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Alexandre G Brolo - One of the best experts on this subject based on the ideXlab platform.

  • surfAce enhAnced rAmAn scAttering sers from Au Ag bimetAllic nAnopArticles the effect of the moleculAr probe
    Chemical Science, 2013
    Co-Authors: Meikun Fan, Fengju Lai, Hunglung Chou, Bingjoe Hwang, Alexandre G Brolo
    Abstract:

    SurfAce-enhAnced RAmAn scAttering (SERS) from moleculAr probes Adsorbed on Au:Ag bimetAllic nAnopArticles with vArious compositions wAs investigAted. Au:Ag bimetAllic nAnopArticles (NPs), with the diAmeters between 3–5 nm, were prepAred And chArActerized by HRTEM And UV-Vis Absorption. Their SERS properties were exAmined by using four different probe molecules, And compAred with NPs mAde of pure Au or Ag. It is found thAt the SERS property of the Alloy NPs is not only dependent on the Au:Ag rAtio of the bimetAllic NPs, but Also on the chemicAl nAture of the SERS probe. For the two positively chArged SERS probes, oxAzine 720 (OxA) And Nile Blue A (NBA), the Alloy NPs with higher Au content provided the lArgest SERS signAl. However, for the probes 4-hydroxythiophenol (HTP) And thiophenol (TP), the best SERS performAnce wAs obtAined for the highest Ag rAtio. DFT cAlculAtions indicAted A chArge-trAnsfer between Au And Ag Atoms in the Alloys, creAting positively chArged domAins rich in Ag Atom, And negAtively chArge regions dominAted by Au Atoms. It is proposed thAt the probe-specific enhAncement is relAted to the selective binding of probe molecules to the pArtiAlly chArged surfAce domAins in the Alloys. Our results suggest thAt SERS substrAte optimizAtions bAsed on bimetAllic nAnopArticles should consider the nAture of the probes And the electronic-induced effects from the Alloys.

  • surfAce enhAnced rAmAn scAttering sers from Au Ag bimetAllic nAnopArticles the effect of the moleculAr probe
    Chemical Science, 2013
    Co-Authors: Hunglung Chou, Bingjoe Hwang, Wanting Lu, Alexandre G Brolo
    Abstract:

    SurfAce-enhAnced RAmAn scAttering (SERS) from moleculAr probes Adsorbed on Au:Ag bimetAllic nAnopArticles with vArious compositions wAs investigAted. Au:Ag bimetAllic nAnopArticles (NPs), with the diAmeters between 3–5 nm, were prepAred And chArActerized by HRTEM And UV-Vis Absorption. Their SERS properties were exAmined by using four different probe molecules, And compAred with NPs mAde of pure Au or Ag. It is found thAt the SERS property of the Alloy NPs is not only dependent on the Au:Ag rAtio of the bimetAllic NPs, but Also on the chemicAl nAture of the SERS probe. For the two positively chArged SERS probes, oxAzine 720 (OxA) And Nile Blue A (NBA), the Alloy NPs with higher Au content provided the lArgest SERS signAl. However, for the probes 4-hydroxythiophenol (HTP) And thiophenol (TP), the best SERS performAnce wAs obtAined for the highest Ag rAtio. DFT cAlculAtions indicAted A chArge-trAnsfer between Au And Ag Atoms in the Alloys, creAting positively chArged domAins rich in Ag Atom, And negAtively chArge regions dominAted by Au Atoms. It is proposed thAt the probe-specific enhAncement is relAted to the selective binding of probe molecules to the pArtiAlly chArged surfAce domAins in the Alloys. Our results suggest thAt SERS substrAte optimizAtions bAsed on bimetAllic nAnopArticles should consider the nAture of the probes And the electronic-induced effects from the Alloys.

  • surfAce enhAnced rAmAn scAttering sers optrodes for multiplexed on chip sensing of Nile Blue A And oxAzine 720
    Lab on a Chip, 2012
    Co-Authors: Meikun Fan, Penghui Wang, Carlos Escobedo, David Sinton, Alexandre G Brolo
    Abstract:

    The fAbricAtion And on-chip integrAtion of surfAce-enhAnced RAmAn scAttering (SERS) optrodes Are presented. In the optrode configurAtion, both the lAser excitAtion And the bAck-scAttered RAmAn signAl Are trAnsmitted through the sAme opticAl fiber. The SERS-Active component of the optrode wAs fAbricAted through the self-Assembly of silver nAnopArticles on the tip of opticAl fibers. The ApplicAtion of SERS optrodes to detect dyes in Aqueous solution indicAted A limit of quAntificAtion below 1 nM, using Nile Blue A As A moleculAr probe. Using the optrode-integrAted microfluidic chip, it wAs possible to detect severAl different dyes from solutions sequentiAlly injected into the sAme chAnnel. This ApproAch for sequentiAl detection of different AnAlytes is ApplicAble to monitoring on-chip chemicAl processes. The nArrow bAndwidth of the vibrAtionAl informAtion generAted by SERS Allowed solutions of different compositions of two chemicAlly similAr dyes to be distinguished using A dilution microfluidic chip. These results demonstrAte the AdvAntAges of the SERS-optrode for microfluidics ApplicAtions by illustrAting the potentiAl of this vibrAtionAl method to quAntify components in A mixture.

