Molecular Heater Research Articles

MOF-derived hierarchical carbon/ZnO hybrid synergistically boosts photothermal conversion and storage capability of phase change materials

The weak photon-capturing ability is a long-standing bottleneck for pristine metal–organic framework (MOF)-based phase change materials (PCMs) in photothermal conversion and latent heat storage applications. Herein, we designed MOF-5-derived hierarchical nanoporous carbon/ZnO nanoparticle hybrid as dual efficient photonic harvester and molecular heater for synergistically boosting photothermal conversion and storage capability of PCMs using an in-situ anchoring strategy. Compared with post-decorated ZnO strategy, ZnO photosensitizers derived in situ from MOF-5 are capable of guaranteeing high dispersibility and enhanced photon-capturing capability in the hierarchical carbon framework. Resultantly, high-performance photothermal composite PCMs are obtained due to the constructed intense and broadband absorption photonic nanoheaters after paraffin wax (PW) is encapsulated inside MOF-5-derived hierarchical nanoporous carbon/ZnO (MOF-5-PC/ZnO). Benefiting from the synergistic effect of dual high-efficiency photonic harvester and molecular heater (MOF-5-derived ZnO nanoparticles and hierarchical nanoporous carbon), PW@MOF-5-PC/ZnO-700 °C composite PCMs obtain the optimal photothermal conversion and storage capacity. Meanwhile, PW@MOF-5-PC/ZnO composite PCMs exhibit superior shape stability, thermal stability, and durable reliability. Importantly, our proposed development strategy of high-efficiency photothermal composite PCMs is universal due to high customization and universality of PCMs and Zn-MOFs.

In situ preparation of light-driven cellulose-Mxene aerogels based composite phase change materials with simultaneously enhanced light-to-heat conversion, heat transfer and heat storage

The latent heats of form-stable composite phase change materials (fs-CPCMs) were usually reduced while synergistically improving their heat transfer and light-to-heat conversion properties. In this work, the polyethylene glycol/MXene-cellulose aerogels (PMC) fs-CPCMs with simultaneously enhanced light-to-heat conversion, heat transfer and heat storage were prepared by one-step in situ encapsulation method based on freezing casting. The light-to-heat conversion efficiency of PMC fs-CPCMs achieved ∼ 91.6% due to the fact that the MXene acted as an effective photon captor and molecular heater under solar irradiation. The heat transfer of PMC fs-CPCMs was effectively improved by dispersed MXene due to the formation of heat conduction network or path. Importantly, the latent heats of PMC fs-CPCMs (about 183 J/g) were not reduced, because 90 wt% PEG was encapsulated in situ during the formation of pore structures of cellulose-Mxene aerogels under freezing casting. Moreover, the PMC fs-CPCMs showed excellent chemical compatibility and acceptable thermal stability.

Plasmonic Ti3C2Tx MXene Enables Highly Efficient Photothermal Conversion for Healable and Transparent Wearable Device.

Skin-mountable and transparent devices are highly desired for next-generation electronic applications but are susceptible to unexpected ruptures or undesired scratches, which can drastically reduce the device lifetime. Developing wearable and transparent materials with healable function that can recover their original functionality after mechanical damage under mild and noninvasive repairing operation is thus imperative. Herein, we demonstrate that the incorporation of ultrasmall quantities of plasmonic silver nanoparticle (AgNP)@MXene nanosheet hybrids to serve as photothermal fillers in waterborne elastic polyurethane enables high transparency as well as effective light-triggered healing capabilities for wearable composite coatings. The AgNP@MXene hybrid functions as a highly effective photon captor, energy transformer, and molecular heater due to the amalgamation of (1) ultrahigh photothermal conversion efficiency, high thermal conductivity, and structural properties of MXene, (2) the outstanding plasmonic effect of AgNPs, and (3) the synergistic effects from their hybrids. The resulting wearable composite coating with ultralow loading of plasmonic AgNP@MXene hybrids (0.08 wt % or 0.024 vol %) can produce a significant temperature increase of ∼111 ± 2.6 °C after the application of 600 mW cm-2 light irradiation for 5 min, while maintaining a high optical transmittance of ∼83% at a thickness of ∼60 μm. This local temperature increase can rapidly heal the mechanical damage to the composite coating, with a healing efficiency above 97%.

Ultrahigh Temperature Graphene Molecular Heater

AbstractAlthough a number of molecular devices have been fabricated successfully, molecular heater still keeps blank. It is of great importance to find a satisfactory molecular building block with thicknesses controlled at the atomic level and outstanding electrical properties to achieve the construction of molecular heater. Graphene, a polycyclic aromatic hydrocarbon molecule with strictly atomic thickness, is known as a superior heat and electricity conductor, which makes it a promising building block of the molecular heater. However, the directly grown graphene on insulated substrate suffers from the significant drawback of low quality and nonuniformity and the transferred graphene is criticized because of its cracks and residues. Therefore, the heat temperature is limited to ≈200 °C in previous graphene‐based heaters. Here, a practical graphene molecular heater (GMH) with extremely high heating temperature up to ≈600 °C at a low voltage of 7.5 V is first constructed, and its heating characteristics are systematically explored. The Joule heating efficiency, temperature distribution, and heating rate of GMH exhibit promising characteristics. The successful construction of GMH suggests a bright future toward the urgent demand of miniaturization for the next‐generation devices.

