Reading the Number of Extra Dimensions in the Spectrum of Hawking Radiation

After a brief review of the production and decay of Schwarzschild-like (4+n)-dimensional black holes in the framework of theories with Large Extra Dimensions, we proceed to derive the greybody factors and emission rates for scalars, fermions and gauge bosons on the brane. We present and discuss analytic and numerical methods for obtaining the above results, and demonstrate that both the amount and type of Hawking radiation emitted by the black hole can help us to determine the number of spacelike dimensions that exist in nature.Comment: 8 pages, Latex file, 1 figure, to appear in the proceedings of the String Phenomenology 2003 Conference, Durham, UK, 29th July-4th August, 200

Direct optical excitation of a fullerene-incarcerated metal ion

The endohedral fullerene Er3N@C80 shows characteristic 1.5 micron photoluminescence at cryogenic temperatures associated with radiative relaxation from the crystal-field split Er3+ 4I13/2 manifold to the 4I15/2 manifold. Previous observations of this luminescence were carried out by photoexcitation of the fullerene cage states leading to relaxation via the ionic states. We present direct non-cage-mediated optical interaction with the erbium ion. We have used this interaction to complete a photoluminescence-excitation map of the Er3+ 4I13/2 manifold. This ability to interact directly with the states of an incarcerated ion suggests the possibility of coherently manipulating fullerene qubit states with light

Semiconducting end-perfluorinated P3HT–fullerenic hybrids as potential additives for P3HT/IC70BA blends

An efficient route to synthesise hybrid polymers consisting of a semiconducting polymer and a fullerene unit, for BHJ OPV devices is presented herein. The synthetic procedure is based on the in situ functionalisation of regioregular polythiophenes of various molecular weights with perfluorophenyl moieties at the ω end position of the polymeric chains, after the GRIM polymerisation reaction. Each of the perfluorophenyl moieties is then decorated with an azide group, and employed in a [3+2] cycloaddition reaction with fullerene species, i.e. C70 or IC70MA, yielding P3HT-fullerene hybrids covalently linked via aziridine bridges. The effectiveness of the purification procedures of the above organic and hybrid materials were evaluated by extended spectroscopic and chromatographic methods. The optical and electrochemical characterisation of the resulting hybrid structures revealed that the unique optoelectronic properties of the P3HT polymers are retained in the hybrid materials. Whereas the morphological properties are largely affected by the introduction of the C70 and IC70MA fullerenes. The enhanced and tunable nanophase separation observed in the polymerfullerene hybrid films coupled with their excellent optoelectronic properties makes them exciting potential polymeric additives for the P3HT:IC70BA active blends

Multiscale interactions of liquid, bubbles and solid phases in ultrasonic fields revealed by multiphysics modelling and ultrafast X-ray imaging

Data availability: Data will be made available on request. Appendix A. Supplementary data: Supplementary data to this article can be found online at: https://doi.org/10.1016/j.ultsonch.2022.106158.Copyright © 2022 The Authors. The volume of fluid (VOF) and continuous surface force (CSF) methods were used to develop a bubble dynamics model for the simulation of bubble oscillation and implosion dynamics under ultrasound. The model was calibrated and validated by the X-ray image data acquired by ultrafast synchrotron X-ray. Coupled bubble interactions with bulk graphite and freely moving particles were also simulated based on the validated model. Simulation and experiments quantified the surface instability developed along the bubble surface under the influence of ultrasound pressure fields. Once the surface instability exceeds a certain amplitude, bubble implosion occurs, creating shock waves and highly deformed, irregular gas-liquid boundaries and smaller bubble fragments. Bubble implosion can produce cyclic impulsive stresses sufficient enough to cause µs fatigue exfoliation of graphite layers. Bubble-particle interaction simulations reveal the underlying mechanisms for efficient particle dispersion or particle wrapping which are all strongly related to the oscillation dynamics of the bubbles and the particle surface properties.UK Engineering and Physical Sciences Research Council (Grant Nos. EP/R031819/1; EP/R031665/1; EP/R031401/1; EP/R031975/1); Royal Society

Effect of Temperature and Acoustic Pressure During Ultrasound Liquid-Phase Processing of Graphite in Water

Copyright © 2021 The Author(s). Ultrasound-assisted liquid-phase exfoliation is a promising method for manufacturing two-dimensional materials. Understanding the effect of ultrasonication parameters such as the temperature and input power on the developed pressure field is pivotal for optimization of the process. Limited research has been carried out to determine the optimal temperature for exfoliation, with some data generating disputed results. Simply maximizing the sonication power does not necessarily produce a higher yield because of shielding. In this study, a high-temperature calibrated cavitometer was used to measure the acoustic pressure generated in different graphite solutions in deionized water at various temperatures (from 10°C to 70°C) and input power conditions (from 20% to 100%). In addition, high-speed optical imaging provided insight on the shock wave generation from transient bubble collapses under different sonication conditions. The optimal sono-exfoliation parameters were determined to be 20% input power at 10°C for graphite flake solution, and 100% input power at 40°C to 50°C for graphite powder solution.UK Engineering and Physical Sciences Research Council (EPSRC) to the project “Sustainable and industrially scalable ultrasonic liquid phase exfoliation technologies for manufacturing 2D advanced functional materials” (EcoUltra2D), with grant nos. EP/R031665/1; EP/R031401/1; EP/R031819/1; EP/R031975/1

