Graphene setting the stage: tracking DNA hybridization with nanoscale resolution

In this study we use nanophotonic effects of graphene to study DNA hybridization: the z−4 nanoscale distance-dependence of the fluorescence lifetime for fluorophores located in the vicinity of graphene is for the first time used to track a DNA hybridization reaction with nanoscale resolution in real time. First, a nanostaircase with ≈2 nm steps from 0 to a total height of 48 nm is used as a nanoruler to confirm the distance dependence law. We find that the axial sensitivity is suited to determine the nanoscale surface roughness of these samples. The proof-of-concept DNA experiments in aqueous medium involve the hybridization of fluorescently labelled DNA beacons attached to CVD grown graphene with complementary (target) DNA added in solution. We track the conformational changes of the beacons statistically by determining the fluorescence lifetimes of the labelling dye and converting them into nanoscale distances from the graphene. In this way, we are able to monitor the vertical displacement of the label during DNA-beacon unfolding with an axial resolution reaching down to 1 nm. The measured distance increase during the DNA hybridization reaction of about 10 nm matches the length of the target DNA strand. Furthermore, the width of the fluorescence lifetime distributions could be used to estimate the molecular tilt angle of the hybridized ds-DNA configuration. The achieved nanoscale sensitivity opens innovation opportunities in material engineering, genetics, biochemistry and medicine.INL received support for this project from the CCDR-N via the project 'Nanotechnology based functional solutions' (Grant No. NORTE-01-0145-FEDER-000019) and from the Portuguese Foundation for Science and Technology (FCT) via the project 'ON4SupremeSens' PTDC/NAN-OPT/29417/2017. Edite Figueiras received a Marie Curie fellowship via the EU-EC COFUND program 'NanoTRAINforGrowth' (Grant No. 600375). U Minho research was partially supported by the FCT in the framework of the Strategic Funding UID/FIS/04650/2013

Spectral-temporal luminescence properties of Colloidal CdSe/ZnS Quantum Dots in relevant polymer matrices for integration in low turn-on voltage AC-driven LEDs

This work employs spectral and spectral-temporal Photoluminescence (PL) spectroscopy techniques to study the radiative mechanisms in colloidal CdSe/ZnS Quantum Dot (QD) thin films without and with 1% PMMA polymer matrix embedding (QDPMMA). The observed bimodal transient-spectral PL distributions reveal bandgap transitions and radiative recombinations after interdot electron transfer. The PMMA polymer embedding protects the QDs during the plasma-sputtering of inorganic layers electroluminescent (EL) devices, with minimal impact on the charge transfer properties. Further, a novel TiO2-based, all-electron bandgap, AC-driven QLED architecture is fabricated, yielding a surprisingly low turn-on voltage, with PL-identical and narrow-band EL emission. The symmetric TiO2 bilayer architecture is a promising test platform for alternative optical active materials.European Commission, Seventh Framework Programme (600375); European Commission, Horizon 2020 Framework Programme (828841); European Regional Development Fund, INTERREG V-A España-Portugal (POCTEP) 2014-2020 (0181_NANOEATERS_1_EP); CCDR-N (NORTE-01-0145-FEDER-000019); Fundação para a Ciência e a Tecnologia (UIDB/04650/2020)

Room-temperature emitters in wafer-scale few-layer hBN by atmospheric pressure CVD

