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The modification of metal oxides with noble metals is one of the most effective means of improving gas-sensing performance of chemiresistors, but it is often accompanied by unintended side effects such as sensor resistance increases up to unmeasurable levels. Herein, a carbonization-oxidation method is demonstrated using ultrasonic spray pyrolysis technique to realize platinum (Pt) single atom (SA) substitutional doping into SnO2 (named PtSA-SnO2). The substitutional doping strategy can obviously enhance gas-sensing properties, and meanwhile decrease sensor resistance by two orders of magnitude (decreased from ≈850 to ≈2 MΩ), which are attributed to the tuning of band gap and fermi-level position, efficient single atom catalysis, and the raising of adsorption capability of formaldehyde, as validated by the state-of-the-art characterizations, such as spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in situ diffuse reflectance infrared Fourier transformed spectra (in situ DRIFT), CO temperature-programmed reduction (CO-TPR), and theoretical calculations. As a proof of concept, the developed PtSA-SnO2 sensor shows humidity-independent (30-70% relative humidity) gas-sensing performance in the selective detection of formaldehyde with high response, distinguishable selectivity (8< Sformaldehyde/Sinterferant <14), and ultra-low detection limit (10 ppb). This work presents a generalized and facile method to design high-performance metal oxides for chemical sensing of volatile organic compounds (VOCs).
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Zeolites are widely used as catalysts and adsorbents in the chemical industry, but their potential for electronic devices has been stunted to date, as they are commonly recognized as electronic insulators. Here, we have for the first time demonstrated that Na-type ZSM-5 zeolites are ultrawide-direct-band-gap semiconductors based on optical spectroscopy, variable-temperature current-voltage characteristics, and photoelectric effect as well as electronic structure theoretical calculations and further unraveled the band-like charge transport mechanism in electrically conductive zeolites. The increase in charge-compensating Na+ cations in Na-ZSM-5 decreases the band gap and affects its density of states, shifting the Fermi level close to the conduction band. Remarkably, the semiconducting Na-ZSM-5 zeolites have been first applied for constructing electrically transduced sensors that can sense trace-level (77 ppb) ammonia with unprecedentedly high sensitivity, negligible cross-sensitivity, and high stability under moisture ambient conditions compared with conventional semiconducting materials and conductive metal-organic frameworks (MOFs). The charge density difference shows that the massive electron transfer between NH3 molecules and Na+ cations ascribed to Lewis acid sites enables electrically transduced chemical sensing. This work opens a new era of zeolites in applications of sensing, optics, and electronics.
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With the development of gas sensor arrays and computational technology, machine olfactory systems have been widely used in environmental monitoring, medical diagnosis, and other fields. The reliable and stable operation of gas sensing systems depends heavily on the accuracy of the sensors outputs. Therefore, the realization of accurate gas sensor array fault diagnosis is essential to monitor the working status of sensor arrays and ensure the normal operation of the whole system. The existing methods extract features from a single dimension and require the separate training of models for multiple diagnosis tasks, which limits diagnostic accuracy and efficiency. To address these limitations, for this study, a novel fault diagnosis network based on multi-dimensional feature fusion, an attention mechanism, and multi-task learning, MAM-Net, was developed and applied to gas sensor arrays. First, feature fusion models were applied to extract deep and comprehensive features from the original data in multiple dimensions. A residual network equipped with convolutional block attention modules and a Bi-LSTM network were designed for two-dimensional and one-dimensional signals to capture spatial and temporal features simultaneously. Subsequently, a concatenation layer was constructed using feature stitching to integrate the fault details of different dimensions and avoid ignoring useful information. Finally, a multi-task learning module was designed for the parallel learning of the sensor fault diagnosis to effectively improve the diagnosis capability. The experimental results derived from using the proposed framework on gas sensor datasets across different amounts of data, balanced and unbalanced datasets, and different experimental settings show that the proposed framework outperforms the other available methods and demonstrates good recognition accuracy and robustness.
