For this work, an integrated system composed of a polypropylene reactor and a palladium on silica monolithic catalyst was designed and manufactured by 3D‐printing. These devices are able to perform solution phase chemistry in a robotic orbital shaker. The capped reactor was obtained in its entirety by 3D‐printing, using polypropylene and fused deposition modeling. The monolithic catalyst was also obtained by 3D‐printing ‐robocasting‐ of a silica support, sintering and subsequent palladium deposition through the wet impregnation method. The catalytic efficiency in Sonogashira or Suzuki reactions as well as the recyclability of the entire system – catalyst+reactor – were studied. The strong electrostatic adsorption (SEA) of the palladium on sintered silica and the reduced mechanical stress produced by the convenient adjustment of the catalyst into the polypropylene reactor makes the catalytic system reusable without significant loss of catalytic activity.
Raman spectroscopy is a label-free technique for the detection and structural analysis of molecular materials. Unfortunately, Raman signals are inherently weak, so a very low number of scattered photons are available for detection.Surface Enhanced Raman Spectroscopy (SERS) is a useful method to amplify weak Raman signals by an increment of the apparent Raman cross-section of the analyte though the local amplification of the electromagnetic field in the close proximity of metal nanostructures caused by the excitation of localized surface plasmon resonances. Laser excitation resonantly drives the metal surface charges, creating highly localized plasmonic light fields at these photonic structures, which are known as hot-spots. Since the Raman signal is proportional to the intensity of the field, when a molecule is bonded, adsorbed or lies close to the enhanced field of a hot-spot, a huge increase in the Raman signal can be observedusually of several orders of magnitude, consequently boosting the sensibility of the technique to concentrations as low as 10 À18 M or even down to single molecule detection [1,2].A key parameter to take into account in SERS experiments is the choice of the enhancing substrate. SERS substrates can be roughly classified into three main classes: 1. Metallic electrodes: These played an important role in the development of SERS. However, their importance has decreased substantially due to development of substrates with higher amplification power. 2. Metal nanoparticles in solution: Colloids have been and still are very important in the development of the technique. The liquid media is a useful aid to drive target molecules to the plasmonic surfaces, but sometimes the analyte is insoluble or incompatible with the liquid media, representing a problem for its easy and general application. 3. Nanostructured substrates: These may be obtained by two main methods: (a) deposition of metal nanoparticles from colloidal solutions by drying or evaporation of solvent onto appropriate substrates, or (b) fabrication of nanostructured metal surfaces, taking advantage of micro and nano-fabrication techniques.The main obstacle limiting the use of SERS as an everyday and routine lab technique is the lack of suitable substrates. Despite the high number of publications and patents where new active materials are proposed, commercial substrates are still scarce and often expensive and quite unstable, e.g. requiring storage in controlled atmospheres and careful handling to maintain their enhancement properties.The image featured on this issue's cover was taken with a field emission scanning electron microscope (FE-SEM Zeiss Ultra-Plus, at 1.5 kV with an in-lens secondary electron detector) and depicts a nanostructured substrate obtained by drying a colloidal solution of gold nanoparticles on a silicon wafer. These substrates are attractive because of the beauty and variety of morphologies, but also due to the simple synthesis of the nanoparticles and the ease of the fabrication process; however, they are often hinder...
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