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The structural characteristics of biological specimens, such as wet proteins and fixed living cells, can be conveniently probed in their host aqueous media using soft X‐rays in the water window region (200–600 eV). Conventional X‐ray detectors in this area exhibit low spatial resolution, have limited sensitivity, and require complex fabrication procedures. Here, many of these limitations are overcome by introducing a direct soft X‐ray detector based on ultrathin tin mono‐sulfide (SnS) nanosheets. The distinguishing characteristic of SnS is its high photon absorption efficiency in the soft X‐ray region. This factor enables the fabricated soft X‐ray detectors to exhibit excellent sensitivity values on the order of 104 μCGyVac−1 cm−2 at peak energies of ≈600 eV. The peak signal is found to be sensitive to the number of stacked SnS layers, with thicker SnS nanosheet assemblies yielding a peak response at higher energies and with peak sensitives of over 2.5 × 104 μCGyVac−1 cm−2 at 1 V. Detailed current–voltage and temporal characteristics of these detectors are also presented. These results showcase the excellent performance of SnS nanosheet‐based soft X‐ray detectors compared to existing direct soft X‐ray detectors, including that of the emerging organic–inorganic perovskite class of materials.

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Microchannel cantilevers are an emerging platform for physical characterization of materials at the picogram level. Here we report on detecting multiple thermal transitions in picogram amounts of two well-known polymers, semicrystalline poly(L-lactide) (PLA) and amorphous poly(methylmethacrylate) (PMMA), using this platform. The polymer samples, when loaded inside the cantilever, affect its resonance frequency due to changes in its total mass and stiffness. When taken through a thermal cycle, the resonance response of the cantilever further changes due to multiple thermal transitions of the samples. Continuous monitoring of the resonance frequency provides information about b-transition (T b ), glass transition (T g ), crystallization (T c ), and melting (T m ) of the confined polymer samples. The measured T g , T c , and T m for PLA were $60, 78, and 154 C, respectively, while the T g and T b for PMMA were 48 and 100 C, respectively. These results are in an agreement with the data obtained from differential scanning calorimetry (DSC). Because of its high sensitivity, this technique is capable of detecting the weaker b-transitions that cannot be observed with conventional DSC.

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