Size-selected gas-phase aggregated metal clusters have long been considered as embryos of materials. However, a significant proportion of these clusters are susceptive to damage when exiting vacuum. Consequently, effective protection is highly desirable. Here a cluster packaging and protection strategy is presented based on controllable cluster beam implantation into polymethyl methacrylate (PMMA). In this strategy, the size selection of gas-phase clusters and the synergistic heating of PMMA during implantation are combined, thereby achieving nondestructive packaging of atomically precise cluster under soft-landing conditions. The packaged clusters exhibit robust and universal protection. Robustness is reflected in the unaltered oxidation resistance of Mo clusters after exposure to air for over 30 days, as well as the effective agglomeration resistance at temperatures up to 100 °C or in liquid. Universality is demonstrated by the successful protection of a wide range of size-selected clusters, including Mo clusters ranging from Mo 2057 to Mo 6 , and Ta 2057 , Cu 923 , W 55 , (Re–Mo) 147 clusters. This protection is attributed to both a stable, albeit weak PMMA-Mo bonding, forming Mo─O─C─C species that stabilize the clusters, and the direct implantation of gas-phase cluster into solid-phase PMMA. This helps pave the way for further investigation and applications of gas-phase metal clusters.
Tetrahydropyran-2-methanol (THPM) is a typical alcohol containing a six-member cyclic ether, which can be considered as the model molecule of cyclic sugar. Herein, vacuum ultraviolet (VUV) photodissociation spectroscopy is employed to study fragmentation pathways and infrared (IR) plus VUV photoionization spectroscopy to investigate the structures of neutral THPM and its clusters with the size up to the trimer. Qualitative structural assignments are confirmed for the neutral species and ions based on MP2/aug-cc-pVTZ and ωB97X-D/cc-pVTZ calculations. The fragment cations at m/z = 84, 85, and 98 arise by the losing of CH 2 OH, CH 3 OH, and H 2 O from the monomer, respectively, as a result of C–C bond and C–O bond dissociation under the VUV (118 nm) radiation. It is found that the loss of CH 3 OH and H 2 O involves hydrogen transfer from the CH 2 group to the dissociating CH 2 and OH groups. Comparing the observed and calculated spectra of the monomer THPM, it suggests that the conformer containing a chair tetrahydropyran ring and an intramolecular hydrogen bond would be dominantly survived in a supersonic beam. Moreover, the IR spectra of larger clusters n > 1 (n = 2, 3) show only the broad hydrogen bonded OH stretch mode, and thus these larger clusters would form a closed-cyclic structure, where all OH groups are participating in hydrogen bonding. Partially the CH stretch positions of THPM clusters do not change significantly with the increasing of cluster size, thus the CH and CH 2 groups are not involved in H-bonding interactions.
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