Ultrasound technology assisted colloidal nanocrystal synthesis and biomedical applications.

Non-invasive and high spatiotemporal resolution mythologies for the diagnosis and treatment of disease in clinical medicine promote the development of modern medicine. Ultrasound (US) technology provides a non-invasive, real-time, and cost-effective clinical imaging modality, which plays a significant role in chemical synthesis and clinical translation, especially in in vivo imaging and cancer therapy. On the one hand, the US treatment is usually accompanied by cavitation, leading to high temperature and pressure, so-called "hot spot", playing a significant role in sonochemical-based colloidal synthesis. Compared with the classical nucleation synthetic method, the sonochemical synthesis strategy presents high efficiency for the fabrication of colloidal nanocrystals due to its fast nucleation and growth procedure. On the other hand, the US is attractive for in vivo and medical treatment, with applications increasing with the development of novel contrast agents, such as the micro and nano bubbles, which are widely used in neuromodulation, with which the US can breach the blood-brain barrier temporarily and safely, opening a new door to neuromodulation and therapy. In terms of cancer treatment, sonodynamic therapy and US-assisted synergetic therapy show great effects against cancer and sonodynamic immunotherapy present unparalleled potentiality compared with other synergetic therapies. Further development of ultrasound technology can revolutionize both chemical synthesis and clinical translation by improving efficiency, precision, and accessibility while reducing environmental impact and enhancing patient care. In this paper, we review the US-assisted sonochemical synthesis and biological applications, to promote the next generation US technology-assisted applications.

Optical format interconversion nodes between OOK and QPSK enabled by a reconfigurable two-dimensional vector mover.

An optical format interconversion scheme between on-off keying (OOK) and quadrature phase shift keying (QPSK) is proposed and verified in this paper. The conversion system mainly consists of a coherent vector combiner and a reconfigurable two-dimensional (2D) vector mover. As a key element of the proposed conversion system, the 2D vector mover is implemented by a non-degenerate phase-sensitive amplifier (PSA). The operating principle and theoretical derivations of the PSA-based 2D vector mover are fully introduced. The reconfigurable transfer characteristics of the vector mover are analyzed under different parameter settings to exhibit the flexible 2D moving function. The signal constellations, eye diagrams, spectrum, error vector magnitudes, and bit error ratios are estimated and depicted to validate the proposed idea. With the input signal-to-noise ratios of 20 dB and 25 dB, error-free conversions are achieved between 50G Baud OOK and QPSK. The scheme proposed in this paper fills the lack of the one-to-one interconversion between OOK and QPSK, and has potential applications in optical interconnect nodes, across-dimensional optical transmissions, and flexible optical transceivers.

Self-illuminating NIR-II bioluminescence imaging probe based on silver sulfide quantum dots.

Bioluminescence (BL) imaging has emerged to tackle the potential challenges of fluorescence (FL) imaging including the autofluorescence background, inhomogeneous illumination over a wide imaging field, and the light-induced overheating effect. Taking advantage of the bioluminescence resonance energy transfer (BRET) mechanism between a conventional luciferin compound and a suitable acceptor, the visible light of the former can be extended to photons with longer wavelengths emitting from the latter. Although BRET-based self-illuminating imaging probes have already been prepared, employing potentially cytotoxic elements as the acceptor with the emission wavelengths which hardly reach the first near-infrared (NIR-I) window, has limited their applications as safe and high performance in vivo imaging agents. Herein, we report a biocompatible, self-illuminating, and second near-infrared (NIR-II) emissive probe to address the cytotoxicity concerns as well as improve the penetration depth and spatiotemporal resolution of BL imaging. To this end, NanoLuc luciferase enzyme molecules were immobilized on the surface of silver sulfide quantum dots to oxidize its luciferin substrate and initiate a single-step BRET mechanism, resulting in NIR-II photons from the quantum dots. The resulting dual modality (BL/FL) probes were successfully applied to in vivo tumor imaging in mice, demonstrating that NIR-II BL signals could be easily detected from the tumor sites, giving rise to ∼2 times higher signal-to-noise ratios compared to those obtained under FL mode. The results indicated that nontoxic NIR-II emitting nanocrystals deserve more attention to be tailored to fill the growing demands of preparing appropriate agents for high quality BL imaging.

