This study presents the results of a replication effort aimed at reproducing key findings fromthe 2012 article "Carbon-Dot-Based Dual-Emission Nanohybrid Produces a Ratiometric Flu-orescent Sensor for In Vivo Imaging of Cellular Copper Ions" by Zhu et al. The original studyclaimed that CQDs functionalized with AE-TPEA (CQDs-TPEA) and their hybrid withCdSe/ZnS quantum dots (CdSe@C-TPEA) exhibited ratiometric fluorescence quenching uponexposure to Cu2+ ions, enabling their application as a dual-emission sensor for intracellular Cu2+imaging. Despite closely following the described synthesis and characterization protocols, wewere unable to reproduce the Cu2+-induced fluorescence quenching, undermining the primaryclaim of the original study and making it impossible to pursue the investigation in live cells.Furthermore, upon close examination of the original data, concerns regarding spectral anoma-lies and potential inconsistencies were raised, prompting us to abort the replication study.

This paper explores gold resonator effects on the optical properties of chemically synthesized clusters of CdSe/CdS/ZnS nanocrystals. To reduce optical losses, the gold is sputtered on the aggregates already embedded in a thin silica shell. This technique also allows to compare optical properties (radiation rate, far field emission) of single aggregates of different diameters before and after gold deposition. Experimental results are supported by finite-difference time domain (FDTD) simulations to understand the size-dependent behavior and the role of dipolar and quadrupolar plasmon resonances.

Optical properties of multilayer semi-conductor nano-emitters are crucially dependent on the relative energy levels of their different components. For core/shell quantum dots, the relative energy difference between conduction band edge of core and shell materials induces, depending on its value, either a confinement of the electron within the core or a delocalization of its wave function within the whole quantum dot. This results in drastic consequences on the energy and the oscillator strength of the transitions. Surprisingly, the literature currently lacks a definitive value for this energy difference, called offset, between the conduction band edge of CdSe and CdS materials. Here, we develop a theoretical model expressing energy levels and considering quantum dot dimension, core/shell interface pressure, ligands and allowing to reliably determine the conduction band offset. Its value is determined experimentally using our model and both optical and X-ray photoelectron (XPS) spectroscopies.

Efficient near-infrared (NIR) light sources are essential for a wide range of applications such as telecommunications, optoelectronic devices, biomedical sciences, infrared imaging, and machine vision. Colloidal quantum dots (QDs) have emerged as a promising platform for NIR technologies due to their tunable optical properties across the NIR spectrum, compatibility with silicon-based technology infrastructure, and ease of large-scale integration into nanophotonic systems. Coupling colloidal QDs with plasmonic structures provides an enhanced control over their optical properties. In this work, we investigate the coupling of a gold plasmonic crescent metasurface with NIR-emitting colloidal PbS/CdS QDs, at the telecommunication wavelength of 1.55 mu m. The metasurface was specifically designed to allow for the selective excitation photoluminescence (PL) enhancement with polarization control, capitalizing on the anisotropic nature of the plasmonic crescents. Maximum PL enhancement factors of 1.6 were observed, with a strong dependence on the excitation wavelength and polarization. These findings, supported by full-wave three-dimensional finite-difference-time-domain (FDTD) numerical simulations, offer strategies to control and optimize the performance of colloidal QD-based NIR light sources for a wide range of applications.

Colloidal semiconductor nanocrystals constitute materials of choice to realize microlasers, thanks to the fine control of their optical and electronic properties and to their solution processability. However, so far, lasing has mostly been obtained under high excitation, in the biexciton regime. Here, we demonstrate instead that, in high-quality cavities, lasing naturally occurs in the single exciton regime. We describe the facile fabrication of nanocrystal-coated polymeric microcavities and study their lasing characteristics. We show that the lasing threshold lies in the submonoexcitonic excitation regime for CdS/CdSe/CdS quantum shells in particular, thanks to the high quality factor of the cavities and high transition cross sections of the quantum shells. We explain these results using a comprehensive model of nanocrystal optical properties. The model correctly reproduces lasing characteristics near and above the threshold. In this regime, in contrast to previous studies, the performance of the microlasers relies mostly on the transition cross section and the Stokes shift and not on biexciton recombination or exciton-biexciton splitting. This improved understanding will enable rational design of colloidal nanocrystals for low-threshold lasing applications.

