Search

Organic molecules having emission in the NIR(II) region are emergent and receiving enormous attention. Unfortunately, attaining accountable organic emission intensity around the NIR(II) region is hampered by the dominant internal conversion operated by the energy gap law, where the emission energy gap and the associated internal reorganization energy λ

A series of NIR-II fluorescent TADF-incorporated polymer dots were successfully synthesized. The function of the TADF moiety was fully studied and the bio-applications of these polymer dots including bone imaging were also demonstrated.

Fluorescence imaging, particularly in the NIR-II region (1000-1700 nm), has become an unprecedented tool for deep-tissue in vivo imaging. Among the fluorescent nanoprobes, semiconducting polymer nanoparticles (Pdots) appear to be a promising agent because of their tunable optical and photophysical properties, ultrahigh brightness, minimal autofluorescence, narrow-size distribution, and low cytotoxicity. This review elucidates the recent advances in Pdots for deep-tissue fluorescence imaging and the facing future translation to clinical use.

Photothermal therapy (PTT) techniques have been developed for years, while active endeavors have been continuously undertaken recently to enhance their efficiency by employing near-infrared light. ...

Bioimaging in the near-infrared window is of great importance to study the dynamic processes in vivo with deep penetration, high spatiotemporal resolution, and minimal tissue absorption, scattering...

Bioimaging in the near-infrared window is of great importance to study the dynamic processes

In recent years, semiconducting polymer dots (Pdots) have attracted enormous attention in applications from fundamental analytical detection to advanced deep-tissue bioimaging due to their ultrahigh fluorescence brightness with excellent photostability and minimal cytotoxicity. Pdots have therefore been widely adopted for a variety types of molecular sensing for analytical detection. More importantly, the recent development of Pdots for use in the optical window between 1000 and 1700 nm, popularly known as the "second near-infrared window" (NIR-II), has emerged as a class of optical transparent imaging technology in the living body. The advantages of the NIR-II region over the traditional NIR-I (700-900 nm) window in fluorescence imaging originate from the reduced autofluorescence, minimal absorption and scattering of light, and improved penetration depths to yield high spatiotemporal images for biological tissues. Herein, we discuss and summarize the recent developments of Pdots employed for analytical detection and NIR-II fluorescence imaging. Starting with their preparation, the recent developments for targeting various analytes are then highlighted. After that, the importance of and latest progress in NIR-II fluorescence imaging using Pdots are reported. Finally, perspectives and challenges associated with the emergence of Pdots in different fields are given.

Semiconducting polymer nanoparticles (Pdots) have been demonstrated to be a promising class of probes for use in fluorometric immunochromatographic test strips (ICTS). The advantages of Pdots in ICTSs include ultrahigh brightness, minimal nonspecific adsorption, and multicolor availability, which together contribute to the high sensitivity, good specificity, and multiplexing ability. These unique properties can therefore circumvent several significant challenges of commercial ICTSs, including insufficient specificity/sensitivity and difficulty in quantitative and multiplexed detection. Here, we developed a colorimetric and fluorescent bimodal readout ICTS based on gold-Pdot nanohybrids for the determination of carcinoembryonic antigen (CEA) and cytokeratin 19 fragment (CYFRA 21-1) expressed abnormally in human blood of non-small-cell lung cancer (NSCLS). The vivid color from Au nanomaterials can be used for rapid qualitative screening (colorimetry) in 15 min, while the bright fluorescence of Pdots is ideal for the advanced quantitative measurements of CEA and CYFRA21-1 concentrations in whole blood samples. This bimodal ICTS platform possesses phenomenal detection sensitivity of 0.07 and 0.12 ng/mL for CYFRA21-1 and CEA, respectively. The accuracy and reliability of this ICTS platform were further evaluated with clinical serum samples from NSCLS patients at different stages, showing good consistency with the results from electrochemiluminescence immunoassay.