Complete Mapping of Interacting Charging States in Single Coupled Colloidal Quantum Dot Molecules.

Colloidal quantum dots (CQDs), major building blocks in modern optoelectronic devices, have so far been synthesized with only one emission center where the exciton resides. Recent development of coupled colloidal quantum dots molecules (CQDM), where two core-shell CQDs are fused to form two emission centers in close proximity, allows exploration of how charge carriers in one CQD affect the charge carriers in the other CQD. Cryogenic single particle spectroscopy reveals that while CQD monomers manifest a simple emission spectrum comprising a main emission peak with well-defined phonon sidebands, CQDMs exhibit a complex spectrum with multiple peaks that are not all spaced according to the known phonon frequencies. Based on complementary emission polarization and time-resolved analysis, this is assigned to fluorescence of the two coupled emission centers. Moreover, the complex peak structure shows correlated spectral diffusion indicative of the coupling between the two emission centers. Utilizing Schrödinger-Poisson self-consistent calculations, we directly map the spectral behavior, alternating between neutral and charged states of the CQDM. Spectral shifts related to electrostatic interaction between a charged emission center and the second emission center are thus fully mapped. Furthermore, effects of moving surface charges are identified, whereby the emission center proximal to the charge shows larger shifts. Instances where the two emission centers are negatively charged simultaneously are also identified. Such detailed mapping of charging states is enabled by the coupling within the CQDM and its anisotropic structure. This understanding of the coupling interactions is progress toward quantum technology and sensing applications based on CQDMs.

Ultrasmall superparamagnetic iron oxide nanoparticles: A next generation contrast agent for magnetic resonance imaging.

As a research hotspot, the development of magnetic resonance imaging (MRI) contrast agents has attracted great attention over the past decades for improving the accuracy of diagnosis. Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles with core diameter smaller than 5.0 nm are expected to become a next generation of contrast agents owing to their excellent MRI performance, long blood circulation time upon proper surface modification, renal clearance capacity, and remarkable biosafety profile. On top of these merits, USPIO nanoparticles are used for developing not only T1 contrast agents, but also T2 /T1 switchable contrast agents via assembly/disassembly approaches. In recent years, as a new type of contrast agents, USPIO nanoparticles have shown considerable applications in the diagnosis of various diseases such as vascular pathological changes and inflammations apart from malignant tumors. In this review, we are focusing on the state-of-the-art developments and the latest applications of USPIO nanoparticles as MRI contrast agents to discuss their advantages and future prospects. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Healing Diabetic Ulcers with MoO3-X Nanodots Possessing Intrinsic ROS-Scavenging and Bacteria-Killing Capacities.

Diabetic ulcers (DUs) appearing as chronic wounds are difficult to heal due to the oxidative stress in the wound microenvironment and their high susceptibility to bacterial infection. A routine treatment combining surgical debridement with anti-infection therapy is widely used for treating DUs in the clinic, but hardly offers a satisfying wound healing outcome. It is known that a long-term antibiotic treatment may also lead to the drug resistance of pathogens. To address these challenges, new strategies combining both reactive oxygen species (ROS) scavenging and bacterial sterilization have been proposed for fighting against DUs. Following this idea, oxygen deficient molybdenum-based nanodots (MoO3-X ) for healing the DUs are reported. The ROS scavenging ability of MoO3-X nanodots is investigated and the antibacterial property of the nanodots is also demonstrated. The systematic cell and animal experimental results indicate that the MoO3-X nanodots can effectively reduce inflammation, promote epithelial cell regeneration, accelerate angiogenesis, and facilitate DUs recovery. Most importantly, they present excellent capacity to diminish infection of methicillin-resistant Staphylococcus aureus, manifesting the potent application prospect of MoO3-X nanodots for diabetic wound therapy.

