Publications by authors named "Chun-Sing Lee"

210 Publications

Photochemical Synthesis of Nonplanar Small Molecules with Ultrafast Nonradiative Decay for Highly Efficient Phototheranostics.

Adv Mater 2021 Jul 28:e2102799. Epub 2021 Jul 28.

Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, P. R. China.

There has been much recent progress in the development of photothermal agents (PTAs) for biomedical and energy applications. Synthesis of organic PTAs typically involves noble metal catalysts and high temperatures. On the other hand, photochemical synthesis, as an alternative and green chemical technology, has obvious merits such as low cost, energy efficiency, and high yields. However, photochemical reactions have rarely been employed for the synthesis of PTAs. Herein, a facile and high-yield photochemical reaction is exploited for synthesizing nonplanar small molecules (NSMs) containing strong Michler's base donors and a tricyanoquinodimethane acceptor as high-performance PTAs. The synthesized NSMs show interesting photophysical properties including good absorption for photons of over 1000 nm wavelength, high near-infrared extinction coefficients, and excellent photothermal performance. Upon assembling the NSMs into nanoparticles (NSMN), they exhibit good biocompatibility, high photostability, and excellent photothermal conversion efficiency of 75%. Excited-state dynamic studies reveal that the NSMN has ultrafast nonradiative decay after photoexcitation. With these unique properties, the NSMN achieves efficient in vivo photoacoustic imaging and photothermal tumor ablation. This work demonstrates the superior potential of photochemical reactions for the synthesis of high-performance molecular PTAs.
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http://dx.doi.org/10.1002/adma.202102799DOI Listing
July 2021

Approaching Efficient and Narrow RGB Electroluminescence from D-A-Type TADF Emitters Containing an Identical Multiple Resonance Backbone as the Acceptor.

ACS Appl Mater Interfaces 2021 Jul 21. Epub 2021 Jul 21.

Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou, Jiangsu 215123, P. R. China.

Highly twisted electron donor (D)-electron acceptor (A)-type thermally activated delayed fluorescence (TADF) emitters can achieve high efficiency while suffering from serious structural relaxations and broad emissions. Multiple resonance (MR)-type TADF emitters can realize narrow emission. However, until now, only a few efficient MR-emitting cores are reported and custom tunning of their emission color remains a major challenge in their wider applications. In this work, by combining the conventional TADF and MR-TADF designs, we demonstrate that color tuning and narrowing the spectral width of conventional TADF emission can be easily achieved simultaneously. We select a prototypical carbonyl (C═O)/N-based MR core as a backbone and attach it with D segments of different electron-donating abilities and numbers to obtain three different TADF emitters with emissions from sky blue to green and orange-red while maintaining the narrow emission of the original MR core. The corresponding sky blue, green, and orange-red organic light-emitting diodes achieve maximum external quantum efficiencies of 20.3, 27.3, and 26.3%, respectively, and narrow full widths at half-maximum all below 0.28 eV. These results provide a new molecular design strategy for developing narrowband TADF emitters with easily tunable emissions covering the full visible range.
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http://dx.doi.org/10.1021/acsami.1c09743DOI Listing
July 2021

Multi-Synergistic Removal of Low-Boiling-Point Contaminants with Efficient Carbon Aerogel-Based Solar Purifier.

ACS Appl Mater Interfaces 2021 Jul 5;13(27):31624-31634. Epub 2021 Jul 5.

Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, P. R. China.

Solar steam generation is considered as an efficient way for addressing water shortage issues seawater desalination and wastewater purification. In a solar evaporator, an absorber would convert optical energy to heat for evaporating nearby water. In this process, many low-boiling-point contaminants can also be evaporated along with water steam, which compromises the effectiveness of purification. There is, so far, no study on the removal of such low-boiling-point contaminants such as organic pesticides in wastewater. To address this problem, we demonstrate a versatile carbon hybrid aerogel (CHA) as a solar powered water purification platform. With an elaborate absorber design, the maximum solar evaporation rate of 2.1 kg m h is achieved under 1 sun illumination. More importantly, CHA can effectively suppress the evaporation of low-boiling-point contaminants including common pesticides and mercury ion its strong adsorption and retention effect. Synergetic steaming and the adsorption of CHA will inspire more paradigms of solar steam generation technologies for applications relevant to detoxification and water remediation.
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http://dx.doi.org/10.1021/acsami.1c06000DOI Listing
July 2021

AlO buffer-facilitated epitaxial growth of high-quality ZnO/ZnS core/shell nanorod arrays.

Nanoscale 2021 Jul;13(26):11525-11533

Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.

II-VI semiconductor heterojunctions show huge potential for application in nanodevice fabrication due to their type-II alignments owing to the better spatial separation of electrons and holes. However, the hetero-epitaxial growth of high-quality heterostructures is still a challenge, especially for materials with large lattice mismatch. In this work, well-aligned single-crystalline ZnO/ZnS core/shell nanorod arrays were obtained by introducing an Al2O3 buffer layer. It is interesting that the nature of the ZnS layer varies with the thickness of the Al2O3 layer. When Al2O3 is less than 2 nm, the interaction between the substrate and epilayer is strong enough to penetrate through the buffer layer, enabling the growth of ZnS on Al2O3-coated ZnO nanorod arrays. On the basis of detailed characterization, a rational growth mechanism of the core/shell heterostructure is proposed, in which the Al2O3 interlayer can eliminate voids due to the Kirkendall effect around the interface and accommodate a misfit dislocation between the inner ZnO and outer ZnS, resulting in more sufficient strain relaxation in the epitaxy. In addition, cathodoluminescence measurements demonstrate that the optical properties of the ZnO/ZnS heterostructure could be effectively improved by taking advantage of the thin Al2O3. The I-V curves characterized by PeakForce tunneling atomic force microscopy reveal that the heterostructure shows a typical rectifying behavior and good photoresponse to ultraviolet light. These findings may provide a reasonable and effective strategy for the growth of highly lattice-mismatched heterostructure arrays buffered by the Al2O3 layer, broadening the options for fabricating heterojunctions and promoting their applications in optoelectronic devices.
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http://dx.doi.org/10.1039/d1nr02613eDOI Listing
July 2021