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A cost-effective and highly reproducible capillary-based surface-enhanced Raman scattering (SERS) platform for sensitive, portable detection and identification of fentanyl is presented. Through encapsulating gold trisoctahedra (Au TOH) in the capillary tube for the first time, the SERS platform was constructed by combining the superior SERS properties of Au TOH and the advantages of capillaries in SERS signal amplification, facile sample extraction, and portable trace analysis. The effects of the size and density of Au TOH on the SERS performance were investigated by experiments and simulations, which showed that the maximum SERS enhancement was obtained for Au TOH with the size of 75 nm when particle density reached 74.54 counts/µm2. The proposed SERS platform possesses good reproducibility with a relative standard deviation (RSD) of less than 5%. As a demonstration, the platform was applied to detect fentanyl spiked in aqueous solution and serum samples with a limit of detection (LOD) as low as 1.86 and 40.63 ng/mL, respectively. We also validated the feasibility of the designed platform for accurate identification of trace fentanyl adulterated in heroin at mass concentration down to 0.1% (10 ng in 10 µg total). Overall, this work advances more explorations on capillary-based SERS platform to benefit portable trace analysis.
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Ouro , Nanopartículas Metálicas , Capilares , Fentanila , Reprodutibilidade dos Testes , Análise Espectral RamanRESUMO
Lipid droplets (LDs), which are ubiquitous organelles existing in almost all eukaryotic cells, have attracted a lot of attention in the field of cell biology over the last decade. For the biological study of LDs via fluorescence imaging, the superior LD fluorescent probes with environmental polarity-sensitive character are highly desired and powerful but are very scarce. Herein, we have newly developed such a kind of fluorescent probe named LDs-Red which enables us to visualize LDs and to further reveal their polarity information. This fluorescent probe displays the advantages of intense red/near-infrared emission, high LD staining specificity, and good photostability; thus, it would be very useful for LD fluorescence imaging application. As a result, the three-dimensional confocal imaging to visualize spatial distribution of LDs and the multicolor confocal imaging to simultaneously observe LDs and other cellular organelles have been realized using this new LD fluorescent probe. Furthermore, the polarity-sensitive emission character of this probe enables us to quantitatively determine the LD polarity via spectral scan imaging. Consequently, the cancer cells (HepG2, HeLa, and Panc02) displaying lower polarity of LDs than the normal cells (L929, U251, and HT22) have been systematically demonstrated. In addition, this polarity-sensitive probe displaying shorter fluorescence wavelengths in cancer cells than in normal cells has an important and potential ability to distinguish them.
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Corantes Fluorescentes , Gotículas Lipídicas , Células HeLa , Humanos , Imagem Óptica , Coloração e RotulagemRESUMO
Modulating the precise self-assembly of functional biomacromolecules is a critical challenge in biotechnology. Herein, functional biomacromolecule-assembled hierarchical hybrid nanoarchitectures in a spatially controlled fashion are synthesized, achieving the biorecognition behavior and signal amplification in the immunoassay simultaneously. Biomacromolecules with sequential assembly on the scaffold through the biomineralization process show significantly enhanced stability, bioactivity, and utilization efficiency, allowing tuning of their functions by modifying their size and composition. The hierarchically hybrid nanoarchitectures show great potential in construction of ultrasensitive immunoassay platforms, achieving a three order-of-magnitude increase in sensitivity. Notably, the well-designed HRP@Ab2 nanoarchitectures allow for optical immunoassays with a detection range from picogram mL-1 to microgram mL-1 on demand, providing great promise for quantitative analysis of both low-abundance and high-residue targets for biomedical applications.
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Testes Imunológicos , Proteínas , ImunoensaioRESUMO
Photocatalytic hydrogen evolution (PHE) over semiconductor photocatalysts is usually constrained by the limited light-harvesting and separation of photogenerated electron-hole pairs. Most of the reported systems focusing on PHE are facilitated by consuming the photoinduced holes with organic sacrificial electron donors (SEDs). The introduction of the SEDs not only causes the environmental problem, but also increases the cost of the reaction. Herein, a dual-functional photocatalyst is developed with the morphology of sandwiched-like hollowed Pd@TiO2 @ZnIn2 S4 nanobox, which is synthesized by choosing microporous zeolites with sub-nanometer-sized Pd nanoparticles (Pd NPs) embedded as the sacrificial templates. The ternary Pd@TiO2 @ZnIn2 S4 photocatalyst exhibits a superior PHE rate (5.35 mmol g-1 h-1 ) and benzylamine oxidation conversion rate (>99%) simultaneously without adding any other SEDs. The PHE performance is superior to the reported composites of TiO2 and ZnIn2 S4 , which is attributed to the elevated light capture ability induced by the hollow structure, and the enhanced charge separation efficiency facilitated by the ultrasmall sized Pd NPs. The unique design presented here holds great potential for other highly efficient cooperative dual-functional photocatalytic reactions.
