Zhongbo Li

Large-scale well-separated Ag nanosheet-assembled micro-hemispheres modified with HS-β-CD as effective SERS substrates for trace detection of PCBs

Large-scale well-separated Ag nanosheet-assembled micro-hemispheres with similar size and morphology were achieved on bare commercial ITO substrates via simple electrodeposition in a mixed aqueous solution of citric acid and AgNO3. It was found that appropriate electrodeposition current density and citric acid concentration are critical to the formation of well-separated nanosheet-assembled micro-hemispheres with similar size and morphology. The well-separated Ag nanosheet-assembled micro-hemispheres with similar size and morphology ensure the good surface-enhanced Raman scattering (SERS) signal reproducibility from different micro-hemispheres, and the sufficient sub-10 nm gaps on the nanosheet-assembled micro-hemispheres guarantee the high SERS sensitivity. By further modifying the Ag nanosheet-assembled micro-hemispheres with mono-6-thio-β-cyclodextrin (HS-β-CD), the SERS detection limit of 3,3′,4,4′-tetrachlorobiphenyl (PCB-77) can be further reduced, and two different polychlorinated biphenyl (PCB) congeners of 2-chlorobiphenyl (PCB-1) and PCB-77 in a mixed solution can be distinguished, indicating that the large-scale well-separated Ag nanosheet-assembled micro-hemispheres modified with HS-β-CD may have great potential as effective SERS substrates for rapid trace detection of PCBs.

Ag Nanoparticle-Grafted PAN-Nanohump Array Films with 3D High-Density Hot Spots as Flexible and Reliable SERS Substrates.

A facile fabrication approach of large-scale flexible films is reported, with one surface side consisting of Ag-nanoparticle (Ag-NP) decorated polyacrylonitrile (PAN) nanohump (denoted as Ag-NPs@PAN-nanohump) arrays. This is achieved via molding PAN films with ordered nanohump arrays on one side and then sputtering much smaller Ag-NPs onto each of the PAN-nanohumps. Surface-enhanced Raman scattering (SERS) activity of the Ag-NPs@PAN-nanohump array films can be improved by curving the flexible PAN film with ordered nanohump arrays during the Ag-sputtering process to increase the density of the Ag-NPs on the sidewalls of the PAN-nanohumps. More 3D hot spots are thus achieved on a large-scale. The Ag-NPs@PAN-nanohump array films show high SERS activity with good Raman signal reproducibility for Rhodamine 6G probe molecules. To trial their practical application, the Ag-NPs@PAN-nanohump array films are employed as SERS substrates for trace detection of trinitrotoluene and a congener of polychlorinated biphenyls. A lower detection limit of 10(-12) m and 10(-5) m can be achieved, respectively. Furthermore, the flexible Ag-NPs@PAN-nanohump array films can also be utilized as swabs to probe traces of methyl parathion on the surface of fruits such as apples. The as-fabricated SERS substrates therefore have promising potential for applications in rapid safety inspection and environmental protection.

Galvanic‐Cell‐Induced Growth of Ag Nanosheet‐Assembled Structures as Sensitive and Reproducible SERS Substrates

SERS up: Ag nanosheet-assembled structures with controlled morphologies were achieved on indium tin oxide substrates by galvanic-cell-induced growth (see figure). These structures exhibit a highly active and homogeneous surface-enhanced Raman scattering (SERS) effect, and show promising potential as reliable SERS substrates for detection of trace polychlorinated biphenyls.

Hexagonally arranged arrays of urchin-like Ag hemispheres decorated with Ag nanoparticles for surface-enhanced Raman scattering substrates

The surface topography of noble metal particles is a significant factor in tailoring surface-enhanced Raman scattering (SERS) properties. Here, we present a simple fabrication route to hexagonally arranged arrays of surface-roughened urchinlike Ag hemispheres (Ag-HSs) decorated with Ag nanoparticles (Ag-NPs) for highly active and reproducible SERS substrates. The urchin-like Ag-HS arrays are achieved by sputtering Ag onto the top surface of a highly ordered porous anodic aluminum oxide (AAO) template to form ordered arrays of smooth Ag-HSs and then by electrodepositing Ag-NPs onto the surface of each Ag-HS. Owing to the ordered arrangement of the Ag-HSs and the improved surface roughness, the urchin-like hierarchical Ag-HS arrays can provide sufficient and uniform “hot spots” for reproducible and highly active SERS effects. Using the urchin-like Ag-HS arrays as SERS substrates, 10−7 M dibutyl phthalate (a member of plasticizers family) and 1.5 × 10−5 M PCB-77 (one congener of polychlorinated biphenyl, a notorious class of pollutants) are identified, showing promising potential for these substrates in the rapid recognition of organic pollutants.

