Carrageenan/polyvinyl alcohol composite film reinforced with spermidine carbon dots: An active packaging material with dual-mode antibacterial activity.

Exploring biopolymer-based antibacterial packaging materials is promising to tackle the issues caused by petroleum plastic pollution and microbial contamination. Herein, a novel packaging material with two antibacterial modes, continuous and efficient, is constructed by dispersing positively charged spermidine carbon dots (Spd-CDs) in a carrageenan/polyvinyl alcohol (CP) composite biopolymer. The obtained nanocomposite film (CP/CDs film) not only gradually releases the ultra-small Spd-CDs but also rapidly generates reactive oxygen species to inhibit the reproduction of E. coli and S. aureus. Benefiting from the complementary advantages of carrageenan and polyvinyl alcohol, as well as the addition of Spd-CDs, the CP/CDs films exhibit high transparency, good mechanical performance, water vapor barrier ability, low migration, etc. The CP/CDs film as a packaging material is validated to be effective in preventing microbial contamination of pork samples. Our prepared nanocomposite film with sustainability and efficient antibacterial properties is expected as food active packaging.

Accelerated Oxygen Evolution Kinetics by Engineering Heterojunction Coupling of Amorphous NiFe Hydr(oxy)oxide Nanosheet Arrays on Self-Supporting Ni-MOFs.

Designing definite transition metal heterointerfaces is considered an effective strategy for the construction of efficient and robust oxygen evolution reaction (OER) electrocatalysts, but rather challenging. Herein, amorphous NiFe hydr(oxy)oxide nanosheet arrays (A-NiFe HNSAs) are grown in situ on the surface of a self-supporting Ni metal-organic frameworks (SNMs) electrode via a combination strategy of ion exchange and hydrolytic co-deposition for efficient and stable large-current-density water oxidation. The existence of the abundant metal-oxygen bonds on the heterointerfaces can not only be of great significance to alter the electronic structure and accelerate the reaction kinetics, but also enable the redistribution of Ni/Fe charge density to effectively control the adsorption behavior of important intermediates with a close to the optimal d-band center, dramatically narrowing the energy barriers of the OER rate-limiting steps. By optimizing the electrode structure, the A-NiFe HNSAs/SNMs-NF exhibits outstanding OER performance with small overpotentials of 223 and 251 mV at 100 and 500 mA cm-2 , a low Tafel slope of 36.3 mV dec-1 , and excellent durability during 120 h at 10 mA cm-2 . This work significantly provides an avenue to understand and realize rationally designed heterointerface structures toward effective oxygen evolution in water-splitting applications.

ZIF-derived Co nanoparticles embedded into N-doped carbon nanotube composites for highly efficient electrochemical detection of nitrofurantoin in food.

Designing efficient and sensitive methods for the detection of nitrofurantoin (NFT) residues is of great importance for food safety and environmental protection. Herein, a composite with cobalt nanoparticles encapsulated in nitrogen-doped carbon nanotube (N/Co@CNTs@CC-II) was synthesized by in-situ growth and sublimation-gas phase transformation strategy and used to establish an ultrasensitive electrochemical sensor for NFT determination. The N/Co@CNTs@CC-II sensor exhibits uniform N doping, fine hollow structure, and abundant active metal sites, which lays a solid foundation for the ultra-sensitive detection of NFT. Benefiting from these advantages, the N/Co@CNTs@CC-II exhibits excellent sensitivity (8.19 µA µM-1 cm-2) and low detection limit (18.41 nM) for NFT detection. The practical feasibility of N/Co@CNTs@CC-II was also demonstrated by the determination of NFT in milk and tap water samples. This study may open up new opportunities for the application of N-doped carbon nanotube materials encapsulating transition metals.

Sn/MoC@NC hollow nanospheres as Schottky catalyst for highly sensitive electrochemical detection of methyl parathion.

