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In this paper, a microstrip resonator based on double split rings is used to build an electron spin resonance (ESR) measurement system. The resonator is optimized by the finite element electromagnetic simulation and the 3 dB bandwidth is 58.7 MHz. Due to the open structure of the resonator, large-size samples with high dielectric loss can be measured nondestructively. The ESR signal of 2,2-diphenyl-1-picrylhydrazyl (DPPH) powder with different quality is measured at room temperature, and the result indicated that the spin detection limit of this system can reach 9.66 ×1012 spins/Gs Hz1/2. It is demonstrated that the system can be used to characterize films deposited on different substrates such as silicon, glasses or ceramics regardless of its high frequency losses through the measurement of DPPH sample spin-coated on silicon and zerodur. Our system provides a convenient approach to research the defect of thin films and to characterize their performances within microwave frequency.

Abstract: Fe2O3@C nanocomposites (denoted as FeC-n, n represents the weight percent of Fe(NO3)3·9H2O in the starting gel) have been fabricated by pyrolyzing Fe(NO3)3·9H2O impregnated starch gels. When the Fe(NO3)3·9H2O content was below 50wt.%, the products contained well dispersive and uniform γ-Fe2O3 nanoparticles that embedded in the carbon matrix. The particle sizes were positively related to the content of Fe(NO3)3·9H2O. The nanocomposites FeC-50 that contained 4.25nm nanoparticles exhibited an enhanced electrochemical performance within the voltage window of −1.3–0.4V in 6molL−1 KOH solutions. The symmetric capacitor of FeC-50 possessed a high specific capacitance (SC) of 267.2Fg−1 at 0.35Ag−1 with a high voltage of 1.4V. [Copyright &y& Elsevier]