Selective surface enhanced Raman detection and effective photocatalytic degradation of sulfonamides antibiotic based on a flexible three-dimensional chitosan/carbon nitride/silver substrate.

The prevalence of sulfonamide residues in aquatic environments poses serious environmental risks, and the sensitive detection and effective degradation of sulfonamides have attracted widespread attention. Here, the environmentally friendly chitosan (CS)/carbon nitride (CN) with three-dimensional porous structure is fabricated by freeze-drying method, and subsequently a new bifunctional flexible substrate (CS/CN/Ag) is prepared by anchoring of small sized AgNPs (6 ∼ 12 nm) on CS/CN. Importantly, the CS/CN/Ag substrate shows high adsorption capacity (∼ 83.06%) for sulfamethoxazole (SMX) solution within 20 mins and the limit of detection can be as low as 7.46 × 10-9 mol·L-1 with an enhancement factor of 3.3 × 105. Also, the CS/CN/Ag substrate displays highly selective for surface-enhanced Raman spectroscopy (SERS) detection of sulfonamides and also shows excellent SERS response for SMX in hospital wastewater samples. In addition, the photocatalytic degradation efficiency of SMX could reach as high as 99.22% within 20 mins of irradiation and the CS/CN/Ag still maintains outstanding photocatalytic performance after six cycles. Moreover, the Ag content in the CS/CN/Ag substrate is only 2.35%, and also the CS/CN/Ag exhibits good uniformity, repeatability, recyclability and stability. Therefore, this flexible and cost-effectively substrate of CS/CN/Ag shows great potential for the simultaneous SERS detection and photocatalytic degradation of pollutants in actual wastewater samples.

A portable architectonics of Al/carbon nitride/metal-organic frameworks anchored Ag nanoparticles for SERS detection and photocatalytic degradation of fungicide.

In recent years, it is urgent to develop bi-functional materials for highly sensitive SERS detection and photocatalytic degradation of contaminants in water of fish pond. Herein, using 5-mercapto-1-methyltetrazole as the ligand, the tree-trunk like zeolitic imidazolate framework (ZIF-8) is induced and in-situ grown on the surface of aluminum/flower carbon nitride (Al/f-C3N4). Then, AgNPs are tightly anchored in ZIF-8 of Al/f-C3N4/ZIF-8 by strong Ag-N and Ag-S bonds, and a portable architecture of Al/f-C3N4/ZIF-8/Ag is successfully prepared. Results indicate that the Al/f-C3N4/ZIF-8/Ag architecture exhibits excellent SERS activity and the detection limit can as low as 2.15 × 10-11 mol⋅L-1 for crystal violet (CV, a typical fungicide). Also, the Al/f-C3N4/ZIF-8/Ag substrate presents good photocatalytic activity for CV molecule, and the degradation efficiency reaches 98.58% after illumination for 90 min. This is mainly due to the good adsorption capacity of ZIF-8 which can enrich more CV molecules and pull them to "hot spots" generated by Ag in Al/f-C3N4/ZIF-8/Ag, and thus SERS response are enhanced significantly. Besides, the strong synergistic effect of f-C3N4, ZIF-8 and AgNPs is also important which facilitates the separation of photogenerated electrons and holes. Thus, the designed portable and bi-functional substrate could be used as a potential material for the detection and removal of CV in practical application.

Aluminum sheet induced flower-like carbon nitride anchored with silver nanowires for highly efficient SERS detection of trace malachite green.