  • surfAce enhAnced resonAnce rAmAn scAttering on gold concentric rings polArizAtion dependence And intensity fluctuAtions
    Journal of Physical Chemistry C, 2012
    Co-Authors: Gustavo F S Andrade, Reuven Gordon, Qiao Min, Alexandre G Brolo
    Abstract:

    The spAtiAl And temporAl dependence of the surfAce-enhAnced resonAnce RAmAn scAttering (SERRS) from Nile Blue A (NBA) Adsorbed on concentric rings on A gold film wAs probed. The SERRS intensity mApping of the concentric rings, obtAined using lineArly polArized excitAtion, wAs well-fitted by A sin2 θ function. This spAtiAl vAriAtion of SERRS intensity from the nAnostructure wAs in good quAlitAtive Agreement with finite-difference time-domAin numericAl cAlculAtions. HistogrAms of the time-dependent SERRS intensities showed A normAl-distribution for concentrAtions of NBA in the micromolAr rAnge And A tAiled distribution for diluted solutions (nAnomolAr rAnge). Time-dependent fluctuAtions of SERRS intensities were observed when the concentrAtions of NBA reAched 200 nM. The mAximum relAtive SERRS intensity And its Absolute vAriAtion, obtAined from the experiments with diluted solutions, wAs much lower thAn previously observed from rAndom substrAtes thAt support SERRS, such As colloids immobilized on glAss. Thi...

  • silver nAnopArticles self Assembly As sers substrAtes with neAr single molecule detection limit
    Physical Chemistry Chemical Physics, 2009
    Co-Authors: Meikun Fan, Alexandre G Brolo
    Abstract:

    Highly sensitive SERS substrAtes with A limit of detection in the zeptomole (for Nile Blue A And oxAzine 720) rAnge were fAbricAted through A bottom-up strAtegy. Ag nAnopArticles (Ag NPs) were self-Assembled onto glAss slides by using 3-mercAptopropyltrimethoxysilAne (MPTMS) sol–gel As linker. The substrAtes were chArActerized by UV-Vis And AFM After eAch deposition of Ag NPs. It wAs found thAt the glAss slide presented just A few Ag NPs AggregAtes scAttered throughout the surfAce After just one deposition. The glAss surfAce wAs grAduAlly covered by A homogeneous distribution of Ag NPs AggregAtes As the deposition number increAsed. SurfAce-enhAnced RAmAn scAttering (SERS) of the substrAtes wAs exAmined At different numbers of Ag NPs deposition using Nile Blue A And oxAzine 720 As probe molecules And two lAser excitAtions (632.8 nm And 785 nm). Optimum SERS wAs observed After six depositions of Ag NPs. SERS mApping indicAted thAt At lower deposition numbers (less thAn 3 Ag NPs depositions) the substrAtes presented A few SERS “hot–spots” rAndomly distributed At the surfAce. After 7 Ag NPs depositions, spAtiAl distribution of the SERS signAl followed A GAussiAn stAtistics, with A percent relAtive stAndArd deviAtion (RSD%) of ∼19%. In Addition, the sAmple-to-sAmple reproducibility of the SERS intensities under both lAser excitAtions wAs lower thAn 20%. It wAs Also found thAt these substrAtes cAn provide giAnt RAmAn signAl enhAncement. At optimum conditions And with A 632.8 nm lAser, the signAl from An estimAted of only ∼44 probe molecules (100× objective) cAn still be detected.

Meikun Fan - One of the best experts on this subject based on the ideXlab platform.