Iron Self-Boosting Polymer Nanoenzyme for Low-Temperature Photothermal-Enhanced Ferrotherapy.

ACS Appl Mater Interfaces 2021 Jul 25;13(26):30274-30283. Epub 2021 Jun 25.

Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon 99077, Hong Kong SAR, P. R. China.

In this work, an iron self-boosting polymer nanoenzyme was prepared by using pyrrole-3-carboxylic acid as a monomer and iron as an oxidizing agent a simple and one-step method [hereafter referred to as FePPy nanoparticles (NPs)]. In fact, researchers previously paid negligible attention on the iron element during the polymerization reaction of polypyrrole, thus the intrinsically catalytic functions and enzymatic activities of the high iron content (wt %: 21.11%) are ignored and not fully explored. As expected, results demonstrate that the as-synthesized FePPy NPs can decompose HO to generate hydroxyl radicals (OH) which exhibit enzyme characteristics, further inducing a nonapoptotic ferroptosis pathway. Moreover, the nanoenzyme shows impressive photothermal properties which can accelerate the Fenton reactions to enhance ferroptosis. The combined photothermal and ferroptosis therapy of FePPy NPs was found to have high efficacy. With the properties of easy synthesis, high efficacy, and good biocompatibility, the FePPy NPs are considered as potential agents for cancer treatments.
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http://dx.doi.org/10.1021/acsami.1c01658DOI Listing
July 2021

Aligned Millineedle Arrays for Solar Power Seawater Desalination with Site-Specific Salt Formation.

Small 2021 Jun 21:e2101487. Epub 2021 Jun 21.

Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, SAR, 999077, P. R. China.

As a sustainable and clean water production technology, solar thermal water evaporation has been extensively studied in the past few years. One challenge is that upon operation, salt would form on surface of the solar absorbers leading to inefficient water supply and light absorption and thus much reduced water vaporization rate. To address this problem, a simple solar evaporator based on an array of aligned millineedles for efficient solar water evaporation and controlled site-specific salt formation is demonstrated. The maximum solar evaporation rate achieved is 2.94 kg m h under one Sun irradiation in brine of high salinity (25 wt% NaCl), achieving energy conversion efficiency of 94.5% simultaneously. More importantly, the spontaneously site-specific salt formation on the tips of millineedles endows this solar evaporator with salt harvesting capacity. Rationally separating the clean water and salt from brine by condensation and gravity assistance, this tip-preferential crystallization solar evaporator is not affected by the salt clogging compared with conventional 2D solar evaporators. This study provides new insights on the design of solar evaporators and advances their applications in sustainable seawater desalination and wastewater management.
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http://dx.doi.org/10.1002/smll.202101487DOI Listing
June 2021

Aqueous MnV O -Zn Battery with High Operating Voltage and Energy Density.

Small 2021 Jul 9;17(28):e2008182. Epub 2021 Jun 9.

Department of Chemistry, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Tat Chee Avenue, Kowloon, 999077, Hong Kong.

Aqueous Zn ion batteries (AZIBs), featuring low cost, long-term cycling stability, and superior safety are promising for applications in advanced energy storage devices. However, they still suffer from unsatisfactory energy density and operating voltage, which are closely related to cathode materials used. Herein, the use of monoclinic MnV O (MVO) is reported, which can be activated for high-capacity Zn ions storage by electrochemically oxidizing part of the Mn to Mn or Mn while the remaining Mn ions act as binders/pillars to hold the layer structure of MVO and maintain its integrity during charging/discharging process. Moreover, after introducing carbon nanotubes (CNT), the MVO:CNT composite not only provides robust 3D Zn-ion diffusion channels but also shows enhanced structural integrity. As a result, a MVO:CNT cathode delivers a high midpoint voltage (1.38 V after 3000 cycles at 2 A g ) and a high energy density of 597.9 W h kg . Moreover, DFT analyses clearly illustrate stepwise Zn ion insertion into the MnV O lattice and ex-situ analyses results further verify the highly structural reversibility of the MnV O cathode upon extended cycling, demonstrating the good potential of MnV O for the establishment of viable aqueous Zn ion battery systems.
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http://dx.doi.org/10.1002/smll.202008182DOI Listing
July 2021

Multifunctional Crosslinking-Enabled Strain-Regulating Crystallization for Stable, Efficient α-FAPbI -Based Perovskite Solar Cells.

Adv Mater 2021 Jul 4;33(29):e2008487. Epub 2021 Jun 4.

Department of Electronic and Information Engineering, Research Institute for Smart Energy (RISE), The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.