The sensitive detection of malachite green (MG) in aquaculture wastewater is necessary for its residual poses a great threat to the living systems. Herein, the flower-like C3N4 (f-C3N4) nanostructure induced by Al sheet in the hydrothermal process is constructed. Subsequently, Ag nanowires (AgNWs) supported on Al/f-C3N4 and the strong interaction between AgNWs and Al/f-C3N4 are confirmed by XPS, Raman spectroscopy, UV-vis diffuse reflectance and fluorescence spectroscopy. Importantly, the portable Al/f-C3N4/AgNWs substrate shows the outstanding SERS response for MG, which is attributed to enhanced electromagnetic effect of AgNWs on large amount of corrugated and creviced regions in the flower-like Al/f-C3N4 and the charge transfer among the components. Also, the prepared Al/f-C3N4 nanostructure provides large specific surface area and abundant "N" active sites for AgNWs, and the high enrichment ability of Al/f-C3N4 towards MG molecules by the strong π-π stacking interaction. The detection limit of Al/f-C3N4/AgNWs for MG is as low as 8.38 × 10-12 mol L-1. The substrate can be reproduced and reused for at least 7 cycles, and the activity can still be kept after laid up for 49 days. Importantly, it unfolds a good sensitivity and selectivity for MG in actual water sample. Results indicate that the Al/f-C3N4/AgNWs substrate has a promising potential in practical application for trace detection of MG.

A stable and plug-and-play aluminium/titanium dioxide/metal-organic framework/silver composite sheet for sensitive Raman detection and photocatalytic removal of 4-aminothiophenol.

The sensitive detection and rapid removal of 4-aminothiophenol (4-ATP, a poisonous pesticide) demand special design to potential substrates. Herein, a metal-organic framework (ZIF-8) and Ag nanoparticles were fabricated one by one on the TiO2 coated Al sheet, and thus the Al-TiO2-ZIF-8-Ag sheet with sandwich structure was successfully synthesized. The cost-effective Al-TiO2-ZIF-8-Ag sheet (3.7 wt% Ag) possessed a low detection concentration of 1 × 10-9 M towards 4-ATP, and surface-enhanced Raman scattering (SERS) analytical enhanced factor (AEF) of the Al-TiO2-ZIF-8-Ag was 2.6 × 106, which was higher than other similar substrates. Furthermore, 4-ATP can be selectively and repeatedly detected on the Al-TiO2-ZIF-8-Ag even through it was in real samples. It indicated that the Al-TiO2-ZIF-8-Ag was a very active and stable SERS materials for the monitoring of 4-ATP. Importantly, the substrate exhibited faster and more efficient photocatalytic activity for 4-ATP degradation. The SERS and photocatalytic mechanisms of 4-ATP on the Al-TiO2-ZIF-8-Ag substrate were proposed. The cost-effective Al-TiO2-ZIF-8-Ag sheet with double function is plug-and-play, and could be used in the detection and treatment of pollutants in wastewater.

Boosting charge separation and nitrogen vacancies in graphitic carbon nitride by implanted strontium vanadate for highly efficient photocatalytic reduction of hexavalent chromium.

Strontium vanadate nanoparticles embedded graphitic carbon nitride (g-C3N4/Sr2V2O7) was facilely prepared in situ via a hydrothermal method. It was shown that the Sr2V2O7 nanoparticles implanted into g-carbon nitride had a small size and high distribution. Importantly, compared with some other photocatalysts, the as-prepared g-C3N4/Sr2V2O7 nanohybrid showed excellent photocatalytic activity for reduction of Cr(vi), and as high as 99% efficiency for Cr(vi) reduction (100 mg L-1) was reached within 8 min. Moreover, its activity was hardly changed after five cycles, demonstrating that the developed g-C3N4/Sr2V2O7 nanohybrid was highly stable and promising an efficacious disposal of Cr(vi) in water. It was confirmed that the improved charge separation owing to more nitrogen vacancies in the hybrid was the main reason for the improved performance of the g-C3N4-Sr2V2O7 nanohybrid.

Photocatalytic activity and the electron transport mechanism of titanium dioxide microsphere/porphyrin implanted with small size copper.

