4,4′-Diaminodiphenyl Sulfone Functionalized SBA-15: Toluene Sensing Properties and Improved Proton Conductivity

4,4′-Diaminodiphenyl sulfone functionalized SBA-15 (DDS/SBA-15) with various loading amounts of DDS has been prepared via a postsynthesis grafting method. The 2D hexagonal mesoporous structures of these hybrids have been confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N₂ adsorption–desorption isotherms. The covalent grafting of DDS onto the SBA-15 was further confirmed by Fourier transform infrared spectroscopy (FT-IR). DDS/SBA-15 based quartz crystal microbalance (QCM) sensor shows good selectivity and quick response toward toluene vapor, and the detection limit is down to 20 ppb. Impedance spectroscopy measurements showed that the proton conductivity properties of DDS/SBA-15 depended on the loading amount of DDS. These hybrids demonstrated improved proton conductivities compared with pristine SBA-15, and a highest value of 2.26 × 10^–4 S cm^–1 has been observed when the DDS loading amount is 0.37 mmol g^–1. Therefore, DDS/SBA-15 could serve as a promising candidate for both volatile organic compound (VOC) vapor sensing and proton conducting materials

Amine-Functionalized SBA-15 with Uniform Morphology and Well-Defined Mesostructure for Highly Sensitive Chemosensors To Detect Formaldehyde Vapor

Amine-functionalized SBA-15 with uniform morphology and well-defined mesostructure was prepared using a postgrafting route. The morphology, mesostructure, and functionality of the materials were characterized by scanning electron microscopy, transmission electron microscopy, small-angle X-ray scattering, nitrogen adsorption–desorption, Fourier transform infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy techniques. The results show that hexagonal lamelliform SBA-15 with a uniform particle size and short vertical channels plays two significant roles in uniformly dispersing amine-functionalizing groups and effectively adjusting the loadings of the functional groups within the mesopore channels. To confirm the potential application of the hybrids in gas sensors, using amine-functionalized SBA-15 as a sensing material and a quartz crystal microbalance as a transducer, a parts per billion level formaldehyde sensor with high sensitivity (response time about 11 s, recovery time about 15 s) and good chemoselectivity was achieved. This material holds great potential in the area of rapid, sensitive, and highly convenient formaldehyde detection

Bimetallic Au@Pt Nanocrystal Sensitization Mesoporous α‑Fe₂O₃ Hollow Nanocubes for Highly Sensitive and Rapid Detection of Fish Freshness at Low Temperature

In this work, we present a new metal oxide semiconductor gas sensor for detecting trimethylamine (TMA) by bimetal Au@Pt-modified α-Fe2O3 hollow nanocubes (NCs) as sensing materials. The structure and morphological characteristics of Au@Pt/α-Fe2O3 were evaluated through multiple analyses, and their gas-sensitive performance was investigated. Compared with the pristine α-Fe2O3 NC sensor, the sensor based on Au@Pt/α-Fe2O3 NCs exhibited faster response time (5 s) and higher response (Ra/Rg = 32) toward 100 ppm TMA gas at a lower temperature (150 °C). Furthermore, we also assessed the Au@Pt/α-Fe2O3 NC sensor for detecting the freshness of Larimichthys crocea which have been observed by headspace solid-phase microextraction and gas chromatography–mass spectrometry. The high performance of the Au@Pt/α-Fe2O3 NCs is attributed to the special hollow morphology with a high specific surface area (212.9 m2/g) and the synergistic effect of the Au@Pt bimetal. The Au@Pt/α-Fe2O3 sensor shows promising application prospects in estimating seafood freshness on the spot

Alkaloid Precipitant Reaction Inspired Controllable Synthesis of Mesoporous Tungsten Oxide Spheres for Biomarker Sensing

Highly porous sensitive materials with well-defined structures and morphologies are extremely desirable for developing high-performance chemiresistive gas sensors. Herein, inspired by the classical alkaloid precipitant reaction, a robust and reliable active mesoporous nitrogen polymer sphere-directed synthesis method was demonstrated for the controllable construction of heteroatom-doped mesoporous tungsten oxide spheres. In the typical synthesis, P-doped mesoporous WO3 monodisperse spheres with radially oriented channels (P-mWO3-R) were obtained with a diameter of ∼180 nm, high specific surface area, and crystalline skeleton. The in situ-introduced P atoms could effectively adjust the coordination environment of W atoms (Wδ+-Ov), giving rise to dramatically enhanced active surface-adsorbed oxygen species and unusual metastable ε-WO3 crystallites. The P-mWO3-R spheres were applied for the sensing of 3-hydroxy-2-butanone (3H2B), a biomarker of foodborne pathogenic bacteria Listeria monocytogenes (LM). The sensor exhibited high sensitivity (Ra/Rg = 29 to 3 ppm), fast response dynamics (26/7 s), outstanding selectivity, and good long-term stability. Furthermore, the device was integrated into a wireless sensing module to realize remote real-time and precise detection of LM in practical applications, making it possible to evaluate food quality using gas sensors conveniently

Hierarchical Flower-like WO₃ Nanospheres Decorated with Bimetallic Au and Pd for Highly Sensitive and Selective Detection of 3‑Hydroxy-2-butanone Biomarker