Rapidly liver-clearable rare-earth core-shell nanoprobe for dual-modal breast cancer imaging in the second near-infrared window.

BACKGROUND: Fluorescence imaging as the beacon for optical navigation has wildly developed in preclinical studies due to its prominent advantages, including noninvasiveness and superior temporal resolution. However, the traditional optical methods based on ultraviolet (UV, 200-400 nm) and visible light (Vis, 400-650 nm) limited by their low penetration, signal-to-noise ratio, and high background auto-fluorescence interference. Therefore, the development of near-infrared-II (NIR-II 1000-1700 nm) nanoprobe attracted significant attentions toward in vivo imaging. Regrettably, most of the NIR-II fluorescence probes, especially for inorganic NPs, were hardly excreted from the reticuloendothelial system (RES), yielding the anonymous long-term circulatory safety issue. RESULTS: Here, we develop a facile strategy for the fabrication of Nd3+-doped rare-earth core-shell nanoparticles (Nd-RENPs), NaGdF4:5%Nd@NaLuF4, with strong emission in the NIR-II window. What's more, the Nd-RENPs could be quickly eliminated from the hepatobiliary pathway, reducing the potential risk with the long-term retention in the RES. Further, the Nd-RENPs are successfully utilized for NIR-II in vivo imaging and magnetic resonance imaging (MRI) contrast agents, enabling the precise detection of breast cancer. CONCLUSIONS: The rationally designed Nd-RENPs nanoprobes manifest rapid-clearance property revealing the potential application toward the noninvasive preoperative imaging of tumor lesions and real-time intra-operative supervision.

Neck Barrier Engineering in Quantum Dot Dimer Molecules via Intraparticle Ripening.

Coupled colloidal quantum dot (CQD) dimers represent a new class of artificial molecules composed of fused core/shell semiconductor nanocrystals. The electronic coupling and wave function hybridization are enabled by the formation of an epitaxial connection with a coherent lattice between the shells of the two neighboring quantum dots where the shell material and its dimensions dictate the quantum barrier characteristics for the charge carriers. Herein we introduce a colloidal approach to control the neck formation at the interface between the two CQDs in such artificial molecular constructs. This allows the tailoring of the neck barrier in prelinked homodimers formed via fusion of multifaceted wurtzite CdSe/CdS CQDs. The effects of reaction time, temperature, and excess ligands are studied. The neck filling process follows an intraparticle ripening mechanism at relatively mild reaction conditions while avoiding interparticle ripening. The degree of surface ligand passivation plays a key role in activating the surface atom diffusion to the neck region. The degree of neck filling strongly depends also on the initial relative orientation of the two CQDs, where homonymous plane attachment allows for facile neck growth, unlike the case of heteronymous plane attachment. Upon neck filling, the observed red-shift of the absorption and fluorescence measured both for ensemble and single dimers is assigned to enhanced hybridization of the confined wave function in CQD dimer molecules, as supported by quantum calculations. The fine-tuning of the particle interface introduced herein provides therefore a powerful tool to further control the extent of hybridization and coupling in CQD molecules.

Rational Constructed Ultra-Small Iron Oxide Nanoprobes Manifesting High Performance for T1-Weighted Magnetic Resonance Imaging of Glioblastoma.