There have been enormous efforts for developing the next generations of fluorometric lateral flow immunochromatographic strip (ICTS) owing to the great advances in fluorescent materials in these years. Here we developed one type of fluorometric ICTS based on ultrabright semiconducting polymer dots (Pdots) in which the traffic light-like signals were created by energy transfer depending on the target concentration. This platform was successfully applied for qualitatively rapid screening and quantitatively precise analysis of prostate-specific antigen (PSA) in 10 min from merely one drop of the whole blood sample. This FRET-created traffic light ICTS possesses excellent specificity and an outstanding detection sensitivity of 0.32 ng/mL for PSA. Moreover, we conducted proof-of-concept experiments to demonstrate its potential for multiplexed detection of cancer biomarkers at the same time in an individual test strip by taking advantage of the traffic light signals. To the best of our knowledge, it is the first model of a traffic light-like immunoassay test strip based on Pdots with multiplexing ability. These results would pave an avenue for designing the next generation of point-of-care diagnostics.

Although enormous efforts have been devoted to the development of new types of fluorometric immunochromatographic test strip (ICTS) with improved sensitivity over the past years, it still remains a big challenge to design ICTS with colorimetric and fluorescent bimodal signal readout for rapid yet accurate detection of cancer markers in a clinic. Scientists have tried to prepare bimodal reporters by combining fluorescent dyes with metal nanomaterials, but their fluorescence was easily quenched by metal nanomaterials through surface energy transfer, making dual colorimetric and fluorometric ICTS very difficult to be achieved. As compared to conventional fluorescent probes, semiconducting polymer dots (Pdots) exhibit extraordinary fluorescence brightness and facile surface functionalization, which are very suitable to be engineered as bimodal signal reporting reagents. Here, we integrated highly fluorescent Pdots with strongly plasmonic Au nanorods to form Pdot-Au hybrid nanocomposites with dual colorimetric and fluorescent readout abilities. We further utilized these nanohybrids in ICTS for qualitatively fast screening (colorimetry) as well as quantitatively accurate determination (fluorometry) of prostate-specific antigen (PSA) within 10 min. By taking advantage of the plasmon-enhanced fluorescence of Pdots on Au nanorods, this immunoassay possesses much better detection sensitivity of 1.07 pg/mL for PSA, which is at least 2 orders of magnitude lower than that of conventional fluorometric ICTS. Moreover, the direct detection of PSA from human whole blood collected without sample pretreatment makes this Pdot-based ICTS platform promising for on-site point-of-care diagnostics.

Semiconducting polymer dots (Pdots) have recently emerged as a new type of ultrabright fluorescent probe that has been proved to be very useful for biomedical imaging. However, Pdots often suffer from serious fluorescence aggregation-caused quenching (ACQ) especially for near-infrared (NIR) fluorescent Pdots. This article compared two strategies to overcome the ACQ effect in near-infrared emissive Pdot systems: aggregation-induced emission (AIE) and anti-aggregation-caused quenching (anti-ACQ). The results show that the anti-ACQ platform outperforms the AIE system. The fluorescence quantum yield of anti-ACQ-based Pdots can be over 50% and the average per-particle brightness of the Pdots is about 5 times higher than that of the commercially available quantum dots. To help understand why the monomer conformations could greatly affect the optical properties of Pdots, molecular dynamics simulations were performed for the first time in such complicated Pdot systems. To demonstrate applications for in vivo fluorescence imaging, both microangiography imaging on living zebrafish embryos and specific tumor targeting on mice were performed. We anticipate that these studies will pave the way for the design of new highly fluorescent Pdot systems.

Developing strategies for preparing high-quality atomically thin two-dimensional (2D) nanomaterials is still an unaccomplished goal. Here we demonstrate that the major pigment used in natural photosynthesis, chlorophyll extracts, can effectively exfoliate bulk graphite, molybdenum dichalcogenides (MoS2) and boron nitride (h-BN) to form high quality thin sheets. The exfoliated MoS2 thin sheets were mixed with high-conducting single-walled carbon nanotubes (SWCNTs) and high surface/bulk ratio Pt nanoparticles (PtNPs) to form flexible MoS2/PtNPs/SWCNT papers for enhanced hydrogen evolution reaction (HER). Detailed electrochemical characterization shows that the flexible MoS2/PtNPs/SWCNT electrode (0.03 at% or 0.26 wt% Pt) exhibited excellent electrocatalytic activity toward the HER with an ultra-high exchange current density of 0.71 mA cm−2 which is identical to that of bulk platinum (Pt), “the gold standard” for hydrogen production, an ultra-low onset potential of −11 mV, a Tafel slope of 38 mV dec−1 and over 100 h of electrochemical durability.