Polymer-Coated Carbon Nanotubes as a Molecular Heater Platform for Hyperthermic Therapy

Carbon nanotubes have been explored as heat-delivery vehicles for thermal ablation of tumors. To use single-walled carbon nanotubes (SWNT) as a “molecular heater” for hyperthermic therapy in cancer treatment, stable dispersibility and smart-targeting potential are necessary. The current study reports the dispersibility and exothermic properties with near-infrared (NIR) exposure for SWNT coated with a copolymer of N-isopropylacrylamide and polyethyleneglycol methacrylate (SWNT/PNIPAM-PEG-hybrid). The SWNT/PNIPAM-PEG hybrid showed stable dispersibility in PBS solution and exothermic potential with NIR exposure. Raman spectroscopy results revealed a hybrid-derived Raman peak in mouse liver and spleen lysates for 7 days post-injection that disappeared by 14 days in all tissues (liver, spleen, heart, lung and kidney). These results suggested that the hybrid did not accumulate in mouse organ tissues in the long-term. The SWNT/PNIPAM-PEG hybrid decreased the cell viability (of mouse macrophages) with heat generation by NIR exposure. The results of this study demonstrate that the SWNT/PNIPAM-PEG hybrid is a useful platform for a “molecular heater” applicable to hyperthermic cancer therapy.

Estimated molecular structure of a carbon nanotube molecular heater based on binding properties to a target protein.

Carbon nanotubes exhibit strong absorbance in the near-infrared (NIR) region and are considered as potent candidates for hyperthermic therapy because they generate significant amounts of heat upon excitation with NIR light. We prepared a single-walled carbon nanotube (SWNT)/IgG complex to use as a "smart molecular heater" for hyperthermic therapy. The aim of the present study was to assess the binding efficiency of DNA-functionalized SWNT/IgG complexes to a target protein. 3 types of complexes with different lengths of spacer arm chain (13.5, 29, and 56 Å) linked to biotinylated IgG were prepared, and we evaluated the effect of the spacer arm length on the specificity, affinity, and capacity of binding to a target protein. Complexes with longer spacer lengths showed increased binding affinity to a target protein. This could be due to a reduction in steric hindrance by increasing the segmental flexibility of the spacer arm. The results of this study suggested that DNA-functionalized SWNT/IgG complexes could act as a heating nano-device for hyperthermic cancer therapy, and the complexes can bind various types of tumor by modifiying the specific antibody.

Ultraviolet-Visible Light-Thermal Conversion Organic Solid-Liquid Phase-Change Materials

UV-vis light-driven organic solid-liquid phase change materials exhibited excellent performances of UV-vis light-harvesting, UV-vis light-thermal conversion and thermal energy storage, which is promoted by UV absorbing dye as an effective ‘‘photon capture and molecular heater’’ for direct and efficient use of solar radiation.

Environment‐sensitive carbon nanotube/polymer composite microhydrogels synthesized via a microfluidic reactor

AbstractMultiwalled carbon nanotubes (MWCNTs)/poly(N‐isopropylacrylamide‐co‐acrylic acid) composite microhydrogels are simply synthesized with controllable size distribution via a microfluidic reactor system. Monomers (N‐isopropylacrylamide and acrylic acid) are rapidly copolymerized (about 3 s) with the embedding of nanoscaled inorganic materials (MWCNTs and hectorites) in microfluidic channels. MWCNTs/hectorites act as “molecular heater” and inorganic crosslinkers in this hydrogel system. As a result, microminiaturization, multifunctionalizaion, and modification of traditional polymer hydrogels are realized simultaneously. Fourier transform infrared spectroscopy is used to confirm polymerization and environment‐sensitive tests are done as well. The resultant microgels exhibit dual near‐infrared and pH response with good reversibility, indicating their potential applications in microreactor fields. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation and binding study of a complex made of DNA-treated single-walled carbon nanotubes and antibody for specific delivery of a “molecular heater” platform

Carbon nanotubes have been explored as heat-delivery vehicles for thermal ablation of tumors. To use single-walled carbon nanotubes (SWNT) as a “molecular heater” for hyperthermia therapy in cancer, stable dispersibility and smart-delivery potential will be needed, as well as lack of toxicity. This paper reports the preparation of a model complex comprising DNA-treated SWNT and anti-human IgG antibody and the specific binding ability of this model complex with the targeted protein, ie, human IgG. Treatment with double-stranded DNA enabled stable dispersibility of a complex composed of SWNT and the antibody under physiological conditions. Quartz crystal microbalance results suggest that there was one immobilized IgG molecule to every 21,700 carbon atoms in the complex containing DNA-treated SWNT and the antibody. The DNA-SWNT antibody complex showed good selectivity for binding to the targeted protein. Binding analysis revealed that treatment with DNA did not interfere with binding affinity or capacity between the immobilized antibody and the targeted protein. The results of this study demonstrate that the DNA-SWNT antibody complex is a useful tool for use as a smart “molecular heater” platform applicable to various types of antibodies targeting a specific antigen.

