Synthesis of Au nanorods in a low pH solution via seed-media method

The gold （Au） nanorods with various aspect ratios are obtained by a seed-media method in low pH growth solution. Transmission electron microscopy （TEM） and UV-visible spectrophotometry are utilized to characterize the Au nanorods, and the longitudinal absorption peak positions of Au nanorods show different shifting trends of the growth evolutions in various low pH （1~3） solutions. Other influential factors on the shape of Au nanorod are also systematically studied under low pH reaction condition. The positions of longitudinal peak shift between 600 nm and 900 nm, with the aspect ratios of Au nanorods varying from 2 to 5 both in the simulation and experimental results. The simulation results are in agreement with experimental ones.

Controllable Synthesis of Au NRs and Its Flexible SERS Optical Fiber Probe with High Sensitivity

The surface-enhanced Raman scattering(SERS) optical fiber probes were successfully prepared by self-assembling on polyelectrolyte multilayers. Gold nanorods(Au NRs) were used as SERS enhancement material to give excellent biological affinity and stability to the SERS optical fiber probes. Au NRs were synthesized by seed growth method. The synergistic effect between AgNO_(3) and surfactant was investigated, and the highest yield was found when AgNO_(3) was 500 uL. Meanwhile, different SERS optical fiber probes were obtained by selecting silane coupling agent, polyelectrolyte multilayer and graphene oxide(GO) to treat quartz fiber. It was found that the SERS optical fiber probes obtained by the self-assembled on polyelectrolyte multilayers method performed better than those by other methods. In addition, Mapping was combined with finite element simulation to analyze the electromagnetic field distribution at the fiber end face.The electromagnetic field distribution of Au NRs was investigated, the difference of electromagnetic field intensity around the Au NRs with different arrangements was compared, the strongest signal was obtained when the Au NRs were head-to-head. Finally, sensitivity of the optimized SERS optical fiber probes could reach 10^(-9)mol/L, with excellent stability and repeatability.

Au nanorods decorated TiO_(2)nanobelts with enhanced full solar spectrum photocatalytic antibacterial activity and the sterilization file cabinet application

TiO_(2)photocatalysts have been widely studied and applied for removing bacteria,but its antibacterial efficiency is limited to the ultraviolet(UV)range of the solar spectrum.In this work,we use the gold(Au)nanorods to enhance the visible and near-infrared(NIR)light absorption of TiO_(2)NBs,a typical UV light photocatalyst,thus the enhancement of its full solar spectrum(UV,visible and NIR)photocatalytic antibacterial properties is achieved.Preliminary surface plasmon resonance(SPR)enhancement photocatalytic antibacterial mechanism is suggested.On one hand,transverse and longitudinal SPR of Au NRs is beneficial for visible and NIR light utilization.On the other hand,Au NRs combined with TiO_(2)NBs to form the heterostructure,which can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination.finally produces the high yield of radical oxygen species and exhibits a superior antibacterial efficiency.Furthermore,we design a sterilization file cabinet with Au NR/TiO_(2)NB heterostructures as the photocatalytic coating plates.Our study reveals that Au NR/TiO_(2)NB heterostructure is a potential candidate for sterilization of bacteria and archives protection.

Surface-roughness-adjustable Au nanorods with strong plasmon absorption and abundant hotspots for improved SERS and photothermal performances

The rational optimization of plasmonic property of metal nanocrystals by manipulating the structure and morphology is crucial for the plasmon-enhanced application and has always been an urgent issue.Herein,Au nanorods with tunable surface roughness are prepared by growing PbS,overgrowing Au,and dissolving PbS nanoparticles on the basis of smooth Au nanorods.The transverse plasmon resonance of Au nanorods is notably improved due to plasmon coupling between Au nanorods and the surface-modified Au nanoparticles,resulting in the strong and full-spectrum light absorption.Numerical simulations demonstrate that the surface-rough Au nanorods have abundant and full-surround hotspots coming from surface particle–particle plasmon coupling between ultrasmall nanogaps,sharp tips,and uneven areas on Au nanorods.With these characters,the surface-roughness-adjustable Au nanorods possess high tunability and enhancement of surface-enhanced Raman scattering(SERS)detection of Rhodamine B and significantly improved photothermal conversion efficiency.Au nanorods with the largest surface roughness have the highest Raman enhancement factor both at 532 and 785 nm laser excitation.Meanwhile,photothermal conversion experiments under near-infrared(808 nm)and simulated sunlight irradiation confirm that the Au nanorods with rough surface have prominent photothermal conversion efficiency and can be regarded as promising candidates for photothermal therapy and solar-driven water evaporation.