Hexagonal boron nitride (hBN) is a two-dimensional, wide band gap semiconductor material suitable for several technologies. 2D hBN appeared as a viable platform to produce bright and optically stable single photon emitters (SPEs) at room temperature, which are in demand for quantum technologies. In this context, one main challenge concerns the upscaling of 2D hBN with uniform spatial and spectral distribution of SPE sources. In this work we optimized the atmospheric-pressure chemical vapor deposition (APCVD) growth and obtained large-area 2D hBN with uniform fluorescence emission properties. We characterized the hBN films by a combination of electron microscopy, Raman and X-ray photoelectron spectroscopy techniques. The extensive characterization revealed few-layer, polycrystalline hBN films (∼3 nm thickness) with balanced stoichiometry and uniformity over 2″ wafer scale. We studied the fluorescence emission properties of the hBN films by multidimensional hyperspectral fluorescence microscopy. We measured simultaneously the spatial position, intensity, and spectral properties of the emitters, which were exposed to continuous illumination over minutes. Three main emission peaks (at 538, 582, and 617 nm) were observed, with associated replica peaks red-shifted by ∼53 nm. A surface emitter density of ∼0.1 emitters/μm2 was found. A comparative test with pristine hBN nanosheets produced by liquid-phase exfoliation (LPE) was performed, finding that CVD and LPE hBN possess analogous spectral emitter categories in terms of peak position/intensity and density. Overall, the line-shape and wavelength of the emission peaks, as well as the other measured features, are consistent with single-photon emission from hBN. The results indicate that APCVD hBN might proficiently serve as a SPE platform for quantum technologies.We acknowledge the financial support of i) the project “GEMIS – Graphene-enhanced Electro Magnetic Interference Shielding,” with the reference POCI-01-0247-FEDER-045939, co-funded by COMPETE 2020 – Operational Programme for Competitiveness and Internationalization and FCT –Science and Technology Foundation, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); ii) the project "Graphene and novel thin films for super-resolution microscopy and bio-sensing" (PTDC/NAN-OPT/29417/2017) financed by ERDF, through the Competitiveness and Internationalization Operational Program (POCI) by Portugal 2020 and by the Portuguese Foundation for Science and Technology (FCT) with references POCI-01-0145-FEDER-029417 and PTDC/NAN-OPT/29417/2017; iii) the FCT in the framework of the Strategic Funding UIDB/04650/2020. One of the authors (T.Q.) acknowledges the FCT financial support under the Quantum Portugal Initiative Ph.D. scholarship SFRH/BD/150646/2020. We acknowledge the support by the INL AEMIS, Micro- and Nanofabrication, and Nanophotonics and Bioimaging research core facilities

Biophysical characterization, nanoscale composition and cell uptake studies of pH-sensitive drug delivery systems

Nanocarrier-based chemotherapy is one of the few nanotechnology-based medical therapies that reached the clinics. This happened already in 1995, when the commercial anti cancer drug delivery system DOXIL® was introduced in the market [1]. Albeit these early developments, still today nanotechnology-based drug delivery systems are far from reaching optimal selectivity and controlled release ability. In our study we use different liposomal formulations designed for pH-sensitive drug release and study their biophysical characteristics, when used for trafficking paclitaxel (PTX) and doxorubicin (DOX), both widely used chemotherapeutic anti-cancer drugs. Our work describes a combined spectroscopy and imaging approach to evaluate the biophysical properties of liposomal formulations. We study the nanoscale composition of the nanocarriers using molecular rulers in a fluorescence quenching assay, and analyze the cell uptake characteristics based on the autofluorescence of DOX using confocal microscopy.info:eu-repo/semantics/publishedVersio

Brain-inspired nanophotonic spike computing:challenges and prospects

Nanophotonic spiking neural networks (SNNs) based on neuron-like excitable subwavelength (submicrometre) devices are of key importance for realizing brain-inspired, power-efficient artificial intelligence (AI) systems with high degree of parallelism and energy efficiency. Despite significant advances in neuromorphic photonics, compact and efficient nanophotonic elements for spiking signal emission and detection, as required for spike-based computation, remain largely unexplored. In this invited perspective, we outline the main challenges, early achievements, and opportunities toward a key-enabling photonic neuro-architecture using III-V/Si integrated spiking nodes based on nanoscale resonant tunnelling diodes (nanoRTDs) with folded negative differential resistance. We utilize nanoRTDs as nonlinear artificial neurons capable of spiking at high-speeds. We discuss the prospects for monolithic integration of nanoRTDs with nanoscale light-emitting diodes and nanolaser diodes, and nanophotodetectors to realize neuron emitter and receiver spiking nodes, respectively. Such layout would have a small footprint, fast operation, and low power consumption, all key requirements for efficient nano-optoelectronic spiking operation. We discuss how silicon photonics interconnects, integrated photorefractive interconnects, and 3D waveguide polymeric interconnections can be used for interconnecting the emitter-receiver spiking photonic neural nodes. Finally, using numerical simulations of artificial neuron models, we present spike-based spatio-temporal learning methods for applications in relevant AI-based functional tasks, such as image pattern recognition, edge detection, and SNNs for inference and learning. Future developments in neuromorphic spiking photonic nanocircuits, as outlined here, will significantly boost the processing and transmission capabilities of next-generation nanophotonic spike-based neuromorphic architectures for energy-efficient AI applications. This perspective paper is a result of the European Union funded research project ChipAI in the frame of the Horizon 2020 Future and Emerging Technologies Open programme.</p

3D Polymer Architectures for the Identification of Optimal Dimensions for Cellular Growth of 3D Cellular Models