α-Formamidinium lead triiodide (α-FAPbI ) represents the state-of-the-art for perovskite solar cells (PSCs) but experiences intrinsic thermally induced tensile strain due to a higher phase-converting temperature, which is a critical instability factor. An in situ crosslinking-enabled strain-regulating crystallization (CSRC) method with trimethylolpropane triacrylate (TMTA) is introduced to precisely regulate the top section of perovskite film where the largest lattice distortion occurs. In CSRC, crosslinking provides in situ perovskite thermal-expansion confinement and strain regulation during the annealing crystallization process, which is proven to be much more effective than the conventional strain-compensation (post-treatment) method. Moreover, CSRC with TMTA successfully achieves multifunctionality simultaneously: the regulation of tensile strain, perovskite defects passivation with an enhanced open-circuit voltage (V  = 50 mV), and enlarged perovskite grain size. The CSRC approach gives significantly enhanced power conversion efficiency (PCE) of 22.39% in α-FAPbI -based PSC versus 20.29% in the control case. More importantly, the control PSCs' instability factor-residual tensile strain-is regulated into compression strain in the CSRC perovskite film through TMTA crosslinking, resulting in not only the best PCE but also outstanding device stability in both long-term storage (over 4000 h with 95% of initial PCE) and light soaking (1248 h with 80% of initial PCE) conditions.
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http://dx.doi.org/10.1002/adma.202008487DOI Listing
July 2021

Top-emitting thermally activated delayed fluorescence organic light-emitting devices with weak light-matter coupling.

Light Sci Appl 2021 Jun 3;10(1):116. Epub 2021 Jun 3.

Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, 999077, Hong Kong SAR, China.

Resonance interaction between a molecular transition and a confined electromagnetic field can lead to weak or strong light-matter coupling. Considering the substantial exciton-phonon coupling in thermally activated delayed fluorescence (TADF) materials, it is thus interesting to explore whether weak light-matter coupling can be used to redistribute optical density of states and to change the rate of radiative decay. Here, we demonstrate that the emission distribution of TADF emitters can be reshaped and narrowed in a top-emitting organic light-emitting device (OLED) with a weakly coupled microcavity. The Purcell effect of weak microcavity is found to be different for TADF emitters with different molecular orientations. We demonstrate that radiative rates of the TADF emitters with vertical orientation can be substantial increased in weakly coupled organic microcavity. These observations can enhance external quantum efficiencies, reduce efficiency roll-off, and improve color-purities of TADF OLEDs, especially for emitters without highly horizontal orientation.
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http://dx.doi.org/10.1038/s41377-021-00559-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8175730PMC
June 2021

Plasmonic-doped melanin-mimic for CXCR4-targeted NIR-II photoacoustic computed tomography-guided photothermal ablation of orthotopic hepatocellular carcinoma.

Acta Biomater 2021 Jul 31;129:245-257. Epub 2021 May 31.

Department of Hepatobiliary Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510280, China; Institute of Digital Intelligence of Zhujiang Hospital of Southern Medical University, Guangzhou, 510280, China; Guangdong Provincial Clinical and Engineering Technology Center of Digital Medicine, Guangzhou, 510280, China. Electronic address:

Effective and noninvasive diagnosis and prompt treatment of early-stage hepatocellular carcinoma (HCC) are urgently needed to reduce its mortality rate. Herein, the integration of high-resolution diagnostic second near-infrared (NIR-II) photoacoustic computed tomography (PACT) and imaging-guided targeted photothermal ablation of orthotopic small HCC (SHCC) is presented for the first time, which was enabled by a plasmonic platinum (Pt)-doped polydopamine melanin-mimic nanoagent. As designed, an antibody-modified nanoagent (designated [email protected]) with a plasmonic blackbody-like NIR absorption and superior photothermal conversion efficiency (71.3%) selectively targeted and killed CXCR4-overexpressing HCC (HepG2) cells, which was validated in in vitro experiments. The targeted accumulation properties of [email protected] in vivo were previously recognized by demonstrating effective NIR-II PA imaging and photothermal ablation in a subcutaneous HCC mouse model. Subsequently, with real-time quantitative guidance by PACT for the accurate diagnosis of intraabdominal SHCC (approximately 4 mm depth), the effective and noninvasive photothermal ablation of SHCCs was successfully demonstrated in an orthotopic tumor-bearing mouse model without damaging adjacent liver tissues. These results show a great potential of NIR-II PACT-guided noninvasive photothermal therapy as an innovative phototheranostic approach and expand the biomedical applications of melanin-mimic materials. STATEMENT OF SIGNIFICANCE: In this paper, we report the first diagnostic NIR-II photoacoustic computed tomography (PACT)-guided noninvasive photothermal ablation of small hepatocellular carcinoma (SHCC) located in deep tissues in orthotopic tumor-bearing mice; this process is empowered by a polydopamine-based melanin-mimic tumor-targeting nanoagent doped with plasmonic platinum that provides superior NIR-II (1064 nm) absorption and photothermal conversion efficiency of 71.3%. Following surface modification with anti-CXCR4 antibodies, the nanoagent (namely [email protected]) can selectively target CXCR4-overexpressed HepG2 carcinoma cells and tumor lesions, and serve as the theranostic agent for both NIR-II PACT-based diagnosis of orthotopic SHCC (diameter less than 5 mm) and efficient NIR-II PTT in vivo. This study may also extend the potential of melanin-derived blackbody materials for optical-biomedical and water distillation applications.
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http://dx.doi.org/10.1016/j.actbio.2021.05.034DOI Listing
July 2021

Compact Biomimetic Hair Sensors Based on Single Silicon Nanowires for Ultrafast and Highly-Sensitive Airflow Detection.

