Lateral Flow Assay Biotesting by Utilizing Plasmonic Nanoparticles Made of Inexpensive Metals─Replacing Colloidal Gold.

Nanoparticles (NPs) can be conjugated with diverse biomolecules and employed in biosensing to detect target analytes in biological samples. This proven concept was primarily used during the COVID-19 pandemic with gold-NP-based lateral flow assays (LFAs). Considering the gold price and its worldwide depletion, here we show that novel plasmonic NPs based on inexpensive metals, titanium nitride (TiN) and copper covered with a gold shell (Cu@Au), perform comparable to or even better than gold nanoparticles. After conjugation, these novel nanoparticles provided high figures of merit for LFA testing, such as high signals and specificity and robust naked-eye signal recognition. Since the main cost of Au NPs in commercial testing kits is the colloidal synthesis, our development with the Cu@Au and the laser-ablation-fabricated TiN NPs is exciting, offering potentially inexpensive plasmonic nanomaterials for various bioapplications. Moreover, our machine learning study showed that biodetection with TiN is more accurate than that with Au.

Imaging Photon-Induced Near-Field Distributions of a Plasmonic, Self-Assembled Vesicle by a Laser-Integrated Electron Microscope.

Plasmonic polymeric nanoassemblies offer valuable opportunities in photoconversion applications. Localized surface plasmon mechanisms behind such nanoassemblies govern their functionalities under light illumination. However, an in-depth investigation at the single nanoparticle (NP) level is still challenging, especially when the buried interface is involved, due to the availability of suitable techniques. Here, we synthesized an anisotropic heterodimer composed of a self-assembled polymer vesicle (THPG) capped with a single gold NP, enabling an 8-fold enhancement in hydrogen generation compared to the nonplasmonic THPG vesicle. We explored the anisotropic heterodimer at the single particle level by employing advanced transmission electron microscopes, including one equipped with a femtosecond pulsed laser, which allows us to visualize the polarization- and frequency-dependent distribution of the enhanced electric near fields at the vicinity of Au cap and Au-polymer interface. These elaborated fundamental findings may guide designing new hybrid nanostructures tailored for plasmon-related applications.

Design of Furan-Based Acceptors for Organic Photovoltaics.

We explore a series of furan-based non-fullerene acceptors and report their optoelectronic properties, solid-state packing, photodegradation mechanism and application in photovoltaic devices. Incorporating furan building blocks leads to the expected enhanced backbone planarity, reduced band gap and red-shifted absorption of these acceptors. Still, their position in the molecule is critical for stability and device performance. We found that the photodegradation of these acceptors originates from two distinct pathways: electrocyclic photoisomerization and Diels-Alder cycloaddition of singlet oxygen. These mechanisms are of general significance to most non-fullerene acceptors, and the photostability depends strongly on the molecular structure. Placement of furans next to the acceptor termini leads to better photostability, well-balanced hole/electron transport, and significantly improved device performance. Methylfuran as the linker offers the best photostability and power conversion efficiency (>14 %), outperforming all furan-based acceptors reported to date and all indacenodithiophene-based acceptors. Our findings show the possibility of photostable furan-based alternatives to the currently omnipresent thiophene-based photovoltaic materials.

Redox-Bipolar Polyimide Two-Dimensional Covalent Organic Framework Cathodes for Durable Aluminium Batteries.

Emerging rechargeable aluminium batteries (RABs) offer a sustainable option for next-generation energy storage technologies with low cost and exemplary safety. However, the development of RABs is restricted by the limited availability of high-performance cathode materials. Herein, we report two polyimide two-dimensional covalent organic frameworks (2D-COFs) cathodes with redox-bipolar capability in RAB. The optimal 2D-COF electrode achieves a high specific capacity of 132 mAh g-1 . Notably, the electrode presents long-term cycling stability (with a negligible ≈0.0007 % capacity decay per cycle), outperforming early reported organic RAB cathodes. 2D-COFs integrate n-type imide and p-type triazine active centres into the periodic porous polymer skeleton. With multiple characterizations, we elucidate the unique Faradaic reaction of the 2D-COF electrode, which involves AlCl2+ and AlCl4 - dual-ions as charge carriers. This work paves the avenue toward novel organic cathodes in RABs.

Highly thermal stable RNase A@PbS/ZnS quantum dots as NIR-IIb image contrast for visualizing temporal changes of microvasculature remodeling in flap.