Developing electrode materials with excellent electrocatalytic properties for detecting pesticide residues plays a vital role in the safety of agricultural products and environmental applications. Herein, we designed a new electrochemical sensor on the basis of N-doped carbon hollow nanospheres modified with Sn/MoC Schottky junction (Sn/MoC@NC) for methyl parathion (MP) detection. The Sn/MoC@NC was prepared by self-assembled polymerization-anchoring strategy and high-temperature carbonization design. Sn/MoC Schottky junction and hollow nanosphere structure endow Sn/MoC@NC with a larger surface area, more active sites, and faster electron transfer, which is beneficial to enhancing its electrocatalytic performance. The structural characterizations and physicochemical properties of Sn/MoC@NC were explored through various microscopy, spectroscopic and electrochemical techniques. The experimental results confirmed that the calibration curve for current and MP concentration (0.05-10 µg/mL) was available under optimized conditions, and the sensitivity and detection limit were respectively determined to be 9.02 µA µM1 cm2 and 8.9 ng/mL. Furthermore, the constructed sensor displayed excellent selectivity, repeatability, and stability, which qualified it for use in detecting MP in grapes and tap water with satisfactory recovery. This work may provide some interesting prospects for constructing high-performance electrocatalysts for MP detection.

Bimetallic-MOF-derived crystalline-amorphous interfacial sites for highly efficient nitrite sensing.

Considering the importance of rapid and effective detection of nitrite in food samples, herein, we report a multistep heterophase synthetic strategy for constructing crystalline-amorphous zinc/cobalt iron porous nanosheets (C-A Zn/Co-Fe PNSs) on carbon cloth. Notably, the C-A Zn/Co-Fe PNSs@CC electrochemical interface consists of interlaced carbon fibers with many uniformly distributed hybrid nanosheets containing crystalline-amorphous interfacial sites. This particular hybrid structure permits local enrichment of nitrite for enhanced nitrite capture efficiency, laying a solid foundation for the ultrasensitive detection of nitrite. In proof-of-concept experiments, we verified that C-A Zn/Co-Fe PNSs@CC could be used to analyze nitrite with good sensitivity and reproducibility. It is worth mentioning that an ultra-low LOD of 0.44 µM was obtained for the detection of nitrite. The designed electrochemical sensor worked well in complex samples such as sausages and tap water under optimal parameters.

Simple high-temperature annealing affords commercial carbon cloth with enhanced electrochemical performance for highly sensitive detection of imidacloprid.

Imidacloprid (IDP) residue in modern agricultural production seriously endangers human health and environmental safety. The establishment of a rapid and efficient method for the detection of IDP residue can effectively prevent its harm to human health. Herein, we demonstrate the carbon cloth (CC) prepared by a high-temperature annealing strategy possesses enhanced electrochemical performance, which could be directly used in electrochemical IDP sensing. Annealed carbon cloth (ACC) is endowed with higher defects, rougher surfaces, more functional groups, more hydrophilic surface, and increased ion-accessible surface area. Furthermore, the ACC electrode shows superior electrocatalytic reduction activity towards IDP, possessing a wide linear range of 5-100 µM, a low detection limit of 0.04 µM, and high sensitivity of 35.58 µA mM-1 cm-2. Meanwhile, this sensor can be applied for sensing IDP in grapes and apples with a good recovery of 96.8-104.1%. Compared with other modified electrodes, the ACC electrode has the advantages of no binder, no complicated modification, excellent detection effect, low cost, and easy large-scale production. Consequently, this work designs a self-supporting metal-free electrode with high electrochemical performance, providing a new idea for the development of environmentally friendly IDP sensors.

Hybrid structures of cobalt-molybdenum bimetallic oxide embedded in flower-like molybdenum disulfide for sensitive detection of the antibiotic drug nitrofurantoin.