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Lipid droplets (LDs) are spherical organelles that participate in numerous biological processes. In order to visualize LDs on the nanoscale, nanoscopy fluorescence imaging is considered as the most attractive technique but is substantially limited by the characteristics of fluorescent probes. Thus, the development of a superior fluorescent probe that is capable of nanoscopy fluorescence imaging has attracted enormous attention. Herein, a benzodithiophene-tetraoxide-based molecule Lipi-BDTO has been developed that can easily undergo the stimulated emission depletion (STED) process and displays high photostability. These two characteristics of fluorescent probes finely satisfy the requirements of STED nanoscopy imaging. Indeed, applying the probe for STED imaging achieves a high resolution of 65 nm, belonging to one of the leading results of LDs fluorescence imaging. Furthermore, the high photostability of this fluorescent probe enables it to monitor the dynamics of LDs by time-lapse STED imaging as well as to visualize the three-dimensional (3D) spatial distribution of LDs by 3D STED imaging. Notably, the resolution of the 3D STED image represents one of the best LDs fluorescence imaging results so far. Besides STED nanoscopy imaging, the superior utility of this fluorescent probe has been also demonstrated in two-color 3D confocal imaging and four-color confocal imaging.
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Corantes Fluorescentes , Gotículas Lipídicas , Células HeLa , Humanos , Microscopia de Fluorescência , Imagem ÓpticaRESUMO
On-site quantitative analysis of pesticide is of significant importance for addressing serious public health issues in clinical, food, and environmental settings. Herein, we designed a novel smartphone-assisted sensing platform for on-site monitoring of 2,4-dichlorophenoxyacetic acid (2,4-D) based on carbon dots/cobalt oxyhydroxide nanosheet (CDs/CoOOH) composite. In this work, a red emissive CDs/CoOOH composite was proposed as a signal indicator for shielding background interference, enhancing anti-interference capability. 2,4-D as an inhibitor of alkaline phosphatase could specifically suppress the production of ascorbic acid, which restrained in situ etching of the CDs/CoOOH composite and further triggered the fluorescence response of the biosensor. By employing a lab-on-smartphone based device and self-designed application software, the fluorescence image was directly captured and analyzed with a sensitive detection limit of 100 µg L-1 for 2,4-D. Merging the CDs/CoOOH composite-based fluorometric system with the smartphone-assisted optical reader, such a cost-effective and portable platform provided a new sight for on-site monitoring of pesticide and expanded application prospect in the field of biological analysis.
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Ácido 2,4-Diclorofenoxiacético/análise , Técnicas Biossensoriais , Carbono/química , Inibidores Enzimáticos/análise , Pontos Quânticos/química , Smartphone , Ácido 2,4-Diclorofenoxiacético/farmacologia , Fosfatase Alcalina/antagonistas & inibidores , Fosfatase Alcalina/metabolismo , Cobalto/química , Inibidores Enzimáticos/farmacologia , Nanopartículas/química , Imagem Óptica , Óxidos/química , Software , Espectrofotometria UltravioletaRESUMO
Synthesis of red emissive carbon dots (CDs) is highly desirable for sensing applications, as they still remain as bottlenecks in terms of precursor synthesis and product purification. Herein, we have designed a new strategy for realizing efficient red emissive CD optimal emission at 610 nm (fluorescence quantum yield ca. 24.0%) based on solvothermal treatment of citric acid and thiourea using dimethylformamide as solvent. Further investigations reveal that the conjugating sp2-domain controlling the incorporation of nitrogen and surface engineering are mainly responsible for the obtained red emission of CDs. Taking advantage of optical properties and abundant surface functional groups, CDs were considered to facilely construct a ratiometric fluorescent platform for quantifying trace levels of organophosphorus pesticides (OPs). Combining the acetylcholinesterase-mediated polymerization of dopamine and the inhibition of pesticide toward the enzyme, the degree of polymerization of dopamine rationally depends on the concentration of OPs. By measuring the fluorescence intensity ratio, the proposed platform exhibited highly selective and robust performance toward OPs, displaying ultrasensitive recognition in the pg L-1 level. The multiexcitation format could efficiently shield background interference from complex samples by introducing a self-calibrated reference signal, which affords accurate and reliable quantitative information, endowing CDs as a universal candidate for a biosensing application by combining target-specific recognition elements.