Listeria monocytogenes, which is abundant in environment, can lead to many kinds of serious illnesses and even death. Nowadays, indirectly detecting the metabolite biomarker of L. monocytogenes, 3-hydroxy-2-butanone, has been verified to be an effective way to evaluate the contamination of L. monocytogenes. However, this detection approach is still limited by sensitivity, selectivity, and ppb-level detection limit. Herein, low-cost and highly sensitive and selective 3-hydroxy-2-butanone sensors have been proposed based on the bimetallic AuPd decorated hierarchical flower-like WO3 nanospheres. Notably, the 1.0 wt % AuPd-WO3 based sensors displayed the highest sensitivity (Ra/Rg = 84 @ 1 ppm) at 250 °C. In addition, the sensors showed outstanding selectivity, rapid response/recovery (8/4 s @ 10 ppm), and low detection limit (100 ppb). Furthermore, the evaluation of L. monocytogenes with high sensitivity and specificity has been achieved using 1.0 wt % AuPd-WO3 based sensors. Such a marvelous sensing performance benefits from the synergistic effect of bimetallic AuPd nanoparticles, which lead to thicker electron depletion layer and increased adsorbed oxygen species. Meanwhile, the unique hierarchical nanostructure of the flower-like WO3 nanospheres benefits the gas-sensing performance. The AuPd-WO3 nanosphere-based sensors exhibit a particular and highly selective method to detect 3-hydroxy-2-butanone, foreseeing a feasible route for the rapid and nondestructive evaluation of foodborne pathogens

Alkaloid Precipitant Reaction Inspired Controllable Synthesis of Mesoporous Tungsten Oxide Spheres for Biomarker Sensing

Highly porous sensitive materials with well-defined structures and morphologies are extremely desirable for developing high-performance chemiresistive gas sensors. Herein, inspired by the classical alkaloid precipitant reaction, a robust and reliable active mesoporous nitrogen polymer sphere-directed synthesis method was demonstrated for the controllable construction of heteroatom-doped mesoporous tungsten oxide spheres. In the typical synthesis, P-doped mesoporous WO3 monodisperse spheres with radially oriented channels (P-mWO3-R) were obtained with a diameter of ∼180 nm, high specific surface area, and crystalline skeleton. The in situ-introduced P atoms could effectively adjust the coordination environment of W atoms (Wδ+-Ov), giving rise to dramatically enhanced active surface-adsorbed oxygen species and unusual metastable ε-WO3 crystallites. The P-mWO3-R spheres were applied for the sensing of 3-hydroxy-2-butanone (3H2B), a biomarker of foodborne pathogenic bacteria Listeria monocytogenes (LM). The sensor exhibited high sensitivity (Ra/Rg = 29 to 3 ppm), fast response dynamics (26/7 s), outstanding selectivity, and good long-term stability. Furthermore, the device was integrated into a wireless sensing module to realize remote real-time and precise detection of LM in practical applications, making it possible to evaluate food quality using gas sensors conveniently

A Robust Graft-to Strategy To Form Multifunctional and Stealth Zwitterionic Polymer-Coated Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles (MSNs) are a new class of carrier materials promising for drug/gene delivery and many other important applications. Stealth coatings are necessary to maintain their stability in complex media. Herein, a biomimetic polymer conjugate containing one ultralow fouling poly­(carboxybetaine) (pCBMA) chain and one surface-adhesive catechol (DOPA) residue group was efficiently grafted to the outer surface of SBA-15 type MSNs using a convenient and robust method. The cytotoxicity of SBA-15-DOPA-pCBMAs was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results showed no significant decrease in cell viability at the tested concentration range. Macrophage cell uptake studies revealed that the uptake ratios of SBA-15-DOPA-pCBMAs were much lower than that of parent MSNs. Furthermore, inductively coupled plasma mass spectrometry (ICP-MS) analysis results showed that after SBA-15-DOPA-pCBMAs were conjugated with a targeting cyclo-[Arg-Gly-Asp-d-Tyr-Lys] (cRGD) peptide, uptake by bovine aortic endothelial cells (BAECs) was notably increased. Results indicated that cRGD-functionalized MSNs were able to selectively interact with cells expressing αvβ3 integrin. Thus, MSNs with DOPA-pCBMAs are promising as stealth multifunctional biocarriers for targeted drug delivery or diagnostics

Bimetallic Au and Pd Nanoparticles Modified WO₃ Nanosheets for Enhancing the Sensitivity and Selectivity of Formaldehyde Assessment in Aquatic Products

Formaldehyde, a common illegal additive in aquatic products, poses a threat to people’s health and lives. In this study, a novel metal oxide semiconductor gas sensor based on AuPd-modified WO3 nanosheets (NSs) had been developed for the highly efficient detection of formaldehyde. WO3 NS modified with 2.0% AuPd nanoparticles showed a higher response (Ra/Rg = 94.2) to 50 ppm of formaldehyde at 210 °C, which was 36 times more than the pristine WO3 NS. In addition, the AuPd/WO3 gas sensor had a relatively short response/recovery time of 10 s/9 s for 50 ppm of formaldehyde at 210 °C, with good immunity to other interfering gases and good stability for formaldehyde. The excellent gas-sensitive performance was attributed to the chemical sensitization of Au, the electronic sensitization of Pd, and the synergistic effect of bimetallic AuPd, which facilitated the recognition and response of formaldehyde molecules. Additionally, the high sensitivity and broad application prospect of the 2.0% AuPd/WO3 NS composite-based sensor in real sample detection were also confirmed by using the above sensor for the detection of formaldehyde in aquatic products such as squid and shrimp