Excessive residues of nitrofurantoin (NFT) can cause serious contamination of water bodies and food, and potential harm to ecosystems and food safety. Given that, rapid and efficient detection of NFT in real samples is of particular importance. MoS2 is a promising electrochemical material for this application. Here, MoS2 was modulated by Metal-organic framework through the interfacial microenvironment to enhance the catalytic activity and carbonized to form Co2Mo3O8 nanosheets with high electrical activity. The resulting Co2Mo3O8/MoS2 hybrid structure can be used to prepare highly sensitive NFT electrochemical sensor. The Co2Mo3O8/MoS2@CC electrochemical sensor exhibits strong electrochemical properties due to its fast electron transfer, excellent electrical conductivity, abundant defect sites, and high redox response. Based on this, this electrochemical sensor exhibited excellent electrocatalytic activity for NFT with a wide linear detection range, low detection limit, and high sensitivity. Moreover, the electrode was successfully applied to detect NFT in milk, honey, and tap water, strongly confirming its potential in real samples. This work could furnish the evidence for interfacial microenvironmental regulation of MoS2, and also offer a novel candidate material for NFT sensing.

Integrating electrochemical sensor based on MoO3/Co3O4 heterostructure for highly sensitive sensing of nitrite in sausages and water.

Considering excess nitrites are detrimental to the human body and environment, designing a rapid, sensitive, and real-time quantitative determination for nitrite is of great significance for environmental preservation and public health. In this paper, Co3O4 nanoflowers coupled with ultrafine MoO3 nanoparticles (MoO3/Co3O4) are obtained via a hybrid electrochemical deposition strategy (HED). The as-designed MoO3/Co3O4/CC integrating electrode exhibits superior electrocatalytic properties towards nitrite oxidation, owing to the synergistic effect between MoO3 and Co3O4 caused by the heterostructure of MoO3/Co3O4. The electrode achieved a low response time of 2 s, an excellent sensitivity of 1704.1 µA mM-1 cm-2, and a low limit of detection of 0.075 µM (S/N = 3). Furthermore, the electrode displays promise for nitrite detection in complex food such as water and sausages samples. Our study will provide a significant strategy for the application of bimetallic heterostructure to explore the design of sensing interfaces.

Innovative ratiometric optical strategy: Nonconjugated polymer dots based fluorescence-scattering dual signal output for sensing mercury ions.

A new ratiometric platform was developed for sensing Hg2+, which combined fluorescence and scattering simultaneously. This ratiometric strategy reflected superiorities over conventional methods, since the two independent signals at irrelevant categories meet the requirements of sufficient wavelength separation, stimulation under one excitation, and collection on single instrument. Herein, nonconjugated polymer dots (N-PDs) were served as the recognition unit for Hg2+ with turn-off fluorescence and turn-on scattering. Additionally, two signal collection tactics were proposed to achieve fluorescence and scattering in a window: one was to record down-conversion fluorescence and second-order scattering spectra (FL@SOS), and the other was to gather the fluorescence excited by second-order diffraction light and first-order scattering (SODL-FL@FOS). This ratiometric sensor exhibited outstanding performance toward Hg2+ in the range of 0.1-50 µM with the detection limit of 27 nM. By contrast, the present proposal provided a more ingenious and scalable way to construct ratiometric sensor than traditional approach.

A Naturally Derived Nanocomposite Film with Photodynamic Antibacterial Activity: New Prospect for Sustainable Food Packaging.

Food packaging with efficient antibacterial ability is highly desirable and challenging in facing the crisis of microbial contamination. However, most present packaging is based on metal-based antibacterial agents and requires a time-consuming antibacterial process. Here, the unique packaging (CC/BB films) featuring aggregation-induced emission behavior and photodynamic inactivation activity is prepared by dispersing self-assembled berberine-baicalin nanoparticles (BB NPs) into a mixed matrix of sodium carboxymethylcellulose-carrageenan (CC). The superiority of this design is that this packaging film can utilize sunlight to generate reactive oxygen species, thus eradicating more than 99% of E. coli and S. aureus within 60 min. Also, this film can release BB NPs to inactivate bacteria under all weather conditions. Surprisingly, the CC/BB nanocomposite film presented excellent mechanical performances (29.80 MPa and 38.65%), hydrophobicity (117.8°), and thermostability. The nanocomposite film is validated to be biocompatible and effective in protecting chicken samples, so this work will provide novel insights to explore safe and efficient antibacterial food packaging.