Surgeons face great challenges in acquiring high-performance imaging because fluorescence probes with desired thermal stability remains rare. Here, hybrid lead sulfide/zinc sulfide quantum dots (PbS/ZnS QDs) nanostructures emitting in the long-wavelength end of the second near-infrared (NIR-IIb) window were synthesized and conjugated with Ribonuclease-A (RNase A). Such formed RNase A@PbS/ZnS QDs exhibited strong NIR IIb fluorescence and thermal stability, as supported by the photoluminescent emission assessment at different temperatures. This will allow the RNase A@PbS/ZnS QDs to provide stable fluorescence signals for long-time intraoperative imaging navigation, despite often happened, undesirable thermal accumulation in vivo. Compared to NIR-IIa fluorescence imaging, NIR-IIb vascular fluorescence imaging achieved larger penetration depth, higher signal/background ratios and nearly zero endogenous tissue autofluorescence. Moreover, these QDs illustrate the reliability during the real-time and long-time precise assessment of flap perfusion by clearly visualizing microvasculature map. These findings contribute to intraoperative imaging navigation with higher precision and lower risk.

Synergistic Effect of Dielectric Property and Energy Transfer on Charge Separation in Non-Fullerene-Based Solar Cells.

In non-fullerene-based photovoltaic devices, it is unclear how excitons efficiently dissociate into charge carriers under small driving force. Here, we developed a modified method to estimate dielectric constants of PM6 donor and non-fullerene acceptors. Surprisingly, most non-fullerene acceptors and blend films showed higher dielectric constants. Moreover, they exhibited larger dielectric constants differences at the optical frequency. These results are likely bound to reduced exciton binding energy and bimolecular recombination. Besides, the overlap between the emission spectrum of donor and absorption spectra of non-fullerene acceptors allowed the energy transfer from donor to acceptors. Hence, based on the synergistic effect of dielectric property and energy transfer resulting in efficient charge separation, our finding paves an alternative path to elucidate the physical working mechanism in non-fullerene-based photovoltaic devices.

Air-Processed, Stable Organic Solar Cells with High Power Conversion Efficiency of 7.41.

High efficiency, excellent stability, and air processability are all important factors to consider in endeavoring to push forward the real-world application of organic solar cells. Herein, an air-processed inverted photovoltaic device built upon a low-bandgap, air-stable, phenanthridinone-based ter-polymer (C150 H218 N6 O6 S4 )n (PDPPPTD) and [6,6]-phenyl-C61 -butyric acid methyl ester (PC61 BM) without involving any additive engineering processes yields a high efficiency of 6.34%. The PDPPPTD/PC61 BM devices also exhibit superior thermal stability and photo-stability as well as long-term stability in ambient atmosphere without any device encapsulation, which show less performance decay as compared to most of the reported organic solar cells. In view of their great potential, solvent additive engineering via adding p-anisaldehyde (AA) is attempted, leading to a further improved efficiency of 7.41%, one of the highest efficiencies for all air-processed and stable organic photovoltaic devices. Moreover, the device stability under different ambient conditions is also further improved with the AA additive engineering. Various characterizations are conducted to probe the structural, morphology, and chemical information in order to correlate the structure with photovoltaic performance. This work paves a way for developing a new generation of air-processable organic solar cells for possible commercial application.

Harnessing the properties of colloidal quantum dots in luminescent solar concentrators.

Luminescent solar concentrators (LSCs) can serve as large-area sunlight collectors, are suitable for applications in high-efficiency and cost-effective photovoltaics (PVs), and provide adaptability to the needs of architects for building-integrated PVs, which makes them an attractive option for transforming buildings into transparent or non-transparent electricity generators. Compared with traditional organic dyes, colloidal semiconducting quantum dots (QDs) are excellent candidates as emitters for LSCs because they exhibit wide size/shape/composition-tunable absorption spectra ranging from ultraviolet to near infrared, significantly overlapping with the solar spectrum. They also feature narrow emission spectra, high photoluminescence quantum yields, high absorption coefficients, solution processability and good photostability. Most importantly, QDs can be engineered to provide a minimal overlap between absorption and emission spectra, which is key to the realization of large-area LSCs with largely suppressed reabsorption energy losses. In this review article, we will first present and discuss the working principle of LSCs, the synthesis of colloidal QDs using wet-chemistry approaches, the optical properties of QDs, their band alignment and the intrinsic relationship between the band energy structure and optical properties of QDs. We focus on emerging architectures, such as core/shell QDs. We then highlight recent progress in QD-based LSCs and their anticipated applications. We conclude this review article with the major challenges and perspectives of LSCs in future commercial technologies.