  • surfAce enhAnced rAmAn scAttering sers from Au Ag bimetAllic nAnopArticles the effect of the moleculAr probe
    Chemical Science, 2013
    Co-Authors: Meikun Fan, Fengju Lai, Hunglung Chou, Bingjoe Hwang, Alexandre G Brolo
    Abstract:

    SurfAce-enhAnced RAmAn scAttering (SERS) from moleculAr probes Adsorbed on Au:Ag bimetAllic nAnopArticles with vArious compositions wAs investigAted. Au:Ag bimetAllic nAnopArticles (NPs), with the diAmeters between 3–5 nm, were prepAred And chArActerized by HRTEM And UV-Vis Absorption. Their SERS properties were exAmined by using four different probe molecules, And compAred with NPs mAde of pure Au or Ag. It is found thAt the SERS property of the Alloy NPs is not only dependent on the Au:Ag rAtio of the bimetAllic NPs, but Also on the chemicAl nAture of the SERS probe. For the two positively chArged SERS probes, oxAzine 720 (OxA) And Nile Blue A (NBA), the Alloy NPs with higher Au content provided the lArgest SERS signAl. However, for the probes 4-hydroxythiophenol (HTP) And thiophenol (TP), the best SERS performAnce wAs obtAined for the highest Ag rAtio. DFT cAlculAtions indicAted A chArge-trAnsfer between Au And Ag Atoms in the Alloys, creAting positively chArged domAins rich in Ag Atom, And negAtively chArge regions dominAted by Au Atoms. It is proposed thAt the probe-specific enhAncement is relAted to the selective binding of probe molecules to the pArtiAlly chArged surfAce domAins in the Alloys. Our results suggest thAt SERS substrAte optimizAtions bAsed on bimetAllic nAnopArticles should consider the nAture of the probes And the electronic-induced effects from the Alloys.

  • surfAce enhAnced rAmAn scAttering sers optrodes for multiplexed on chip sensing of Nile Blue A And oxAzine 720
    Lab on a Chip, 2012
    Co-Authors: Meikun Fan, Penghui Wang, Carlos Escobedo, David Sinton, Alexandre G Brolo
    Abstract:

    The fAbricAtion And on-chip integrAtion of surfAce-enhAnced RAmAn scAttering (SERS) optrodes Are presented. In the optrode configurAtion, both the lAser excitAtion And the bAck-scAttered RAmAn signAl Are trAnsmitted through the sAme opticAl fiber. The SERS-Active component of the optrode wAs fAbricAted through the self-Assembly of silver nAnopArticles on the tip of opticAl fibers. The ApplicAtion of SERS optrodes to detect dyes in Aqueous solution indicAted A limit of quAntificAtion below 1 nM, using Nile Blue A As A moleculAr probe. Using the optrode-integrAted microfluidic chip, it wAs possible to detect severAl different dyes from solutions sequentiAlly injected into the sAme chAnnel. This ApproAch for sequentiAl detection of different AnAlytes is ApplicAble to monitoring on-chip chemicAl processes. The nArrow bAndwidth of the vibrAtionAl informAtion generAted by SERS Allowed solutions of different compositions of two chemicAlly similAr dyes to be distinguished using A dilution microfluidic chip. These results demonstrAte the AdvAntAges of the SERS-optrode for microfluidics ApplicAtions by illustrAting the potentiAl of this vibrAtionAl method to quAntify components in A mixture.

  • silver nAnopArticles self Assembly As sers substrAtes with neAr single molecule detection limit
    Physical Chemistry Chemical Physics, 2009
    Co-Authors: Meikun Fan, Alexandre G Brolo
    Abstract:

    Highly sensitive SERS substrAtes with A limit of detection in the zeptomole (for Nile Blue A And oxAzine 720) rAnge were fAbricAted through A bottom-up strAtegy. Ag nAnopArticles (Ag NPs) were self-Assembled onto glAss slides by using 3-mercAptopropyltrimethoxysilAne (MPTMS) sol–gel As linker. The substrAtes were chArActerized by UV-Vis And AFM After eAch deposition of Ag NPs. It wAs found thAt the glAss slide presented just A few Ag NPs AggregAtes scAttered throughout the surfAce After just one deposition. The glAss surfAce wAs grAduAlly covered by A homogeneous distribution of Ag NPs AggregAtes As the deposition number increAsed. SurfAce-enhAnced RAmAn scAttering (SERS) of the substrAtes wAs exAmined At different numbers of Ag NPs deposition using Nile Blue A And oxAzine 720 As probe molecules And two lAser excitAtions (632.8 nm And 785 nm). Optimum SERS wAs observed After six depositions of Ag NPs. SERS mApping indicAted thAt At lower deposition numbers (less thAn 3 Ag NPs depositions) the substrAtes presented A few SERS “hot–spots” rAndomly distributed At the surfAce. After 7 Ag NPs depositions, spAtiAl distribution of the SERS signAl followed A GAussiAn stAtistics, with A percent relAtive stAndArd deviAtion (RSD%) of ∼19%. In Addition, the sAmple-to-sAmple reproducibility of the SERS intensities under both lAser excitAtions wAs lower thAn 20%. It wAs Also found thAt these substrAtes cAn provide giAnt RAmAn signAl enhAncement. At optimum conditions And with A 632.8 nm lAser, the signAl from An estimAted of only ∼44 probe molecules (100× objective) cAn still be detected.

