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Fighting aggregation-caused quenching and leakage of dyes in fluorescent polymer nanoparticles: universal role of counterion
摘要： Dye-loaded polymer nanoparticles (NPs) emerge as a powerful tool for bioimaging applications, owing to their exceptional brightness and controlled small size. However, aggregation-caused quenching (ACQ) and leakage of dyes at high loading remain important challenges of these nanomaterials. The use of bulky hydrophobic counterions has been recently proposed as an effective approach to minimize ACQ and dye leakage, but the role of counterion structure is still poorly understood. Here, a systematic study based on ten counterions, ranging from small hydrophilic perchlorate up to large hydrophobic tetraphenylborate derivatives, reveals how counterion nature can control encapsulation and emission of a cationic dye (rhodamine B octadecyl ester) in NPs prepared by nanoprecipitation of a biodegradable polymer, poly-lactide-co-glycolide (PLGA). We found that increase in counterion hydrophobicity enhances dye encapsulation efficiency and prevents dye adsorption at the particle surface. Cellular imaging studies revealed that ≥95% encapsulation efficiency, achieved with most hydrophobic counterions (fluorinated tetraphenylborates), is absolutely required, because non-encapsulated dye species at the NPs surface are the origin of dye leakage and strong background in cells. The size of counterions is found to be essential to prevent ACQ, where the largest species, serving as effective spacer between dyes, provide the highest fluorescence quantum yield. Moreover, we found that the most hydrophobic counterions favor dye-dye coupling inside NPs, leading to ON/OFF fluorescence switching of single particles. By contrast, less hydrophobic counterions tend to disperse dyes in the polymer matrix favoring stable emission of NPs. The obtained structure-property relationships validate the counterion-based approach as a mature concept to fight ACQ and dye leakage in the development of advanced polymeric nanomaterials with controlled optical properties.
关键词： dye-loaded polymer nanoparticles,fluorescent nanoparticles,bulky hydrophobic counterion,aggregation-caused quenching,bioimaging
更新于2025-09-23 15:23:52
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CePd‐Nanoparticles‐Incorporated Carbon Nanofibers as Efficient Counter Electrode for DSSCs
摘要： In this study, the cerium-palladium (CePd) incorporated carbon nanofibers (CNFs) were manufactured by low-cost and versatile electrospinning technique and successfully applied as a counter electrode to fabricate the dye-sensitized solar cells (DSSCs). The utilized physiochemical techniques, X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FESEM), and transmission electron microscope (TEM) confirmed the formation of carbon nanofibers (CNFs) incorporated by Ce and Pd nanoparticles. CePd incorporated CNFs were preliminary presented good electrocatalytic activity towards the iodide redox couple, as investigated by cyclic voltammetry. The DSSC fabricated using CePd incorporated CNFs based counter electrode (CE) attained an applicable power conversion efficiency (PCE) of 4.52% along with open circuit voltage (VOC) of 0.739 V, a short-circuit current density (JSC) of 11.42 mA/cm2 and fill factor (FF) of 0.54. According to primary results, the CePd incorporated CNFs based CE is a promising, and cost-effective alternative CE for photoelectrochemical devices.
关键词： Alloys nanoparticles,Solar cells,Electrocatalyst,Cyclic voltammetry,Carbon nanofibers
更新于2025-09-23 15:23:52
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Fabrication of Large Area Sub-200 nm Conducting Electrode Arrays by Self-Confinement of Spincoated Metal Nanoparticle Inks
摘要： Here, the fabrication of sub-200 nm metal wires from commercial silver inks with 50 nm particle size, 100 times narrower than with typical low-resolution ink-jet and screen printing in flexible electronics, is demonstrated. Using a combination of spincoating on prepatterned polymer substrates and flash lamp annealing, nanoparticles merge to wires featuring good electrical conductivity. With this method less than 150 nm thin wires can be generated from 2 μm wide or smaller V-grooves due to adapted dilution of particle content, self-confinement in V-grooves, shrinkage of line width during solvent evaporation, and sintering. After nanoimprinting, grooves made from PMMA are smoothened out by thermal reflow without affecting the wires. The resistivity of 300 μm long, 400 nm wires is similar to more conventional ink-jet printed wires with 10–50 μm widths.
