This paper presents a surface plasmon resonance system based on a polymer prism chip. The device allows operation in both the angular and wavelength interrogation modes. The biochip design is discussed emphasizing the effect of the ambient temperature over the optical behavior. Birefringence effect, biochip polishing, and responsivity are also reported. The basic mathematical formulation for both operating modes is discussed, and morphological parameters are considered in the data analysis. Experimental sensorgrams obtained at both interrogation modes with the same polymer prism chip are presented and compared. The experimental sensorgrams obtained with assays providing reversible (phosphate buffered saline and hypochlorite solutions) and irreversible (neutravindin solution) bindings demonstrate the feasibility of the proposed design.

The sensing properties of thin copper (Cu) films near the surface plasmon resonance (SPR), were re-evaluated for the metal-air and metal-water interfaces and compared with gold (Au) films. For this, we used three different SPR sensing designs, i.e., a prism-based set-up, an optical fiber-based system, and a grating coupler-based solution. Optimum SPR-excitation conditions are restricted to a Cu-metal film thickness of 45±5 nm for the ATR set-up in aqueous solution. The impacts of the surface Cu-oxide layer were discussed and prevented employing an Au ultra-thin protective overlayer. This strategy proved to be efficient for non-reversible binding. Cu-SPR responsivities are higher for the prism-based set-up (quite similar to Au-SPR ones) than the ones for the optical fiber-based system and a grating coupler-based solution. In contrast to thin Au films, bovine serum albumin (BSA) and other proteins do not bind irreversibly onto thin Cu-films. Our findings confirm the suitability of thin copper films for selected SPR sensing applications.

Surface plasmon resonance (SPR) sensors, utilizing thin aluminum (Al) films, are reported. The sensor designs are based in the novel optical trapezoidal prism chip, made from either polymer or BK7 glass. Optimum Al-film thickness was determined to 20 ± 5 nm, and deposited by thermal e-beam evaporation and rf-magnetron sputtering. Upon contact to air, and in de-ionized aqueous solution, a self-limited surface oxide layer forms. Determined by ellipsometric recordings, its thickness grows from 4.6 ± 0.6 nm in air to 12.3 ± 2 nm in the wet interface. A single SP-resonance applies to the dry interface. Unusual spectral broadening, due to the presence of multiple resonances, is predicted and experimentally verified at the wet interface. The Al-oxide adlayer is beneficial in the angular interrogation, where the instrumental response approaches the one exhibited by the noble metals. Under wavelength interrogation conditions, the presence of the Al-oxide adlayer causes severe degradation of the sensor response. Both, angular and wavelength interrogation at the metal-aqueous solution interface were exploited experimentally and compared with theoretical predictions regarding the sensing features of gold (Au), copper (Cu), and silver (Ag) metal films as well. Limitations, cost aspects and alternative routes to overcome degradation and the loss of SPR-activity in the presence of ionic phosphate buffered saline aqueous solutions are outlined for Al-films.