Fluorescence probes emitting in the second near-infrared (NIR-II, 1000-1700 nm) window with the ability for deep-tissue imaging in mammals herald a new era in surgical methodology. However, the brightness of these NIR-II probes is still far from satisfactory due to their low fluorescence quantum yields (QYs), preventing the observation of high-resolution images such as whole-organ vascular networks in real time. Described here is the molecular engineering of a series of semiconducting polymer dots (Pdots) incorporated with aggregation-induced emission moieties to exhibit the QYs as high as 14% in the NIR-II window. Benefiting from the ultrahigh brightness, a 1400 nm long-pass filter is utilized to realize in vivo 3D tumor mapping in mice. To further understand how the geometrical and electron structures of the semiconducting polymers affect their optical properties, the in-depth and thorough density-functional theory calculations are performed to interpret the experimental results. This study lays the groundwork for further molecular design of highly bright NIR-II Pdots.

Two-dimensional micro-scale Rayleigh–Benard flows are investigated numerically using direct simulation Monte Carlo method. An enclosure of length-to-height aspect ratio of AS = 4 is taken to explore the influence of initial setting of simulated molecules. The simulation domain is divided into 81 × 21 sampling cells and the range of Rayleigh number from 3000 to 10 000 corresponds to the convection state. Cases of 8, 10, 12, 14, 16 and 24 simulated particles in each collision cell are examined. It is shown that flow patterns with three-, four- or five-roll modes may appear depending on the number of simulated particles.

This study investigates numerically the convective instabilities of rarefied gas in two-dimensional enclosures by the direct-simulation Monte Carlo (DSMC) method. A simulation using an enclosure with length-to-height aspect ratio AS = 2.016 is conducted to validate the value of the critical Rayleigh number on the onset of convection. Enclosures of AS = 2 and 4 are chosen to explore the influences of the Knudsen number Kn and initial wall temperatures on the flow. The results indicate that the different initial conditions may cause multiple solutions for the convection rolls and the Boussinesq approximation is no longer valid for rarefied gases of high Kn.

This paper is the second of two papers that presents the results of an extensive study of turbulent heat transfer and pressure drop in a horizontal tubes with strip-type inserts. Experimental data were taken for air for a class of strip inserts (longitudinal strip and crossed-strip). The insert was characterized by the parameters of 1 6 AR 6 5 and R � ( ¼ 0.5 and 1). Friction factor data (from Part I) and temperature measurements were used to understand the underlying physical phenomena responsible for the heat transfer enhancement for 6500 6 Re 6 19 500. Nusselt numbers were between four and two times the bare tube values at low Re and high Re, respectively. Performance evaluation index R1 (constant pumping power) and R2 (constant heat duty) were made and an optimum condition would be thus found.

A 28-year-old offshore worker attended accident and emergency department with a tender benign-feeling lump inferior to the left testis. He was previously investigated abroad with an ultrasound scan showing a homogenous mass posterior to the left testis. Subsequent CT was unremarkable. As there was no clinical suspicion of malignancy, a scrotal exploration was performed. During scrotal exploration, the left testicular mass appeared to be a supernumerary testis, which shared the same tunica albuginea. Histology has confirmed the diagnosis. Polyorchidism is an extremely rare congenital anomaly, and can be associated with hydrocele, testicular torsion or rarely malignancy. Leung has classified polyorchidism in four types. This case has been described as type 2; the supernumerary testis shares the epididymis and the vas deferens of the other testis. Treatment can either be conservative or surgical excision. However, if the supernumerary testis is asymptomatic, with negative tumour markers and radiological findings, surgery can be avoided.