Nano Lett 2021 06 29;21(11):4684-4691. Epub 2021 May 29.

Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, People's Republic of China.

Wearable sensors that can mimic functionalities of human bodies have attracted intense recent attention. However, research on wearable airflow sensors is still lagging behind. Herein, we report a biomimetic hair sensor based on a single ultralong silicon nanowire (SiNW-BHS) for airflow detection. In our device, the SiNW can provide both mechanical and electrical responses in airflow, which enables a simple and compact design. The SiNW-BHSs can detect airflow with a low detection limit (<0.15 m/s) and a record-high response speed (response time <40 ms). The compact design of the SiNW-BHSs also enables easy integration of an array of devices onto a flexible substrate to mimic human skin to provide comprehensive airflow information including wind speed, incident position, incident angle, and so forth. This work provides novel-designed BHSs for ultrafast and highly sensitive airflow detection, showing great potential for applications such as e-skins, wearable electronics, and robotics.
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http://dx.doi.org/10.1021/acs.nanolett.1c00852DOI Listing
June 2021

Self-assembly of Amphiphilic Porphyrins To Construct Nanoparticles for Highly Efficient Photodynamic Therapy.

Chemistry 2021 May 7. Epub 2021 May 7.

Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.

Hydrophobic photosensitizers greatly affect cell permeability and enrichment in tumors, but they cannot be used directly for clinical applications because they always aggregate in water, preventing their circulation in the blood and accumulation in tumor cells. As a result, amphiphilic photosensitizers are highly desirable. Although nanomaterial-based photosensitizers can solve water solubility, they have the disadvantages of complicated operation, poor reproducibility, low drug loading, and poor stability. In this work, an efficient synthesis strategy is proposed that converts small molecules into nanoparticles in 100 % aqueous solution by molecular assembly without the addition of any foreign species. Three photosensitizers with triphenylphosphine units and ethylene glycol chains of different lengths, TPP-PPh , TPP-PPh -2PEG and TPP-PPh -4PEG, were synthesized to improve amphiphilicity. Of the three photosensitizers, TPP-PPh -4PEG is the most efficient (singlet oxygen yield: 0.89) for tumor photodynamic therapy not only because of its definite constituent, but also because its amphiphilic structure allows it to self-assemble in water.
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http://dx.doi.org/10.1002/chem.202101199DOI Listing
May 2021

Single molecular nanomedicine with NIR light-initiated superoxide radical, singlet oxygen and thermal generation for hypoxia-overcoming cancer therapy.

Nanoscale 2021 May;13(17):8012-8016

Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong.

While photodynamic therapy (PDT) of cancer has attracted much recent attention, its general applications are limited by the shallow tissue penetration depth of short-wavelength photons and the low oxygen contents in typical solid tumors. Herein, we develop small molecule (BthB)-based nanoparticles (NPs) which not only generate heat for effective photothermal therapy (PTT), but also generate superoxide radicals (O2˙-) for hypoxia-overcoming photodynamic therapy (PDT) upon irradiation with an 808 nm laser. To the best of our knowledge, there are few reports of organic PDT agents which can work in hypoxia upon irradiation with photons having wavelengths longer than 800 nm. With the merits of NIR-excitability for better penetration depth, the BthB NPs are demonstrated both in vitro and in vivo to be highly effective for cancer ablation.
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http://dx.doi.org/10.1039/d1nr01094hDOI Listing
May 2021

Ultrasound-Enhanced Self-Exciting Photodynamic Therapy Based on Hypocrellin B.

Chem Asian J 2021 May 21;16(10):1221-1224. Epub 2021 Apr 21.

Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.

Peroxalate CL as an energy source to excite photosensitizers has attracted tremendous attention in photodynamic therapy (PDT). In this work, peroxyoxalate CPPO and hypocrellin B (HB)-based nanoparticles (CBNPs) for ultrasound (US)-enhanced self-exciting PDT were designed and prepared. CBNPs showed an excellent therapeutic effect against cancer cells with the assistance of US. This US-enhanced-chemiluminescence system avoids the dependence on external light and provides an example for inspiring more effective and precise strategies for cancer treatment.
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http://dx.doi.org/10.1002/asia.202100205DOI Listing
May 2021

Achieving high singlet-oxygen generation by applying the heavy-atom effect to thermally activated delayed fluorescent materials.

Chem Commun (Camb) 2021 May;57(40):4902-4905

Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong, 999077, P. R. China. and Joint Laboratory of Nano-Organic Functional Materials and Devices (TIPC and CityU), City University of Hong Kong, Kowloon, Hong Kong SAR, P. R. China.

A bromine-substituted thermally activated delayed fluorescent (TADF) molecule AQCzBr2 is designed with both small singlet-triplet splitting (ΔEST) and increased spin-orbit coupling (SOC) to boost intersystem crossing (ISC) for singlet oxygen generation. AQCzBr2 nanoparticles (NPs) demonstrate high productivity of singlet oxygen generation (ΦΔ = 0.91) which allows highly efficient photodynamic therapy toward cancer cells.
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http://dx.doi.org/10.1039/d0cc08323bDOI Listing
May 2021

Contact lenses coated with hybrid multifunctional ternary nanocoatings (Phytomolecule-coated ZnO nanoparticles:Gallic Acid:Tobramycin) for the treatment of bacterial and fungal keratitis.

