Graphene oxide and its derivatives have been widely explored for their antimicrobial properties due to their high surface-to-volume ratios and unique chemical and physical properties. However, little information is available on their effects on viruses. In this study, we report the broad-spectrum antiviral activity of GO against pseudorabies virus (PRV, a DNA virus) and porcine epidemic diarrhea virus (PEDV, an RNA virus). Our results showed that GO significantly suppressed the infection of PRV and PEDV for a 2 log reduction in virus titers at noncytotoxic concentrations. The potent antiviral activity of both GO and rGO can be attributed to the unique single-layer structure and negative charge. First, GO exhibited potent antiviral activity when conjugated with PVP, a nonionic polymer, but not when conjugated with PDDA, a cationic polymer. Additionally, the precursors Gt and GtO showed much weaker antiviral activity than monolayer GO and rGO, suggesting that the nanosheet structure is important for antiviral properties. Furthermore, GO inactivated both viruses by structural destruction prior to viral entry. The overall results suggest the potential of graphene oxide as a novel promising antiviral agent with a broad and potent antiviral activity.

Rapid sampling and multicomponent detection are crucial for monitoring of pesticide residues analysis. Here, a gecko-inspired nanotentacle surface-enhanced Raman spectroscopy (G-SERS) platform is proposed for the first time for the simultaneous detection of three kinds of pesticides via a simple and intuitive "press and peeled-off" approach. The G-SERS platform obtained from seeding deposition of silver nanoparticles (Ag NPs) on 3D PDMS nanotentacle array is flexible and free-standing. Compared with other substrates, this G-SERS substrate can simultaneously provide outstanding SERS activity (enhancement factor = 1.2 × 10), superior reproducibility (RSD = 5.8%) and countless flexible nanoscale "tentacles" (∼6.7 × 10/cm). Moreover, the high density of "tentacles" can freely approach the microarea and enable efficient target collection, which were confirmed by SEM and HPLC. By direct sampling from cucumber, apple, and grape surfaces, thiram (TMTD), methyl parathion (MPT), malachite green (MG), and their multiple components have been rapidly and reliably determined. For example, under the optimal conditions, a sensitivity of 1.6 ng/cm (S/N = 3) for TMTD was obtained on apple peels with a correlation coefficient (R) of 0.99. Therefore, the G-SERS substrate could offer a great practical potential for on-spot identification of various pesticide residues on real samples.

Surface-enhanced Raman spectroscopy (SERS) is a promising analytical tool, but simultaneous detection of multiple targets using SERS remains a challenge. Herein, a cauliflower-inspired 3D SERS substrate with intense hot spots was prepared through sputtering Au nanoparticles (Au NPs) on the surface of polydimethylsiloxane coated anodic aluminum oxide (PDMS@AAO) complex substrate. As a result, the cauliflower-inspired 3D SERS substrate achieved the highest SERS activities at a sputtering time of 8 min. Under the optimal conditions, this SERS substrate possessed a low detection limit of 10–12 M, excellent enhancement uniformity (relative standard deviation, RSD = 4.57%) and high enhancement factor (2.2 × 106) for 4-mercaptobenzoic acid (4-MBA). Furthermore, the results of Raman showed that the 3D-Nanocauliflower SERS substrates could realize the simultaneous label-free detection for three mycotoxins (aflatoxin B1, deoxynivalenol, and zearalenone) in maize for the first time. It behaved good linear relationship between the concentrations and Raman intensities of aflatoxin B1, zearalenone, and deoxynivalenol. For the three mycotoxins, this method exhibited the limit of detection (LOD) of 1.8, 47.7, and 24.8 ng/mL (S/N = 3), respectively. The 3D-Nanocauliflower SERS substrates with dense hot spots presented remarkable SERS effect and activity, which could be act as a potential candidate for SERS substrate applied in the rapid and label-free detection.

