Dual-mode surface-enhanced Raman scattering (SERS)–surface-enhanced fluorescence (SEF) composite nanoparticles have been developed for possible use as oil reservoir tracers. These composite nanoparticles are composed of metal Ag nanostructured cores, specific dye molecules, and a SiO2 shell coating. Herein, we show that the embedded dye molecules are detectable by both Raman and fluorescence spectroscopies and yield dramatically enhanced detectability due to strong SERS–SEF phenomena with limits of detection (LOD) as low as 1 ppb by fluorescence spectroscopy and 10 ppb by Raman spectroscopy. To determine the optimal structures for signal enhancement for both SERS and SEF, we show how these phenomena are significantly affected by morphologies of the composite nanoparticles. The aggregation status of metal dots and the distance between the metal and dye probe molecules are the crucial factors for enhancement of SERS and SEF signals. Through well-controlled one-pot reactions in microemulsion media, composite nanoparticles with designed morphologies, Ag@SiO2 core–shell structures, or Ag@SiO2/Ag satellite structures have been synthesized, and various dyes have been encoded into these composite nanoparticles. We have demonstrated that the Ag@SiO2/Ag satellite nanoparticles exhibit the highest dye molecule signal enhancement through both SERS and SEF phenomena. Imaging studies on the detection and mobility of these specifically designed nanoparticles in microchannels show their detection within micron-sized pores and at low concentrations. The multifunctional composite nanoparticles presented herein contain different dyes which exhibit different fluorescence emission wavelengths and fingerprinted Raman signals. Thus, these strategically designed nanoparticles provide a possible pathway for future use as barcoded smart reservoir tracers.

Among the various preparation methods for nanocrystalline alloys, ionic liquid electrodeposition at low temperature is of interest for its scalability and efficiency. To achieve nanostructures with stabilized structures, it is desirable to directly deposit alloys in which the grain boundaries are decorated with a segregated alloying element. Here a combination of atom probe tomography and aberration corrected scanning transmission electron microscopy are used to confirm that in Al-Mn nanocrystalline alloys deposited from an ionic liquid, Mn is slightly segregated at grain boundaries in the as-deposited condition. The apparent heat of grain boundary segregation is calculated to lie between 1100 and 1500 J mol-1 , which aligns reasonably well with a value calculated using a Miedema-based segregation model, and which is also in line with a more refined CALPHAD-type estimation if it is assumed that the Al-Mn deposits are not fully equilibrated at the deposition temperature.

The structural stability of nanocrystalline aluminum-manganese (Al-6.5 at.%. Mn) alloys is studied in the temperature range of 200 to 400 °C. Transmission electron microscopy shows that grain growth in this alloy is subdued by the presence of Mn, such that 100 nm or finer grain sizes can be retained at 200 and 300 °C even after 1 month of annealing. In contrast, the principal mode of instability in the alloy is the precipitation of the equilibrium Al 6 Mn phase, which was observed to form at much shorter time scales and is present at 300 and 400 °C after just 30 minutes. Differential scanning calorimetry was used to study the kinetics of the Al 6 Mn reaction using Johnson-Mehl-Avrami-Kolmogorov analysis and construct a time-temperaturetransformation (TTT) diagram for this process. It is found that this Al-Mn single-phase nanostructured alloy can be stable against forming the Al 6 Mn phase and against grain growth for several months below 200 °C and for short thermal excursions up to 300 °C.