Conversional fluorescent kiwi peel phenolic extracts: Sensing of Hg2+ and Cu2+, imaging of HeLa cells and their antioxidant activity.

The valorization, resource generation and the functional characteristic exploration of domestic waste still face enormous challenges. Kiwi peels, a common kind of fruit waste, contain a large amount of phenolic substances, including polyphenols, flavonoids, etc., which can be explored and reused in food and biomedical fields. By ultrasonic assisted extraction technology, we obtained conversional fluorescence kiwi peel phenolic extracts (PE) which possessed gradient magenta fluorescence relying on the content of ethanol in the solution, as well as strong antioxidant activity. Besides, metal ions sensing assay revealed that PE can specifically sense Hg2+ and Cu2+ (LOD: 1.16 and 0.17 µM, respectively) accompanied with a fluorescence conversion from magenta fluorescence to blue. Moreover, employing the prepared PE as fluorescent probes, imaging of HeLa cells can be easily achieved with satisfactory resolution. Additionally, PE was incorporated into the gelatin matrix, successfully fabricating a green, edible degradable film with excellent antioxidant activity.

Surface engineering of carbon selenide nanofilms on carbon cloth: An advanced and ultrasensitive self-supporting binder-free electrode for nitrite sensing.

Large uptakes of nitrite have been proven to be detrimental to human health, therefore, the development of high-performance nitrite sensors is highly emergent. Herein, a carbon selenide nanofilms modified carbon fiber cloth (CSe2 NF/CC) electrode was obtained via in-situ synthesis to detect nitrite. The electrode integrates the collective merits of macroporous CC and pleated carbon selenide nanofilms, possessing a low overpotential of 0.83 V, a high electrochemical active surface area (EASA) of 5.39 cm2, great electrical conductivity, and fast charge transport as well as ion diffusion. The proposed electrode achieved a low limit of detection of 0.04 µmol L-1 (S/N = 3), a high sensitivity of 2048.56 µA mmol L-1 cm-2, excellent selectivity, and long-term stability. Additionally, the CSe2 NF/CC was successfully used for nitrite detection in different food samples such as pickled vegetables and sausage samples.

Antimonene Quantum Dots as an Emerging Fluorescent Nanoprobe for the pH-Mediated Dual-Channel Detection of Tetracyclines.

Antimonene quantum dots (AMQDs) are attracting considerable attention due to their fascinating physicochemical properties. However, research on their semiconductor characteristics, especially the photoluminescence performance, is still in a preliminary stage and the experimental verification is scarcely reported, significantly restricting their further applications. Herein, the photoluminescence property of AMQDs is experimentally verified. The AMQDs are prepared by probe sonication-assisted liquid-phase exfoliation and show robust blue fluorescence, and the photoluminescence is hardly affected by pH. In view of the derivatization reaction of tetracyclines (TET) at different pHs, AMQDs are developed as a pH-mediated dual-channel ratiometric fluorescent probe for TET detection. Under acidic conditions, the AMQDs' probe exhibits unique recognition behavior due to the inherent fluorescence of TET and the solvent-enhancing effect, that is, the fluorescence changes from blue to red. Under alkaline conditions, this fluorescent probe realizes the transition from blue to yellow-green because of the decomposition of TET. The limits of detection are 27 × 10-9 and 74 × 10-9 m, respectively. The high sensitivity and remarkable fluorescence changes make AMQDs ideal probes for TET sensing. Additionally, this is the first report on the photoluminescence property of AMQDs. It is believed that this work will open a new avenue for AMQDs in optical sensing fields.

Surface morphology-controllable magnetic covalent organic frameworks: A novel electrocatalyst for simultaneously high-performance detection of p-nitrophenol and o-nitrophenol.

