In the present research work, a highly recyclable catalyst of Ag-based agarose (HRC-Ag/Agar) hydrogel was successfully fabricated through a simple and e cient in situ reduction method without the aid of additional surface active agent. The interaction between the rich -OH groups in agarose and the Ag nanoparticles can effectively control the growth and dispersion of Ag nanoparticles in the HRC-Ag/Agar hydrogel. Moreover, HRC-Ag/Agar hydrogel without freeze drying and calcination can be directly used as a highly active catalysts in reducing aromatic organic pollutants (4-NP, RhB and MB) by KBH 4 . HRC-Ag/Agar hydrogel also show great advantages in separation and reusability of catalysts due to Ag attach to the agarose toughly via the interaction between Ag NPs and -OH groups and the chemical reactant has no signi cant damage to the Ag NPs, which can maintain high catalytic e ciency with no signi cant loss during ten cycles testing. The advantages of simple synthetic procedure, no secondary pollution, strong stability and the product easily separated make the HRC-Ag/Agar hydrogel have great potential prospect for environmental applications. The successful synthesis of the material was con rmed through SEM, EDS, XRD, Raman and FTIR techniques.

In the present research work, a highly recyclable catalyst of Ag-based agarose (HRC-Ag/Agar) hydrogel was successfully fabricated through a simple and efficient in situ reduction method without the aid of additional surface active agent. The interaction between the rich -OH groups in agarose and the Ag nanoparticles can effectively control the growth and dispersion of Ag nanoparticles in the HRC-Ag/Agar hydrogel. Moreover, HRC-Ag/Agar hydrogel without freeze drying and calcination can be directly used as a highly active catalysts in reducing aromatic organic pollutants (4-NP, RhB and MB) by KBH4. HRC-Ag/Agar hydrogel also show great advantages in separation and reusability of catalysts due to Ag attach to the agarose toughly via the interaction between Ag NPs and –OH groups and the chemical reactant has no significant damage to the Ag NPs, which can maintain high catalytic efficiency with no significant loss during ten cycles testing. The advantages of simple synthetic procedure, no secondary pollution, strong stability and the product easily separated make the HRC-Ag/Agar hydrogel have great potential prospect for environmental applications. The successful synthesis of the material was confirmed through SEM, EDS, XRD, Raman and FTIR techniques.

The nfrared (IR) band contains rich matter information, and has great scientific interest and technological importance in practical applications in various fields, [1] such as thermal imaging, [2] chemical sensor, [3,4,5] optical communication, [6] and medical diagnosis. [7] IR plasmonic nanostructures [8,9] supporting IR light-matter interaction in nanoscale, which contribute strongly enhanced local electromagnetic field, are essential for ultrasensitive IR spectroscopy, photodetections, modulation, and generation.Strong IR absorption can be achieved by exploiting the strong optical near-field in the vicinity of resonant metallic nanostructures. [10][11][12][13] Nevertheless, the metal plasmonic nanostructures [14,15] are ultimately limited by the spatially non-homogenous, relatively poor field confinement and large radiation losses in IR band. In contrast, the electromagnetic fields of graphene plasmonic nanostructures [14,15] display Broadband infrared (IR) absorption is sought after for wide range of applications. Graphene can support IR plasmonic waves tightly bound to its surface, leading to an intensified near-field. However, the excitation of graphene plasmonic waves usually relies on resonances. Thus, it is still difficult to directly obtain both high near-field intensity and high absorption rate in ultra-broad IR band. Herein, a novel method is proposed to directly realize high nearfield intensity in broadband IR band by graphene coated manganous oxide microwires featured hierarchical nanostructures (HNSs-MnO@Gr MWs) both experimentally and theoretically. Both near-field intensity and IR absorption of HNSs-MnO@Gr MWs are enhanced by at least one order of magnitude compared to microwires with smooth surfaces. The results demonstrate that the HNSs-MnO@Gr MWs support vibrational sensing of small organic molecules, covering the whole fingerprint region and function group region. Compared with the graphene-flake-based enhancers, the signal enhancement factors reach a record high of 10 3 . Furthermore, just a single HNSs-MnO@Gr MW can be constructed to realize sensitively photoresponse with high responsivity (over 3000 V W −1 ) from near-IR to mid-IR. The graphene coated dielectric hierarchical micro/nanoplatform with enhanced nearfield intensity is scalable and can harness for potential applications including spectroscopy, optoelectronics, and sensing.

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