To obtain efficient photocatalysts by coupling architectures, developing novel materials and elucidating the charge transport mechanism at the semiconductor interface are vital. Herein, a special nanocomposite (TiO2 microsphere/CuNPs/THPP) for photocatalytic hydrogen production was facilely fabricated with copper nanoparticles (CuNPs) as the interfacial linker of the TiO2 microspheres and meso-tetra(p-hydroxypheny)porphyrin (THPP). The assembly mode of the nanocomposite was studied in detail. It was found that the CuNPs implanted at the interface of the TiO2 microspheres and THPP can dramatically strengthen the interaction between the TiO2 microspheres and THPP, and improve the separation and transfer of photo-produced charges. Therefore, the nanocomposite displayed excellent performance for photocatalytic hydrogen production. Moreover, by recycling hydrogen production, it is demonstrated that the nanocomposite was a highly efficient and long-term stable photocatalyst. By investigating the energy band location and the charge transfer, the photocatalytic mechanism over the special nanocomposite was explored and proposed to explain the better activity of the TiO2 microsphere/CuNPs/THPP photocatalytic system. It will be helpful to provide deep insights into the construction of efficient photocatalytic systems.

A novel AuNPs-based nanosensors for smart detection of NO with low concentration.

A novel method for detection of nitric oxide (NO) was developed by the structural transition of oxidized cytochrome c (Cyt c III) on gold nanoparticles (AuNPs)/glycine (Gly)/graphene quantum dots (GQDs) composite using surface-enhanced Raman scattering (SERS) spectroscopy. Importantly, the composite can be used as a good SERS substrate for the selective detection of trace NO based on the interaction of the Cyt c (III) and NO, and the structural transition of oxidized Cyt c III on AuNPs/Gly/GQDs composite. The NO concentration in real seawater sample was determined to be 7.28 × 10-8 M. Combined with the interaction of the Cyt c (III) and NO, and the structural transition of oxidized Cyt c (III) on AuNPs/Gly/GQDs composite, a novel AuNPs-based SERS probe for the selective detection of trace NO was constructed, and the detection limit for NO can reach about ~10-8 M.

The study of a novel cobalt-implanted pyridylporphyrin/graphene oxide nanohybrid for enhanced photocatalytic hydrogen evolution and its electron transfer mechanism.

A metallic cobalt nanoparticle-implanted 5,15-diphenyl-10,20-di(4-pyridyl) porphyrin (DPyP)/graphene oxide (GO) nanohybrid (GO-Co-DPyP) was facilely fabricated. By means of XPS, XRD, Raman spectroscopy and UV-vis spectroscopy, it was demonstrated that on implanting metallic cobalt nanoparticles (Co NPs) in the GO, stronger interaction between GO and DPyP can be achieved, which enlarged the included angle between DPyP and GO. The nanohybrid was benifical for light absorption and photo-induced electron transfer. Furthermore, photocatalytic activity for hydrogen evolution over the nanohybrid was investigated. We found that higher activity over the GO-Co-DPyP nanohybrid was obtained, which was about two times higher than that of Co2+ implanted in the GO (GO-Co2+-DPyP). Combined with the results of fluorescence spectra and photoelectronic spectra, the electron transfer mechanism for hydrogen evolution was clarified. This study will provide some theoretical and experimental basis for the assembly and photocatalytic performance of GO-based composites by interfacial modification.

Graphene quantum dots supported by graphene oxide as a sensitive fluorescence nanosensor for cytochrome c detection and intracellular imaging.

A new class of cytochrome c (Cyt c) detection fluorescence sensor (GQDs-GO) based on graphene quantum dots (GQDs) supported by graphene oxide (GO) has been developed through simply mixing a certain amount of GQDs and GO. It is found that fluorescence "turn on" or "turn off" can be adjusted easily according to the concentration of Cyt c. When the concentration of Cyt c is lower than 1.9 µmol L-1, the fluorescence is "turn on", whereas it is "turn off" beyond 1.9 µmol L-1. The process is fast and can be completed within 10 s. By means of UV-vis absorption spectra, it is demonstrated that the changed fluorescence comes from the different interactions among GQDs, GO and Cyt c. Additionally, the GQDs-GO shows a high selectivity for Cyt c detection, and further exhibits favorable intracellular imaging in A549 cells. This study opens a new direction for developing a low-cost, highly efficient, GQDs-based fluorescence sensor for Cyt c detection, which make it very attractive for biological imaging applications.