The operational instability of perovskite solar cells (PSCs) remains a key obstacle to their long-term performance and commercial deployment. While extensive efforts have been made to understand degradation mechanisms, direct probing of the buried interfaces, where critical degradation often initiates, has remained elusive. In this work, we introduce a new in situ methodology that harnesses the nanothermometric properties of embedded upconversion nanoparticles (UCNPs) placed at the buried perovskite/hole transport layer (HTL) interface. This approach allows, for the first time, real-time tracking of local interfacial temperature evolution during light-induced accelerated degradation, while simultaneously monitoring the device's optical and photovoltaic performance. Applied to PSCs with different perovskite compositions, this technique reveals non-trivial thermal signatures and distinct degradation regimes correlated with structural and optical changes observed via ex situ characterizations. The results uncover a dynamic interplay between heat accumulation, phase transformation, and material decomposition, offering insights into the spatiotemporal evolution of PSC degradation. Our work demonstrates that nanoscale thermal sensing at buried interfaces provides a powerful new diagnostic tool to elucidate the internal degradation pathways of perovskite solar cells.

Optical properties of multilayer semi-conductor nano-emitters are crucially dependent on the relative energy levelsof their different components. For core/shell quantum dots, the relative energy difference between conduction bandedge of core and shell materials induces, depending on its value, either a confinement of the electron within the coreor a delocalization of its wave function within the whole quantum dot. This results in drastic consequences on theenergy and the oscillator strength of the fundamental transition. Surprisingly, the literature currently lacks a definitivevalue for the energy difference between CdSe and CdS conduction band edges as most of the experimental studiesprovide values corresponding to specific geometries of quantum dots. Here, we develop a full theoretical modelexpressing energy levels considering core/shell interface pressure, ligands and enabling the accurate prediction ofthe bandgap value with the nanocrystal size. It allows to reliably determine the energy difference between theconduction band edge of CdSe and CdS materials, known as the conduction band offset, in such a way that this valuecan later be used to model quantum dots of any geometry. This value is determined using our model and two differentexperimental methods: optical spectroscopy and X-ray photoemission (XPS) experiments.

Abstract Background In the treatment of oral cavity cancer, margin status is one of the most critical prognostic factors. Positive margins are associated with higher local recurrence and lower survival rates. Therefore, the universal goal of oral surgical oncology is to achieve microscopically clear margins. Near-infrared fluorescence guided surgery (FGS) could improve surgical resection using fluorescent probes. αVβ6 integrin has shown great potential for cancer targeting due to its overexpression in oral cancers. Red fluorescent contrast agent IRDye 680 coupled with anti-αVβ6 peptide (IRDye-A20) represents an asset to improve FGS of oral cancer. This study investigates the potential of IRDye-A20 as a selective imaging agent in 3D three-dimensional tongue cancer cells. Methods αVβ6 integrin expression was evaluated by RT-qPCR and Western Blotting in 2D HSC-3 human tongue cancer cells and MRC-5 human fibroblasts. Targeting ability of IRDye-A20 was studied in both cell lines by flow cytometry technique. 3D tumor spheroid models, homotypic (HSC-3) and stroma-enriched heterotypic (HSC-3/MRC-5) spheroids were produced by liquid overlay procedure and further characterized using (immuno)histological and fluorescence-based techniques. IRDye-A20 selectivity was evaluated in each type of spheroids and each cell population. Results αVβ6 integrin was overexpressed in 2D HSC-3 cancer cells but not in MRC-5 fibroblasts and consistently, only HSC-3 were labelled with IRDye-A20. Round shaped spheroids with an average diameter of 400 μm were produced with a final ratio of 55%/45% between HSC-3 and MRC-5 cells, respectively. Immunofluorescence experiments demonstrated an uniform expression of αVβ6 integrin in homotypic spheroid, while its expression was restricted to cancer cells only in heterotypic spheroid. In stroma-enriched 3D model, Cytokeratin 19 and E-cadherin were expressed only by cancer cells while vimentin and fibronectin were expressed by fibroblasts. Using flow cytometry, we demonstrated that IRDye-A20 labeled the whole homotypic spheroid, while in the heterotypic model all cancer cells were highly fluorescent, with a negligible fluorescence in fibroblasts. Conclusions The present study demonstrated an efficient selective targeting of A20FMDV2-conjugated IRDye 680 in 3D tongue cancer cells stroma-enriched spheroids. Thus, IRDye-A20 could be a promising candidate for the future development of the fluorescence-guided surgery of oral cancers. Graphical Abstract