Precise diagnosis and monitoring of cancer depend on the development of advanced technologies for in vivo imaging. Owing to the merits of outstanding spatial resolution and excellent soft-tissue contrast, the application of magnetic resonance imaging (MRI) in biomedicine is of great importance. Herein, Angiopep-2 (ANG), which can simultaneously help to cross the blood-brain barrier and target the glioblastoma cells, was rationally combined with the 3.3 nm-sized ultra-small iron oxide (Fe3O4) to construct high-performance MRI nanoprobes (Fe3O4-ANG NPs) for glioblastoma diagnosis. The in vitro experiments show that the resultant Fe3O4-ANG NPs not only exhibit favorable relaxation properties and colloidal stability, but also have low toxicity and high specificity to glioblastoma cells, which provide critical prerequisites for the in vivo tumor imaging. Furthermore, in vivo imaging results show that the Fe3O4-ANG NPs exhibit good targeting ability toward subcutaneous and orthotopic glioblastoma model, manifesting an obvious contrast enhancement effect on the T1-weighted MR image, which demonstrates promising potential in clinical application.

Semiconductor Bow-Tie Nanoantenna from Coupled Colloidal Quantum Dot Molecules.

Top-down fabricated nanoantenna architectures of both metallic and dielectric materials show powerful functionalities for Raman and fluorescence enhancement with relevance to single molecule sensing while inducing directionality of chromophore emission with implications for single photon sources. We synthesize the smallest bow-tie nanoantenna by selective tip-to-tip fusion of two tetrahedral colloidal quantum dots (CQDs) forming a dimer. While the tetrahedral monomers emit non-polarized light, the bow-tie architecture manifests nanoantenna functionality of enhanced emission polarization along the bow-tie axis, as predicted theoretically and revealed by single-particle spectroscopy. Theory also predicts the formation of an electric-field hotspot at the bow-tie epicenter. This is utilized for selective light-induced photocatalytic metal growth at that location, unlike growth on the free tips in dark conditions, thus demonstrating bow-tie dimer functionality as a photochemical reaction center.

Dual Active Center-Assembled Cu31S16-Co9-xNixS8 Heterodimers: Coherent Interface Engineering Induces Multihole Accumulation for Light-Enhanced Electrocatalytic Oxygen Evolution.

The design of low-cost yet highly efficient electrocatalysts plays a critical role in energy storage and conversion reactions. The oxygen evolution reaction (OER) is considered a bottleneck of electrochemical water splitting for hydrogen fuel generation. It is still challenging to extract a high density of charge carriers in noble-metal-free alternative catalysts to facilitate sluggish kinetics. Herein, we report the rational design and coherent interface engineering for combining light-harvesting Cu31S16 with electroactive Co9-xNixS8 (x = 0-9) to form novel Cu31S16-Co9-xNixS8 heterodimers. By delicately controlling the kinetic growth in a seed-mediated growth method, the bifunctional centers, even with two distinct crystal phases, were integrated into a synergistic architecture, which achieved full-spectrum solar energy capture and light conversion to drive and activate the electrochemical reaction. Benefiting from the well-defined structure, high-quality interface, oriented attachment, and optimal Co/Ni bimetal ratio, Cu31S16-Co7.2Ni1.8S8 produces a dramatically reduced overpotential (242 mV at 10 mA cm-2) with a shift of 83 mV under visible-light excitation, achieving a 4.5-fold higher turnover frequency than that of its unirradiated Co7.2Ni1.8S8 counterpart. This enhanced performance also far exceeds commercial RuO2 (358 mV at 10 mA cm-2) and most nonprecious-metal nanocatalysts. Further mechanistic studies reveal that coherent interface engineering leads to a strong photo/electricity coupling effect and efficient spatial charge separation, which induces sufficient hot holes that eventually accumulate at the electroactive sites to accelerate the multihole-involved OER. This work would open up new opportunities for the fabrication of non-noble metal electrocatalysts and management of charge carriers.

2D-to-1D constellation reforming using phase-sensitive amplifier-based constellation squeezing and shifting.