Acta Biomater 2021 Jul 15;128:262-276. Epub 2021 Apr 15.

Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong. Electronic address:

Contact lenses are widely used for visual corrections. However, while wearing contact lenses, eyes typically face discomforts (itching, irritation, burning, etc.) due to foreign object sensation, lack of oxygen permeability, and tear film disruption as opposed to a lack of wetting agents. Eyes are also prone to ocular infections such as bacterial keratitis (BK) and fungal keratitis (FK) and inflammatory events such as contact lens-related acute red eye (CLARE), contact lens peripheral ulcer (CLPU), and infiltrative keratitis (IK) caused by pathogenic bacterial and fungal strains that contaminate contact lenses. Therefore, a good design of contact lenses should adequately address the need for wetting, the supply of antioxidants, and antifouling and antimicrobial efficacy. Here, we developed multifunctional gallic acid (GA), phytomolecules-coated zinc oxide nanoparticles (ZN), and phytomolecules-coated zinc oxide nanoparticles + gallic acid + tobramycin (ZGT)-coated contact lenses using a sonochemical technique. The coated contact lenses exhibited significant antibacterial (>log 5.60), antifungal, and antibiofilm performance against BK-causing multidrug resistant bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia. coli) and FK-related pathogenic fungal strains (Candida albicans, Aspergillus fumigatus, and Fusarium solani). The gallic acid, tobramycin, and phytomolecules-coated zinc oxide nanoparticles have different functionalities (-OH, -NH, -COOH, -COH, etc.) that enhanced wettability of the coated contact lenses as compared to that of uncoated ones and further enabled them to exhibit remarkable antifouling property by prohibiting adhesion of platelets and proteins. The coated contact lenses also showed significant antioxidant activity by scavenging DPPH and good cytocompatibility to human corneal epithelial cells and keratinocytes cell lines. STATEMENT OF SIGNIFICANCE: • Multifunctional coated lenses were developed with an efficient sonochemical approach. • Lens surface was modified with nanocoatings of ZnO nanoparticles, gallic acid, and tobramycin. • This synergistic combination endowed the lenses with remarkable antimicrobial activity. • Coated lenses also showed noteworthy antifouling and biofilm inhibition activities. • Coated lenses showed good antioxidant, biocompatibility, and wettability characteristics.
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http://dx.doi.org/10.1016/j.actbio.2021.04.014DOI Listing
July 2021

2D materials for conducting holes from grain boundaries in perovskite solar cells.

Light Sci Appl 2021 Mar 31;10(1):68. Epub 2021 Mar 31.

Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.

Grain boundaries in organic-inorganic halide perovskite solar cells (PSCs) have been found to be detrimental to the photovoltaic performance of devices. Here, we develop a unique approach to overcome this problem by modifying the edges of perovskite grain boundaries with flakes of high-mobility two-dimensional (2D) materials via a convenient solution process. A synergistic effect between the 2D flakes and perovskite grain boundaries is observed for the first time, which can significantly enhance the performance of PSCs. We find that the 2D flakes can conduct holes from the grain boundaries to the hole transport layers in PSCs, thereby making hole channels in the grain boundaries of the devices. Hence, 2D flakes with high carrier mobilities and short distances to grain boundaries can induce a more pronounced performance enhancement of the devices. This work presents a cost-effective strategy for improving the performance of PSCs by using high-mobility 2D materials.
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http://dx.doi.org/10.1038/s41377-021-00515-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8012639PMC
March 2021

A Diradicaloid Small Molecular Nanotheranostic with Strong Near-Infrared Absorbance for Effective Cancer Photoacoustic Imaging and Photothermal Therapy.

ACS Appl Mater Interfaces 2021 Apr 31;13(14):15983-15991. Epub 2021 Mar 31.

Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, P.R. China.

Organic small molecule-based phototheranostics hold great promise for clinical translation by virtue of their distinct chemical structure, easy reproducibility, and high purity. However, reported molecular agents typically have relatively low optical absorbances, particularly over the near-infrared (NIR) region, and this limits their phototheranostic performance. Herein, we first exploit a diradicaloid molecular structure for enhancing NIR absorption to facilitate efficient photoacoustic imaging (PAI)-guided photothermal therapy (PTT). The donor-acceptor interaction in the diradicaloid molecule (DRM) leads to strong charge transfer resulting on obvious diradical characteristics, which is beneficial for NIR absorption. The DRM possesses excellent light-harvesting ability, with a mass extinction coefficient of ∼220 L g cm, which is much higher than those (∼5-100 L g cm) of typical organic molecules. After assembling into nanoparticles, they show good water dispersibility, good photostability, and impressive performance for PAI-guided PTT and . The impressive and performances show that developing small molecules with diradicaloid structures can be an effective approach for enhancing NIR harvesting capability for biomedical applications.
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http://dx.doi.org/10.1021/acsami.0c21889DOI Listing
April 2021

Recent Progress of Alkyl Radicals Generation-Based Agents for Biomedical Applications.

Adv Healthc Mater 2021 05 18;10(10):e2100055. Epub 2021 Mar 18.

Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, P. R. China.

