The first detailed study on the performance of a ZnO-based cryogenic scintillating bolometer as a detector to search for rare processes in zinc isotopes was carried out. A 7.2 g ZnO low-temperature detector, containing more than 80% of zinc in its mass, exhibits good energy resolution of baseline noise 1.0–2.7 keV FWHM at various working temperatures resulting in a low-energy threshold for the experiment, 2.0–6.0 keV. The light yield for β/γ events was measured as 1.5(3) keV/MeV, while it varies for α particles in the range of 0.2–3.0 keV/MeV. The detector demonstrates an effective identification of β/γ events from α events using time-properties of only heat signals. The radiopurity of the ZnO crystal was evaluated using the Inductively Coupled Plasma Mass Spectrometry, an ultra-low-background High Purity Ge  γ-spectrometer, and bolometric measurements. Only limits were set at the level of 𝒪(1–100) mBq/kg on activities of  40K, 137Cs and daughter nuclides from the U/Th natural decay chains. The total internal α-activity was measured as 22(2) mBq/kg, with a major contribution caused by 6(1) mBq/kg of 232Th and 12(2) mBq/kg of  234U. Limits on double beta decay (DBD) processes in ^64Zn and 70Zn isotopes were set on the level of 𝒪(1017–1018) yr for various decay modes, profiting from 271 h of acquired background data in the above-ground lab. This study shows a good potential for ZnO-based scintillating bolometers to search for DBD processes of Zn isotopes, especially in 64Zn, with the most prominent spectral features at ∼ 10–20 keV, like the two-neutrino double electron capture. A 10 kg-scale experiment can reach the experimental sensitivity at the level of  𝒪(1024) yr.

A 510 day long-term measurement of a 45.3 g platinum foil acting as the sample and high voltage contact in an ultra-low-background high purity germanium detector was performed at Laboratori Nazionali del Gran Sasso (Italy). The data was used for a detailed study of double beta decay modes in natural platinum isotopes. Limits are set in the range $${\mathcal {O}}(10^{14}{-} 10^{19})$$ O ( 10 14 - 10 19 )  years (90% C.L.) for several double beta decay transitions to excited states confirming, and partially extending existing limits. The highest sensitivity of the measurement, greater than $$10^{19}$$ 10 19  years, was achieved for the two neutrino and neutrinoless double beta decay modes of the isotope $$^{198}$$ 198 Pt. Additionally, novel limits for inelastic dark matter scattering on $$^{195}$$ 195 Pt are placed up to mass splittings of approximately 500 keV. We analyze several techniques to extend the sensitivity and propose a few approaches for future medium-scale experiments with platinum-group elements.

The Scintillating Bubble Chamber (SBC) collaboration is combining the well-established liquid argon and bubble chamber technologies to search for low-mass, GeV-scale dark matter. Liquid-noble bubble chambers benefit from the excellent electron-recoil insensitivity inherent in bubble chambers with the addition of energy reconstruction provided from the scintillation signal for background rejection. The projected sensitivity with a quasi-background-free 10-kg-year exposure at a 100 eV nuclear recoil threshold is approximately 10^{-43} cm−43cm^2$ for a 1 GeV/c^22 dark matter mass.