Covalent organic frameworks (COFs) have attracted tremendous interest due to their promising applications, including electrocatalysis originating from their unique structural features. However, it remains a challenge to prepare COFs for p-nitrophenol (PNP) and o-nitrophenol (ONP) electrocatalysis because it is quite difficult to manipulate their dimension, composition, and morphology with abundant active sites. Here, a facile ambient temperature synthesis of unique Fe3O4-based magnetic COFs nanosphere (Fe3O4@AT-COFs) with different surface morphologic structure is reported, which exhibits higher surface area, good water dispersity, long-term stability, excellent electrical conductivity and pre-concentration effect. The prepared Fe3O4@AT-COF-based electrochemical sensor is then directly employed for the simultaneous detection of PNP and ONP with a wide linear detection range of 10-3000 µM and low detection limits (LOD) of 0.2361 µM and 0.6568 µM, respectively. Meanwhile, the Fe3O4@AT-COF can be also well-applied in lake and tap water for monitoring PNP and ONP with outstanding sensitivity and reliability, which is expect to be a high-efficient electrocatalyst with great promise for signal amplification of electrochemical sensing.

Electrochemical behavior of reduced graphene oxide/cyclodextrins sensors for ultrasensitive detection of imidacloprid in brown rice.

Various pesticides employed in modern agriculture result in large amounts of pesticide residues in agricultural production, greatly threatening human health. Herein, we report a facile approach to fabricate a reduced graphene oxide/cyclodextrin modified glassy carbon electrode (rGO/CD/GCE) for the sensitive electrochemical sensing of imidacloprid (IDP). Three different modified electrodes using CDs (α-, ß-, γ-CD) were fabricated, and their electrochemical performance was further studied. The results demonstrate that α-CD possesses the best signal amplification for IDP. Compared with wet-chemical synthesis of rGO/CDs (W-rGO/CDs), the electrochemical synthesis of rGO/CDs (E-rGO/CDs) produced sensors that showed better performance for IDP sensing. Taking advantage of prepared E-rGO/α-CD nanocomposite, the fabricated sensor offered a low detection limit (0.02 µM) with a wider linear range (0.5-40 µM) and long-term stability. The new sensor was successfully applied for the detection of IDP in brown rice, providing a new technique for efficient and convenient monitoring of pesticide residues in food.

Multifunctional Magnetic Copper Ferrite Nanoparticles as Fenton-like Reaction and Near-Infrared Photothermal Agents for Synergetic Antibacterial Therapy.

Synergistic therapeutic strategies for bacterial infection have attracted extensive attentions owing to their enhanced therapeutic effects and less adverse effects compared with monotherapy. Herein, we report a novel synergistic antibacterial platform that integrates the nanocatalytic antibacterial therapy and photothermal therapy (PTT) by hemoglobin-functionalized copper ferrite nanoparticles (Hb-CFNPs). In the presence of a low concentration of hydrogen peroxide (H2O2), the excellent Fenton and Fenton-like reaction activity of Hb-CFNPs can effectively catalyze the decomposition of H2O2 to produce hydroxyl radicals (·OH), rendering an increase in the permeability of the bacterial cell membrane and the sensitivity to heat. With the assistance of NIR irradiation, hyperthermia generated by Hb-CFNPs can induce the death of the damaged bacteria. Additionally, owing to the outstanding magnetic property of Hb-CFNPs, it can improve the photothermal efficiency by about 20 times via magnetic enrichment, which facilitates to realize excellent bactericidal efficacy at a very low experimental dose (20 µg/mL). In vitro antibacterial experiment shows that this synergistic antibacterial strategy has a broad-spectrum antibacterial property against Gram-negative Escherichia coli (E. coli, 100%) and Gram-positive Staphylococcus aureus (S. aureus, 96.4%). More importantly, in vivo S. aureus-infected abscess treatment studies indicate that Hb-CFNPs can serve as an antibacterial candidate with negligible toxicity to realize synergistic treatment of bacterial infections through catalytic and photothermal effects. Accordingly, this study proposes a novel, high-efficiency, and multifunctional therapeutic system for the treatment of bacterial infection, which will open up a new avenue for the design of synergistic antibacterial systems in the future.

Silicon-doped carbon quantum dots with blue and green emission are a viable ratiometric fluorescent probe for hydroquinone.