Urchin-like Au-nanoparticles@Ag-nanohemisphere arrays as active SERS-substrates for recognition of PCBs

A simple fabrication route is developed for ordered urchin-like Au-nanoparticles decorated Ag-nanohemisphere nanodot arrays with a highly active and reproducible surface-enhanced Raman scattering effect for rapid recognition of 4-chlorinated biphenyl.

An ordered array of hierarchical spheres for surface-enhanced Raman scattering detection of traces of pesticide.

An ordered array of hierarchically-structured core-nanosphere@space-layer@shell-nanoparticles has been fabricated for surface-enhanced Raman scattering (SERS) detection. To fabricate this hierarchically-structured chip, a long-range ordered array of Au/Ag-nanospheres is first patterned in the nano-bowls on the planar surface of ordered nanoporous anodic titanium oxide template. A ultra-thin alumina middle space-layer is then conformally coated on the Au/Ag-nanospheres, and Ag-nanoparticles are finally deposited on the surface of the alumina space-layer to form an ordered array of Au/Ag-nanosphere@Al2O3-layer@Ag-nanoparticles. Finite-difference time-domain simulation shows that SERS hot spots are created between the neighboring Ag-nanoparticles. The ordered array of hierarchical nanostructures is used as the SERS-substrate for a trial detection of methyl parathion (a pesticide) in water and a limit of detection of 1 nM is reached, indicating its promising potential in rapid monitoring of organic pollutants in aquatic environment.

CNTs-anchored egg shell membrane decorated with Ag-NPs as cheap but effective SERS substrates

We report a simple approach for the fabrication of cheap but effective surface-enhanced Raman scattering (SERS) active substrates consisting of natural egg shell membrane (ESM) grafted with Ag-nanoparticles (Ag-NPs) decorated carbon nanotubes (CNTs) (denoted as Ag-NPs@CNTs@ESM), via ultrasonic adsorption of CNTs on the ESM and the subsequent Ag-sputtering. As high density Ag-NPs were sputtered onto each CNT anchored on the ESM nanofiber, homogeneous nanoscaled gaps between the neighboring Ag-NPs were achieved, leading to high SERS activity with excellent SERS signal homogeneity over the whole membrane. Using the Ag-NPs@CNTs@ESM membranes as SERS-substrates, methyl parathion (one of the most hazardous insecticides), PCB-3 (one congener of polychlorinated biphenyls belonging to persistent organic pollutants) and bovine serum albumin (BSA, biomolecules) with a concentration down to 10−11 M, 10−6 M and 0.1 ppb were detected respectively, showing promising potentials in rapid trace detection of environmental pollutants and biochemicals.摘要本文报道了一种利用具有均匀纤维网络结构的鸡蛋膜作为三维骨架, 制备碳纳米管/鸡蛋膜复合表面增强Raman散射SERS)衬底的简单廉价的方法. 首先, 借助超声吸附, 将碳纳米管组装到经过前处理的鸡蛋膜纤维的表面, 得到均匀的碳纳米管/鸡蛋膜复合膜; 后, 借助溅射方法, 将银纳米颗粒组装到碳纳米管和鸡蛋膜纤维的表面, 得到银纳米颗粒修饰的碳纳米管/鸡蛋膜复合膜. 这种方法制备的复合膜表面的碳纳米管对小分子目标分析物有很好的吸附和富集作用; 同时, 由于高密度银纳米颗粒的存在, 衬底表面有大量的SERS活性位点, 因此这种复合膜是一种有效的SERS衬底. 研究表明, 采用这种银纳米颗粒修饰的碳纳米管/鸡蛋膜复合SERS衬底, 可实现对农药甲基对硫磷、 多氯联苯以及生物分子牛血清蛋白等的快速痕量识别. 由于该衬底的制备方法简单、 原材料环保且来源广泛、 衬底的活性高, 所以该衬底在基于SERS技术对环境污染物和生物分子的快速痕量检测方面具有广泛的应用前景.