Photodynamic therapy (PDT) is extensively explored for anticancer and antibacterial applications. It typically relies on oxygen-dependent generation of reactive oxygen species (ROS) to realize its killing effect. This type of therapy modality shows compromised therapeutic results for treating hypoxic tumors or bacteria-infected wounds. Recently, alkyl radicals attracted much attention as they can be generated from some azo-based initiators only under mild heat stimulus without oxygen participation. Many nanocarriers or hydrogel systems have been developed to load and deliver these radical initiators to lesion sites for theranostics. These systems show good anticancer or antimicrobial effect in hypoxic environment and some of them possess specific imaging abilities providing precise guidance for treatment. This review summarizes the developed materials that aim at treating hypoxic cancer and bacteria-infected wound by using this kind of oxygen-irrelevant alkyl radicals. Based on the carrier components, these agents are divided into three groups: inorganic, organic, as well as inorganic and organic hybrid carrier-based therapeutic systems. The construction of these agents and their specific advantages in biomedical field are highlighted. Finally, the existing problems and future promising development directions are discussed.
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http://dx.doi.org/10.1002/adhm.202100055DOI Listing
May 2021

Water-Soluble Organic Nanoparticles with Programable Intermolecular Charge Transfer for NIR-II Photothermal Anti-Bacterial Therapy.

Angew Chem Int Ed Engl 2021 05 16;60(21):11758-11762. Epub 2021 Apr 16.

Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, P. R. China.

Extensive recent efforts have been put on the design of high-performance organic near-infrared (NIR) photothermal agents (PTAs), especially over NIR-II bio-window (1000-1350 nm). So far, the development is mainly limited by the rarity of molecules with good NIR-II response. Here, we report organic nanoparticles of intermolecular charge-transfer complexes (CTCs) with easily programmable optical absorption. By employing different common donor and acceptor molecules to form CTC nanoparticles (CT NPs), absorption peaks of CT NPs can be controllably tuned from the NIR-I to NIR-II region. Notably, CT NPs formed with perylene and TCNQ have a considerably red-shifted absorption peak at 1040 nm and achieves a good photothermal conversion efficiency of 42 % under 1064 nm excitation. These nanoparticles were used for antibacterial application with effective activity towards both Gram-negative and Gram-positive bacteria. This work opens a new avenue into the development of efficient PTAs.
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http://dx.doi.org/10.1002/anie.202101406DOI Listing
May 2021

A double-crosslinked self-healing antibacterial hydrogel with enhanced mechanical performance for wound treatment.

Acta Biomater 2021 04 30;124:139-152. Epub 2021 Jan 30.

Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, PR China. Electronic address:

Self-healing hydrogel systems usually suffer from poor mechanical performance stemmed from weaker and reversible non-covalent interactions or dynamic chemical bonds, which hamper their practical applications. This issue is addressed by adopting a double-crosslinking design involving both dynamic Schiff base bonds and non-dynamic photo-induced crosslinking. This leads to the formation of a special topological structure which simultaneously provide good self-healing capability and enhanced mechanical performance (elastic recovery and tensile modulus of 157.4 kPa, close to modulus of native skin). The quaternary ammonium and protonated amino groups can provide superior antibacterial capability; and Schiff base formation between residual aldehyde groups and amino groups on tissue surface contribute to hydrogel's adhesion to tissues (5.9 kPa). Furthermore, the multifunctional hydrogels with desirable mechanical performance, self-healing capability, superior antibacterial capability and tissue adhesion can significantly promote healing of infectious cutaneous wound, tissue remodeling and regeneration.
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http://dx.doi.org/10.1016/j.actbio.2021.01.038DOI Listing
April 2021

Near-infrared small molecule coupled with rigidness and flexibility for high-performance multimodal imaging-guided photodynamic and photothermal synergistic therapy.

Nanoscale Horiz 2021 02 14;6(2):177-185. Epub 2021 Jan 14.

Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong 999077, P. R. China.

Photodynamic therapy (PDT) synergized photothermal therapy (PTT) shows superior clinical application prospects than single PDT or PTT. On the other hand, multimodal imaging can delineate comprehensive information about the lesion site and thus help to improve therapy accuracy. However, integrating all these functions into one single molecule is challenging, let alone balancing and maximizing the efficacy of each function. Herein, a near-infrared (NIR) small molecule (ETTC) with an "acceptor-donor-acceptor" structure was designed and synthesized by coupling rigity and flexibility to simultaneously achieve NIR-II fluorescence imaging (NIR-II FLI), photoacoustic imaging, PTT and PDT. The efficacy of each functionality was well balanced and optimized (NIR-II quantum yield: 3.0%; reactive oxygen species generation: 3.2-fold higher than ICG; photothermal conversion efficiency: 52.8%), which may be attributed to the coupling of the rigid and flexible structures in ETTC to tactically manipulate the energy dissipation paths (non-radiative against radiative decay). As a proof-of-concept, under the effective guidance of local-tumor imaging by PA and whole-body imaging by NIR-II FL, complete tumor eradication was achieved via PDT and PTT combinational therapy. This work provides a novel perspective into conceiving and developing single molecule for efficient versatile biomedical applications.
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http://dx.doi.org/10.1039/d0nh00672fDOI Listing
February 2021

In Situ Scanning Transmission Electron Microscopy Observations of Fracture at the Atomic Scale.

Phys Rev Lett 2020 Dec;125(24):246102

Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China.

