Da Lyu

Bio: Da Lyu is an academic researcher from National University of Singapore. The author has contributed to research in topics: Surface plasmon resonance & Photothermal therapy. The author has an hindex of 4, co-authored 5 publications receiving 84 citations.

Quantitative Design of Bright Fluorophores and AIEgens by the Accurate Prediction of Twisted Intramolecular Charge Transfer (TICT)

Abstract: Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high-performance fluorophores and AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time-dependent density functional theory (TD-DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)-based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27-fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates.

Simultaneous Imaging and Selective Photothermal Therapy through Aptamer-Driven Au Nanosphere Clustering.

Abstract: Gold (Au) nanoparticles display enhanced near-infrared (NIR) photothermal effects upon the formation of clusters. We studied the photothermal properties of Au nanosphere clusters on the single-particle level using photothermal heterodyne imaging (PTHI) microscopy to understand the enhancement mechanisms. NIR photothermal responses of Au nanoparticle clusters were found to significantly increase from monomers to trimers. The averaged PTHI signal intensity of Au nanosphere dimers and trimers is ∼10 and ∼25 times that of monomers. The NIR photothermal effect of clustered nanospheres strongly correlates with their longitudinal plasmon mode. Clustered Au nanospheres were demonstrated to exhibit dual-capability NIR photothermal imaging and therapy of human prostate cancer cells with high efficiency and selectivity. This strategy can be potentially utilized for simultaneous cancer imaging and therapy with 3D selectivity.

Aggregation induced emission enhancement by plasmon coupling of noble metal nanoparticles

Abstract: Materials that display aggregation induced emission (AIE) can offer large contrast ratio for highly sensitive fluorescence based applications such as sensing and imaging. Conventional AIE chromophores are generally based on improved emission quantum yield due to reduced nonradiative decay rates by restriction of intramolecular motion. In this work we present another type of AIE phenomenon with a totally different working mechanism. It is based on aggregation induced plasmon coupling of metal nanoparticles (NPs) to simultaneously enhance the excitation efficiency and radiative decay rate of chromophores. The unique surface plasmon resonance (SPR) properties of noble metal NPs can give rise to a significantly enhanced local electric field to modulate the optical properties of nearby chromophores. Plasmon coupling interactions between adjacent metal NPs can cause giant enhancement in the local electric field and consequently even stronger enhancing capability. The working principle was demonstrated by using rhodamine B isothiocyanate (RiTC) as the model chromophore and cysteine as the coupling agent to induce aggregation of noble metal NPs. The fluorescence of RiTC was pre-quenched by attaching to the surface of Au and core–shell Au@Ag NPs. Upon addition of cysteine to induce the aggregation of RiTC conjugated Au@Ag NPs, the fluorescence of RiTC was significantly enhanced to a level much beyond that of fluorescence recovery. A series of core–shell Au@Ag NPs with different Ag shell thicknesses have been prepared to optimize the performance of aggregation induced plasmon coupling enhanced fluorescence. The optimum enhancement effect was achieved for Au@Ag NPs with a 5.6 nm Ag shell, which enhanced the fluorescence intensity of RiTC in the coupled nanostructures to be 44.8 times stronger than that of pre-quenched RiTC and 7.6 times that of free RiTC. Based on this method, the limit of detection of 3.4 pM was obtained for the detection of cysteine, which is highly selective and more sensitive than most previously reported methods. This quenched-enhanced (off–on) method is highly sensitive, simple, straightforward and universal, and can be easily extended for the detection of other analytes.

Activity‐Based NIR Enzyme Fluorescent Probes for the Diagnosis of Tumors and Image‐Guided Surgery

Abstract: Near-infrared (NIR) activatable fluorescent probes have been considered to be the effective edge tools for the investigation of cell biology and disease diagnosis because of their outstanding advantages. Related genes involved in tumor genesis and progression regulate the overexpression of certain enzymes. Owing to the distinctive characteristics of quick reaction time and favorable pharmacokinetics, enzyme-reactive NIR optical probes have shown great potential in the diagnosis of tumorigenesis and in image-guided intraoperative surgeries with high signal-to-noise ratios. In this review, we mainly summarize the latest advancements in enzyme-reactive NIR fluorescent probes from design strategy to biomedical application. Specifically, some challenges and prospects in this field are presented at the end of the review, which will be beneficial to innovatively construct new multifunctional fluorescent probes and actively promote their clinical transformation in the future.

