A multifunctional ribonuclease A-conjugated carbon dot cluster nanosystem for synchronous cancer imaging and therapy

Carbon dots exhibit great potential in applications such as molecular imaging and in vivo molecular tracking. However, how to enhance fluorescence intensity of carbon dots has become a great challenge. Herein, we report for the first time a new strategy to synthesize fluorescent carbon dots (C-dots) with high quantum yields by using ribonuclease A (RNase A) as a biomolecular templating agent under microwave irradiation. The synthesized RNase A-conjugated carbon dots (RNase A@C-dots) exhibited quantum yields of 24.20%. The fluorescent color of the RNase A@C-dots can easily be adjusted by varying the microwave reaction time and microwave power. Moreover, the emission wavelength and intensity of RNase A@C-dots displayed a marked excitation wavelength-dependent character. As the excitation wavelength alters from 300 to 500 nm, the photoluminescence (PL) peak exhibits gradually redshifts from 450 to 550 nm, and the intensity reaches its maximum at an excitation wavelength of 380 nm. Its Stokes shift is about 80 nm. Notably, the PL intensity is gradually decreasing as the pH increases, almost linearly dependent, and it reaches the maximum at a pH = 2 condition; the emission peaks also show clearly a redshift, which may be caused by the high activity and perfective dispersion of RNase A in a lower pH solution. In high pH solution, RNase A tends to form RNase A warped carbon dot nanoclusters. Cell imaging confirmed that the RNase A@C-dots could enter into the cytoplasm through cell endocytosis. 3D confocal imaging and transmission electron microscopy observation confirmed partial RNase A@C-dots located inside the nucleus. MTT and real-time cell electronic sensing (RT-CES) analysis showed that the RNase A@C-dots could effectively inhibit the growth of MGC-803 cells. Intra-tumor injection test of RNase A@C-dots showed that RNase A@C-dots could be used for imaging in vivo gastric cancer cells. In conclusion, the as-prepared RNase A@C-dots are suitable for simultaneous therapy and in vivo fluorescence imaging of nude mice loaded with gastric cancer or other tumors

Gradient metasurfaces: a review of fundamentals and applications

In the wake of intense research on metamaterials the two-dimensional analogue, known as metasurfaces, has attracted progressively increasing attention in recent years due to the ease of fabrication and smaller insertion losses, while enabling an unprecedented control over spatial distributions of transmitted and reflected optical fields. Metasurfaces represent optically thin planar arrays of resonant subwavelength elements that can be arranged in a strictly or quasi periodic fashion, or even in an aperiodic manner, depending on targeted optical wavefronts to be molded with their help. This paper reviews a broad subclass of metasurfaces, viz. gradient metasurfaces, which are devised to exhibit spatially varying optical responses resulting in spatially varying amplitudes, phases and polarizations of scattered fields. Starting with introducing the concept of gradient metasurfaces, we present classification of different metasurfaces from the viewpoint of their responses, differentiating electrical-dipole, geometric, reflective and Huygens' metasurfaces. The fundamental building blocks essential for the realization of metasurfaces are then discussed in order to elucidate the underlying physics of various physical realizations of both plasmonic and purely dielectric metasurfaces. We then overview the main applications of gradient metasurfaces, including waveplates, flat lenses, spiral phase plates, broadband absorbers, color printing, holograms, polarimeters and surface wave couplers. The review is terminated with a short section on recently developed nonlinear metasurfaces, followed by the outlook presenting our view on possible future developments and perspectives for future applications.Comment: Accepted for publication in Reports on Progress in Physic

Optimized, versatile diamond-based sensors : materials, fabrication and novel applications