The development of whispering gallery mode (WGM) cavities as integrated light sources and sensors requires a scalable, low-cost fabrication of high-quality microcavities with integrated light sources. In particular, semiconductor quantum dots (QDs) are promising nanoemitters with highly desirable photostability and tunable optical properties, but their controlled coupling to polymeric microcavities is hampered by chemical incompatibility between the QD surface ligands and the high refractive index polymers used to fabricate microcavities. In this paper, we present a new type of polymeric WGM microdisk cavity realized by photolithography on an industrial photosensitive epoxy resin. We demonstrate the homogeneous labeling of these microcavities by CdSe/CdS/Zns QDs, thanks to a novel surface ligand and the coupling of their emission to WGMs from the microdisk cavity. The spectral properties of the WGM-coupled emission are consistent with electromagnetic simulations and indicate that the WGM quality factors can reach values higher than 6000. This demonstrates that the photolithography of high refractive epoxy resins followed by the integration of functionalized QDs enables the realization of well-controlled, high-quality WGM microresonators.

Background Oral squamous cell carcinoma (OSCC) treatment mainly relies on surgery. The status of surgical margin is a major prognostic factor for patients as positive margins are associated with lower survival. However, the anatomical particularities of this area complicate margin establishment. Fluorescence guided surgery (FGS) could be employed as an intraoperative technique to improve tumor resection and margin investigation. Quantum dots (QDs) serve as ideal contrast agents in this technique due to their brightness and stability. Since αVβ6 integrin is overexpressed in OSCC, coupling QDs with A20FMDV2 peptide (QDs-A20) targeting the αVβ6 integrin constitute a real opportunity. This study investigates the accumulation of QDs-A20 in 2D and 3D tongue cancer models, as well as QDs coupled to a scrambled version of this peptide (QDs-Scr) or without peptide (QDs-SPP), for imaging purposes. Methods CdSeCdS/ZnS quantum dots were coated with sulfobetaine polymers (QDs-SPP) and conjugated to A20FMDV2 peptide (QDs-A20) or its scrambled version (QDs-Scr). Two-dimensional (2D) and three-dimensional (3D) tongue cancer cells HSC-3 were employed to test the effectiveness of intracellular accumulation of all types of QDs. Targeting ability of each QDs was assessed by flow cytometry, while the depth of penetration into cancerous spheroids was assessed by fluorescence microscopy. Results QDs coating with sulfobetaines polymers (QDs-SPP) completely prevented their internalization by HSC-3 cells in 2D and 3D models, making QDs stealthy and preventing their non-specific accumulation. Conversely, peptides conjugated QDs (QDs-A20 & QDs-Scr) labeled HSC-3 monolayers and managed to label spheroid periphery up to 23 µm deep. However, no difference in accumulation was found between these two QDs whereas only A20 peptide could potentially target αVβ6 integrin. It appears that peptide conjugation increased QDs zeta potential, promoting their adsorption and subsequent endocytosis by cells, independently from αVβ6 integrin. Conclusions The present study highlighted the impact of peptide conjugation on QDs internalization in 2D and 3D tongue cancer cell models. QDs-SPP were stealthy and did not accumulate in cells. Peptides conjugated QDs could be used as contrast agents, but in a passive targeting approach. Modifications to surface chemistry are required to target αVβ6 integrin through active targeting. This study also highlights the need for controls such as scrambled peptides, the absence of which can lead to misinterpretation of results.

During adhesion and migration, single cells interact with their environment through various physicochemical force and sensing. In addition, geometrical and mechanical constraints provided by in vivo micro-environment must be mimicked in single-cell adhesion assays if one does not want to produce artifactual results [1]. Hence, we propose a FRET-based imaging technique that will integrate in its core this micro structuration and biochemical necessities: Non-radiative excitation fluorescence (NEF) nanoscopy.