In this paper, a phase-sensitive amplifier (PSA)-based two dimensional (2D)-to-one dimensional (1D) constellation reforming system is proposed and analyzed in detail. The proposed system theoretically realizes seven kinds of 10 GBaud quadrature amplitude modulation (QAM)-to-pulse amplitude modulation (PAM) conversions, including quadrature phase shift keying-to-PAM4 and 8QAM-to-PAM8 conversions. The constellation reforming system consists of a constellation squeezing PSA and a multi-level vector moving PSA. The operating principle and formula derivations of constellation squeezing and vector moving processes are fully explained, including the PSA transfer characteristics and PSA gain axis angle analytical solutions. When implementing QAM-to-PAM conversions, the constellations, spectra, eye diagrams, error vector magnitudes and bit error ratio (BER) performances of the QAM and PAM signals are measured. For 8QAM-to-PAM8 conversion, with the input OSNR of 25 dB and 30 dB, at the BER of 10-3, the converted PAM8 shows the receiver OSNR of 38.9 dB and 35.2 dB, respectively. The proposed and verified 2D-to-1D constellation reforming system builds an optical bridge connecting long-haul and short-reach networks, which can be employed in the format conversion, high-order format signal generation and shaping, and flexible information aggregation/de-aggregation.

Coupled Colloidal Quantum Dot Molecules.

ConspectusElectronic coupling and hence hybridization of atoms serves as the basis for the rich properties for the endless library of naturally occurring molecules. Colloidal quantum dots (CQDs) manifesting quantum strong confinement possess atomic-like characteristics with s and p electronic levels, which popularized the notion of CQDs as artificial atoms. Continuing this analogy, when two atoms are close enough to form a molecule so that their orbitals start overlapping, the orbitals energies start to split into bonding and antibonding states made out of hybridized orbitals. The same concept is also applicable for two fused core-shell nanocrystals in close proximity. Their band edge states, which dictate the emitted photon energy, start to hybridize, changing their electronic and optical properties. Thus, an exciting direction of "artificial molecules" emerges, leading to a multitude of possibilities for creating a library of new hybrid nanostructures with novel optoelectronic properties with relevance toward diverse applications including quantum technologies.The controlled separation and the barrier height between two adjacent quantum dots are key variables for dictating the magnitude of the coupling energy of the confined wave functions. In the past, coupled double quantum dot architectures prepared by molecular beam epitaxy revealed a coupling energy of few millielectron volts, which limits the applications to mostly cryogenic operation. The realization of artificial quantum molecules with sufficient coupling energy detectable at room temperature calls for the use of colloidal semiconductor nanocrystal building blocks. Moreover, the tunable surface chemistry widely opens the predesigned attachment strategies as well as the solution processing ability of the prepared artificial molecules, making the colloidal nanocrystals as an ideal candidate for this purpose. Despite several approaches that demonstrated enabling of the coupled structures, a general and reproducible method applicable to a broad range of colloidal quantum materials is needed for systematic tailoring of the coupling strength based on a dictated barrierThis Account addresses the development of nanocrystal chemistry to create coupled colloidal quantum dot molecules and to study the controlled electronic coupling and their emergent properties. The simplest nanocrystal molecule, a homodimer formed from two core/shell nanocrystal monomers, in analogy to homonuclear diatomic molecules, serves as a model system. The shell material of the two CQDs is structurally fused, resulting in a continuous crystal. This lowers the potential energy barrier, enabling the hybridization of the electronic wave functions. The direct manifestation of the hybridization reflects on the band edge transition shifting toward lower energy and is clearly resolved at room temperature. The hybridization energy within the single homodimer molecule is strongly correlated with the extent of structural continuity, the delocalization of the exciton wave function, and the barrier thickness as calculated numerically. The hybridization impacts the emitted photon statistics manifesting faster radiative decay rate, photon bunching effect, and modified Auger recombination pathway compared to the monomer artificial atoms. Future perspectives for the nanocrystals chemistry paradigm are also highlighted.

Phase-sensitive amplifier-based optical conversion for direct detection of complex modulation format to bridge long-haul transmissions and short-reach interconnects.

