Fuzhou University

In this study, Surface-enhanced Raman Spectroscopy (SERS) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to investigate the molecular changes in Escherichia coli (E. coli) induced by exposure to ampicillin (AMP), enrofloxacin (ENR), ciprofloxacin (CIP), and norfloxacin (NFX) over time. The optimal concentration of E. coli for SERS analysis was determined to be 50 μL of bacterial suspension, diluted six times to achieve an OD600 ≈ 0.1. The primary changes in the SERS spectra were observed at 1267 cm^-1, corresponding to the amide III band in proteins, while the FTIR spectra revealed significant changes in the 1200-900 cm^-1 range, associated with carbohydrates, under AMP treatment. ENR, CIP, and NFX, which are quinolone antibiotics, act as inhibitors of DNA synthesis. The main changes in the SERS spectra for antibiotic-resistant E. coli were observed at 760 cm^-1 (attributed to cytosine and uracil), 960 cm^-1 (CN stretching and CC deformation), and 1140 cm^-1 (COC stretching and ring breathing). In the FTIR spectra, significant changes were detected at 1655 cm^-1, 1544 cm^-1, and 1239 cm^-1, corresponding to the amide I, amide II, and amide III bands, respectively. The combination of SERS and FTIR with principal component analysis (PCA) enabled the detection of molecular modifications in antibiotic-resistant E. coli exposed to different classes of antibiotics. These findings enhance our understanding of the mechanisms of action of antibiotics in bacteria.

Given the significant impact of Fe³⁺ and ascorbic acid (AA) on human health, the development of an efficient sensor for their detection is of critical importance. In this study, a novel fluorescent probe composed of ultrathin boron nanosheets (Ultrathin BNSs) is introduced for the sensitive detection of both Fe³⁺ and AA in human serum. Ultrathin BNSs, exhibiting a fluorescence quantum yield of up to 6.8 % and minimal cytotoxicity, can be directly synthesized from boron through an ultrasound-assisted liquid-phase exfoliation (LPE) method. These Ultrathin BNSs demonstrate a selective and responsive fluorescence "on-off-on" mechanism toward Fe³⁺ and AA, governed by the induction and removal of an electron-transfer effect. The presence of Fe³⁺ induces non-radiative electron transfer, resulting in fluorescence quenching of the Ultrathin BNSs. In contrast, the introduction of AA facilitates the dissociation of Fe³⁺ from the Ultrathin BNSs/Fe³⁺ complex, leading to fluorescence recovery. When utilized as a fluorescent nanoprobe, Ultrathin BNSs exhibit a strong linear correlation with Fe³⁺ concentrations ranging from 0.2 to 150 µM and AA concentrations between 1.5 and 110 µM. Additionally, the limits of detection (LOD) for Fe³⁺ and AA reach 0.2 µM and 1.5 µM, respectively, demonstrating superior performance compared to numerous previously reported fluorescent probes. The feasibility of this Ultrathin BNSs-based sensor for AA detection in human serum was further examined, yielding satisfactory outcomes. It is expected that our strategy may offer a new approach for developing rapid, low cost and sensitive ultrathin BNSs-based sensors for biological sensing and environmetal applications.

The construction of hierarchical thermoplastic polyurethane (TPU) composites with superior flame retardant and electromagnetic shielding capabilities hold significant practical importance.In this work, TPU composites loaded with a multilayer core-shell flame retardant (APP@CoAl-LDH@Si) and a modified conductive nanofiller (MWCNT-NH₂-PA) were firstly prepared through the melt blending method, acting as surface layer.Addnl., multilayered MXene films functionalized by bacterial cellulose (BC) and dopamine hydrochloride (DA) were fabricated via a facile and efficient vacuum filtration approach.Finally, a PBM film was utilized as an intermediate layer to construct hierarchical TPU composites.The results indicated that the introduction of 10 wt% APP@CoAl-LDH@Si hybrid, the peak heat release rate, total heat release, peak smoke production rate, and total smoke release of the TPU composites were decreased by 83.0%, 61.3%, 48.5% and 66.9%, resp., compared with those of pure TPU due to the free radicals capture effect of APP, and the flame-retardant functions of LDH and silane.Moreover, the hierarchical TPU/APP@CoAl-LDH@Si/CP1-PBM exhibited excellent electromagnetic shielding performance, achieving 43.6 dB in the X-band because of multiple reflection losses, interface polarization losses, and charge carrier movement-induced thermal dissipation.Extraordinarily, the A and R coefficients were reversed in the X and K bands.This phenomenon was attributed to the different degrees of confinement of the multilayer structure to electromagnetic waves with different wavelengths.This work presents a novel model for the design and preparation of high-performance polymer composites with multiple properties and regulation mechanism.