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Carbono/química , Técnicas de Química Analítica/instrumentação , Nanopartículas/química , Compostos Organofosforados/análise , Praguicidas/análise , Cor , Modelos Moleculares , Conformação MolecularRESUMO
Palladium-doped SnO2 nanomaterials, with palladium in fractions from 0 to 10 mol% were hydrothermally synthesized and characterized by XRD, FESEM, TEM, and XPS. Their gas sensing properties were studied in two temperature ranges of 75-95 °C and 160-210 °C. The sensor using 5 mol% Pd-doped SnO2 exhibits temperature-dependent sensing property. NO2 can be detected at 80 °C, while H2S is preferably detected at 180 °C. The response to 10 ppm H2S is 50 times higher than that of the undoped sample. Its detection limit is 500 ppb. For NO2, the sensor exhibited strong response and a lower detection limit of 20 ppb. In view of the selective detection of H2S and NO2 by regulating the temperature, palladium-doped SnO2 has great prospects in the detection of H2S and NO2. Graphical abstract Schematic of the gas sensing mechanism of the S-5% Pd doped SnO2.
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Hollow sphere composites were synthesized by a template-free hydrothermal method from MoO3 and In2O3. The spheres have a typical size of 800 ± 50 nm and were characterized by XRD, FESEM, TEM, XPS. Gas sensors based on samples with different Mo/In composite ratios were fabricated and their gas sensing properties were studied. The results show that a Mo:In ratio of 1:1 in the composite gives the highest response, typically at a working temperature of 250 °C. The response increases to 38 when exposed to 100 ppm acetone at 250 °C. This is 13.6 times better than when using pure MoO3. The sensor shows improved selectivity, response, repeatability and long-term stability. Typical features include a large specific surface area, and high levels of chemisorbed oxygen and defective oxygen sites. The N-N heterojunction theory was used to explain the improvement of gas sensing performance. Graphical abstract Schematic presentation of MoO3 and In2O3 composites and response test graph for 100 ppm acetone. The sensor based on this composite exhibits a very high response (38) to acetone at 250 °C and very fast response time (2 s).
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The construction of ammonia gas sensors with wide detection ranges is important for exhalation diagnosis and environmental pollution monitoring. To achieve a wide detection range, sensitive materials must possess excellent spatial confinement and large active surfaces to enhance gas adsorption. In this study, an ammonia microwave gas sensor with a wide detection range of 10 ppb-0.55 v/v% at room temperature was fabricated by incorporating hollow multishelled-structured BaTiO3 (HoMS-BaTiO3). The effect of the number of shells and the quantity of the sensitive material on the gas-sensing performance was investigated, and two-layered HoMS-BaTiO3 demonstrated the best response at high concentrations (0.15-0.55 v/v%). Conversely, single-layered HoMS-BaTiO3 displayed outstanding performance at low concentrations (10 ppb-0.15 v/v%). The lower the quantity of the sensitive material, the higher the response. This study offers a method for preparing room-temperature ammonia sensors with a wide detection range and reveals the link between the structure and quantity of sensitive materials and gas-sensing performance.