Single-Homology-Arm Linear DNA Recombination by the Nonhomologous End Joining Pathway as a Novel and Simple Gene Inactivation Method: a Proof-of-Concept Study in Dietzia sp. Strain DQ12-45-1b.

Nonhomologous end joining (NHEJ) is critical for genome stability because of its roles in double-strand break repair. Ku and ligase D (LigD) are the crucial proteins in this process, and strains expressing Ku and LigD can cyclize linear DNA in vivo Here, we established a proof-of-concept single-homology-arm linear DNA recombination for gene inactivation or genome editing by which cyclization of linear DNA in vivo by NHEJ could be used to generate nonreplicable circular DNA and could allow allelic exchanges between the circular DNA and the chromosome. We achieved this approach in Dietzia sp. strain DQ12-45-1b, which expresses Ku and LigD homologs and presents NHEJ activity. By transforming the strain with a linear DNA single homolog to the sequence in the chromosome, we mutated the genome. This method did not require the screening of suitable plasmids and was easy and time-effective. Bioinformatic analysis showed that more than 20% of prokaryotic organisms contain Ku and LigD, suggesting the wide distribution of NHEJ activities. Moreover, an Escherichia coli strain also showed NHEJ activity when the Ku and LigD of Dietzia sp. DQ12-45-1b were introduced and expressed in it. Therefore, this method may be a widely applicable genome editing tool for diverse prokaryotic organisms, especially for nonmodel microorganisms.IMPORTANCE Many nonmodel Gram-positive bacteria lack efficient genetic manipulation systems, but they express genes encoding Ku and LigD. The NHEJ pathway in Dietzia sp. DQ12-45-1b was evaluated and was used to successfully knock out 11 genes in the genome. Since bioinformatic studies revealed that the putative genes encoding Ku and LigD ubiquitously exist in phylogenetically diverse bacteria and archaea, the single-homology-arm linear DNA recombination by the NHEJ pathway could be a potentially applicable genetic manipulation method for diverse nonmodel prokaryotic organisms.

Colloidal Metal Nanoparticles Prepared by Laser Ablation and their Applications.

This review article highlights the recent advances of the synthesis and application of metal nanoparticles (NPs) fabricated via pulsed laser ablation in liquid (PLAL) phase and also introduces relevant NP formation mechanisms. Although wet-chemical approaches have been well established to synthesize colloidal metal NPs with various components and structures, some inherent drawbacks, such as reaction residuals and/or contaminations, largely limit some of their applications. The PLAL method has recently been developed as an alternative approach and received increasing attention for colloidal NP preparation, without involving complicated chemical reactions. In certain cases, by using PLAL, ligand-free and surface-clean NPs can be obtained and well dispersed in liquid, leading to the formation of a "surface-clean" NP dispersion. This unique feature renders PLAL-synthesised metal NPs attractive candidates for many interesting applications in catalysis, biology, sensing, and clean energy generation and storage. We conclude this review by proposing several interesting research directions and future challenges, from PLAL fabrication to applications. We hope this review can serve as a good reference and help with the further development of PLAL-NPs and their diverse applications.

Towards understanding the unusual photoluminescence intensity variation of ultrasmall colloidal PbS quantum dots with the formation of a thin CdS shell.

In this study, we report anomalous size-dependent photoluminescence (PL) intensity variation of PbS quantum dots (QDs) with the formation of a thin CdS shell via a microwave-assisted cation exchange approach. Thin shell formation has been established as an effective strategy for increasing the PL of QDs. Nonetheless, herein we observed an unusual PL decrease in ultrasmall QDs upon shell formation. We attempted to understand this abnormal phenomenon from the perspective of trap density variation and the probability of electrons and holes reaching surface defects. To this end, the quantum yield (QY) and PL lifetime (on the ns-µs time scales) of pristine PbS QDs and PbS/CdS core/shell QDs were measured and the radiative and non-radiative recombination rates were derived and compared. Moreover, transient absorption (TA) analysis (on the fs-ns time scale) was performed to better understand exciton dynamics at early times that lead to and affect longer time dynamics and optical properties such as PL. These experimental results, in conjunction with theoretical calculations of electron and hole wave functions, provide a complete picture of the photophysics governing the core/shell system. A model was proposed to explain the size-dependent optical and dynamic properties observed.

Semiconductor and metallic core-shell nanostructures: synthesis and applications in solar cells and catalysis.