Ordered arrays of Ag nanodendrite clusters as effective surface-enhanced Raman scattering substrates

We report a cheap synthetic approach to large-area ordered Ag nanodendrite cluster arrays as effective surface-enhanced Raman scattering (SERS) substrates, on a Zn plate coated with periodical porous photoresist via galvanic replacement reaction of Zn and AgNO3 in aqueous solution. Due to the geometrical confinement of the porous photoresist template coated on the Zn plate, the well-positioned Ag nanodendrite clusters are distributed on the Zn plate in ordered arrays. It is demonstrated that citric acid is essential to the formation of the nanodendrite cluster arrays. The resultant Ag nanodendrite cluster arrays not only have high SERS-activity to rhodamine 6G with good signal reproducibility but also can identify thiram (a widely-used pesticide) even at 0.1 μM level, showing potential in SERS-based detection of pesticide remnants in the environment.

Galvanic-Cell-Reaction-Driven Deposition of Large-Area Au Nanourchin Arrays for Surface-Enhanced Raman Scattering

Here we report a low-cost synthetic approach for the direct fabrication of large-area Au nanourchin arrays on indium tin oxide (ITO) via a facile galvanic-cell-reaction-driven deposition in an aqueous solution of chloroauric acid and poly(vinyl pyrrolidone) (PVP). The homogeneous Au nanourchins are composed of abundant sharp nanotips, which can served as nanoantennas and increase the local electromagnetic field enhancement dramatically. Finite element theoretical calculations confirm the strong electromagnetic field can be created around the sharp nanotips and located in the nanogaps between adjacent tips of the Au nanourchins. In addition, the interparticle nanogaps between the neighboring Au nanourchins may create additional hotspots, which can induce the higher electromagnetic field intensity. By using rhodamine 6G as a test molecule, the large-area Au nanourchin arrays on ITO exhibit active, uniform, and reproducible surface-enhanced Raman scattering (SERS) effect. To trial their practical application, the Au nanourchin arrays are utilized as SERS substrates to detect 3,3’,4,4’-tetrachlorobiphenyl (PCB-77) one congener of polychlorinated biphenyls (PCBs) as a notorious class of persistent organic pollutants. The characteristic Raman peaks can be still identified when the concentration of PCB-77 is down to 5 × 10−6 M.

Controllable fabrication of Ag-nanoplate-decorated PAN-nanopillar arrays and their application in surface-enhanced Raman scattering

We report a facile and low-cost approach for fabrication of large-scale surface-enhanced Raman scattering (SERS) active substrates composed of Ag-nanoplates (Ag-NPs) decorated polyacrylonitrile nanopillar (denoted as Ag-NPs@PAN-nanopillar) arrays, via a consecutive process of molding PAN-nanopillar arrays, sputtering Au-nanoparticles onto the PAN-nanopillar arrays as a conducting layer, and decorating the PAN-nanopillars with Ag-nanoplates. The Ag-nanoplate distribution density on the PAN-nanopillars can be tailored by tuning the concentration of citric acid and the Ag-deposition duration, and high SERS sensitivity can thus be achieved by optimizing the density of Ag-nanoplates. The adjacent Ag-nanoplates induced “hot spots” are densely and uniformly distributed in the three dimensional (3D) space around the PAN-nanopillar arrays, and thus Ag-NPs@PAN-nanopillar arrays generated sensitive and homogenous SERS signals when using rhodamine 6G as a probed molecule. Using the Ag-NPs@PAN-nanopillar arrays as SERS substrates, 10−7 M methyl parathion (organophosphorus insecticide) and 10−6 M PCB-77 (one congener of polychlorinated biphenyls belonging to persistent organic pollutants) are identified. Therefore the SERS-active substrates have potential in SERS-based rapid detection of environmental organic pollutants.