Lignocellulosic biomass: a sustainable platform for the production of bio-based chemicals and polymers

The demand for petroleum dependent chemicals and materials has been increasing despite the dwindling of their fossil resources. As the dead-end of petroleum based industry has started to appear, today's modern society has to implement alternative energy and valuable chemical resources immediately. Owing to the importance of lignocellulosic biomass being the most abundant and bio-renewable biomass on earth, this critical review provides insights into the potential of lignocellulosic biomass as an alternative platform to fossil resources. In this context, over 200 value-added compounds, which can be derived from lignocellulosic biomass by various treatment methods, are presented with their references. Lignocellulosic biomass based polymers and their commercial importance are also reported mainly in the frame of these compounds. This review article aims to draw the map of lignocellulosic biomass derived chemicals and their synthetic polymers, and to reveal the scope of this map in today's modern chemical and polymer industry.

High-precision gas sensors operated at room temperature are attractive for various real-time gas monitoring applications, with advantages including low energy consumption, cost effectiveness and device miniaturization/flexibility. Studies on sensing materials, which play a key role in good gas sensing performance, are currently focused extensively on semiconducting metal oxide nanostructures (SMONs) used in the conventional resistance type gas sensors. This topical review highlights the designs and mechanisms of different SMONs with various patterns (e.g. nanoparticles, nanowires, nanosheets, nanorods, nanotubes, nanofilms, etc.) for gas sensors to detect various hazardous gases at room temperature. The key topics include (1) single phase SMONs including both n-type and p-type ones; (2) noble metal nanoparticle and metal ion modified SMONs; (3) composite oxides of SMONs; (4) composites of SMONs with carbon nanomaterials. Enhancement of the sensing performance of SMONs at room temperature can also be realized using a photo-activation effect such as ultraviolet light. SMON based mechanically flexible and wearable room temperature gas sensors are also discussed. Various mechanisms have been discussed for the enhanced sensing performance, which include redox reactions, heterojunction generation, formation of metal sulfides and the spillover effect. Finally, major challenges and prospects for the SMON based room temperature gas sensors are highlighted.

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Advances in designs and mechanisms of semiconducting metal oxide nanostructures for high-precision gas sensors operated at room temperature

Utilization of diffusive solar energy through photocatalytic processes for environmental purification and fuel production has long been pursued. However, efficient capture of visible-near-infrared (NIR) photons, especially for those with wavelengths longer than 600 nm, is a demanding quest in photocatalysis owing to their relatively low energy. In recent years, benefiting from the advances in photoactive material design, photocatalytic reaction system optimization, and new emerging mechanisms for long-wavelength photon activation, increasing numbers of studies on the harnessing of visible-NIR light for solar-to-chemical energy conversion have been reported. Here, the aim is to comprehensively summarize the progress in this area. The main strategies of the long-wavelength visible-NIR photon capture and the explicitly engineered material systems, i.e., narrow optical gap, photosensitizers, upconversion, and photothermal materials, are elaborated. In addition, the advances in long-wavelength light-driven photo- and photothermal-catalytic environmental remediation and fuel production are discussed. It is anticipated that this review presents the forefront achievements in visible-NIR photon capture and at the same time promotes the development of novel visible-NIR photon harnessing catalysts toward efficient solar energy utilization.

Visible‐to‐NIR Photon Harvesting: Progressive Engineering of Catalysts for Solar‐Powered Environmental Purification and Fuel Production

Activatable theranostic agents that can be activated by tumor microenvironment possess higher specificity and sensitivity. Here, activatable nanozyme-mediated 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) loaded ABTS@MIL-100/poly(vinylpyrrolidine) (AMP) nanoreactors (NRs) are developed for imaging-guided combined tumor therapy. The as-constructed AMP NRs can be specifically activated by the tumor microenvironment through a nanozyme-mediated "two-step rocket-launching-like" process to turn on its photoacoustic imaging signal and photothermal therapy (PTT) function. In addition, simultaneously producing hydroxyl radicals in response to the high H2 O2 level of the tumor microenvironment and disrupting intracellular glutathione (GSH) endows the AMP NRs with the ability of enhanced chemodynamic therapy (ECDT), thereby leading to more efficient therapeutic outcome in combination with tumor-triggered PTT. More importantly, the H2 O2 -activated and acid-enhanced properties enable the AMP NRs to be specific to tumors, leaving the normal tissues unharmed. These remarkable features of AMP NRs may open a new avenue to explore nanozyme-involved nanoreactors for intelligent, accurate, and noninvasive cancer theranostics.