The formation, propagation, and structure of nanoscale cracks determine the failure mechanics of engineered materials. Herein, we have captured, with atomic resolution and in real time, unit cell-by-unit cell lattice-trapped cracking in two-dimensional (2D) rhenium disulfide (ReS_{2}) using in situ aberration corrected scanning transmission electron microscopy (STEM). Our real time observations of atomic configurations and corresponding strain fields in propagating cracks directly reveal the atomistic fracture mechanisms. The entirely brittle fracture with non-blunted crack tips as well as perfect healing of cracks have been observed. The mode I fracture toughness of 2D ReS_{2} is measured. Our experiments have bridged the linear elastic deformation zone and the ultimate nm-sized nonlinear deformation zone inside the crack tip. The dynamics of fracture has been explained by the atomic lattice trapping model. The direct visualization on the strain field in the ongoing crack tips and the gained insights of discrete bond breaking or healing in cracks will facilitate deeper insights into how atoms are able to withstand exceptionally large strains at the crack tips.
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http://dx.doi.org/10.1103/PhysRevLett.125.246102DOI Listing
December 2020

Anomalous fracture in two-dimensional rhenium disulfide.

Sci Adv 2020 Nov 18;6(47). Epub 2020 Nov 18.

Department of Applied Physics, Hong Kong Polytechnic University, Kowloon, Hong Kong, China.

Low-dimensional materials usually exhibit mechanical properties from those of their bulk counterparts. Here, we show in two-dimensional (2D) rhenium disulfide (ReS) that the fracture processes are dominated by a variety of previously unidentified phenomena, which are not present in bulk materials. Through direct transmission electron microscopy observations at the atomic scale, the structures close to the brittle crack tip zones are clearly revealed. Notably, the lattice reconstructions initiated at the postcrack edges can impose additional strain on the crack tips, modifying the fracture toughness of this material. Moreover, the monatomic thickness allows the restacking of postcrack edges in the shear strain-dominated cracks, which is potentially useful for the rational design of 2D stacking contacts in atomic width. Our studies provide critical insights into the atomistic processes of fracture and unveil the origin of the brittleness in the 2D materials.
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http://dx.doi.org/10.1126/sciadv.abc2282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7673817PMC
November 2020

Regulating Surface Termination for Efficient Inverted Perovskite Solar Cells with Greater Than 23% Efficiency.

J Am Chem Soc 2020 Nov 15;142(47):20134-20142. Epub 2020 Nov 15.

Department of Materials Science & Engineering, University of Washington, Seattle, Washington 98195, United States.

Passivating surface and bulk defects of perovskite films has been proven to be an effective way to minimize nonradiative recombination losses in perovskite solar cells (PVSCs). The lattice interference and perturbation of atomic periodicity at the perovskite surfaces often significantly affect the material properties and device efficiencies. By tailoring the terminal groups on the perovskite surface and modifying the surface chemical environment, the defects can be reduced to enhance the photovoltaic performance and stability of derived PVSCs. Here, we report a rationally designed bifunctional molecule, piperazinium iodide (), containing both RNH and RNH groups on the same six-membered ring, behaving both as an electron donor and an electron acceptor to react with different surface-terminating ends on perovskite films. The resulting perovskite films after defect passivation show released surface residual stress, suppressed nonradiative recombination loss, and more -type characteristics for sufficient energy transfer. Consequently, charge recombination is significantly suppressed to result in a high open-circuit voltage () of 1.17 V and a reduced loss of 0.33 V. A very high power conversion efficiency (PCE) of 23.37% (with 22.75% certified) could be achieved, which is the highest value reported for inverted PVSCs. Our work reveals a very effective way of using rationally designed bifunctional molecules to simultaneously enhance the device performance and stability.
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http://dx.doi.org/10.1021/jacs.0c09845DOI Listing
November 2020

Water-Splitting Based and Related Therapeutic Effects: Evolving Concepts, Progress, and Perspectives.

Small 2020 11 30;16(47):e2004551. Epub 2020 Oct 30.

Department of Chemistry, Institution Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, P. R. China.

Water-splitting has been extensively studied especially for energy applications. It is often not paid with enough attention for biomedical applications. In fact, several innovative breakthroughs have been achieved in the past few years by employing water-splitting for treating cancer and other diseases. Interestingly, among these important works, only two reports have mentioned the term "water-splitting." For this reason, the importance of water-splitting for biomedical applications is significantly underestimated. This progress work is written with the aims to explain and summarize how the principle of water-splitting is employed to achieve therapeutic results not offered by conventional approaches. It is expected that this progress report will not only explain the importance of water-splitting to scientists in the biomedical fields, it should also draw attention from scientists working on energy applications of water-splitting.
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http://dx.doi.org/10.1002/smll.202004551DOI Listing
November 2020

Spontaneously Ordered Hierarchical Two-Dimensional Wrinkle Patterns in Two-Dimensional Materials.

Nano Lett 2020 Nov 26;20(11):8420-8425. Epub 2020 Oct 26.

Department of Chemistry and Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong China.

Achieving two-dimensionally (2D) ordered surface wrinkle patterns is still challenging not only for the atomic-thick 2D materials but also in general for all soft surfaces. Normally disordered 2D wrinkle patterns on isotropic surfaces can be rendered via biaxial straining. Here, we report that the 1D and 2D ordered wrinkle patterns in 2D materials can be produced by sequential wrinkling controlled by thermal straining and vertical spatial confinement. The various hierarchical patterns in 2D materials generated by our method are highly periodic, and the hexagonal crystal symmetry is obeyed. More interestingly, these patterns can be maintained in suspended monolayers after delamination from the underlying surfaces which shows the great application potentials. Our new approach can simplify the patterning processes on 2D layered materials and reduce the risk of damage compared to conventional lithography methods, and numerous engineering applications that require nanoscale ordered surface texturing could be empowered.
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http://dx.doi.org/10.1021/acs.nanolett.0c03819DOI Listing
November 2020

Managing Locally Excited and Charge-Transfer Triplet States to Facilitate Up-Conversion in Red TADF Emitters That Are Available for Both Vacuum- and Solution-Processes.