Principles of Aggregation‐Induced Emission: Design of Deactivation Pathways for Advanced AIEgens and Applications

Abstract: Twenty years ago, the concept of aggregation-induced emission (AIE) was proposed, and this unique luminescent property has attracted scientific interest ever since. However, AIE denominates only the phenomenon, while the details of its underlying guiding principles remain to be elucidated. This minireview discusses the basic principles of AIE based on our previous mechanistic study of the photophysical behavior of 9,10-bis(N,N-dialkylamino)anthracene (BDAA) and the corresponding mechanistic analysis by quantum chemical calculations. BDAA comprises an anthracene core and small electron donors, which allows the quantum chemical aspects of AIE to be discussed. The key factor for AIE is the control over the non-radiative decay (deactivation) pathway, which can be visualized by considering the conical intersection (CI) on a potential energy surface. Controlling the conical intersection (CI) on the potential energy surface enables the separate formation of fluorescent (CI:high) and non-fluorescent (CI:low) molecules [control of conical intersection accessibility (CCIA)]. The novelty and originality of AIE in the field of photochemistry lies in the creation of functionality by design and in the active control over deactivation pathways. Moreover, we provide a new design strategy for AIE luminogens (AIEgens) and discuss selected examples.

Stimuli-Responsive AIEgens

Abstract: The unique advantages and the exciting application prospects of AIEgens have triggered booming developments in this area in recent years. Among them, stimuli-responsive AIEgens have received particular attention and impressive progress, and they have been demonstrated to show tremendous potential in many fields from physical chemistry to materials science and to biology and medicine. Here, the recent achievements of stimuli-responsive AIEgens in terms of seven most representative types of stimuli including force, light, polarity, temperature, electricity, ion, and pH, are summarized. Based on typical examples, it is illustrated how each type of systems realize the desired stimuli-responsive performance for various applications. The key work principles behind them are ultimately deciphered and figured out to offer new insights and guidelines for the design and engineering of the next-generation stimuli-responsive luminescent materials for more broad applications.

Twisted intramolecular charge transfer (TICT) and twists beyond TICT: from mechanisms to rational designs of bright and sensitive fluorophores

Abstract: The twisted intramolecular charge transfer (TICT) mechanism has guided the development of numerous bright and sensitive fluorophores. This review briefly overviews the history of establishing the TICT mechanism, and systematically summarizes the molecular design strategies in modulating the TICT tendency of various organic fluorophores towards different applications, along with key milestone studies and representative examples. Additionally, we also succinctly review the twisted intramolecular charge shuttle (TICS) and twists during photoinduced electron transfer (PET), and compare their similarities and differences with TICT, with emphasis on understanding the structure–property relationships between the twisted geometries and how they can directly affect the fluorescence of the molecules. Such structure–property relationships presented herein will greatly aid the rational development of fluorophores that involve molecular twisting in the excited state.

Bright and Stable NIR-II J-Aggregated AIE Dibodipy-Based Fluorescent Probe for Dynamic In Vivo Bioimaging

Abstract: Organic dyes emitting in the second near-infrared (NIR-II, 900-1700 nm) window, with high molar extinction coefficients (MEC) and quantum yields (QY) in aqueous, are essential for in vivo bioimaging and biosensing. In this work, we developed a dibodipy-based aggregation-induced emission (AIE) fluorescent probe, THPP, to meet this aim. THPP exhibits a high MEC and has intensified absorption and emission in J-aggregated state, which significantly enhance the fluorescence intensity (≈55 folds) and extend the maximal absorption/emission wavelengths to 970/1010 nm in NIR-II region. Based on the bright THPP, imaging with a high frame rate (34 frames per second) at a deep "valid penetration depth" up to 6 mm can be achieved. This enabled simultaneous and dynamic imaging of vasculatures and deep tissues. Besides, we succeeded in monitoring the respiratory rate of acute-lung-injury mice and tracing the collateral circulation process with a high frame rate.