A radiative cooling structural material.

Reducing human reliance on energy-inefficient cooling methods such as air conditioning would have a large impact on the global energy landscape. By a process of complete delignification and densification of wood, we developed a structural material with a mechanical strength of 404.3 megapascals, more than eight times that of natural wood. The cellulose nanofibers in our engineered material backscatter solar radiation and emit strongly in mid-infrared wavelengths, resulting in continuous subambient cooling during both day and night. We model the potential impact of our cooling wood and find energy savings between 20 and 60%, which is most pronounced in hot and dry climates

Single-digit-micrometer thickness wood speaker

Partial funding for Open Access provided by the UMD Libraries' Open Access Publishing Fund.Thin films of several microns in thickness are ubiquitously used in packaging, electronics, and acoustic sensors. Here we demonstrate that natural wood can be directly converted into an ultrathin film with a record-small thickness of less than 10 μm through partial delignification followed by densification. Benefiting from this aligned and laminated structure, the ultrathin wood film exhibits excellent mechanical properties with a high tensile strength of 342 MPa and a Young’s modulus of 43.6 GPa, respectively. The material’s ultrathin thickness and exceptional mechanical strength enable excellent acoustic properties with a 1.83-times higher resonance frequency and a 1.25-times greater displacement amplitude than a commercial polypropylene diaphragm found in an audio speaker. As a proof-of-concept, we directly use the ultrathin wood film as a diaphragm in a real speaker that can output music. The ultrathin wood film with excellent mechanical property and acoustic performance is a promising candidate for next-generation acoustic speakers

Molecular Containers Derived from [60]Fullerene through Peroxide Chemistry

CONSPECTUS: Molecular containers can keep guest molecules in a confined space that is completely separated from the solution. They have wide potential applications, including selective trapping of reactive intermediates, catalysis within the cavity, and molecular delivery. Numerous molecular containers have been prepared through covalent bonds, metal-ligand interactions and H-bonding or hydrophobic interactions. Fullerenes are all-carbon molecules with a spherical structure. Partial opening of the cage structure results in open-cage fullerenes, which can serve as molecular containers for various small molecules and atoms. Compared with classical molecular containers, open-cage fullerenes exhibit some unusual phenomena because of the unique structure of the fullerene cage. The synthesis of an open-cage fullerene with a large enough orifice as a molecular container requires consecutive cleavage of multiple fullerene skeleton bonds within a local area on the cage surface. In spite of the difficulty, remarkable progress has been achieved. Several reactions have been reported to cleave fullerene C-C bonds selectively to form open-cage fullerenes, some of which have been successfully used as molecular containers for molecules such as H2O. The size and shape of the orifice play a key role in the encapsulation of the guest molecule. To date the focus in this area has been the preparation of open-cage fullerenes and encapsulation of small molecules. Little information has been reported about the functional properties of these host-guest systems. Potential applications of these systems need to be explored. This Account mainly presents our results on the encapsulation of small molecules in open-cage fullerenes prepared in my group. The preparation of our open-cage fullerenes is based on fullerene-mixed peroxides, which are briefly mentioned herein. The encapsulation and release of a single molecule of water is discussed in detail. Quantitative water encapsulation was achieved by heating the open-cage fullerene in a homogeneous CDCl3/H2O/EtOH mixture at 80 degrees C for 18 h. The kinetics of the water release process was studied by blackbody IR radiation-induced dissociation (BIRD) and theoretical calculations. The trapped water could also be released by H-bonding with HF. To control the encapsulation and release processes, we prepared open-cage fullerenes with a switchable stopper on the rim of the orifice. Besides H2O, encapsulations of H-2, HF, CO, O-2, and H2O2 were also achieved by using different open-cage fullerenes. The encapsulation of CO is quite unusual in that the trapped CO is derived from a fullerene skeleton carbon that was pushed into the cavity by oxidation under ambient conditions at room temperature. The trapped O-2/H2O2 could be released slowly under mild conditions, and these systems are now being studied as a new type of oxygen-releasing materials for biomedical research. The present results demonstrate that open-cage fullerenes are suitable molecular containers for small molecules. Our future work will focus on optimizing the conditions for the preparation of open-cage fullerenes and applications of open-cage fullerenes in areas such as oxygen delivery for photodynamic therapy

Peroxide-Mediated Selective Cleavage of [60]Fullerene Skeleton Bonds: Towards the Synthesis of Open-Cage Fulleroid C55O5

Replacement of a pentagon in [60]fullerene with five oxygen atoms yields the open-cage compound C55O5 with five carbonyl groups on the rim of the orifice. Our attempts to synthesize such a target molecule starting from C-60 have led us to prepare the fullerene-mixed peroxides such as C-60(OO-t-Bu)(6) with all the peroxo addends surrounding the same pentagon. Further investigations of the peroxide chemistry have generated various open-cage fullerene derivatives, including the carbon monoxide encapsulated endohedral compound CO@C59O6. This Personal Account mainly discusses peroxide-based processes resulting in selective cleavage of the fullerene skeleton bonds

Selective Addition of Secondary Amines to C-60: Formation of Penta- and Hexaamino[60]fullerenes

Secondary amines are well-known to add to [60]fullerene to form the tetraamino epoxy adduct C-60(O)(NR1R2)(4) under both photolysis and thermal conditions in the presence of oxygen. We have now found that pentaamino hydroxyl adduct C-60(OH)(NR1R2)(5) and hexaamino adduct C-60(NR1R2)(6) can be formed as the major products in the dark in the presence of oxygen. Key steps of the reaction mechanism probably involve repeated oxygen oxidation of the radical ion pair between fullerene and amines

Synthesis of Isomerically Pure Multi-aniline C-60 Adducts with Cyclopentadienyl Addition Pattern

Unlike aliphatic amines, anilines cannot react directly with fullerenes to form isomerically pure fullerene multi-adducts. In the present work several anilino C-60 derivatives are prepared through BiCl3-mediated replacement reactions of C-60 derivatives that contain secondary amino addends. All new anilino C-60 derivatives have a cyclopentadienyl addition pattern and contain multiple anilino addends up to 5

Selective Multiamination of C-70 Leading to Curved p Systems with 60, 58, 56, and 50 p Electrons

Secondary aliphatic amines add to a pole pentagon of [70] fullerene in the presence of N-fluorobenzenesulfonimide to form cyclopentadienyl-type adducts, C-70(NSO2Ph)( NR1R2) 4 (1), which can be converted into analogous C-70 derivatives such as C-70(NHSO2Ph)(NHTol) 5 (2). Further addition reactions of either 1 or 2 take place selectively at the opposite pole pentagon of the C-70 'cage, thus forming curved p systems with a reduced number of p electrons, and the products include a dodecakis-adduct with a Vogtle belt motif