Nanoscience News (<front>)

Advanced Materials, EarlyView.

Abstract

Metal defect engineering is a highly effective strategy for addressing the prevalent high overpotential issues associated with transition metal oxides functioning as dual-function commercial oxygen reduction reaction/ oxygen evolution reaction catalysts for increasing their activity and stability. However, the high formation energy of metal defects poses a challenge to the development of strategies to precisely control the selectivity during metal defect formation. We used density functional theory calculations to demonstrate that altering the pathway of metal defect formation released metal atoms as metal chlorides, which effectively reduced the formation energy of defects. The metal defects on the monometallic metal oxide surface (Mn, Fe, Co, and Ni) are selectively produced using chlorine plasma. The characterization and density functional theory calculations reveal that catalytic activity is enhanced owing to electronic delocalization induced by metal defects, which reduces the theoretical overpotential. Notably, ab initio molecular dynamics calculations, ex-situ XPS, and in-situ ATR-SEIRAS suggested that metal defects effectively improved the adsorption of reactive species on active sites and enhanced the efficiency of product desorption, thereby boosting catalytic performance.

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Abstract

Cancer stem cells (CSCs) are one of the determinants of tumor heterogeneity and are characterized by self-renewal, high tumorigenicity, invasiveness, and resistance to various therapies. To overcome the resistance of traditional tumor therapies resulting from CSCs, a strategy of double drug sequential therapy (DDST) for CSC-enriched tumors is proposed in this study and was realized utilizing our developed double layered hollow mesoporous cuprous oxide nanoparticles (DL-HMCONs). The high drug loading contents of camptothecin (CPT) and all-trans retinoic acid (ATRA) demonstrate that our DL-HMCON can be used as a generic drug delivery system (DDS). ATRA and CPT can be sequentially loaded in and released from CPT3@ATRA3@DL-HMCON@HA. The DDST mechanisms of CPT3@ATRA3@DL-HMCON@HA for CSC-containing tumors have been demonstrated as follows: 1) the first release of ATRA from the outer layer induces differentiation from CSCs with high drug resistance to non-CSCs with low drug resistance; 2) the second release of CPT from the inner layer causes apoptosis of non-CSCs; and 3) the third release of Cu+ from DL-HMCON itself triggers the Fenton-like reaction and GSH depletion, resulting in ferroptosis of non-CSCs. Our CPT3@ATRA3@DL-HMCON@HA has been verified to possess high DDST efficacy for CSC-enriched tumors with high biosafety.

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Abstract

We report a new nanoporous amorphous carbon (NAC) structure that achieves both ultrahigh strength and high electrical conductivity, which are usually incompatible in porous materials. By using modified spark plasma sintering, we create three amorphous carbon phases with different atomic bonding configurations. The composite consists of an amorphous sp2-carbon matrix mixed with amorphous sp3-carbon and amorphous graphitic motif. NAC structure has isotropic electrical conductivity of up to 12,000 S/m, a Young's modulus of up to ∼5 GPa, and Vickers hardness of over 900 MPa. These properties are superior to those of existing conductive nanoporous materials. Direct investigation of the multiscale structure of this material through transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and machine learning-based electron tomography revealed that the origin of the remarkable material properties is the well-organized sp2/sp3 amorphous carbon phases with a core-shell-like architecture, where the sp3-rich carbon forms a resilient core surrounded by a conductive sp2-rich layer. Our research not only introduces novel material with exceptional properties, but also opens new opportunities for exploring amorphous structures and designing high-performance materials.