关键词： self-confinement,V-groove,flash lamp annealing,nanoimprint lithography,silver nanoparticles
更新于2025-09-23 15:23:52
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NIR light-triggered gelling <i>in situ</i> of porous silicon nanoparticles/PEGDA hybrid hydrogels for localized combinatorial therapy of cancer cells
摘要： Porous silicon-based nanocomposite hydrogels were readily constructed with the gelation of poly(ethylene glycol) double acrylates (PEGDA) macromers, due to the initiation of singlet oxygen photosensitized with porous silicon nanoparticles (PSiNPs) under near-infrared (NIR) light irradiation. Multifunctional PSiNPs/PEGDA nanocomposite hydrogels showed strong ?uorescence, excellent biodegradability, signi?cant photothermal effect, and sustained drug release with high ef?ciency (>80%). Finally, in situ growth of PSiNPs/PEGDA hybrid hydrogels on cancer cells was also achieved by NIR light, and then their biodegradation, drug release and synergistic chemo-phototherapeutic ef?cacy were further demonstrated, which could provide a signi?cant localized inhibition for the viability, adherence, and migration of cancer cells in vitro. Thus, we suggested that these resultant hybrid hydrogels would have important potential on local cancer therapy in future clinical practice.
关键词： porous silicon nanoparticles,hybrid hydrogels,therapy,insitu gelation,localized cancer
更新于2025-09-23 15:23:52
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Structural characterization of bulk and nanoparticle lead halide perovskite thin films by (S)TEM techniques
摘要： Lead halide (APbX3) perovskites, in polycrystalline thin films but also perovskite nanoparticles (NPs) have demonstrated excellent performances to implement a new generation of photovoltaic and photonic devices. The structural characterization of APbX3 thin films using (scanning) transmission electron microscopy ((S)TEM) techniques can provide valuable information that can be used to understand and model their optoelectronic performance and device properties. However, since APbX3 perovskites are soft materials, their characterization using (S)TEM is challenging. Here, we study and compare the structural properties of two different metal halide APbX3 perovskite thin films: bulk CH3NH3PbI3 prepared by spin-coating of the precursors in solution and CsPbBr3 colloidal NPs synthetized and deposited by doctor blading. Both specimen preparation methods and working conditions for analysis by (S)TEM are properly optimized. We show that CH3NH3PbI3 thin films grown by a one-step method results in the formation of tetragonal perovskite thin films with good adherence to an underlying TiO2 layer, which is characterized by a photoluminescence (PL) emission band centered at 775 nm. The perovskite thin films based on CsPbBr3 colloidal NPs, which are used as the building blocks of the film, they are preserved by the deposition process, even if small gaps are observed between adjacent NPs. The crystal structure of CsPbBr3 NPs is cubic, which is beneficial for optical properties due to its optimal band gap. The absorption and PL spectra measured in both the thin film and the colloidal solution of CsPbBr3 NPs are very similar, indicating a good homogeneity of the thin films and the absence of aggregation of NPs. However, a particular care was required to avoid long electron irradiation times during our structural studies, even at a low voltage of 80 kV, as the material was observed to decompose through Pb segregation.
关键词： structural characterization,TEM,thin films,optoelectronics,STEM,nanoparticles,perovskite
更新于2025-09-23 15:23:52
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Subchronic intravenous toxicity study of biofunctional ZnO and its application as a fluorescence probe for cell-specific targeting
摘要： Successful development of safe and highly effective nanoprobes for targeted imaging of in vivo early cancer is a great challenge. Herein, we choose the visible‐light emitting zinc oxide non–core/shell type nanoparticle (NP) fluorophores (ZHIE) as prototypical materials. We have reported on these materials previously. The results showed that the ZHIE NPs exhibited good water solubility and good biocompatibility. This study was conducted to investigate the toxicity of ZHIE NPs when intravenously administered to mice repeatedly at the dose required for successful tumor imaging in vivo. Anti‐macrophage‐1 antigen (Mac1), a macrophage differentiation antigen, antibody‐conjugated ZHIE NPs successfully realized targeted imaging of murine macrophage cell line Raw264.7 cells. In conclusion, ZHIE NPs are not toxic in vivo and antibody‐conjugated ZHIE NPs have great potential in applications, such as single cell labeling.
关键词： subchronic toxicity,zinc oxide (ZnO) nanoparticles,fluorescence probe
更新于2025-09-23 15:23:52
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Surface chemical states of gold nanoparticles prepared using the solution-plasma method in a CsCl aqueous solution
摘要： In this study, gold nanoparticles (AuNPs) prepared in a 5 mM CsCl aqueous solution using the solution‐plasma method are characterized via transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy with synchrotron radiation (SR‐XPS). The particle diameter is measured over the process time via TEM. During the solution‐plasma process, small particles of 2.1 to 2.2‐nm diameter are generated in the CsCl aqueous solution; these particles then enlarge via Ostwald ripening over time until they reach an equilibrium size of ~13 nm after 36 days. In addition, the surface chemical states of the AuNPs are characterized at different depths via SR‐XPS. The SR‐XPS measurements obtained using incident X‐ray energy (hν) of 945.0 eV revealed that Cs─Au, Cl─Au, and Cs─Cl─Au bonds are present 1.2 nm below the surface. The measurements obtained at an incident X‐ray energy of 2515.0 eV showed that Cs─Cl─Au bonding is also present 2.5 nm below the surface, indicating that Cs and Cl strongly interact with Au. The TEM and SR‐XPS measurements revealed that 2 processes occur cyclically during the growth process via Ostwald ripening: (i) the Cs and Cl in the aqueous solution adsorb on the AuNP surface and (ii) Au atoms subsequently bond to the AuNPs surface.