An optical conversion node scheme for direct detection of complex modulation format is proposed to bridge long-haul transmissions and short-reach interconnects. A noisy 10G Baud quadrature phase shift keying signal is converted into a 10G Baud normal 4-level pulse amplitude modulation (PAM4) signal by the node. The conversion node is realized mainly relies on four-wave mixing-based phase-sensitive amplifiers. The power ratio and constellation shape of the converted PAM4 both can be flexibly designed based on network demands and five kinds of uniform or non-uniform PAM4s are generated to verify the shaping functionality. With the input optical signal-to-noise ratio range of (10 dB∼30 dB), the key indicators of the signals went through every part are measured, includes constellations, eye diagrams, error vector magnitudes, bit error rates, normalized impact factors of phase and amplitude. The proposed node scheme has great application potential in intermediate nodes for bridging long-haul transmissions and short-reach interconnects, hierarchical modulation and flexible constellations design for advanced format signals.

Colloidal quantum dot molecules manifesting quantum coupling at room temperature.

Coupling of atoms is the basis of chemistry, yielding the beauty and richness of molecules. We utilize semiconductor nanocrystals as artificial atoms to form nanocrystal molecules that are structurally and electronically coupled. CdSe/CdS core/shell nanocrystals are linked to form dimers which are then fused via constrained oriented attachment. The possible nanocrystal facets in which such fusion takes place are analyzed with atomic resolution revealing the distribution of possible crystal fusion scenarios. Coherent coupling and wave-function hybridization are manifested by a redshift of the band gap, in agreement with quantum mechanical simulations. Single nanoparticle spectroscopy unravels the attributes of coupled nanocrystal dimers related to the unique combination of quantum mechanical tunneling and energy transfer mechanisms. This sets the stage for nanocrystal chemistry to yield a diverse selection of coupled nanocrystal molecules constructed from controlled core/shell nanocrystal building blocks. These are of direct relevance for numerous applications in displays, sensing, biological tagging and emerging quantum technologies.

Electronic coupling in colloidal quantum dot molecules; the case of CdSe/CdS core/shell homodimers.

Coupled colloidal quantum dot molecules composed of two fused CdSe/CdS core/shell sphere monomers were recently presented. Upon fusion, the potential energy landscape changes into two quantum dots separated by a pretuned potential barrier with energetics dictated by the conduction and valence band offsets of the core/shell semiconductors and the width controlled by the shell thickness and the fusion reaction conditions. In close proximity of the two nanocrystals, orbital hybridization occurs, forming bonding and antibonding states in analogy to the hydrogen molecule. In this study, we examine theoretically the electronic and optical signatures of such a quantum dot dimer compared to its monomer core/shell building-blocks. We examine the effects of different core sizes, barrier widths, different band offsets, and neck sizes at the interface of the fused facets on the system wave-functions and energetics. Due to the higher effective mass of the hole and the large valence band offset, the hole still essentially resides in either of the cores, breaking the symmetry of the potential for the electron as well. We found that the dimer signature is well expressed in a red shift of the band gap both in absorption and emission, in slower radiative lifetimes and in an absorption cross section which is significantly enhanced relative to the monomers at energies above the shell absorption onset, while remains essentially at the same level near the band-edge. This study provides essential guidance to predesign of coupled quantum dot molecules with specific attributes which can be utilized for various new opto-electronic applications.

Solvent Tailored Strategy for Synthesis of Ultrasmall Ag2S Quantum Dots with Near-Infrared-II Luminescence.

Highly luminescent semiconductor with ultrasmall size is always desirable for biomedical applications. Here, we developed a novel solvent-directing strategy to prepare ultrasmall monodispersed Ag2S quantum dots (QDs) with strong luminescence in the second near infrared (NIR-II) range (1000∼1400 nm). The particle size and luminescence of these Ag2S QDs could be desirably tuned by adjusting the solvents of the system. With further surface modification, the hydrophilic Ag2S QDs could be successfully utilised for cancerous cells imaging, indicating great potentials in biomedical fields.

