Dataset of 3D computer models of Late Miocene Mount Messenger Formation outcrops in New Zealand, built with UAV drones.

The aim of constructing 3D computer models of outcrops of the Mount Messenger Formation using unmanned aerial vehicle (UAV) drone technology was to enable better visualization and potential for analysis of deep-water sedimentary systems in Taranaki Basin, New Zealand. The Late Miocene-aged strata crop out along the north Taranaki coast of western North Island, New Zealand. The Mount Messenger Formation sandstone and siltstone beds are outstanding examples of deep-water sedimentary strata. These strata can be observed in outcrop sections, as well as in offshore drillholes (wireline logs) and in seismic reflection data acquired immediately offshore of the north Taranaki coastal section. In previous research undertaken on the Mount Messenger Formation in North Taranaki Basin, geologists used photographs and coupled these with observations and descriptions of strata in the field. Modern UAV drone technology now enables 3D perspectives to be obtained of outcrop sections, which greatly improves geometrical analysis of the rocks. This type of analysis, coupled with mapping of seismic reflection data in the immediate offshore area has enabled us to better understand the nature of Mount Messenger Formation deep-water sedimentary strata and to interpret the associated paleogeography with implications for energy resource exploration and evaluation. Using UAV drone photogrammetry, we acquired ∼3000 images of the Mount Messenger Formation outcrop at four locations along the north Taranaki coast. Drone surveys were conducted using a real-time kinetic (RTK) global positioning system (GPS) for accurate geolocation. The surveys were conducted on a DJI Phantom 4 drone, with a focal length of 24 mm with a 20-megapixel resolution. Survey images overlapped by 80-90%. The drone work adhered to the rules and regulations of the Aviation Security Service and the University of Waikato, New Zealand. Images were captured using programmed flight paths where the drone faced the outcrops at distances ranging from ∼3-7 m. 3D computer models were constructed using Pix4Dmapper version 4.4.12 to generate dense 3D point clouds, digital surface models (DSMs), triangle meshes, and orthomosaic images of the outcrops (i.e., 3D models). Once the 3D computer models of the outcrops were constructed, they were exported out of Pix4Dmapper as ArcGIS Scene Layer Package format (.slpk) and loaded into ArcGIS Pro version 3.0.3 for further analysis. The 3D computer models comprise a rich and valuable scientific dataset that can enhance geological analysis of sedimentary strata beyond the capabilities of photographs and manual fieldwork. These models allow desktop analysis of the geology and "virtual fieldwork" by imaging areas that are commonly inaccessible on foot due to their high elevation above ground level, location in rugged and steep terrane, as well as periodic intertidal flooding. This electronic geological dataset is stored in commonly used spatial format and plain-text ASCII files, allowing the preservation of geological data in digital records, especially when the outcrops are prone to erosion and cover by vegetation. The drone model dataset can be reused by the scientific community for virtual geological fieldwork, as petroleum and water reservoir analogues, as well as for research on coastal, environmental and geotechnical topics.

Abandonment and rapid infilling of a tide-dominated distributary channel at 0.7 ka in the Mekong River Delta.

The Ba Lai distributary channel of the Mekong River Delta was abandoned and infilled with sediment during the Late Holocene, providing a unique opportunity to investigate the sediment fill, timing and mechanisms of channel abandonment in tide-dominated deltaic systems. Based on analysis and age dating of four sediment cores, we show that the channel was active since 2.6 ka and was abandoned at 0.7 ka as marked by the abrupt disappearance of the sand fraction and increase in organic matter and sediment accumulation rate. We estimate that the channel might have been filled in a time range of 45-263 years after detachment from the deltaic network, with sediment accumulation rates of centimetres to decimetres per year, rapidly storing approximately 600 Mt of organic-rich mud. We suggest that the channel was abandoned due to a sediment buildup favoured by an increase in regional sediment supply to the delta. This study highlights that mechanisms for abandonment and infilling of tide-dominated deltaic channels do not entirely fit widely used models developed for fluvial-dominated environments. Their abandonment might be driven by autogenic factors related to the river-tidal and deltaic dynamics and favoured by allogenic factors (e.g., human impact and/or climate change).

Ligand cleavage enables formation of 1,2-ethanedithiol capped colloidal quantum dot solids.

Colloidal quantum dots have garnered significant interest in optoelectronics, particularly in quantum dot solar cells (QDSCs). Here we report QDSCs fabricated using a ligand that is modified, following film formation, such that it becomes an efficient hole transport layer. The ligand, O-((9H-fluoren-9-yl)methyl) S-(2-mercaptoethyl) carbonothioate (FMT), contains the surface ligand 1,2-ethanedithiol (EDT) protected at one end using fluorenylmethyloxycarbonyl (Fmoc). The strategy enables deprotection following colloidal deposition, producing films containing quantum dots whose surfaces are more thoroughly covered with the remaining EDT molecules. To compare fabrication methods, we deposited CQDs onto the active layer: in one case, the traditional EDT-PbS/EDT-PbS is used, while in the other EDT-PbS/FMT-PbS is used. The devices based on the new EDT/FMT match the PCE values of EDT/EDT controls, and maintain a higher PCE over an 18 day storage interval, a finding we attribute to an increased thiol coverage using the FMT protocol.

Role of Surface Morphology on Exciton Recombination in Single Quantum Dot-in-Rods Revealed by Optical and Atomic Structure Correlation.

The physical structure of colloidal quantum dot (QD) nanostructures strongly influences their optical and electronic behavior. A fundamental understanding of this interplay between structure and function is crucial to fully tailor the performance of QDs and their assemblies. Here, by directly correlating the atomic and chemical structure of single CdSe-CdS quantum dot-in-rods with time-resolved fluorescence measurements on the same structures, we identify morphological irregularities at their surfaces that moderate photoluminescence efficiencies. We find that two nonradiative exciton recombination mechanisms are triggered by these imperfections: charging and trap-assisted nonradiative processes. Furthermore, we show that the proximity of the surface defects to the CdSe core of the core-shell structures influences whether the charging or trap-assisted nonradiative channel dominates exciton recombination. Our results extend to other QD nanostructures and emphasize surface roughness as a crucial parameter when designing colloidal QDs with specific excitonic fates.

Design of a Hole Trapping Ligand.

A new ligand that covalently attaches to the surface of colloidal CdSe/CdS nanorods and can simultaneously chelate a molecular metal center is described. The dithiocarbamate-bipyridine ligand system facilitates hole transfer through energetic overlap at the inorganic-organic interface and conjugation through the organic ligand to a chelated metal center. Density functional theory calculations show that the coordination of the free ligand to a CdS surface causes the formation of two hybridized molecular states that lie in the band gap of CdS. The further chelation of Fe(II) to the bipyridine moiety causes the presence of seven midgap states. Hole transfer from the CdS valence band to the midgap states is dipole allowed and occurs at a faster rate than what is experimentally known for the CdSe/CdS band-edge radiative recombination. In the case of the ligand bound with iron, a two-step process emerges that places the hole on the iron, again at rates much faster than band gap recombination. The system was experimentally assembled and characterized via UV-vis absorbance spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence spectroscopy, and energy dispersive X-ray spectroscopy. Theoretically predicted red shifts in absorbance were observed experimentally, as well as the expected quench in photoluminescence and lifetimes in time-resolved photoluminescence.