Dendritic Forest-Like Ag Nanostructures Prepared Using Fluoride-Assisted Galvanic Replacement Reaction for SERS Applications

Dendritic forest-like Ag nanostructures were deposited on a silicon wafer through fluoride-assisted galvanic replacement reaction (FAGRR) in aqueous AgNO₃ and buffered oxide etchant. The prepared nanostructures were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma–optical emission spectroscopy, a surface profiler (alpha step), and X-ray diffraction. Additionally, the dendritic forest-like Ag nanostructures were characterized using surface-enhanced Raman scattering (SERS) when a 4-mercaptobenzoic acid (4-MBA) monolayer was adsorbed on the Ag surface. The Ag nanostructures exhibited intense SERS signal from 4-MBA because of their rough surface, and this intense signal led to an intense local electromagnetic field upon electromagnetic excitation. The enhancement factor for 4-MBA molecules adsorbed on the Ag nanostructures was calculated to be 9.18 × 10⁸. Furthermore, common Raman reporters such as rhodamine 6G, 4-aminothiolphenol, 5,5′-dithiobis-2-nitrobenzoic acid, and carboxyfluorescein (FAM) were characterized on these dendritic forest-like Ag nanostructures, leading to the development of an ultrasensitive SERS-based DNA sensor with a limit of detection of 33.5 nM of 15-mer oligonucleotide.

Preparation and heat insulation of Gemini-halloysite aerogel/concrete composites

In our previous research, the utilization of Gemini surfactants to control the dispersion and interaction of HNTs aerogels (HCAs) in the concrete matrix had obtained positive research results. In order to further deepen the research in this field, in this work, a Gemini surfactant with a new structure was synthesized, the surface modification characteristics of HCAs in a series of concrete systems were also investigated. Microstructures and properties of the composites were characterized by using scanning electron microscope (SEM), Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), and so on. The results showed that the newly synthesized Gemini surfactants had an ideal modification effect on the surface of HCAs. Compared with other traditional surfactants, Gemini had better hydrophobic and mechanical properties. Different molecular layers with hydrophilicity or hydrophobicity were constructed on the HCAs surface. The introduction of the modified HCAs could significantly improve the heat insulation performance and mechanical strength of concrete. The improvement of the above comprehensive properties could not have significant difference due to the different types of concrete matrix.

Rapid fabrication of three-dimensional flower-like gold microstructures on flexible substrate for SERS applications

In this work, hierarchical flower-like gold microstructures (HFGMs) are synthesized on a flexible PET film substrate by electrochemical deposition method as a SERS sensor without surfactant or directing agent. The effects of deposition current and electrolyte concentration on morphology and SERS performance are discussed to find the optimal preparation conditions. SERS activity of samples with different morphologies was investigated by comparing experiments and the mechanism was discussed. It shows the HFGMs with 3D nanoflakes and nanosheet tips present outstanding SERS activity with ultrasensitive detection limits. The lowest concentration of R6G that can be detected is 10^-10 M, and the characteristic signals of thiram can be detected as low as 0.1 ppm. The HFGMs substrate show great potential of application in trace detection by SERS.

A Tetraphenylethene Luminogen-Functionalized Gemini Surfactant for Simple and Controllable Fabrication of Hollow Mesoporous Silica Nanorods with Enhanced Fluorescence

Nanoparticles that possess unique structures and properties are highly desired in the production of multifunctional materials because of their combinational performance. In this study, a facile and effective fabricating strategy is developed to controllably prepare fluorescent hollow mesoporous silica nanorods via the cetyltrimethylammonium bromide (CTAB) and tetraphenylethene (TPE) luminogen-functionalized gemini surfactant (C_TPE-C₆-C_TPE) guided dual-templating approach. Because of its unique chemical structure, water solubility, surface activity, and fluorescent properties, the designed C_TPE-C₆-C_TPE will not only provide an anchored fluorophore for silica nanoparticles but also serve as an intimate partner of CTAB to regulate their construction in the structure-directing process. By properly tuning the molar ratio of CTAB/C_TPE-C₆-C_TPE, the shape-controlled aggregation-induced emission hollow mesoporous silica nanoparticles (AIE-MSNs) can be prepared directly, producing two kinds of silica nanorods (AIE-MSNs-15 and AIE-MSNs-7). In particular, the incorporated bulky TPE luminogens will not only endow AIE-MSNs-7 with enhanced fluorescence intensity (2.3-fold) after the removal of CTAB but also bring about high accessible surface area (606.6 m²/g) and larger pore size (3.2 nm) and pore volume (0.634 cm³/g) for effective loading and sustained release of the hydrophobic anticancer drug camptothecin. C_TPE-C₆-C_TPE enriches the family of gemini surfactants and provides important insights into the convenient fabrication of advanced fluorescent mesoporous materials.

One-step green synthesis of silver nanobelts assisted by sodium carboxymethylcellulose for catalytic reduction of 4-nitrophenol

Large-scale, ultra-long AgNBs were prepared via a green approach assisted by CMC for the highly efficient catalytic reduction of 4-nitrophenol.

Gemini surfactant with pyrrolidinium head groups and a hydroxyl-substituted spacer: surface properties and assisted one-pot synthesis of dendritic Au nanocrystals

Dendritic Au NCs were facilely prepared by a one-pot method at room temperature with the assistance of gemini surfactant.