Angew Chem Int Ed Engl 2021 Feb 27;60(5):2478-2484. Epub 2020 Nov 27.

Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.

Developing red thermally activated delayed fluorescence (TADF) emitters for high-performance OLEDs is still facing great challenge. Herein, three red TADF emitters, pDBBPZ-DPXZ, pDTBPZ-DPXZ, and oDTBPZ-DPXZ, are designed and synthesized with same donor-acceptor (D-A) backbone with different peripheral groups attaching on the A moieties. Their lowest triplet states change from locally excited to charge transfer character leading to significantly enhance reverse intersystem crossing process. In particular, oDTBPZ-DPXZ exhibits efficient TADF feature and exciton utilization. It not only achieves an external quantum efficiency (EQE) of 20.1 % in red vacuum-processed OLED, but also realize a high EQE of 18.5 % in a solution-processed OLED, which is among the best results in solution-processed red TADF OLEDs. This work provides an effective strategy for designing red TADF molecules by managing energy level alignments to facilitate the up-conversion process and thus enhance exciton harvesting.
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http://dx.doi.org/10.1002/anie.202012070DOI Listing
February 2021

Pseudocapacitive Ti-Doped Niobium Pentoxide Nanoflake Structure Design for a Fast Kinetics Anode toward a High-Performance Mg-Ion-Based Dual-Ion Battery.

ACS Appl Mater Interfaces 2020 Oct 12;12(42):47539-47547. Epub 2020 Oct 12.

Center of Super-Diamond and Advanced Film (COSDAF) and Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong SAR 999077, China.

Magnesium-ion batteries (MIBs) have received increasing attention for next-generation energy storage recently because of the natural abundance, high capacity, and dendrite-free deposition of Mg. However, their applications are hindered by irreversible Mg anode plating in conventional electrolytes and the lack of cathode materials, demonstrating high working voltage, satisfactory Mg diffusivity, and long cycling life. In this work, we first developed a novel magnesium-ion based dual-ion battery (Mg-DIB) by utilizing expanded graphite as the cathode and Ti-doped niobium pentoxide nanoflakes (Ti-NbO NFs) as the anode. The Ti-NbO NFs showed hierarchical structures of microspheres with diameters of 4-5 μm assembled by nanoflakes. For the first time, the Mg-ion storage mechanism in Ti-NbO NFs was investigated. Benefiting from the hierarchical structure design and pseudocapacitive intercalation behavior of Mg ions, the Ti-NbO NF anode exhibited fast Mg-ion diffusion. Consequently, the Mg-DIB exhibited a high discharge capacity of 93 mA h g at 1 C (1 C corresponding to 100 mA g), along with good long-term cycling performance with a capacity retention of 79% at 3 C after 500 cycles. The Mg-DIB also demonstrated a capacity retention of 77% at 5C, indicating its good rate performance. Moreover, the Mg-DIB exhibited a high discharge medium voltage of ∼1.83 V, thus enabling a high energy density of 174 W h kg at 183 W kg and 122 W h kg at a high power density of 845 W kg, among the best of the reported magnesium-ion full batteries. Our work provides a new strategy to improve the performance of MIBs and other rechargeable batteries.
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http://dx.doi.org/10.1021/acsami.0c13045DOI Listing
October 2020

Real-Time Pharmaceutical Evaluations of Near-Infrared II Fluorescent Nanomedicine Bound Polyethylene Glycol Ligands for Tumor Photothermal Ablation.

ACS Nano 2020 10 17;14(10):13681-13690. Epub 2020 Sep 17.

Translational Medicine Center, Key Laboratory of Molecular Target & Clinical Pharmacology, School of Pharmaceutical Sciences & The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou 510260, P. R. China.

Pharmaceutical evaluations of nanomedicines are of great significance for their further launch into industry and clinic. Near-infrared (NIR) fluorescence imaging plays essential roles in preclinical drug development by providing important insights into the biodistributions of drugs with deep tissue penetration and high spatiotemporal resolution. However, NIR-II fluorescence imaging has rarely been exploited for real-time pharmaceutical evaluations of nanomedicine. Herein, we developed a highly emissive NIR-II luminophore to establish a versatile nanoplatform to noninvasively monitor the metabolism of nanomedicines bound various polyethylene glycol (PEG) ligands in a real-time manner. An alternative D-A-D conjugated oligomer (DTTB) was synthesized to achieve NIR-II emission peaked at ∼1050 nm with high fluorescence QYs of 13.4% and a large absorption coefficient. By anchoring with the DTTB molecule, intrinsically fluorescent micelles were fabricated and bound with PEG ligands at various chain lengths. NIR-II fluorescence and photoacoustic imaging results revealed that an appropriate PEG chain length could effectively contribute to the longer blood circulation and better tumor targeting. therapeutic experiments also confirmed the optimized nanomedicines have efficient photothermal elimination of tumors and good biosafety. This work offered an alternative highly fluorescent NIR-II material and demonstrated a promising approach for real-time pharmaceutical evaluation of nanomedicine .
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http://dx.doi.org/10.1021/acsnano.0c05885DOI Listing
October 2020
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