Carbon-based nanomaterials have been widely developed into innovative antimicrobial agents due to their advantages of high surface-to-volume ratio, extremely high mechanical strength, and distinct physicochemical properties. Here, the nanocomposite of graphene oxide/graphitic carbon nitride (GO/g-C3N4), a free-metal photocatalyst, was fabricated through sonication at room temperature and its antibacterial activity against Escherichia coli (E. coli) was investigated. The 100 μg/mL GO/g-C3N4 composite was found to kill 97.9% of E. coli after 120 min visible light irradiation, which was further confirmed by fluorescent-based cell membrane integrity assay. Additionally, the holes produced by photocatalysis were confirmed by electron spin resonance (ESR) spectra and trapping experiments to participate in photocatalytic sterilization as principal active species and were further verified by transmission electron microscopy (TEM) and scanning electron microscope (SEM) to lead to the distortion and rupture of cell membrane and finally cell death. Further photoluminescence (PL) spectra, cyclic voltammetry, photocurrent generation, and impedance spectroscopy (EIS) characterization revealed that the introduction of GO contributed to separate photogenerated electrons and prevents the electron–hole pairs of g-C3N4 from recombing to generate more h+, thus directly improving the bactericidal ability of GO/g-C3N4. Reusability assays indicated that the GO/g-C3N4 retained more than 90% of activity after four cycles of use. This study facilitates an in-depth understanding of the mechanism of visible light-driven disinfection and provides an ideal candidate sterilizing agent for treating microbial-contaminated water.

Nanoparticle-based antibacterial agents have emerged as an interdisciplinary field involving medicine, material science, biology, and chemistry because of their size-dependent qualities, high surface-to-volume ratio, and unique physiochemical properties. Some of them have shown great promise for their application in plant protection and nutrition. Here, GO-AgNPs nanocomposite was fabricated through interfacial electrostatic self-assembly and its antifungal activity against phytopathogen Fusarium graminearum was investigated in vitro and in vivo for the first time. The results demonstrated that the GO-AgNPs nanocomposite showed almost a 3- and 7-fold increase of inhibition efficiency over pure AgNPs and GO suspension, respectively. The spore germination inhibition was stimulated by a relatively low concentration of 4.68 μg/mL (minimum inhibition concentration (MIC)). The spores and hyphae were damaged, which might be caused by an antibacterial mechanism from the remarkable synergistic effect of GO-AgNPs, inducing physical injury and chemical reactive oxygen species generation. More importantly, the chemical reduction of GO mediated by fungal spores was possibly contributed to the high antimicrobial activity of GO-AgNPs. Furthermore, the GO-AgNPs nanocomposite showed a significant effect in controlling the leaf spot disease infected by F. graminearum in the detached leaf experiment. All the results from this research suggest that the GO-AgNPs nanocomposite developed in this work has the potential as a promising material for the development of novel antimicrobial agents against pathogenic fungi or bacteria.

A three-dimensional (3D) biomimetic SERS substrate with hierarchical nanogaps was formed on the bioscaffold arrays of cicada wings by one-step and reagents-free ion-sputtering techniques. This approach requires a minimal fabrication effort and cost and offers Ag nanoislands and Ag nanoflowers with four types of nanogaps (<10 nm) on the chitin nanopillars to generate a high density of hotspots (∼2000/μm2). The 3D biomimetic substrate shows a low detection limit to Rhodamine 6G (10(-13) M), high average enhancement factor (EF, 5.8×10(7)), excellent signal uniformity (5.4%), good stability, and suitability in biosensing. Furthermore, the finite-difference time-domain (FDTD) electric-field-distribution simulations illustrate that the 3D biomimetic SERS substrate provides the high-density hotspot area within a detection volumem, resulting in enormous SERS enhancement. In addition, the conspicuous far-field plasmon resonance peaks were not found to be a strong requirement for a high EF in 3D biomimetic substrates. Additionally, the novel substrate was applied in label-free animal viruses detection and differentiation with small amounts (1.0 μL) and low concentrations of analyte (1×10(3) PFU/mL), and it exhibited potential as an effective SERS platform for virus detection and sensing.

In this paper, a simple method to fabricate a three-dimensional (3D) nanostructure decorated with Ag nanoparticles for surface-enhanced Raman scattering (SERS) is demonstrated. Highly ordered porous anodic aluminum oxide (AAO) templates were employed to construct these compound nanostructures. First, the AAO templates were fabricated using a two-step anodization approach. Second, an alternating current (AC) electrochemical deposition was used to fill AAO templates with Ag nanoparticles. Taking 4-mercaptopyridine (4-MPy) as the probing molecule, high-quality SERS spectra were observed. The UV-vis mirror reflection spectra were measured to investigate the surface plasma resonance (SPR) absorbance. An interesting phenomenon of SPR-affected thin film interference was observed. SERS mapping was performed to characterize the homogeneity of as-prepared substrates. Good homogeneity and stability make these substrates good candidates for SERS spectroscopy.

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