Gold nanoparticles conjugated dopamine as sensing platform for SERS detection.

In this work, the properties of dopamine and dopamine-quinone on gold nanoparticles (Au NPs) surface were studied by the constructed Au NPs/dopamine sensing platform using surface enhanced Raman scattering (SERS) spectroscopy. Interestingly, the Au NPs/dopamine-quinone exhibited the characteristic Raman band at 1270, 1335 and 1480 cm(-1) at pH 10.0, whereas, no obvious Raman band of Au NPs/dopamine was observed at pH = 6.0. Also, dopamine-quinone could be reduced by glutathione (GSH) and dopamine could be oxidized easily by superoxide radical anion (O2(-)), thus, this sensing platform could be used to determine the concentration of GSH and O2(-) in a wide range. Importantly, the utility of Au NPs/dopamine platform was demonstrated in living HeLa and normal human liver (HL-7702) cells, and responded to the concentration changes of reactive oxygen species (ROS) in real time.

Photoelectronically active, metal organic framework films prepared by self-directed assembly of silanized porphyrin cobalt monomers.

A novel and facile approach for preparing highly oriented porphyrin metal-organic framework films on various substrates is explored by employing self-directed assembly of silanized porphyrin cobalt monomers (SPCMs). The three-dimensional ordered porphyrin films display excellent photo-electronic performance.

Redox heme-proteins mediated fluorescence of CdSe/ZnS quantum dots.

The redox properties of cytochrome c (Cyt c), hemoglobin (Hb) and myoglobin (Mb) were studied based on electrostatic interactions between Thioglycolic acid (TGA) capped CdSe/ZnS quantum dots (QDs) and proteins. Results indicated that only Cyt c quenched the fluorescence of the QDs at pH>8.0. Under the optimized conditions, a significant fluorescence recovery of the QDs' system was observed when the reduced form of Cyt c incubated with TGA capped QDs, however, the reduced state of Hb and Mb resulted in a more fluorescence quenching on the same size of QDs. Interestingly, the fluorescence changes of QDs-proteins could be switched by modulating the redox potentials of proteins-attached QDs. Moreover, only the oxidized Cyt c form was reduced by the generated O2(-) that significantly enhanced the fluorescence of the QDs' system, which was also demonstrated by fluorescence imaging in HeLa cells.

Self-assembling of helical poly(phenylacetylene) carrying L-valine pendants in solution, on mica substrate, and on water surface.

In the present work, we investigated self-assembling of a poly(phenylacetylene) carrying L-valine pendants (PPA-Val) in a water/methanol solution, upon evaporation of the solution on mica, and on the water surface. With intercalation of a fluorescence probe of Ru(phen)2(dppx)2+ (phen = 1,10-phenanthroline, dppx=7,8-dimethyldipyridophenazine) into the hydrophobic cavities associated by the PPA-Val chains, their helical structures were directly detected in solution with an in situ fluorescence microscope. Helical aggregates were observed with AFM upon evaporation of the solvents, suggesting that the helical structures in the solution are the building blocks of the helical aggregates. Self-assembling structures of PPA-Val on the water surface were, however, very different from that formed upon evaporation of its THF solution on the mica surface. The polymer chains associated into a monolayer of extended fibers on the water surface, whereas superhelical fibers formed on the mica surface. Water molecules play a critical role in inducing the polymer to form diverse morphological structures in its bulk solution and on its surface. In solution, the isotropic hydrophobic effect drove the polymer chains to form superhelical aggregates, while on the water surface, the hydrophobic effect concentrated mainly on the lateral part of the polymer, thus giving a monolayer of extended fibers.