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Abstract

Germanium-based monochalcogenides (i.e., GeS and GeSe) with desirable properties are promising candidates for the development of next-generation optoelectronic devices. However, they are still stuck with challenges, such as relatively fixed electronic band structure, unconfigurable optoelectronic characteristics, and difficulty in achieving free-standing growth. Herein, we demonstrate that two-dimensional (2D) free-standing GeS1-xSex (0 ≤ x ≤ 1) nanoplates can be grown by low-pressure rapid physical vapor deposition, fulfilling a continuously composition-tunable optical bandgap and electronic band structure. By leveraging the synergistic effect of composition-dependent modulation and free-standing growth, GeS1-xSex-based optoelectronic devices exhibit significantly configurable hole mobility from 6.22 × 10−4 to 1.24 cm2V−1s−1 and tunable responsivity from 8.6 to 311 A/W (635 nm), as x varies from 0 to 1. Furthermore, the polarimetric sensitivity can be tailored from 4.3 (GeS0.29Se0.71) to 1.8 (GeSe) benefiting from alloy engineering. Finally, the tailored imaging capability is also demonstrated to show the application potential of GeS1-xSex alloy nanoplates. This work broadens the functionality of conventional binary materials and motivates the development of tailored polarimetric optoelectronic devices.

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Abstract

High-entropy alloy nanoparticles (HEAs) show great potential in emerging electrocatalysis due to their combination and optimization of multiple elements. However, synthesized HEAs often exhibit a weak interface with the conductive substrate, hindering their applications in long-term catalysis and energy conversion. Herein, we report a highly active and durable electrocatalyst composed of quinary HEAs (PtNiCoFeCu) encapsulated inside the activated carbonized wood (ACW). The self-encapsulation of HEAs is achieved during Joule heating synthesis (2060 K, 2 s) where HEAs naturally nucleate at the defect sites; In the meantime, HEAs catalyze the deposition of mobile carbon atoms to form a protective few-layer carbon shell during the rapid quenching process, thus remarkably strengthening the interface stability between HEAs and ACW. As a result, the HEAs@ACW shows not only favorable activity with an overpotential of 7 mV at 10 mA cm−2 for hydrogen evolution but also negligible attenuation during a 500-h stability test, which is superior to most reported electrocatalysts. The design of self-encapsulated HEAs inside ACW provides a critical strategy to enhance both activity and stability, which is also applicable to many other energy conversion technologies.

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Abstract

Composite materials comprising polymers and inorganic nanoparticles are promising for energy storage applications, though challenges in controlling nanoparticle dispersion often result in performance bottlenecks. Realizing nanocomposites with controlled nanoparticle locations and distributions within polymer microdomains is highly desirable for improving energy storage capabilities but has been a persistent challenge, impeding the in-depth understanding of the structure–performance relationship. In this study, we employed a facile entropy-driven self-assembly approach to fabricate block copolymer-based supramolecular nanocomposite films with highly ordered lamellar structures, which were then used in electrostatic film capacitors. The oriented interfacial barriers and well-distributed inorganic nanoparticles within the self-assembled multilaminate nanocomposites effectively suppress leakage current and mitigate the risk of breakdown, showing superior dielectric strength compared to their disordered counterparts. Consequently, the lamellar nanocomposite films with optimized composition exhibit high energy efficiency (>90% at 650 MV m–1), along with remarkable energy density and power density. Moreover, finite element simulations and statistical modeling have provided theoretical insights into the impact of the lamellar structure on electrical conduction, electric field distribution and electrical tree propagation. This work marks a significant advancement in the design of organic–inorganic hybrids for energy storage, establishing a well-defined correlation between microstructure and performance.

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Abstract

Conjugated polymers are promising materials for thermoelectric applications, however, at present few effective and well understood strategies exist to further advance their thermoelectric performance. Here we report a new model system for better understanding the key factors governing their thermoelectric properties: aligned, ribbon-phase poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) doped by ion-exchange doping. Using a range of microstructural and spectroscopic methods we study the effect of controlled incorporation of tie-chains between the crystalline domains through blending of high and low molecular weight chains. The tie chains provide efficient transport pathways between crystalline domains and lead to significantly enhanced electrical conductivity of 4810.1 S/cm, that is not accompanied by a reduction in Seebeck coefficient nor a large increase in thermal conductivity. We demonstrate respectable power factors of 172.6 µW m−1 K−2 in this model system. Our approach is generally applicable to a wide range of semicrystalline conjugated polymers and could provide an effective pathway for further enhancing their thermoelectric properties and overcome traditional trade-offs in optimization of thermoelectric performance.