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Amônia , Compostos de Bário , Micro-Ondas , Temperatura , Titânio , Amônia/análise , Compostos de Bário/química , Titânio/química , Limite de Detecção , Gases/análise , Gases/químicaRESUMO
The biomimetic enzyme cascade system plays a key role in biosensing as a sophisticated signal transduction and amplification strategy. However, constructing a regulated enzyme cascade sensing system remains challenging due to the mismatch of multiple enzyme activities and poor stability. Herein, we design an efficient dual-enhanced enzyme cascade hybrid system (UFD-DEC) containing DNA-controlled nanozymes (Fe-cdDNA) and enzyme (urease) via combining the electrostatic contact effect with the hydrogel-directed confinement effect. Precise modulation of Fe-cdDNA nanozyme by DNA offers a means to control its catalytic efficiency. This regulated UFD-DEC system accelerates the reaction rate and provides remarkable stability compared with the free enzyme system. Benefiting from the plasticity properties of hydrogels, a "lab-in-a-tube" platform was constructed by encapsulating UFD-DEC in a microcentrifuge tube. Such a UFD-DEC-based hydrogel tube exhibits sufficient adaptability to profile urea when used in conjunction with a smartphone-assisted image processing algorithm, which on-site delivers urea information with a detection limit of 0.12 mmol L-1. This customizable and inexpensive miniaturized biosensor platform for monitoring urea may facilitate point-of-care testing applications.
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Técnicas Biossensoriais , Hidrogéis , Limite de Detecção , Urease , Técnicas Biossensoriais/métodos , Hidrogéis/química , Urease/química , Ureia/análise , Ureia/química , DNA Catalítico/química , DNA/químicaRESUMO
Monitoring organophosphorus pesticides is significant for food safety assessment. Herein, we developed upconversion nanoparticles (UCNPs)-based self-ratiometric fluorescent platform for the detection of chlorpyrifos. The UCNPs have the ability to confine the detection and reference functions in one nanoparticle. Specifically, the blue upconversion (UC) emission (448 nm) in the shell layer of UCNPs is quenched by the product of the acetylcholinesterase-mediated reaction, while the red UC emission (652 nm) from the core remains constant as a self-calibrated reference signal. Employing the inhibition property of chlorpyrifos, self-proportional fluorescence is employed to detect chlorpyrifos. As proof-of-concept, test strips are fabricated by loading the UCNPs onto filter paper. Combined with the smartphone and image-processing algorithm, chlorpyrifos quantitative testing is achieved with a detection limit of 14.4843 ng mL-1. This portable platform displays anti-interference capability and high stability in the complicated matrix, making it an effective candidate for on-site application.
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Clorpirifos , Nanopartículas , Praguicidas , Praguicidas/análise , Acetilcolinesterase , Compostos Organofosforados , CorantesRESUMO
Chiral assemblies have become one of the most active research areas due to their versatility, playing an increasingly important role in bio-detection, imaging and therapy. In this work, chiral UCNPs/CuxOS@ZIF nanoprobes are prepared by encapsulating upconversion nanoparticles (UCNPs) and CuxOS nanoparticles (NPs) into zeolitic imidazolate framework-8 (ZIF-8). The novel excited-state energy distribution-modulated upconversion nanostructure (NaYbF4@NaYF4: Yb, Er) is selected as the fluorescence source and energy donor for highly efficient fluorescence resonance energy transfer (FRET). CuxOS NP is employed as chiral source and energy acceptor to quench upconversion luminescence (UCL) and provide circular dichroism (CD) signal. Utilizing the natural adsorption and sorting advantages of ZIF-8, the designed nanoprobe can isolate the influence of other common disruptors, thus achieve ultra-sensitive and highly selective UCL/CD dual-mode quantification of H2S in aqueous solution and in living cells. Notably, the nanoprobe is also capable of in vivo intra-tumoral H2S tracking. Our work highlights the multifunctional properties of chiral nanocomposites in sensing and opens a new vision and idea for the preparation and application of chiral nanomaterials in biomedical and biological analysis.
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Given the potential dangers of thiram to food safety, constructing a facile sensor is significantly critical. Herein, we presented a colorimetric sensor based on glutathioneiron hybrid (GSH-Fe) nanozyme for specific and stable detection of thiram. The GSH-Fe nanozyme exhibits good peroxidase-mimicking activity with comparable Michaelis constant (Km = 0.551 mM) to the natural enzyme. Thiram pesticides can specifically limit the catalytic activity of GSH-Fe nanozyme via surface passivation, causing the change of colorimetric signal. It is worth mentioning that the platform was used to prepare a portable hydrogel kit for rapid qualitative monitoring of thiram. Coupling with an image-processing algorithm, the colorimetric image of the hydrogel reactor is converted into the data information for accurate quantification of thiram with a detection limit of 0.3 µg mL-1. The sensing system has good selectivity and high stability, with recovery rates in fruit juice samples ranging from 92.4% to 106.9%.