Flexible generation of 28 Gbps PAM4 60 GHz/80 GHz radio over fiber signal by injection locking of direct multilevel modulated laser to spacing-tunable two-tone light.

To meet the ever-increasing bandwidth demands in the future broadband wireless networks, the millimeter-wave (mm-wave) frequency region is being actively perused, owing to its broad bandwidth and high frequencies. In this paper, a photonic mm-wave system is proposed and experimentally demonstrated based on the injection locking of a direct multilevel modulated laser to a spacing-tunable two-tone light. Since the mm-wave frequency of the generated signal is locked to the frequency spacing of the injected two-tone light, it shows better frequency stabilization than the schemes based on two free-running lasers. Moreover, by simply tuning the tone spacing, the mm-wave frequency could be easily re-configured, offering flexibility in the mm-wave signal generation. Instead of using complex and expensive optical modulators, the multilevel modulation on the mm-wave data carrier is implemented through the direct multilevel modulation of a laser and the injection locking. A 28 Gbps four-level pulse amplitude modulation (PAM4) is realized by biasing a 10 G-class laser at a current far from the threshold, providing a cost-effective and simple mm-wave generation scheme. In the experiment, a photonic approach to generating 28 Gbps PAM4 60 GHz/80 GHz mm-wave signals is experimentally demonstrated. A power penalty of less than 0.2 dB is observed for the filtered-out PAM4 signals with respect to the original PAM4. Besides, an ultra-low phase noise of up to -98 dBc/Hz is obtained for the mm-wave carriers after the injection locking. The proposed scheme possesses the flexibility and frequency stability of the mm-wave frequency, and also has low cost and implementation complexity.

Fluorine Grafted Cu7S4-Au Heterodimers for Multimodal Imaging Guided Photothermal Therapy with High Penetration Depth.

We report the multifunctional nanocomposites (NCs) consisting of 19F-moieties grafted Cu7S4-Au nanoparticles (NPs) for negligible background 19F-magnetic resonance imaging (19F-MRI) and computed tomography (CT) imaging guided photothermal therapy. The localized surface plasmon resonance (LSPR) absorption can be reasonably tuned to the in vivo transparent window (800-900 nm) by coupling Au (<10 nm, LSPR ∼530 nm) with Cu7S4 (<15 nm, LSPR ∼1500 nm) into Cu7S4-Au heterodimers. The in vivo photothermal tests show that Cu7S4-Au show deeper light penetration with 808 nm irradiation, better photothermal efficacy, and less damage to normal tissues than Cu7S4 with 1500 nm irradiation. Moreover, compared to traditional 1H-MRI, the 19F-MRI based on these NCs demonstrates much better sensitivity due to the negligible background. This work offers a promising strategy for multimodal imaging guided photothermal therapy of deep tissue with good efficacy.

Optical modulation format conversion from one QPSK to one BPSK with information-integrity-employing phase-sensitive amplifier.

In this paper, a scheme for optical modulation format conversion from one 20 Gbps quadrature phase-shift keying (QPSK) signal to one 20 Gbps binary phase-shift keying (BPSK) signal with information integrity is proposed and verified by simulation. The theory of degenerate phase-sensitive amplifier (PSA) employed as a phase de-multiplexer is derived in detail and used to decompose the in- (I) and quadrature- (Q) phase components of QPSK. Then the I and Q components are parallel-to-series converted into one BPSK. The constellations show that the phase noise of the original signal is effectively restrained by the conversion system through use of the PSA. The error vector magnitude and bit-error rate (BER) of the QPSK, converted BPSK, and a back-to-back BPSK are measured and compared with each other. We find that the BER performance of the converted BPSK is better than QPSK and maintains the original information integrity with different input signal quality. Some potential issues are also discussed as to practical implementation of the scheme. This modulation-format-conversion scheme has potential applications in improving the signal BER performance and flexible transmitters and receivers in software-defined networks.