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Digital Participatory Tools for Rural Communities in India to Adapt to Climate Change

With weather patterns becoming erratic, rural communities in India dependent upon agriculture, livestock, and forests for their sustenance face an intersecting crisis of environment, livelihood, and social justice. Navigating this crisis requires a multi-dimensional approach of sustainable natural resource management, done in an equitable manner to benefit the most marginalized populations, and with collectivization efforts to improve consensus building and cooperation in communities. Can data and digital technologies play a role here? I will describe the complexity of socio-ecological problems in the context of rural central India and opportunities for ICT -based interventions that can enable communities to build a shared understanding of changes taking place in their landscape, use it to plan and demand natural resource management works, and bring changes in their day-to-day resource utilization and regeneration practices. Our work leverages geospatial algorithms, machine learning on satellite data, and novel data oranization and visualization ideas, that sit in a technology stack of building blocks on which further new innovations can be created. We are also attempting a co-creation methodology to build this stack through collaboration across disciplines and borders, to solve for complexities that are beyond a single research group to manage.

Bio:

Aaditeshwar Seth is a Professor in the Department of Computer Science and Engineering at the Indian Institute of Technology Delhi, and co-founder of the social technology enterprise Gram Vaani. He is passionate about building appropriate technologies and participatory tools that can empower marginalized and oppressed communities to collectivize and voice themselves. Several million people, and over 150 organizations worldwide, have directly touched technology platforms built by Aaditeshwar’s team at Gram Vaani and his students at the ACT4D (Appropriate Computing Technologies for Development) research group at IIT Delhi. Many elements of their work have also been adopted by government departments and have influenced the use of technologies for development in the social sector. He is a recipient of the ACM SIGCHI Social Impact Award for 2022. His book published in 2022, Technology and (Dis)Empowerment: A Call to Technologists, argues that the primary goal of technologists should be to bring equality and overturn unjust social and economic structures through their inventions. He is currently focused on building the CoRE Stack (Commoning for Resilience and Equality), a digital public infrastructure for climate change adaptation, using which rural communities can be empowered with tools that enable them to manage their landscapes in a sustainable manner.

• Speaker: Aaditeshwar Seth, Indian Institute of Technology Delhi
• Friday 03 May 2024, 13:00-14:00
• Venue: FW11, William Gates Building. Zoom link: https://cl-cam-ac-uk.zoom.us/j/4361570789?pwd=Nkl2T3ZLaTZwRm05bzRTOUUxY3Q4QT09&from=addon .
• Series: Energy and Environment Group, Department of CST; organiser: lyr24.

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A biography of Tor - a cultural and technological history of power, privacy, and global politics at the internet's core

In the seminar, Dr Ben Collier will introduce the new book, Tor: From the Dark Web to the Future of Privacy (MIT Press, 2024).

SPEAKERS

• Chair: Prof Alice Hutchings
• Speaker 1: Dr Ben Collier
• Speaker 2: Professor Steven Murdoch

5:00pm, 26th April 2024 LT2 - William Gates Building 15 JJ Thomson Avenue, Cambridge, CB3 0FD

A biography of Tor – a cultural and technological history of power, privacy, and global politics at the internet’s core. Tor, one of the most important and misunderstood technologies of the digital age, is best known as the infrastructure underpinning the so-called Dark Web. But the real ‘dark web,’ when it comes to Tor, is the hidden history brought to light in this book: where this complex and contested infrastructure came from, why it exists, and how it connects with global power in intricate and intimate ways. In Tor: From the Dark Web to the Future of Privacy, Ben Collier has written, in essence, a biography of Tor – a cultural and technological history of power, privacy, politics, and empire in the deepest reaches of the internet.