Near-infrared response Pt-tipped Au nanorods/g-C_(3)N_(4) realizes photolysis of water to produce hydrogen

The search for a suitable cocatalyst for graphitic carbon nitride(g-C_(3)N_(4)) to realize efficient photocatalytic hydrogen(H_(2)) evolution has been regarded as one of the most valid tactics to alleviate energy crisis.Herein,a ternary Pt-tipped Au nanorods(Pt-Au)/g-C_(3)N_(4) heterostructure is constructed,which shows excellent H_(2) production performance in visible and near-infrared(NIR) region,especially in NIR region with a rate of 51.6 μmol g^(-1)h^(-1).Therein,not only is the optical absorption ability of g-C_(3)N_(4) broadened,the light absorption range is also extended to NIR region through introduction of Pt-Au architectures.Besides,analysis of the hot electrons generated in energy relaxation of plasmon indicates hot electron transfers fromexcited Au nanorods to Pt nanoparticles,resulting in H_(2) evolution.Compared with bare g-C_(3)N_(4),the superior photocatalytic activity could be attributed to the surface plasmon resonance effect(SPR) of Au nanorods and the electron-sink function of Pt nanoparticles.This work provides an insight into the improvement of photocatalytic performance via combination of NIR-responsive plasmon metal with photocatalysts.

Fine-tune chiroptical activity in discrete chiral Au nanorods

Accurate researches on the surface plasmon resonance(SPR)-based applications of chiral plasmonic metal nanoparticles(NPs)still remain a great challenge.Herein,a series of chiral plasmonic metal NPs,e.g.,chiral Au nanorods(c-Au NRs),c-Au@Ag core–shell,and c-Au@TiO_(2) core–shell NRs,with different chiroptical activities have been produced.Plasmonic circular dichroism(PCD)bands of c-Au NRs can be precisely tailored by tuning the longitudinal SPR(LSPR)and amount of Au NRs as seeds.Besides,a shift of PCD bands within ultraviolet–visible–near infrared ray(UV–vis–NIR)region can also be achieved through the functionalization of a shell of another metal or semiconductor.Interestingly,chirality transfer from c-Au core to Ag shell leads to new PCD bands at the near-UV region.The tuning of PCD bands and chirality transfer are confirmed by our developed theoretical model.Developing chiral Au NRs-based chiral plasmonic nanomaterials with tunable chiroptical activities will be helpful to understand the structure-direct PCD and to extend circularly polarized-based applications.

Controllable synthesis of Au-TiO2 nanodumbbell photocatalysts with spatial redox region

Photocatalytic water splitting has increasingly attracted attention as one of the most useful methods of converting solar energy into chemical fuel.However,the undesirable reverse reaction significantly limits the enhancement of efficiency.Herein,we fabricated an Au nanorods/TiO2 nanodumbbells structure photocatalyst(Au NRs/TiO2 NDs)via a facile synthetic strategy,which has spatially separated oxidation and reduction reaction zones.Owing to the unique structure,the charge separation of these photocatalysts can be significantly improved and the reverse reaction can be efficiently inhibited.The photogenerated electrons were injected from the TiO2 to the Au NRs,and a positively charged TiO2 region and negatively charged Au region were formed under UV irradiation.An enhanced hydrogen production performance was obtained compared with that seen in normal Au-TiO2 heterostructure.Under optimized conditions,the H2-production rate can reach up to 60,264μmol/g/h,about six times higher than previously reported Au/TiO2 photocatalysts.Besides this,our work also demonstrates the key factors of precise synthesis of the Au NRs/TiO2 NDs structure,which provides a new perspective and experience for the design of similar catalysts.