Visible light-driven organic form-stable phase change materials for solar energy storage

A novel visible light-driven organic form-stable phase change material (VLDOPCM) exhibited excellent performances of light-harvesting, light-thermal conversion, thermal energy storage and form-stable effect, which is promoted by the dye as an effective “photon capture and molecular heater” for direct and efficient use of solar radiation.

Novel organic solar thermal energy storage materials: efficient visible light-driven reversible solid–liquid phase transition

Solar-thermal energy conversion and storage are one promising solution to directly and efficiently harvest energy from solar radiation. We reported novel organic photothermal conversion-thermal storage materials (OPTCMs) displaying a rapid visible light-harvesting, light-thermal conversion and solid–liquid phase transition thermal energy storage characteristic for solar energy, which is promoted by a dye as an effective “photon capturer and molecular heater” for direct and efficient use of solar radiation.

Pulsed-laser induced flocculation of carbon nanotubes solubilized by an anthracene-carrying polymer

Single-walled carbon nanotubes (SWNTs), solubilized individually in dimethylformamide using a polymer with anthracene groups or in aqueous micelle of sodium dodecyl sulfate (SDS), were irradiated with near-infrared (IR) pulsed-laser light. Near-IR light was absorbed by the SWNTs and converted to heat through photothermal conversion of SWNTs, which did not greatly degrade the polymer wrapping the SWNTs. The local and transient heat via the irradiation resulted in SWNT-flocculation with raising the macroscopic temperature of the solution. No such irradiation effect was recognized for the SWNTs/SDS aqueous solution. The present finding reveals that carbon nanotubes act as a ‘molecular heater’ that triggers structural changes of carbon nanotube nanocomposites.

Energy Transfer from Photoexcited Electronic States to the Thermal Modes

Abstract Energy transfer processes from a photoexcited ion and molecules to solvents were studied from the rate of the temperature rise of the solvent using several newly developed techniques: temperature grating, temperature lens, acoustic peak delay, and molecular heater–molecular thermometer methods. These energy transfer processes are closely related to the well-studied vibrational relaxation (cooling) process but the overall energy transfer process can be monitored by detecting the time course of the matrix heating. In aqueous solution, most of the energy of a photoexcited ion transfers to the thermal mode within 2–3 ps after the populational relaxation to a lower electronic state. In organic solvents, the process is described by roughly two kinetics: fast ( ≤ 1 ps) and slow (20–30 ps). This two-phase kinetics was explained by a simple thermalization model; the initial fast process represents the energy transfer to the doorway molecules in the first solvent shell molecules and the slower one represents the thermal diffusion process from the hot solvent molecules to the bulk solvent molecules. A new molecular heater-molecular thermometer integrated system is also described.

High Temporally and Spatially Resolved Thermal Energy Detection after Nonradiative Transition in Solution Using a Molecular Heater−Molecular Thermometer Integrated System

High Temporally and Spatially Resolved Thermal Energy Detection after Nonradiative Transition in Solution Using a Molecular Heater−Molecular Thermometer Integrated System

Comparison of the Ablation Behavior of Polymer Films in the IR and UV with Nanosecond and Picosecond Pulses

Experiments are performed to compare the ablation behavior in the IR and UV spectral regions of a doped standard polymer, PMMA, and a specially tailored photopolymer, i.e., a triazene copolyester, to elucidate the underlying mechanisms. The results are discussed in light of current theories about photochemical and photothermal pathways of ablation. Further experiments are performed with nanosecond and picosecond pulses to study the impact of pulse length on the material. From the failure to induce ablation in the IR by doping the specialty polymer with an optical molecular heater we conclude that etching in the UV of this compound is mainly governed by a photochemical process. This result is contrasted by successful ablation of doped PMMA in the IR via a thermal unzipping mechanism. With respect to practical applications, the results show convincingly that the presence of an absorbing chromophore in the polymer is a prerequisite for achieving high-resolution structuring, since molecular absorption is requ...

Direct measurement of polymer temperature during laser ablation using a molecular thermometer

Photothermal laser ablation is studied using poly-(methyl methacrylate) films doped with a dye, IR-165, which functions as a molecular heater and thermometer. Direct optical measurements of temperature are performed on samples heated by 100 ns near-IR pulses at 1.064 μm, at rates dT/dt≊5×109 deg/s. Below ablation threshold, the heat capacity measured by optical calorimetry is precisely the value obtained by conventional calorimetry. At ablation threshold, the peak surface temperature is Tabl=600 °C. The increase in heat capacity observed above threshold, together with the results of a conventional thermal analysis, is used to determine the weight fraction of material decomposed at ablation time χth=0.02. With increasing pulse energy, the fraction decomposed increases and a more forceful ablation is observed, but the surface temperature does not continue to increase past Tlim=715 °C, which is determined to be the limiting temperature for thermal decomposition.