The story of Tor begins in the 1990s with its creation by the US Navy’s Naval Research Lab, from a convergence of different cultural worlds. Drawing on in-depth interviews with designers, developers, activists, and users, along with twenty years of mailing lists, design documents, reporting, and legal papers, Collier traces Tor’s evolution from those early days to its current operation on the frontlines of global digital power – including the strange collaboration between US military scientists and a group of freewheeling hackers called the Cypherpunks. As Collier charts the rise and fall of three different cultures in Tor’s diverse community – the engineers, the maintainers, and the activists, each with a distinct understanding of and vision for Tor – he reckons with Tor’s complicated, changing relationship with contemporary US empire. Ultimately, the book reveals how different groups of users have repurposed Tor and built new technologies and worlds of their own around it, with profound implications for the future of the Internet.

The link for registration is (essential for those attending online) is: https://forms.gle/3o5Mjz8MevwEcbpc9

Zoom link: https://cam-ac-uk.zoom.us/j/86325192347?pwd=RTB0Vm85eXdMbmF5TnV4ZXdOWllYQT09

• Speaker: Ben Collier, University of Edinburgh
• Friday 26 April 2024, 17:00-18:00
• Venue: Online & LT2, Computer Laboratory, William Gates Building..
• Series: Computer Laboratory Security Seminar; organiser: Hridoy Sankar Dutta.

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Overcoming challenges to sustainable heat using physics-informed machine learning

Heat pumps represent a sustainable heating technology that will play a crucial role in achieving Net Zero and decarbonisation goals in the UK. Increasing data availability from Building Management Systems and the rise of physics-based learning algorithms offer a solution to the problem of assessing the energy efficiency and maintenance requirements of an aging national heat pump fleet.

• Speaker: Javier Sandoval
• Thursday 02 May 2024, 13:10-14:00
• Venue: Richard King room, Darwin College.
• Series: Darwin College Science Seminars; organiser: Dr Sandra Petrus-Reurer.

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Large-scale flow structures in turbulent Rayleigh-Bénard convection: Dynamical origin, formation, and role in material transport

The interplay of gravity with mass density inhomogeneities introduces natural (thermal) convection and represents the essential mechanism by which heat is transported in natural flows. Simultaneously, natural flows are often far more extended in the horizontal direction than in the vertical one. Motivated by these two observations and the various geo- and astrophysical applications (e.g. the solar convection zone), 3-dimensional Rayleigh-Bénard convection as the paradigm of thermal convection has been studied. This talk will cover some recent results from studying the impact of thermal (and mechanical) boundary conditions on large-scale flow structures in Rayleigh-Bénard convection by means of direct numerical simulations. It will be shown that thermal boundary conditions are crucial to the formation of long-living large-scale (turbulent) flow structures. In particular, a slow transient aggregation process — that only stops once the horizontal extent of the domain is reached — can be found once the fluid layer is subjected to Neumann-type constant heat flux boundary conditions. As a result, the temperature field in the domain is separated into one extended hot and another extended cold region. We trace this mechanism of self-organisation of flow structures back to secondary instabilities as well as an inverse cascade in spectral space. The talk will finish with a brief overview of our work on the identification of those large-scale flow structures by the use of unsupervised machine learning based on Lagrangian particle data.

• Speaker: Philipp Vieweg
• Monday 29 April 2024, 12:30-13:30
• Venue: MR5, CMS.
• Series: Geophysical and Environmental Processes; organiser: Prof. John R. Taylor.

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Iterative active learning for the rapid discovery of best-in-class multispecific antibody therapeutics

The emergence of ML-enabled technology platforms that aim to enhance molecule performance have the potential to revolutionize the way we approach drug discovery. However, without a purpose-built tech stack that puts data quality at the heart, many are destined to fail. This talk will focus on the deep integration of predictive assays, data generation, data capturing, and data pre-processing needed to enable iterative active learning cycles for lead optimization.

Link to join virtually: https://cam-ac-uk.zoom.us/j/81322468305

This talk is being recorded.

