In this study, electrodeposition (ED) combined with a spark discharge-facilitated laser-induced breakdown spectroscopy—referred to as SD-LIBS—was employed for highly sensitive detection of trace chromium (Cr) in aqueous solutions. First, trace Cr ions in water were preconcentrated on the outer surface of an ultra-pure aluminum base by ED, effectively addressing the issue of poor detection sensitivity when LIBS is applied directly to liquid samples. Subsequently, SD-LIBS was employed for the analysis of the chromium (Cr) deposited on the aluminum (Al) exterior, where the spark discharge significantly enhanced the emission intensities of the Cr (I) spectral lines centered at 425.43 nm, 427.48 nm, and 428.90 nm. Based on the calibration curves obtained from standard solutions, the limits for the detection (LoD) with respect to chromium (Cr) under different discharge voltages were determined. With the elevation of discharge voltage over the 0–2 kV range, the LoDs of the neutral chromium (Cr) line I corresponding to 425.43 nm and 428.90 nm, the concentration levels of 3.86 n and 5.13 ng decreased to 1.19 ng and 1.57 ng, respectively, with all values referenced per milliliter. These results demonstrate that spark discharge further improves the detection sensitivity of LIBS in aqueous environments. Overall, the combined ED+SD-LIBS approach exhibits excellent analytical performance for trace metal detection in water, offering promising potential for water quality monitoring applications.

RMB₆-TMB₂ (RM = rare earth elements, TM = transition metal elements) composites retain superior field emission properties of RMB₆ while addressing its inherent mechanical limitations by constructing a eutectic structure with TMB₂. Herein, an in situ route for synthesizing RMB₆-TMB₂ composite nanopowders with homogeneous phase distribution using reduction reactions was proposed. The LaB₆-ZrB₂ composite nanopowders were synthesized in situ for the first time using sodium borohydride (NaBH₄) as both a reducing agent and boron source, with lanthanum oxide (La₂O₃) and zirconium dioxide (ZrO₂) serving as metal sources. The effects of the synthesis temperature on phase compositions and microstructure of the composites were systematically investigated. The LaB₆-ZrB₂ system with a eutectic weight ratio exhibited an accelerated reaction rate, achieving a complete reaction at 1000 °C, 300 °C lower than that of single-phase ZrB₂ synthesis. The composite phases were uniformly distributed even at nanoscale. The composite powder displayed an average particle size of ~170 nm when synthesized at 1300 °C. With the benefit of the in situ synthesis method, LaB₆-TiB₂, CeB₆-ZrB₂, and CeB₆-TiB₂ composite powders were successfully synthesized. This process effectively addresses phase separation and contamination issues typically associated with traditional mixing methods, providing a scalable precursor for high-performance RMB₆-TMB₂ composites.