Organ-on-chips and scaffolds for tissue engineering are vital assay tools for pre-clinical testing and prediction of human response to drugs and toxins, while providing an ethical sound replacement for animal testing. A success criterion for these models is the ability to have structural parameters for optimized performance. Here we show that two-photon polymerization fabrication can create 3D test platforms, where scaffold parameters can be directly analyzed by their effects on cell growth and movement. We design and fabricate a 3D grid structure, consisting of wall structures with niches of various dimensions for probing cell attachment and movement, while providing easy access for fluorescence imaging. The 3D structures are fabricated from bio-compatible polymer SZ2080 and subsequently seeded with A549 lung epithelia cells. The seeded structures are imaged with confocal microscopy, where spectral imaging with linear unmixing is used to separate auto-fluorescence scaffold contribution from the cell fluorescence. The volume of cellular material present in different sections of the structures is analyzed, to study the influence of structural parameters on cell distribution. Furthermore, time-lapse studies are performed to map the relation between scaffold parameters and cell movement. In the future, this kind of differentiated 3D growth platform, could be applied for optimized culture growth, cell differentiation, and advanced cell therapies

Smart drug delivery systems for cancer therapy

Ideal nanocarrier-based therapy, contains first a controlled mechanism for drug delivery, to minimize side effects in healthy tissues, and second has the ability to provide a controlled drug release to extend the therapeutic duration of the therapeutic treatment. Nanocarrier based chemotherapy is one of the few nanotechnology-based medical therapies that reached the clinics, already in 1995, when the commercial anti cancer drug delivery system DOXIL® was introduced in the market, but available systems are far from optimal selectivity and controlled release. Our work describes a combined spectroscopy and imaging study to evaluate the two aspects of a smart drug delivery system. In our study we used these DODAX:MO (1:2) formulations with a diameter of approx. 100 nm to study the biophysical characteristics when used for trafficking paclitaxel (PTX) and doxorubicin (DOX), both widely used chemotherapeutic anti-cancer drugs. Taking advantage of the of DOX intrinsic fluorescence also the cell uptake is studied for DODAB:MO (1:2) liposomal formulations.info:eu-repo/semantics/publishedVersio

Oscillator Finite-Difference Time-Domain (O-FDTD) electric field propagation model: integrated photonics and networks

The recently developed Lorentz Oscillator Model-inspired Oscillator Finite-Difference Time-Domain (O-FDTD) is one of the simplest FDTD models ever proposed, using a single field equation for electric field propagation. We demonstrate its versatility on various scales and benchmark its simulation performance against theory, conventional FDTD simulations, and experimental observations. The model’s broad applicability is demonstrated for (but not limited to) three contrasting realms: integrated photonics components on the nano- and micrometer scale, city-wide propagating radiofrequency signals reaching into the hundreds of meters scale, and for the first time, in support of 3D optical waveguide design that may play a key role in neuromorphic photonic computational devices

Cityscape LoRa signal propagation predicted and tested using real-world building-data based O-FDTD simulations and experimental characterization

The age of the Internet of Things (IoT) and smart cities calls for low-power wireless communication networks, for which the Long-Range (LoRa) is a rising star. Efficient network engineering requires the accurate prediction of the Received Signal Strength Indicator (RSSI) spatial distribution. However, the most commonly used models either lack the physical accurateness, resolution, or versatility for cityscape real-world building distribution-based RSSI predictions. For this purpose, we apply the 2D electric field wave-propagation Oscillator Finite-Difference Time-Domain (O-FDTD) method, using the complex dielectric permittivity to model reflection and absorption effects by concrete walls and the receiver sensitivity as the threshold to obtain a simulated coverage area in a 600 × 600 m2 square. Further, we report a simple and low-cost method to experimentally determine the signal coverage area based on mapping communication response-time delays. The simulations show a strong building influence on the RSSI, compared against the Free-Space Path (FSPL) model. We obtain a spatial overlap of 84% between the O-FDTD simulated and experimental signal coverage maps. Our proof-of-concept approach is thoroughly discussed compared to previous works, outlining error sources and possible future improvements. O-FDTD is demonstrated to be most promising for both indoors and outdoors applications and presents a powerful tool for IoT and smart city planners.European Commission | Ref. 0181 NANOEATERS 1 EPComissão de Coordenação e Desenvolvimento Regional do Norte (Portugal) | Ref. NORTE-01-0145-FEDER-000019European Commission | Ref. FETOPEN-01-2018-2019-2020, n. 828841Xunta de Galicia | Ref. ED431B 2018/57Ministerio de Economía, Industria y Competitividad (España) | Ref. FIS2017-83762-