An Integrated Enhancement Solution for 24-hour Colorful Imaging

The current industry practice for 24-hour outdoor imaging is to use a silicon camera supplemented with near-infrared (NIR) illumination. This will result in color images with poor contrast at daytime and absence of chrominance at nighttime. For this dilemma, all existing solutions try to capture RGB and NIR images separately. However, they need additional hardware support and suffer from various drawbacks, including short service life, high price, specific usage scenario, etc. In this paper, we propose a novel and integrated enhancement solution that produces clear color images, whether at abundant sunlight daytime or extremely low-light nighttime. Our key idea is to separate the VIS and NIR information from mixed signals, and enhance the VIS signal adaptively with the NIR signal as assistance. To this end, we build an optical system to collect a new VIS-NIR-MIX dataset and present a physically meaningful image processing algorithm based on CNN. Extensive experiments show outstanding results, which demonstrate the effectiveness of our solution.Comment: AAAI 2020 (Oral

Carbon Dots: Synthesis, Characterization, and Investigation of Optical Properties

Recently, carbon nanoparticles have emerged to represent a new class of zero-dimensional carbon nanostructures in contrast to the more beautiful and defined C60-fullerenes. Despite their undefined and seemingly uninspiring properties, surface passivation or functionalization reveals high performance optical properties intrinsic to the carbon nanoparticles, resulting in “core-shell” nanostructures dubbed carbon dots (CDots). Generally defined as small carbon nanoparticles with various surface passivation schemes (i.e. organic or biological molecules), CDots display bright and colorful fluorescence emissions in addition to high performance photoinduced redox, and other properties, rivaling those of the more traditional semiconductor quantum dots (QDs) while retaining the biologically and environmentally benign characteristics of carbon. In this dissertation, CDots were synthesized through the surface functionalization of carbon nanoparticles with 2,2’-(ethylenedioxy)-bis(ethylamine) (EDA), forming a highly stable aqueous suspension of EDA-CDots. The resulting dispersion could be considered “solution-like”, allowing for the analysis and characterization of these CDots with solution phase spectroscopy techniques, and were shown to be highly fluorescent and structurally compact, with the brightest fluorescence emissions occurring over the spectral region covered by popular fluorescent proteins, such as green fluorescent proteins (GFPs). In terms of photoexcited state properties, photoinduced redox interactions of these CDots with of nitrotoluenes were probed through fluorescence quenching using steady-state and time-resolved fluorescence spectroscopy techniques. The emission properties of EDA-CDots were efficiently quenched by nitrotoluenes, which, mechanistically, result from highly efficient diffusion-controlled electron-transfer interactions at low quencher concentrations. Excitation wavelength dependent emission properties of CDots were systematically studied in steady-state and time-resolved fluorescence regimes. CDots were shown to exhibit characteristic emission properties with strong excitation wavelength dependence for fluorescence quantum yields, while the fluorescence lifetimes only exhibited weak excitation wavelength dependencies. In order to better understand CDots fluorescence emissions and a photoexcited state deactivation mechanisms, a model consisting of two sequential processes leading to fluorescence emissions has been constructed, in which one process is primarily responsible for the observed excitation wavelength dependent emissions. In an effort to specifically tailor the optical properties of carbon dots, core modified CDots have recently been reported, such that red sensitive chromophores, such as Nile blue (NB), are incorporated into the core carbon structure of polyethylene glycol functionalized CDots. The resulting nanostructure exhibits enhanced optical properties beyond what should be expected for the combination of these two species. The modified core structure displays an electronically integrated photoexcited state with excellent optical properties, such as effective visible and near-IR photon-harvesting, corresponding bright fluorescent emissions, and efficient photoninduced electron transfer (PET) serving as both excellent electron donors and acceptors