关键词： solution‐plasma method,TEM,gold nanoparticles,XPS,surface chemical states
更新于2025-09-23 15:23:52
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Green Synthesis of Flower‐Like BiVO <sub/>4</sub> Nanoparticles by Solution Combustion Method Using Lemon ( <i>Citrus Limon</i> ) Juice as a Fuel: Photocatalytic and Electrochemical Study
摘要： BiVO4 have been proven to be one of the most promising photocatalyst for degradation of organic dyes and also exhibit good electrochemical performances in heavy metal detection. Herein, we have developed a simple, economic and low-cost combustion synthesis of BiVO4 nanoparticles using bismuth nitrate as an oxidiser, lemon (Citrus Limon) juice as fuel. The prepared nanoparticles were characterized by Powder X-ray diffractometer (PXRD), Fourier Transform-Infrared spectroscopy (FTIR), Diffused Reflectance Spectroscopy (DRS), Photoluminescence Spectroscopy (PL), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analytical techniques. Flower-like morphology BiVO4 nanoparticles were observed for higher ratio of fuel (Citrus Limon). BiVO4 nanoparticles showed an excellent photocatalytic activity towards degradation of Indigo Carmine dye in solution. Further, BiVO4 modified electrode was examined for the detection of Hg (II) using electrochemical techniques.
关键词： BiVO4,Nanoparticles,Electrochemical performance,Photocatalytic activity,Photoluminescence
更新于2025-09-23 15:23:52
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Valorization of mutant Bacillus licheniformis M09 supernatant for green synthesis of silver nanoparticles: photocatalytic dye degradation, antibacterial activity, and cytotoxicity
摘要： The present study reports the optimization of a green method for the synthesis of silver nanoparticles (AgNPs) via reduction of Ag+ ions using cell-free supernatant of mutant Bacillus licheniformis M09. UV–Visible spectroscopy showing an absorption peak at ~ 430 nm confirmed the synthesis of AgNPs. Transmission electron microscope (TEM) analysis exhibited spherical AgNPs within the size range of 10–30 nm. Fourier transform infrared (FTIR) measurements assured the presence of effective functional molecules which could be responsible for stabilizing the AgNPs. X-ray diffraction (XRD) pattern verified the crystalline nature of AgNPs. Furthermore, the synthesized AgNPs showed an excellent photocatalytic degradation of methylene blue dye in less than 3 h under visible light proving their potential as a catalytic agent for bioremediation for next-generation dye degradation in effluent treatment. The AgNPs demonstrated antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens which endorsed its suitability as agents to extend shelf-life in food packaging and food safety applications. The results also revealed a strong concentration-dependent cytotoxicity of AgNPs against human breast adenocarcinoma cells (MCF-7), while 15.07 μg/mL of IC50 was attained. The outcome suggests the possible application of these AgNPs in nanomedicine formulations. Thus, these findings propose promising ways for the valorization of the waste fermentation supernatant left after cell harvesting and desired metabolite extraction.
关键词： Methylene blue,Antibacterial,Photocatalytic dye degradation,Cytotoxicity effects,Bacillus licheniformis M09,Silver nanoparticles
更新于2025-09-23 15:23:52
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Photoactive Gel for Assisted Cleaning during Olive Mill Wastewater Membrane Microfiltration
摘要： A photoactive gel has been fabricated on the surface of polyethylene membranes for enhancing the fouling resistance during olive mill wastewater treatment. Light and pH responsive materials have been introduced in the membrane surface through the build up of a layer-by-layer pattern, which is formed by photocatalytic nanoparticles and ionic polyelectrolytes. The best working conditions to contrast foulants adsorption have been explored and identified. Repulsive interfacial forces and assisted transfer of foulants to catalytic sites have been envisaged as crucial factors for contrasting the decline of the flux during microfiltration. Tests in submerged configuration have been implemented for six continuous hours under irradiation at two different pH conditions. As a result, a worthy efficiency of the photoactive gel has been reached when suitable chemical microenvironments have been generated along the shell side of the membranes. No additional chemical reagents or expensive back-flushing procedures have been necessary to further clean the membranes; rather, fast and reversible pH switches have been enough to remove residues, thereby preserving the integrity of the layer-by-layer (LBL) complex onto the membrane surface.
关键词： submerged microfiltration,layer-by-layer,titanium oxide nanoparticles,water treatment,self-cleaning
更新于2025-09-23 15:23:52