Nano-heterostructures have attracted great attention due to their extraordinary properties beyond those of their single-component counterparts. This review focuses on a specific type of hybrid structures: core-shell structures. In particular, we present and discuss the recent wet-chemical synthesis approaches for semiconductor and metallic core-shell nanostructures, and their relevant properties and potential applications in photovoltaics and catalysis, respectively.

Enhanced photocatalysis of metal/covalent organic frameworks by plasmonic nanoparticles and homo/hetero-junctions.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have garnered attention in photocatalysis due to their unique features including extensive surface area, adjustable pores, and the ability to incorporate various functional groups. However, challenges such as limited visible light absorption and rapid electron-hole recombination often hinder their photocatalytic efficiency. Recent developments have introduced plasmonic nanoparticles (NPs) and junctions to enhance the photocatalytic performance of MOFs/COFs. This paper provides a comprehensive review of recent advancements in MOF/COF-based photocatalysts improved by integration of plasmonic NPs and junctions. We begin by examining the utilization of plasmonic NPs, known for absorbing longer-wavelength light compared to typical MOFs/COFs. These NPs exhibit localized surface plasmon resonance (LSPR) when excited, effectively enhancing the photocatalytic performance of MOFs/COFs. Moreover, we discuss the role of homo/hetero-junctions in facilitating charge separation, further boosting the photocatalytic performance of MOFs/COFs. The mechanisms behind the improved photocatalytic performance of these composites are discussed, along with an assessment of challenges and opportunities in the field, guiding future research directions.

Construction of Ultrathin BiVO4-Au-Cu2O Nanosheets with Multiple Charge Transfer Paths for Effective Visible-Light-Driven Photocatalytic Degradation of Tetracycline.

In this study, unique BiVO4-Au-Cu2O nanosheets (NSs) are well designed and multiple charge transfer paths are consequently constructed. The X-ray photoelectron spectroscopy measurement during a light off-on-off cycle and redox capability tests of the photo-generated charge carriers confirmed the formation of Z-scheme heterojunction, which can facilitate the charge carrier separation and transfer and maintain the original strong redox potentials of the respective component in the heterojunction. The ultrathin 2D structure of the BiVO4 NSs provided sufficient surface area for the photocatalytic reaction. The local surface plasmon resonance (LSPR) effect of the electron mediator, Au NPs, enhanced the light absorption and promoted the excitation of hot electrons. The multiple charge transfer paths effectively promoted the separation and transfer of the charge carrier. The synergism of the abovementioned properties endowed the BiVO4-Au-Cu2O NSs with satisfactory photocatalytic activity in the degradation of tetracycline (Tc) with a removal rate of ≈80% within 30 min under visible light irradiation. The degradation products during the photocatalysis are confirmed by using ultra-high performance liquid chromatography-mass spectrometry and the plausible degradation pathways of Tc are consequently proposed. This work paves a strategy for developing highly efficient visible-light-driven photocatalysts with multiple charge transfer paths for removing organic contaminants in water.

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets.

Graphitic carbon nitride (g-C3N4) is a metal-free photocatalyst used for visible-driven hydrogen production, CO2 reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C3N4 nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO3), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10-2 min-1mg-1. This represents the highest k value ever reported using C3N4-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C3N4 nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h-1 g-1. Through a profound analysis of all the samples' structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C3N4 sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation.

Lateral Flow Assays Biotesting by Utilizing Plasmonic Nanoparticles Made of Inexpensive Metals - Replacing Colloidal Gold.

Nanoparticles (NPs) can be conjugated with diverse biomolecules and employed in biosensing to detect target analytes in biological samples. This proven concept was primarily used during the COVID-19 pandemic with gold NPs-based lateral flow assays (LFAs). Considering the gold price and its worldwide depletion, here we show that novel plasmonic nanoparticles (NPs) based on inexpensive metals, titanium nitride (TiN) and copper covered with a gold shell (Cu@Au), perform comparable or even better than gold nanoparticles. After conjugation, these novel nanoparticles provided high figures of merit for LFA testing, such as high signals and specificity and robust naked-eye signal recognition. To the best of our knowledge, our study represents the 1st application of laser-ablation-fabricated nanoparticles (TiN) in the LFA and dot-blot biotesting. Since the main cost of the Au NPs in commercial testing kits is in the colloidal synthesis, our development with TiN is very exciting, offering potentially very inexpensive plasmonic nanomaterials for various bio-testing applications. Moreover, our machine learning study showed that the bio-detection with TiN is more accurate than that with Au.

Asymmetric silver "nanocarrot" structures: solution synthesis and their asymmetric plasmonic resonances.