Plasmon-Mediated Drilling in Thin Metallic Nanostructures

Tetrahedral nanopyramids made of silver and gold over ITO/glass surfaces are fabricated. Our protocol is based on nanosphere lithography (NSL) with the deposition of thicker metal layers. After removing the microspheres used in the NSL process, an array of metallic tetrahedral nanostructures of ~350-400 nm height is formed. The reported procedure avoids the use of any stabilizing surfactant molecules that are generally necessary to segregate the individual particles onto surfaces. We focus here on the optical and the physical properties of these plasmonic surfaces using near-field spectroscopy in conjunction with finite difference time domain (FDTD) modeling of the electric field. Remarkably, FDTD shows that the localized surface plasmon resonance is confined in the plane formed by the edges of two facing pyramids that is parallel to the polarization of the impinging excitation laser. The variable gap between the edges of two adjacent pyramids shows a broader localized surface plasmon and larger specific surface as opposed to the usual nanotriangle array. Localized enhancement of the electric field is experimentally investigated by coating the plasmonic surface with a thin film of photosensitive azopolymer onto the surface of the nanopyramids. The reported deformation upon radiation of the surface topography is visualized by atomic force microscopy and suggests the potentiality of these 3D nanopyramids for near-field enhancement. This last feature is clearly confirmed by surface-enhanced Raman scattering measurement with 4-nitrothiophenol molecules deposited on the pyramid platforms. The potentiality of such 3D nanostructures in plasmonics and surface spectroscopy is thus clearly demonstrated

Development of an Electrical Impedance Tomography Algorithm to Estimate the Scalp and Skull Conductivity

Tese de mestrado, Engenharia Biomédica e Biofísica , 2022, Universidade de Lisboa, Faculdade de CiênciasElectrical impedance tomography (EIT) is a technique used to estimate the conductivity value of biological tissues. EIT comprises two parts: forward and inverse solver. The forward solver aims measuring the electric potential in the brain after applying constant current directly on the scalp by at least two electrodes. Then, the inverse solver uses those electric potential values to predict the conductivity of the brain tissues. The project described in this report aimed to evaluate the possibility of using an EIT algorithm to predict scalp and skull conductivities to generate more realist head models. These heads models are used to generate transcranial direct current stimulation (tDCS) electrode montages for patients with mental disorders. This project took place in Neuroelectrics, a company already with a pipeline able to generate these montages based on the anatomy of the patient but using standard conductivity values for brain tissues. After testing the EIT algorithm, the project also aimed to evaluate the impact of using standard head models or personalized ones not only with the anatomy of the patient but also with the correct values for conductivity brain tissues on the generation of tDCS electrode montages. In fact, the results of this study showed that changes in the conductivity values can have a huge impact in the electric field applied in the brain, which means that it is important to generate a montage that takes the correct values into account instead of standard ones. In more detail, after comparing the error obtained with montages generated by template head model used in Neuroelectrics and montages generated by EIT template developed in this project, it was possible to state that there was a reduction around 21% in the error of the average of the electric field applied in the brain and a reduction around 10% in the error of the focality of the stimulation

Extending the body: a niche design for seamstresses

As consumers, we are faced with a glut of products, the source of which we are dimly aware. Being unaware of the source of products, we are also unaware of the conditions under which they are produced. Designers often have an analogous relation with users. Unless we are directly involved with field research or user testing, we have an indirect relationship with our audience; hence, the conditions under which the products designed are actually used. To add to the gulf between users and designers, we are often tasked with designing mass-produced items meant to serve the needs of a vast population of users. With such an approach, a diversity of users and practices are overlooked. And tools are not always optimized to suit a specific task or audience. As an antithesis to this scenario, this thesis seeks out a local context for design solutions. Research was carried out at a local garment factory, resulting in the design of a work- surface solution for seamstresses. By focusing on a specific local context of user artifact interaction, a niche design process is derived. Traditional product design research methods entailing field work and user-centered design are supplemented with Human-Computer Interaction theories such as Activity Theory, and frameworks borrowed from the interdisciplinary study of extended cognition. A softening of the boundary of the individual is an umbrella idea connecting these various frameworks. Humans are seen as adaptive and plastic systems adopting tools and technologies as cognitive enhancements. The work surface design for seamstresses that is arrived at is evaluated in terms of its potential as a cognitive enhancement. The author seeks to put forth a rudimentary notion of a niche design process that seeks out local contexts and adapts design to specific audiences