Silicon-doped carbon quantum dots (Si-CQDs) were employed to fabricate a ratiometric fluorometric probe that shows high selectivity for hydroquinone (HQ). The Si-CQDs were prepared through hydrothermal treatment of N-[3-(trimethoxysilyl)propyl]-ethylenediamine. If HQ is oxidized in a solution of the Si-CQDs, 1,4-benzoquinone will be formed which quenches the blue fluorescence (with excitation/emission peaks at 360/435 nm) of the Si-CQDs. Simultaneously, intense green fluorescence (with a emission peak at 513 nm) appears, probably due to the formation of n-π clathrates or of a quinone imine between 1,4-benzoquinone and amino groups on the surface of the Si-CQDs. The ratio of the green and blue fluorescence can be applied to the determination of HQ with a 0.077 µM detection limit. The analytical range extends from 1 to 40 µM. Graphical abstract Schematic of a silicon-doped carbon quantum dot-based ratiometric fluorescence probe with blue and green emission for the visual and fluorometric determination of hydroquinone.

A screen printed carbon electrode modified with a lamellar nanocomposite containing dendritic silver nanostructures, reduced graphene oxide, and ß-cyclodextrin for voltammetric sensing of nitrite.

A disposable sensor is described for the determination of nitrite. A screen printed carbon electrode (SPCE) was modified with a 3D lamellar nanocomposite prepared by one-step electrodeposition from dendritic silver nanostructures, reduced graphene oxide, and ß-cyclodextrin. The modified SPCE exhibits high electrocatalytic activity toward nitrite oxidation, typically at a working potential at around 0.76 V (vs. Ag/AgCl). Sensitive and selective voltammetric detection of nitrite is demonstrated. The linear range extends from 1 to 2000 µM, the detection limit is 0.24 µM, and the sensitivity is 585.7 µA mM-1 cm-2. The method was applied to the determination of nitrite in (spiked) pickles. Graphical abstract Schematic presentation of fabrication of a screen printed carbon electrode modified with a lamellar nanocomposite containing dendritic silver nanostructures, reduced graphene oxide, and ß-cyclodextrin. Graphical abstract contains poor quality of text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.We have provided the original format of graphical abstract in the attachment.

Highly sensitive and reproducible non-enzymatic glucose sensor fabricated by drop-casting novel nanocomposite with 3D architecture and tailorable properties prepared in controllable way.

Novel nanocomposite has tailorable properties and ordered 3D architecture similar to the structure of materials prepared by electrodeposition which is convenient and efficient but the reproducibility is limited because of the uncontrollable preparation process, was scientifically synthetized in controllable way and used for non-enzymatic glucose sensor for the first time. Flower-like α-Ni(OH)2 with high specific surface areas and good anion transport ability benefited from its distinctive stacking faults and turbostratic disorder structure was synthesized through facile one-step hydrothermal method. Oversaturated gold nanoparticles (AuNPs) have been innovatively decorated on flower-like α-Ni(OH)2 to improve the electrical conductivity, in turn, AuNPs would possess the higher catalytic activity when supported on Ni(OH)2, so the resultant AuNPs decorated α-Ni(OH)2 (AuNPs@α-Ni(OH)2) also has excellent synergistic catalytic effect and improved selectivity. On this basis, ß-cyclodextrins functionalized reduced graphene oxide (ß-rGO) with enhanced dispersivity was scientifically added at optimized proportion to reduce the interparticle resistance of AuNPs@α-Ni(OH)2 as 2D electron transport channels, and to improve film-forming ability of the obtained nanocomposite via forming stable 3D network structure. Non-enzymatic glucose sensor fabricated through drop-casting the prepared nanocomposite on glass carbon electrode has high sensitivity up to 559.314µAmM-1cm-2 over the low concentration range and 327.199µAmM-1cm-2 over the higher concentration range, comparable to the sensors modified by electrodeposition method, indicating that prepared nanocomposite with controlling nanoscale composition and architectures based on rational design is an effective strategy to construct electrochemical sensor with excellent performance.