An efficient light-to-heat conversion coupling photothermal effect and exothermic chemical reaction in Au NRs/V_(2)C MXene membranes for high-performance laser ignition

MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.

High Temperature Seedless Synthesis of Au NRs Using BDAC/CTAB Co-surfactant

Au nanorods have been successfully synthesized at 90 ℃ by using hexadecyltrimethylammonium bromide （CTAB） and benzyldimethylammoniumchloride hydrate （BDAC） co-surfactant. At 90 ℃, the reaction time was less than 10 s, and the longitudinal surface plasmon absorption band could vary between 680 and 770 nm by adjusting the molar ratio of BDAC to CTAB from 2 to 0.5. At 90 ℃, nanorods with a longitudinal surface plasmon absorption peak of 770 nm can be obtained when the molar ratio of BDAC to CTAB was 3：2.

Engineering surface strain for site-selective island growth of Au on anisotropic Au nanostructures

Controlled growth of islands on plasmonic metal nanoparticles represents a novel strategy in creating unique morphologies that are difficult to achieve by conventional colloidal synthesis processes,where the nanoparticle morphologies are typically determined by the preferential development of certain crystal facets.This work exploits an effective surface-engineering strategy for site-selective island growth of Au on anisotropic Au nanostructures.Selective ligand modification is first employed to direct the site-selective deposition of a thin transition layer of a secondary metal,e.g.,Pd,which has a considerable lattice mismatch with Au.The selective deposition of Pd on the original seeds produces a high contrast in the surface strain that guides the subsequent site-selective growth of Au islands.This strategy proves effective in not only inducing the island growth of Au on Au nanostructures but also manipulating the location of grown islands.By taking advantage of the iodide-assisted oxidative ripening process and the surface strain profile on Au nanostructures,we further demonstrate the precise control of the islands’number,coverage,and wetting degree,allowing fine-tuning of nanoparticles’optical properties.

Separation of Gold Nanorods Using Density Gradient Ultracentrifugation

High quality gold nanorods （NRs） with a monodisperse size and aspect ratio are essential for many applications. Here, we describe how nearly monodisperse gold NRs can be separated from polydisperse samples using density gradient ultracentrifugation. Size and dimension analysis by transmission electron microscopy （TEM） and absorption spectroscopy revealed that the Au NRs were separated mainly as a function of their aspect ratio The surface-enhanced Raman scattering （SERS） activity of Au NRs with lower aspect ratio is notably stronger than that of NRs with higher aspect ratio under 633 nm laser excitation, due to the size-dependent absorption of the longitudinal plasmon band. The separation approach provides a method to improve the quality of NRs produced by large scale synthetic methods.

Construction of triblock copolymer-gold nanorod composites for fluorescence resonance energy transfer via pH-sensitive allosteric

To explore the effects of microenvironmental adjustments on fluorescence,a pH-sensitive nanocomposite system based on fluorescence resonance energy transfer(FRET)was constructed.The model system included a modified triblock copolymer(polyhistidine-b-polyethylene glycol-b-polycaprolactone)and gold nanoparticles.A near-infrared dye was used as the donor,and spectrally matched gold nanorods,attached after C-terminus modification with α-lipoic acid,were used as the receptor to realize control of the FRET effect over the fluorescence intensity for two polymer configurational changes(i.e.,"folded"and"stretched"states)in response to pH.After synthesis and characterization,we investigated the self-assembly behavior of the system.Analysis by quartz crystal microbalance revealed the pH sensitivity of the polymer,which exhibited"folding"and"stretching"states with changes in pH,providing a structural basis for the FRET effect.Fluorescence spectrophotometry investigations also revealed the regulatory impact of the assembled system on fluorescence.