Here we report the wet-chemical synthesis of asymmetric one-dimensional (1D) silver "nanocarrot" structures that exhibit mixed twins and stacking fault domains along the <111> direction. Oriented attachment is the dominant mechanism for anisotropic growth. Multipolar plasmon resonances up to fourth order were measured by optical extinction spectroscopy and electron energy-loss spectroscopy (EELS) and are in agreement with theoretical calculations. Compared with those of symmetric 1D nanostructures of similar length, the dipole modes of the nanocarrots show a clear red shift, and the EELS maps show an asymmetric distribution of the resonant plasmonic fields and a compression of the resonance node spacing toward the tail. In addition, increasing the length of the nanocarrots causes an increase in the intensity and a steady red shift of the longitudinal surface plasmon resonance peaks. The silver nanocarrots also show very high sensitivity to the refractive index of their environment (890 ± 87 nm per refractive index unit).

Plasmonic nanorice antenna on triangle nanoarray for surface-enhanced Raman scattering detection of hepatitis B virus DNA.

The sensitivity and the limit of detection of Raman sensors are limited by the extremely small scattering cross section of Raman labels. Silver nanorice antennae are coupled with a patterned gold triangle nanoarray chip to create spatially broadened plasmonic "hot spots", which enables a large density of Raman labels to experience strong local electromagnetic field. Finite difference time domain simulations have confirmed that the quasi-periodic structure increases the intensity and the area of the surface plasmon resonance (SPR), which enhances the surface-enhanced Raman scattering (SERS) signal significantly. The SERS signal of the nanorice/DNA/nanoarray chip is compared with that of the nanorice/DNA/film chip. The SERS signal is greatly enhanced when the Ag nanorices are coupled to the periodic Au nanoarray instead of the planar film chip. The resulting spatially broadened SPR field enables the SERS biosensor with a limit of detection of 50 aM toward hepatitis B virus DNA with the capability of discriminating a single-base mutant of DNA. This sensing platform can be extended to detect other chemical species and biomolecules such as proteins and small molecules.

Light polarization-controlled shape-memory polymer/gold nanorod composite.

It is demonstrated that light polarization can be used to control photothermal effect-based shape-memory polymers (SMPs). Gold nanorods (AuNRs) are embedded in poly(vinyl alcohol) (PVA) and aligned by stretching the composite film. By changing the polarization direction of the incident laser at 785 nm with respect to the film stretching direction, the magnitude of the longitudinal surface plasmon resonance of AuNRs can be varied continuously, which determines the amount of heat generated upon laser exposure and thus the local temperature rise in the composite relative to the glass transition of the PVA matrix. Consequently, the temporary-to-permanent shape recovery process of the composite can be made to occur to different extents by tuning the polarization of laser while keeping all other conditions unchanged. This finding enhances the toolbox for controlling light-triggered SMPs.

Purification and sidewall functionalization of multiwalled carbon nanotubes and resulting bioactivity in two macrophage models.

This study examined the consequences of surface carboxylation of multiwalled carbon nanotubes (MWCNT) on bioactivity. Since commercial raw MWCNT contain impurities that may affect their bioactivity, HCl refluxing was exploited to purify raw "as-received" MWCNT by removing the amorphous carbon layer on the MWCNT surface and reducing the metal impurities (e.g. Ni). The removal of amorphous carbon layer was confirmed by Raman spectroscopy and thermogravimetric analysis. Furthermore, the HCl-purified MWCNT provided more available reaction sites, leading to enhanced sidewall functionalization. The sidewall of HCl-purified MWCNT was further functionalized with the -COOH moiety by HNO(3) oxidation. This process resulted in four distinct MWCNT: raw, purified, -COOH-terminated raw MWCNT, and -COOH-terminated purified MWCNT. Freshly isolated alveolar macrophages from C57Bl/6 mice were exposed to these nanomaterials to determine the effects of the surface chemistry on the bioactivity in terms of cell viability and inflammasome activation. Inflammasome activation was confirmed using inhibitors of cathepsin B and Caspase-1. Purification reduced the cell toxicity and inflammasome activation slightly compared to raw MWCNT. In contrast, functionalization of MWCNT with the -COOH group dramatically reduced the cytotoxicity and inflammasome activation. Similar results were seen using THP-1 cells supporting their potential use for high-throughput screening. This study demonstrated that the toxicity and bioactivity of MWCNT were diminished by removal of the Ni contamination and/or addition of -COOH groups to the sidewalls.