Fabrication of Functional Polymer Structures through Bottom-Up Selective Vapor Deposition from Bottom-Up Conductive Templates

An electrically induced bottom-up process was introduced for the fabrication of multifunctional nanostructures of polymers. Without requiring complicated photolithography or printing techniques, the fabrication process first produced a conducting template by colloidal lithography to create an interconnected conduction pathway. By supplying an electrical charge to the conducting network, the conducting areas were enabled with a highly energized surface that generally deactivated the adsorbed reactive species and inhibited the vapor deposition of poly-<i>p</i>-xylylene polymers. However, the template allowed the deposition of ordered poly-<i>p</i>-xylylene nanostructures only on the confined and negative areas of the conducting template, in a relatively large centimeter-scale production. The wide selection of functionality and multifunctional capability of poly-<i>p</i>-xylylenes naturally rendered the synergistic and orthogonal chemical reactivity of the resulting nanostructures. With only a few steps, the construction of a nanometer topology with the functionalization of multiple chemical conducts can be achieved, and the selected deposition process represents a state-of-the-art nanostructure fabrication in a simple and versatile approach from the bottom up

Selective SERS Detecting of Hydrophobic Microorganisms by Tricomponent Nanohybrids of Silver–Silicate-Platelet–Surfactant

Nanohybrids consisting of silver nanoparticles (Ag), clay platelets, and a nonionic surfactant were prepared and used as the substrate for surface-enhanced Raman scattering (SERS). The nanoscale silicate platelets (SP) (with dimensions of 100 × 100 nm² and a thickness of ∼1 nm) were previously prepared from exfoliation of the natural layered silicates. The tricomponent nanohybrids, Ag-SP-surfactant (Ag-SP-S), were prepared by in situ reduction of AgNO₃ in the presence of clay and the surfactant. The clay platelets with a large surface area and ionic charge (ca. 18 000 sodium ions per platelet) allowed for the stabilization of Ag nanoparticles in the range of 10–30 nm in diameter. With the addition of a nonionic surfactant such as poly­(oxyethylene) alkyl ether, the tricomponent Ag-SP-S nanohybrids possessed an altered affinity for contacting microorganisms. The particle size and interparticle gaps between neighboring Ag on SP were characterized by TEM. The surface tension of Ag-SP and Ag-SP-S in water implied different interactions between Ag and hydrophobic bacteria (Escherichia coli and Mycobacterium smegmatis). By increasing the surfactant content in Ag-SP-S, the SERS peak intensity was dramatically enhanced compared to the Ag-SP counterpart. The nanohybrids, Ag-SP and Ag-SP-S, with the advantages of varying hydrophobic affinity, floating in medium, and 3D hot-junction enhancement could be tailored for use as SERS substrates. The selective detection of hydrophobic microorganisms and larger biological cells makes SERS a possible rapid, label-free, and culture-free method of biodetection

First Observation of Physically Capturing and Maneuvering Bacteria using Magnetic Clays

A new class of nanohybrids composed of structurally exfoliated silicate platelets and magnetic iron oxide nanoparticles was synthesized and shown to be capable of capturing microbes in liquid microbiological media. Nanoscale silicate platelets with an approximate thickness of 1.0 nm were prepared from the naturally occurring mineral clays montmorillonite and mica; these clays yielded platelets with lateral dimensions on the order of 80–100 nm and 300–1000 nm, respectively. The magnetic Fe₃O₄ nanoparticles, approximately 8.3 nm in diameter, were coated in situ onto the silicates during the synthesis process, which involved the coprecipitation of aqueous Fe²⁺/Fe³⁺ salts. Owing to the high surface area-to-volume ratios and the presence of ionically charged groups (i.e., SiO^–Na⁺), the silicate nanoplatelets exhibited intense noncovalent bonding forces between Fe₃O₄ nanoparticles and the surrounding microorganisms. The Fe₃O₄-on-nanoplatelet nanohybrids enabled the entrapment of bacterial cells in liquid microbiological media. These captured bacteria formed bacterial aggregates on the order of micrometers that became physically maneuverable under a magnetic field. This phenomenon was demonstrated with <i>Staphylococcus aureus</i> in liquid microbiological media by physically removing them using a magnetic bar; in two experimental examples, bacterial concentrations were reduced from 10⁶ to 10² and from 10⁴ to 10⁰ CFU/mL (colony formation unit/mL con). Under a scanning electron microscope, these bacteria appeared to have rough and wrinkled surfaces due to the accumulated silicate platelets. Furthermore, the external application of a high-frequency magnetic field completely destroyed these aggregated microbes by the magnetically induced heat. Hence, the newly developed nanohybrids were shown to be viable for physically capturing microbes and also for potential hyperthermia treatment applications

Preparation of Amphiphilic Ag-Polyethylenimine Dendritic Polymer Nanocapsules for Surface-Enhanced Raman Scattering Detection

According to recent research, amphiphilic surfactants can stabilize metal nanoparticles because of their excellent dispersibility. Therefore, herein, amphiphilic polyethylenimine (PEI) dendritic polymer nanocapsules were synthesized by using PEI and poly(urea/malonamide) dendrons of different generations. Then, silver nanoparticles (AgNPs) were immobilized on PEI dendritic polymer nanocapsules for surface-enhanced Raman scattering (SERS) detection. Well-designed amphiphilic PEI dendrons possessed abundant nucleation sites for AgNP reduction, which could directly reduce silver ions to AgNPs without additional reducing agents at room temperature, showing the stronger reducing capability than pristine PEI. The size and interparticle gap of AgNPs were manipulated by varying the size of the PEI dendritic polymer and the ratio of PEI dendritic nanocapsules/AgNO3. As a result, the Ag-PEI-dendritic polymer was able to perform Raman enhancing capability. Especially, a sample, namely, Ag-PEI-G0.5, exhibited the strongest Raman enhancement effect, due to the optimal size and interparticle gap of AgNPs. The Ag-PEI dendritic SERS nanocapsules could rapidly and reproducibly detect many kinds of biomolecules (adenine, methylene blue, and beta-carotene) with a linear calibration curve. The limit of detection (LOD) of adenine was lower than 10–7 M. Therefore, this facile method to in situ prepare Ag-PEI dendritic SERS nanocapsules (reducing agent free) possesses high potential to be applied in rapid SERS detection for the quantitative analysis of biomolecules

Additional file 1: of Core-shell of FePt@SiO2-Au magnetic nanoparticles for rapid SERS detection

TEM images of core-shell nanoparticles. Figure S1. TEM images of (A) FePt@SiO2-N and (B) gold nanoparticles (scale bar: 50 nm). Figure S2. TEM images of Au-FePt@SiO2-N with various EDS concentration: (A) 0 mM, (B) 0.1 M, (C) 0.2 M, (D) 0.3 M, (E) 0.4 M and (F) 0.5 M (scale bar: 50 nm). Figure S3. TEM images of Au-FePt@SiO2-N (0.3 M) with various gold concentration: (A) 0 μM, (B) 47.6 μM, (C) 95.2 μM, (D)142.8 μM, (E)190.4 μM, and (F) 238 μM (scale bar, 100 nm