• Speaker: Dr Leonard Wossnig - CTO at LabGenius and Honorary Research Fellow in Computer Science at UCL
• Wednesday 15 May 2024, 15:05-15:55
• Venue: Lecture Theatre 1, Computer Laboratory, William Gates Building.
• Series: Wednesday Seminars - Department of Computer Science and Technology ; organiser: Ben Karniely.

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Bridging Length Scales in Electrolyte Transport Theory via the Onsager Framework

Improved understanding of transport in concentrated electrolyte solutions has important implications for energy storage, water purification, biological applications, and more. This understanding should ideally persist across length scales: we desire both continuum-level insight into macroscopic concentration and electric potential profiles as well as a molecular-level understanding of the mechanisms governing ion motion. However, the most ubiquitous theory to describe continuum-level electrolyte transport, the Stefan-Maxwell equations, yields transport coefficients which lack clear molecular-level interpretation and cannot be easily computed from molecular simulations.

In this talk, I will present the development of an alternative theory, the Onsager transport framework, to analyze transport at both the continuum and molecular levels. I discuss the integration of continuum mechanics, nonequilibrium thermodynamics, and electromagnetism to derive internal entropy production in electrolytes, yielding the Onsager transport equations: linear laws relating the electrochemical potential gradients and fluxes of each species in solution. At the atomistic level, the transport coefficients emerging from this theory directly quantify correlations in ion motion. These transport coefficients may be computed directly from molecular simulations using Green-Kubo relations derived from Onsager’s regression hypothesis. At the continuum level, the Onsager transport framework provides governing equations for solving macroscopic boundary value problems in electrochemical systems. I will present applications of the theory to both nonaqueous polyelectrolyte solutions for Li-ion batteries as well as nanoconfined electrolytes, demonstrating how the Onsager framework allows us to quantify non-ideal contributions to transport which are very challenging to access experimentally but strongly impact transport in these systems. Overall, this work provides a paradigm for rigorously analyzing transport across length scales in complex electrolyte solutions.

References

K. D. Fong, H. K. Bergstrom, B. D. McCloskey, K. K. Mandadapu. “Transport Phenomena in Electrolyte Solutions: Non-Equilibrium Thermodynamics and Statistical Mechanics.” AIChE Journal, 2020, 66, 12: e17091.

K. D. Fong, J. Self, B. D. McCloskey, K. A. Persson. “Ion Correlations and Their Impact on Transport in Polymer-Based Electrolytes.” Macromolecules, 2021, 54, 6: 2575-2591.

K. D. Fong, J. Self, B. D. McCloskey, K. A. Persson. “Onsager Transport Coefficients and Transference Numbers in Polyelectrolyte Solutions and Polymerized Ionic Liquids.” Macromolecules, 2020, 53, 21: 9503-9512.

• Speaker: Dr Kara Fong, University of Cambridge
• Wednesday 15 May 2024, 14:30-15:30
• Venue: Unilever Lecture Theatre, Yusuf Hamied Department of Chemistry.
• Series: Theory - Chemistry Research Interest Group; organiser: Lisa Masters.

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Unifying the mechanisms of the hippocampal and prefrontal cognitive maps

Cognitive maps have emerged as leading candidates, both conceptually and neurally, for explaining how brains seamlessly generalize structured knowledge across apparently different scenarios. Two brain systems are implicated in cognitive mapping: the hippocampal formation and the prefrontal cortex. Neural activity in these brain regions, however, differs during the same task, indicating that the regions have different mechanisms for cognitive mapping. In this talk, we first provide a mechanistic understanding of how the hippocampal and prefrontal systems could build cognitive maps (with the hippocampal mechanism related to transformers and the prefrontal mechanism related to RNNs/SSMs); second, we demonstrate how these two mechanisms explain a wealth of neural data in both brain regions; and lastly, we prove that the two different mechanisms are, in fact, mathematically equivalent.