Ultrasonic exfoliation of graphene in water: A key parameter study

Liquid Phase Exfoliation (LPE) is an efficient method for graphene flake exfoliation and considered to be compatible with industrial production requirements. However, most of available LPE methods require the uses of harmful and expensive solvents for chemical exfoliation prior to mechanical dispersion of the flakes, and therefore an additional step is needed to remove the contamination caused by the added chemicals, making the process complex, costly, unsafe and detrimental to the environment. By studying the effects of key ultrasonic LPE parameters, our study demonstrates the possibility to control the production and quality of few-layer graphene flakes in pure water in a relatively short period of time. The driving frequency of an ultrasonic source, a higher acoustic cavitation intensity and uniform distribution of the cavitation events in the sonicated volume are the key parameters for controlling the thickness, surface area and production yield of few-layer graphene flakes. The results are discussed in the context of mechanical exfoliation. This opens a direction for developing LPE into a cost effective, clean, environmentally friendly, and scalable manufacturing process for the next generation of two-dimensional nanomaterials for industrial-scale applications.UK Engineering and Physical Sciences Research Council (EPSRC) “Sustainable and industrially scalable ultrasonic liquid phase exfoliation technologies for manufacturing 2D advanced functional materials” (EcoUltra2D) (grant nos. EP/R031665/1; EP/R031401/1; EP/R031819/1; EP/R031975/1); Royal Society

Effects of green solvents and surfactants on the characteristics of few-layer graphene produced by dual-frequency ultrasonic liquid phase exfoliation technique

Appendix A. Supplementary data: available online at https://www.sciencedirect.com/science/article/pii/S0008622323000696?via%3Dihub#appsec1 .Copyright © 2023 The Authors. . Nowadays, one of the promising methods for scalable graphene production is ultrasound-aided liquid phase exfoliation (ULPE) of graphite. Two current limiting factors of ULPE are the use of harmful solutions (such as N-Methyl-2-pyrrolidone or Dimethylformamide) and a relatively low graphene yield. In this study, we demonstrate a new dual frequency (20 kHz and 1174 kHz) ULPE approach in various eco-friendly media, which enabled us to produce various few-layer graphene (FLG) solutions of high quality. By implementing sophisticated characterisation techniques consisting of Raman spectroscopy, UV–vis spectroscopy and high-resolution electron microscopy, the final graphene flakes structure was confirmed to correlate the properties of each individual solution. The thinner (∼3 layers) and larger (∼1.5 μm2) flakes were observed while using just water, with the highest yield (11%) of smaller FLG flakes to be achieved in the mixture of water and a surfactant. In order to understand the cavitation mechanism in different solutions, the ULPE process was investigated by acoustic measurements. This study demonstrates the crucial role of ethanol (as a solvent) and surfactants as it regulates the cavitation power and intensity of the ultrasonic field and, thereby, the cavitation effectiveness. It is suggested that the mixture of water, ethanol and a surfactant is the best medium for ULPE process where a high yield of low-defective FLG flakes can be obtained in a solution stable at least for 3 months (around 80%).This study is a part of the project “Sustainable and industrially scalable ultrasonic liquid phase exfoliation technologies for manufacturing 2D advanced functional materials” (EcoUltra2D) funded by the UK Engineering and Physical Sciences Research Council (EPSRC) under the grant nos. EP/R031665/1; EP/R031401/1; EP/R031819/1; EP/R031975/1

Bang-bang control of fullerene qubits using ultra-fast phase gates

Quantum mechanics permits an entity, such as an atom, to exist in a superposition of multiple states simultaneously. Quantum information processing (QIP) harnesses this profound phenomenon to manipulate information in radically new ways. A fundamental challenge in all QIP technologies is the corruption of superposition in a quantum bit (qubit) through interaction with its environment. Quantum bang-bang control provides a solution by repeatedly applying `kicks' to a qubit, thus disrupting an environmental interaction. However, the speed and precision required for the kick operations has presented an obstacle to experimental realization. Here we demonstrate a phase gate of unprecedented speed on a nuclear spin qubit in a fullerene molecule (N@C60), and use it to bang-bang decouple the qubit from a strong environmental interaction. We can thus trap the qubit in closed cycles on the Bloch sphere, or lock it in a given state for an arbitrary period. Our procedure uses operations on a second qubit, an electron spin, in order to generate an arbitrary phase on the nuclear qubit. We anticipate the approach will be vital for QIP technologies, especially at the molecular scale where other strategies, such as electrode switching, are unfeasible

Pauli spin blockade in carbon nanotube double quantum dots

We report Pauli spin blockade in an impurity defined carbon nanotube double quantum dot. We observe a pronounced current suppression for negative source-drain bias voltages which is investigated for both symmetric and asymmetric coupling of the quantum dots to the leads. The measured differential conductance agrees well with a theoretical model of a double quantum dot system in the spin-blockade regime which allows us to estimate the occupation probabilities of the relevant singlet and triplet states. This work shows that effective spin-to-charge conversion in nanotube quantum dots is feasible and opens the possibility of single-spin readout in a material that is not limited by hyperfine interaction with nuclear spins.Comment: 7 pages, 5 figure