Quantum sensing as one of the backbones of the second quantum revolution is about to enable a variety of novel applications requiring good spatial resolution and sensitivity. The atomic-sized, negatively charged nitrogen vacancy (NV) color center in single crystal diamond was found to enable magnetic field sensing at the nanoscale. Magnetic sensing using NV centers is enabled by bright photostable emission and optically addressable spin states. Due to its extraordinary coherence time, sensitivities of few nT\Hz^(1/2) can be achieved under ambient conditions. To enhance the spatial resolution of NV-based sensing, it is necessary to approach the NV center to a sample to investigate. Here, a challenging nanofabrication procedure is needed to sculpt the diamond into a photonic nanostructure usable as a scanning probe tip. In this thesis, we report on the progress towards optimizing the applicability of NV centers as quantum sensors. We investigate novel material systems promising for upscaling nanofabrication. By introducing a novel approach to enhance the adhesion of etch masks and novel plasma treatments, we optimize the reliability of the nanofabrication procedure. In addition, we study a novel near-field interaction-based sensing resource. By investigating the interaction of shallow NV centers with a monolayer of WSe2, we were able to show simultaneous near-field and magnetic field sensing using the NV center.Als eine der Säulen der zweiten Quanten-Revolution ermöglicht die Quantensensorik viele neue Anwendungen, die eine gute Ortsau ösung und Sensitivität benötigen. Das atomar kleine, negativ geladene Stickstoff-Fehlstellen (NV) Farbzentrum in einkristallinem Diamant ermöglicht das Detektieren von Magnetfeldern auf Nanomaÿstäben. Magnetfelddetektion mittels NV Zentren wird durch helle, photostabile Emission und optisch adressierbare Spin-Zustände ermöglicht. Aufgrund seiner auÿergewöhnlichen Kohärenzzeit erreicht es Sensitivitäten von einigen nT/Hz^(1/2) unter Umgebungsbedingungen. Zur Verbesserung der Ortsauflösung NV-basierter Sensorik, muss das NV-Zentrum an die zu untersuchende Probe angenähert werden. Dies erfordert einen herausfordernden Nanfabrikationsprozess, um den Diamanten in eine photonische Struktur zu formen, die als Rastersonde nutzbar ist. Diese Arbeit beschreibt Fortschritte zur Optimierung der Anwendbarkeit von NV-Zentren als Quantensensoren. Wir untersuchen neuartige Materialien, die vielversprechend für die Skalierbarkeit des Prozesses sind. Durch neue Ansätze zur Verbesserung der Adhäsion von Ätzmasken und neue Plasmabehandlungen optimieren wir die Zuverlässigkeit der Nanofabrikation. Zudem analysieren wir einen neuen, auf Nahfeldwechselwirkung beruhenden Sensorikansatz. Bei der Untersuchung der Wechselwirkung von oberflächennahen NV-Zentren mit monolagigem WSe2 konnten wir das gleichzeitige Erfassen von Nah- und magnetischen Feldern mittels NV-Zentren zeigen

Non-Destructive Characterization of Magnetic Polymeric Scaffolds using Terahertz Time-of-Flight Imaging

Magnetic Scaffolds MagS are 3D composite materials, in which magnetic nanoparticles (MNPs) are used to load a polymeric matrix. Due to their wide use in various medical applications, there is an increasing demand of advanced techniques for non-destructive quality assessment procedures aimed at verifying the absence of defects and, more generally, dedicated to the characterization of MagS. In this framework, the use of TeraHertz (THz) waves for the non-destructive characterization of multifunctional scaffolds represents an open challenge for the scientific community. This paper deals with an approach for the characterization of MagS by means of a THz time-domain system used in reflection mode. THz analyses are performed on poly($\epsilon$ - capprolactone) (PCL) scaffolds magnetized with iron oxide (Fe $_{3}$ O$_{4}$) MNPs through a drop-casting deposition and tuned to obtain different distributions of MNP in the biomaterial. The proposed data processing approach allows a quantitative characterization MagS, in terms of their (estimated) thickness and refractive index. Moreover, the proposed procedure allows to identify the areas of the scaffold wherein MNP are mainly concentrated and thus, it gives us information about MNP spatial distribution

Rare earth based nanostructured materials: Synthesis, functionalization, properties and bioimaging and biosensing applications

Rare earth based nanostructures constitute a type of functional materials widely used and studied in the recent literature. The purpose of this review is to provide a general and comprehensive overview of the current state of the art, with special focus on the commonly employed synthesis methods and functionalization strategies of rare earth based nanoparticles and on their different bioimaging and biosensing applications. The luminescent (including downconversion, upconversion and permanent luminescence) and magnetic properties of rare earth based nanoparticles, as well as their ability to absorb X-rays, will also be explained and connected with their luminescent, magnetic resonance and X-ray computed tomography bioimaging applications, respectively. This review is not only restricted to nanoparticles, and recent advances reported for in other nanostructures containing rare earths, such as metal organic frameworks and lanthanide complexes conjugated with biological structures, will also be commented on.European Union 267226Ministerio de Economía y Competitividad MAT2014-54852-

Biocompatible technique for nanoscale magnetic field sensing with Nitrogen-Vacancy centers

The possibility of using Nitrogen-vacancy centers in diamonds to measure nanoscale magnetic fields with unprecedented sensitivity is one of the most significant achievements of quantum sensing. Here we present an innovative experimental set-up, showing an achieved sensitivity comparable to the state of the art ODMR protocols if the sensing volume is taken into account. The apparatus allows magnetic sensing in biological samples such as individual cells, as it is characterized by a small sensing volume and full bio-compatibility. The sensitivity at different optical powers is studied to extend this technique to the intercellular scale.Comment: 6 pages, 5 figure