This study represents a novel approach for the fabrication of resonant dielectric microdisks enabling high quality microcavities. By spinning semi-conducting quantum dots of CdSe/CdS onto the microstructures and exciting using a UV 405nm laser beam, fluorescence is observed. Finding pave the way four further investigation into the lasing effect.

Group II-VI semiconductor nanoplatelets (NPLs) with atomically defined thicknesses and extended atomically flat (001) facets are used for ligand binding and chiro-optical effects. In this study, we demonstrate that tartrate ligands, anchored by two carboxylate groups, chelate the (001) facets of NPLs at an average ratio of one tartrate molecule to two cadmium (Cd) surface atoms. This assembly of chiral molecules on inorganic nanocrystals generates a circular dichroism g-factor as high as 1.3 x 10-2 at the first excitonic transition wavelength of NPLs. Tartrate ligands induce an orthorhombic distortion of the initially "cubic" crystal structure, classifying the NPLs within the 222-point group. Unlike spherical nanocrystals, where it is difficult to discern whether chiral ligands affect only the surface atoms or the entire crystal structure, our findings unequivocally show that the crystal structure of NPLs is modified due to their thinness and atomically precise thickness. The in-plane lattice parameters experience compressive and tensile stresses, significantly splitting the heavy-hole and light-hole bands. Additionally, tartrate ligands adopt different conformations on the NPL surface over time, resulting in dynamic changes in the circular dichroism signal, including an inversion of its sign.

We investigate the photon statistics of the light emitted by single self-assembled hybrid gold-CdSe/CdS/CdZnS colloidal nanocrystal supraparticles through the detailed analysis of the intensity autocorrelation functiong(2)(τ). We first reveal that, despite the large number of nanocrystals involved in the supraparticle emission, antibunching can be observed. We then present a model based on non-coherent Förster energy transfer and Auger recombination that well captures photon antibunching. Finally, we demonstrate that some supraparticles exhibit a bunching effect at short time scales corresponding to coherent collective emission.

Gold nanoparticles, such as nanorods (AuNRs), present exceptionally high absorption cross sections that can be tuned to the near-infrared (NIR), the optimal window for light penetration in biological tissues. This makes them valuable photosensitizers for the treatment of cancer using photothermal therapy, where absorbed light energy is converted into heat. In addition, there is a strong interest in using hot electron carriers generated in AuNRs by NIR irradiation to produce cytotoxic radical oxygen species in order to enhance the efficiency of the phototherapy. Here, we show that hybrid nanoparticles composed of AuNRs with TiO2 deposited at their extremities are efficient sensitizers to produce hydroxyl radical species under NIR irradiation. We attribute this phenomenon to the transfer of hot electrons generated from the plasmon excitation in AuNR to the TiO2 tips, followed by reduction of dioxygen. We then functionalize these hybrid AuNR/TiO2 nanoparticles with block poly(ethylene glycol)-phosphonate polymer ligands to stabilize them in a physiological medium. We finally demonstrate that the photodynamic effect induces cell death upon irradiation with a greater efficiency than the photothermal effect alone.

Single core/shell CdSe/CdS colloidal nanocrystals are usually used as efficient single photon sources working at room temperature, with a narrow spectrum of =30nm. For large shell, they evidence a strong resistance to high excitation and can withstand a few 106W/cm2,. Under high excitation their emission change dramatically, emission evolves non linearly with laser excitation power and the spectrum range can reach a few 100nm. In order to understand such a behavior, we use a statistical description of the electrons and holes population as fermi dirac distributions, followed by radiative recombination of excitons, which describes well experimental results.

We present here a new kind of laser microcavity to be used as a biosensor. It is based on dielectric pillar fabricated by photolithography with a negative photoresist resist, transparent and having a high index in the visible. The pillars are infiltrated by colloidal core/shell CdSe/CdS nanocrystals or nanoplatelets with appropriate surface ligands so that the nanoemitters get into the pillars, but remain close to the surface and homogeneously dispersed. The nanoemitter fluorescence excite whispering gallery resonant modes. We present here numerical and experimental results demonstrating the quality of the pillars and evidencing the resonant modes.