• Speaker: James Whittington, Sir Henry Wellcome Postdoctoral Fellow, Stanford University & Oxford University
• Wednesday 08 May 2024, 12:15-13:15
• Venue: CBL Seminar Room, Engineering Department, 4th floor Baker building.
• Series: Computational Neuroscience; organiser: Samuel Eckmann.

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Energy Environ. Sci., 2024, Accepted Manuscript
DOI: 10.1039/D4EE00798K, PaperShaoke Guo, Shendong Tan, Jiabin Ma, Likun Chen, Ke Yang, Qiannan Zhu, Yuetao Ma, Peiran Shi, Yinping Wei, Xufei An, Qingkang Ren, Yanfei Huang, Yingman Zhu, Ye Cheng, Wei Lv, Tingzheng Hou, Ming Liu, Yanbing He, Quanhong Yang, Feiyu Kang
In composite solid-state electrolytes, the functional fillers with ferroelectric properties have demonstrated their ability to prompt the dissociation of lithium salt (LiFSI), thereby significantly enhancing ionic conductivity. However, the underlying...
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Automated Fact-Checking of Climate Change Claims with Large Language Models

Abstract not available

• Speaker: Dominik Stammbach, ETH Zürich
• Friday 10 May 2024, 13:00-14:00
• Venue: FW26, William Gates Building. Zoom link: https://cl-cam-ac-uk.zoom.us/j/4361570789?pwd=Nkl2T3ZLaTZwRm05bzRTOUUxY3Q4QT09&from=addon .
• Series: Energy and Environment Group, Department of CST; organiser: lyr24.

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Anticyclotomic $p$-adic $L$-functions for families of $U_n \times U_{n+1}$

I will report on recent work on the construction of anticyclotomic $p$-adic $L$-functions for Rankin—Selberg products. I will explain how by $p$-adically interpolating the branching law for the spherical pair $\left(U_n, U_n \times U_{n+1}\right),$ we can construct a $p$-adic $L$-function attached to cohomological automorphic representations of $U_n \times U_{n+1}$. Due to the recent proof of the unitary Gan—Gross—Prasad conjecture, this $p$-adic $L$-function interpolates the square root of all critical $L$-values, including anticyclotomic variation. Time allowing, I will explain how we can extend this result to the Coleman family of an automorphic representation.

• Speaker: Xenia Dimitrakopoulou (Warwick)
• Tuesday 30 April 2024, 14:30-15:30
• Venue: MR13.
• Series: Number Theory Seminar; organiser: Jef Laga.

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Abstract

In organic photovoltaic cells, the solution-aggregation effect (SAE) is long considered a critical factor in achieving high power-conversion efficiencies for polymer donor (PD)/non-fullerene acceptor (NFA) blend systems. However, the underlying mechanism has yet to be fully understood. Herein, based on an extensive study of blends consisting of the representative 2D-benzodithiophene-based PDs and acceptor-donor-acceptor-type NFAs, we demonstrate that SAE shows a strong correlation with the aggregation kinetics during solidification, and the aggregation competition between PD and NFA determines the phase separation of blend film and thus the photovoltaic performance. PDs with strong SAEs enable earlier aggregation evolutions than NFAs, resulting in well-known polymer-templated fibrillar network structures and superior PCEs. With the weakening of PDs’ aggregation effects, NFAs, showing stronger tendencies to aggregate, tend to form oversized domains, leading to significantly reduced external quantum efficiencies and fill factors. These trends reveal the importance of matching SAE between PD and NFA. We further evaluate the aggregation abilities of various materials and provide the aggregation ability/photovoltaic parameter diagrams of 64 PD/NFA combinations. Our work proposes a guiding criteria and facile approach to match efficient PD/NFA systems.

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Title to be confirmed

Abstract not available

• Speaker: Frank Pollmann, TU Munich
• Thursday 20 February 2025, 14:00-15:00
• Venue: TCM Seminar Room.
• Series: Theory of Condensed Matter; organiser: Gaurav.

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