Biodegradable Nitrogen-Doped Carbon Nanodots for Non-Invasive Photoacoustic Imaging and Photothermal Therapy

Multifunctional nanoparticles have been widely investigated for biomedical applications, such as imaging, therapy, and drug delivery. Especially, photoactive nanoparticles have received great attention as theranostic agents because of their heat-generating abilities after exposure to laser irradiation. However, photostability and safety issues have been the technical hurdles for further clinical applications. Here, we designed nitrogen (N)-doped carbon nanodots (N-CNDs) that have strong absorption in the near-infrared region, high photostability, and excellent biodegradability. Optimized N-CNDs can be utilized not only as a new photoacoustic (PA) imaging agent but also as a superior photothermal therapy (PTT) agent in vivo because of their strong optical absorption at a specific wavelength. We used N-CNDs to perform in vivo/ex vivo noninvasive PA imaging of sentinel lymph nodes via local delivery and performed PTT for cancer ablation therapy. Finally, biodegradation and renal clearance were confirmed by performing whole-body PA monitoring and a degradation test

Porous Silicon Photonics for Label-Free Interferometric Biosensing and Flat Optics

This dissertation uses porous silicon as a material platform to explore novel optical effects in three domains: (i) It studies dispersion engineering in integrated waveguides to achieve high performance group index sensing. With proper design parameters, the sensor waveguides can theoretically achieve 6 times larger group index shift compared to the actual bulk effective refractive index shift. We demonstrate the guided mode confinement factor to be a key parameter in design and implementation of these waveguides. (ii) It explores multicolor laser illumination to experimentally demonstrate perceptually enhanced colorimetric sensing, overcoming the limitations faced by many contemporary colorimetric sensors. Our technique allows our sensor to achieve ~ 7 to 30 times higher sensitivities and ~ 30 to 1000 times lower limits of detection compared to current colorimetric sensors. (iii) It develops a novel imprinting technique to laterally pattern arbitrary refractive index on the porous silicon surface to realize nanoscale flat optical components. We demonstrate and characterize imprinted flat lens arrays and show how myriads of possible applications are to be implemented using this nanoimprinting technique. While the material primarily used in this dissertation is porous silicon, many of the demonstrated techniques are generalizable and can be extended towards other materials of interest to achieve high performance patterning and sensing

Turning date palm fronds into biocompatible mesoporous fluorescent carbon dots

Here, we demonstrate the synthesis of mesoporous carbon dots (Cdot) from date palm fronds and their excellent excitation wavelength-independent photoluminescence (PL), with high photo- and storage-stability, superior biocompatibility and thermal and electrical conductivity for the first-time by a simple, green, one-step carbonization method. Interestingly, the as-obtained Cdot manifest the spherical shape of about 50 nm average diameter having surface mesopores of size less than 10 nm with sp2 hybridized carbon. The as-synthesised mesoporous Cdot, first of its kind, evince yellow-green PL (preferred over blue PL for biological applications) around 450 nm under excitation wavelength range of 320–420 nm with absolute quantum yield of 33.7% exhibiting high photo- and storage-stability. The thermal and electrical conductivity of Cdot/water nanofluids without any surfactants is illustrated. Application of Cdot as interfacial material in organic photovoltaic cell is manifested. The Cdot exhib visible sunlight driven photocatalytic and antibacterial activity. Mesoporous Cdot further reveal excellent biocompatibility with fibroblast cell (greater than 95% viability). The novelty of this study in the formation of multifunctional mesoporous Cdot from date palm fronds could inspire both research and industrial interests in the synthesis of biomass-derived Cdot and their application in a wide array of fields