicate solutions (pH > 11), incipient formation of ferrihydr ...

Pergamon-Elsevier Science Ltd2021

Colloidal-ALD-Grown Core/Shell CdSe/CdS Nanoplatelets as Seen by DNP Enhanced PASS-PIETA NMR Spectroscopy

David Lyndon Emsley, Brennan James Walder, Laura Piveteau

Ligand exchange and CdS shell growth onto colloidal CdSe nanoplatelets (NPLs) using colloidal atomic layer deposition (c-ALD) were investigated by solid-state nuclear magnetic resonance (NMR) experiments, in particular, dynamic nuclear polarization (DNP) e ...

2020

Cd-113 Solid-State NMR at 21.1 T Reveals the Local Structure and Passivation Mechanism of Cadmium in Hybrid and All-Inorganic Halide Perovskites

David Lyndon Emsley, Dominik Józef Kubicki, Albert Hofstetter, Daniel Prochowicz, Brennan James Walder

Cadmium doping has recently emerged as an efficacious strategy for defect suppression and band gap tuning in hybrid as well as all-inorganic halide perovskites. However, the cadmium speciation in these materials is unknown. Here, we use high-field cadmium- ...

2020

Hyperpolarization transfer pathways in inorganic materials

David Lyndon Emsley, Brennan James Walder, Pinelopi Moutzouri, Nicolas Luc Matthey, Snaedis Björgvinsdóttir

Dynamic nuclear polarization can be used to hyperpolarize the bulk of proton-free inorganic materials in magic angle spinning NMR experiments. The hyperpolarization is generated on the surface of the material with incipient wetness impregnation and from th ...

Academic Press Inc - Elsevier Science2020

The Atomic-Level Structure of Cementitious Calcium Aluminate Silicate Hydrate

David Lyndon Emsley, Karen Scrivener, Paul Bowen, Pierrick Berruyer, Brennan James Walder, Pinelopi Moutzouri, Aslam Kunhi Mohamed, Jirawan Siramanont, Maya Nicole Harris, Mattia Negroni

Despite use of blended cements containing significant amounts of aluminum for over 30 years, the structural nature of aluminum in the main hydration product, calcium aluminate silicate hydrate (C-A-S-H), remains elusive. Using first-principles calculations ...

2020

Measurement of Proton Spin Diffusivity in Hydrated Cementitious Solids

David Lyndon Emsley, Brennan James Walder, Federico Maria Paruzzo, Jayasubba Reddy Yarava, Bradley Floyd Chmelka

The study of hydration and crystallization processes involving inorganic oxides is often complicated by poor long-range order and the formation of heterogeneous domains or surface layers. In solid-state NMR, H-1-H-1 spin diffusion analyses can provide info ...

2019

Atomic-level passivation mechanism of ammonium salts enabling highly efficient perovskite solar cells

Michael Graetzel, Shaik Mohammed Zakeeruddin, David Lyndon Emsley, Jacques-Edouard Moser, Jingshan Luo, Dominik Józef Kubicki, Fabrizio Giordano, Brennan James Walder, Andrés Burgos Caminal, Essa Awadh R Alharbi

The high conversion efficiency has made metal halide perovskite solar cells a real break-through in thin film photovoltaic technology in recent years. Here, we introduce a straight-forward strategy to reduce the level of electronic defects present at the i ...

Nature Research2019

Characterization of semiconductor nanocrystals using advanced NMR spectroscopy

David Lyndon Emsley, Brennan James Walder, Laura Piveteau

AMER CHEMICAL SOC2019

Chemical exchange at the ferroelectric phase transition of lead germanate revealed by solid state Pb-207 nuclear magnetic resonance

David Lyndon Emsley, Arnaud Magrez, Brennan James Walder, Jasmine Viger-Gravel, Claudia Esther Avalos

The nature of the dynamics and structural changes that take place at the ferroelectric phase transition in lead oxides is a rich field of study. Solid-state nuclear magnetic resonance (NMR) of Pb-207 is well suited to study the local structure and disorder ...

ROYAL SOC CHEMISTRY2019

Line narrowing in H-1 NMR of powdered organic solids with TOP-CT-MAS experiments at ultra-fast MAS

David Lyndon Emsley, Brennan James Walder, Federico Maria Paruzzo

The residual broadening observed in H-1 spectra of rigid organic solids at natural abundance under 111 kHz magic angle spinning (MAS) is typically a few hundred Hertz. Here we show that refocusable and non-refocusable interactions contribute roughly equall ...

Academic Press Inc - Elsevier Science2019