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Colorimetria , Sucos de Frutas e Vegetais , Glutationa , Ferro , Tiram , Colorimetria/instrumentação , Sucos de Frutas e Vegetais/análise , Ferro/química , Ferro/análise , Glutationa/química , Glutationa/análise , Tiram/análise , Tiram/química , Contaminação de Alimentos/análise , Praguicidas/análise , Praguicidas/química , Limite de Detecção , Técnicas Biossensoriais/instrumentaçãoRESUMO
On-site quantitative analysis of pesticide residues is crucial for monitoring environmental quality and ensuring food safety. Herein, we have developed a reliable hydrogel portable kit using NaYbF4@NaYF4: Yb, Tm upconversion nanoparticles (UCNPs) combined with MnO2 nanoflakes. This portable kit is integrated with a smartphone reader and Python-assisted analysis platform to enable sample-to-result analysis for chlorpyrifos. The novel UCNPs maximizes energy donation to MnO2 acceptor by employing 100 % of activator Yb3+ in the nucleus for NIR excitation energy collection and confining emitter Tm3+ to the surface layer to shorten energy transfer distance. Under NIR excitation, efficient quenching of upconversion blue-violet emission by MnO2 nanoflakes occurs, and the quenched emission is recovered with acetylcholinesterase-mediated reactions. This process allows for the determination of chlorpyrifos by inhibiting enzymatic activity. The UCNPs/MnO2 were embedded to fabricate a hydrogel portable kit, the blue-violet emission images captured by smartphone were converted into corresponding gray values by Python-assisted superiority chart algorithm which achieves a real-time rapid quantitative analysis of chlorpyrifos with a detection limit of 0.17 ng mL-1. At the same time, pseudo-color images were also added by Python in "one run" to distinguish images clearly. This sensor detection with Python-assisted analysis platform provides a new perspective on pesticide monitoring and broadens the application prospects in bioanalysis.
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N-butanol (C4H9OH) is a volatile organic compound (VOC) that is susceptible to industrial explosions. It has become imperative to develop n-butanol sensors with high selectivity and fast response and recovery kinetics. CdS/Ag2S composite nanomaterials were designed and prepared by the solvothermal method. The incorporation of Ag2S engendered a notable augmentation in specific surface area and a consequential narrow band gap. The CdS/Ag2S-based sensor with 3% molar ratio of Ag2S, operating at 200 °C, demonstrated a remarkably elevated response (S = Ra/Rg = 24.5) when exposed to 100 ppm n-butanol, surpassing the pristine CdS by a factor of approximately four. Furthermore, this sensor exhibited notably shortened response and recovery times, at a mere 4 s and 1 s, respectively. These improvements were ascribed to the one-dimensional single-crystal nanorod structure of CdS, which provided an effective path for expedited electron transport along its axial dimension. Additionally, the electron and chemical sensitization effects resulting from the modification with precious metal sulfides Ag2S were the primary reasons for enhancing the sensor response. This work can contribute to mitigating the safety risks associated with the use of n-butanol in industrial processes.
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Plant-wearable sensors provide real-time information that enables pesticide inputs to be finely tuned and play critical roles in precision agriculture. However, tracking pesticide information in living plants remains a formidable challenge owing to inadequate shape adaptabilities and low in-field sensor sensitivities. In this study, plant-wearable hydrogel discs are designed by embedding a dual-shelled upconversion-nanoparticles@zeolitic-imidazolate-framework@polydopamine (UCNPs@ZIF@PDA) composite in double-network hydrogels to deliver on-site pesticide-residue information. Benefiting from the enzyme-mimetic catalytic activity of ZIFs and enzyme triggered-responsive property of PDA shell, the hydrogel discs are endowed with high sensing sensitivity toward 2,4-dichlorophenoxyacetic acid pesticide at the nanogram per milliliter level via boosting fluorescence quenching efficiency. Notably, hydrogel discs mounted on tomato plants exhibit sufficient adaptability to profile dynamic pesticide degradation when used in conjunction with an ImageJ processing algorithm, which is practically applicable. Such hydrogel discs form a noninvasive and low-cost toolkit for the on-site acquisition of pesticide information, thereby contributing to the precise management of the health status of a plant and the judicious development of precision agriculture.