A Tumor-Microenvironment-Activated Nanozyme-Mediated Theranostic Nanoreactor for Imaging-Guided Combined Tumor Therapy.

We report the facile one-pot synthesis of self-organized W18O49 networks. The W18O49 networks show strong localized surface plasmon resonance. Interestingly, the W18O49 networks show unexpected capability in photocatalytic dehydration of isopropyl alcohol to propylene depending on their defect structure caused by large quantities of oxygen vacancy.

W18O49 nanowire networks for catalyzed dehydration of isopropyl alcohol to propylene under visible light

Large-scale, ultrathin, and (001) facet exposed anatase TiO2 nanosheet superstructures were synthesized by a facile one-step solvothermal method. The length and width of the nanosheets was as high as 1.5–2 μm, while the thickness of the nanosheets was only about 2–4 nm. The anatase TiO2 nanosheet superstructures have superior photocatalytic performance.

Large-scale, ultrathin and (001) facet exposed TiO2 nanosheet superstructures and their applications in photocatalysis

Increasing the sensitivity of non-noble metal surface-enhanced Raman spectroscopy (SERS) is an urgent issue that needs to be solved at present. Herein, metallic W18O49 nanowires with a strong localized surface plasmon resonance (LSPR) effect are prepared. Interestingly, the LSPR peaks of these nanowires would undergo a strong blue shift from near-infrared (NIR) to visible light regions as the aggregation degree of the nanowires increases. By narrowing the gap between the LSPR absorption peak and the Raman excitation wavelength (532 nm), the oriented W18O49 bundles with a LSPR peak centered at 561 nm have greatly improved SERS sensitivity compared with that of the dispersed nanowires with a LSPR peak centered at 1025 nm. Enhancement mechanism investigation shows that the high sensitivity can be attributed to the synergistic effect of LSPR coupling among the oriented ultrathin nanowires and oxygen vacancy (Vo)-assisted charge transfer.

Improved Surface-Enhanced Raman Spectroscopy Sensitivity on Metallic Tungsten Oxide by the Synergistic Effect of Surface Plasmon Resonance Coupling and Charge Transfer.

Semiconductor-based surface-enhanced Raman spectroscopy is getting more and more attention because of its great price advantage. One of the biggest obstacles to the large-scale application of it is the poor stability. Here, we report that plasmonic MoO2 nanospheres can be used as a highly sensitive and stable semiconducting-substrate material for surface-enhanced Raman scattering (SERS). By using the MoO2 nanospheres as Raman substrates, a series of typical compounds with high attention can be accurately detected. This new non-noble metal substrate material shows a very high detection limit of 10–8 M, and exhibits great near-field enhancement with one of the highest enhancement factor of 4.8 × 106 reported to date. More importantly, the oxide with intermediate valence displays unexpected ultrahigh stability, which can withstand the corrosion of strong acid and strong alkali as well as 150 °C high temperature oxidation in air. Moreover, the accurate detection of multicomponent samples was also successful o...

Wentao Li

Papers

W18O49 nanowire networks for catalyzed dehydration of isopropyl alcohol to propylene under visible light

Large-scale, ultrathin and (001) facet exposed TiO2 nanosheet superstructures and their applications in photocatalysis

Improved Surface-Enhanced Raman Spectroscopy Sensitivity on Metallic Tungsten Oxide by the Synergistic Effect of Surface Plasmon Resonance Coupling and Charge Transfer.

Plasmonic MoO2 Nanospheres as a Highly Sensitive and Stable Non-Noble Metal Substrate for Multicomponent Surface-Enhanced Raman Analysis

Highly stable molybdenum dioxide nanoparticles with strong plasmon resonance are promising in photothermal cancer therapy.