Yanying Rao - One of the best experts on this subject based on the ideXlab platform.

  • minimAlly invAsive surfAce enhAnced rAmAn scAttering detection with depth profiles bAsed on A surfAce enhAnced rAmAn scAttering Active Acupuncture needle
    Analytical Chemistry, 2011
    Co-Authors: Jian Dong, Qingfeng Chen, Chunhui Rong, Yanying Rao
    Abstract:

    To obtAin depth profiles of surfAce-enhAnced RAmAn scAttering (SERS) informAtion in living systems, A SERS-Active needle wAs structured by Acupuncture needles, gold nAnoshells (GNSs), And polystyrene, which were used As cArriers, SERS-Active elements to be Absorbed on the cArriers, And coAtings to protect the Absorbed GNSs from being erAsed during insertion, respectively. The SERS-Active needle is minimAlly invAsive for entering And exiting the body. The interspAces between the GNSs becAme vessels to collect diffused fluids At different depths After A SERS-Active needle wAs inserted into An AgArose gel, And the SERS intensity profile on the SERS-Active needle coincided with the concentrAtion profile of Nile Blue A (NBA) in the gel. SERS detection in vitro Avoided the signAl AttenuAtion in gels, And the SERS detection At different spots of the SERS-Active needle provided A depth profile of the NBA molecule in the gel. In vivo experiments of NBA And 6-mercAptopurine confirmed thAt the SERS-Active needle cou...

  • minimAlly invAsive surfAce enhAnced rAmAn scAttering detection with depth profiles bAsed on A surfAce enhAnced rAmAn scAttering Active Acupuncture needle
    Analytical Chemistry, 2011
    Co-Authors: Jian Dong, Qingfeng Chen, Chunhui Rong, Yanying Rao
    Abstract:

    To obtAin depth profiles of surfAce-enhAnced RAmAn scAttering (SERS) informAtion in living systems, A SERS-Active needle wAs structured by Acupuncture needles, gold nAnoshells (GNSs), And polystyrene, which were used As cArriers, SERS-Active elements to be Absorbed on the cArriers, And coAtings to protect the Absorbed GNSs from being erAsed during insertion, respectively. The SERS-Active needle is minimAlly invAsive for entering And exiting the body. The interspAces between the GNSs becAme vessels to collect diffused fluids At different depths After A SERS-Active needle wAs inserted into An AgArose gel, And the SERS intensity profile on the SERS-Active needle coincided with the concentrAtion profile of Nile Blue A (NBA) in the gel. SERS detection in vitro Avoided the signAl AttenuAtion in gels, And the SERS detection At different spots of the SERS-Active needle provided A depth profile of the NBA molecule in the gel. In vivo experiments of NBA And 6-mercAptopurine confirmed thAt the SERS-Active needle could collect fluids in living systems eAsily with minimAl invAsion And provide informAtion About depth profiles of tArget molecules in tissues.

Christopher M.a. Brett - One of the best experts on this subject based on the ideXlab platform.

  • A novel Amperometric sensor for Ascorbic Acid bAsed on poly(Nile Blue A) And functionAlised multi-wAlled cArbon nAnotube modified electrodes
    Talanta, 2013
    Co-Authors: Dilek Kul, Rasa Pauliukaite, M. Emilia Ghica, Christopher M.a. Brett
    Abstract:

    A new type of modified electrode sensor for Ascorbic Acid hAs been prepAred by deposition of multi-wAlled cArbon nAnotubes (MWCNT) And poly(Nile Blue A) on the surfAce of glAssy cArbon electrodes. Nile Blue A wAs electropolymerised either beneAth (directly on glAssy cArbon) or onto the MWCNT lAyer by potentiAl cycling in phosphAte buffer solution At pH 6.0. ChArActerisAtion of the modified electrodes wAs cArried out by cyclic voltAmmetry And electrochemicAl impedAnce spectroscopy. QuAntitAtive determinAtion of AscorbAte wAs Achieved by cyclic voltAmmetry And fixed potentiAl Amperometry in phosphAte buffer solution At pH 5.3. The modified electrodes exhibited good sensitivity, wide lineAr rAnge, A detection limit of 1.6 μM And good stAbility, showing thAt they cAn be used As sensors for Ascorbic Acid. There is no interference from compounds commonly found in clinicAl And phArmAceuticAl sAmples And the determinAtion of Ascorbic Acid in commerciAl tAblet sAmples wAs successfully performed.

Jian Dong - One of the best experts on this subject based on the ideXlab platform.

  • minimAlly invAsive surfAce enhAnced rAmAn scAttering detection with depth profiles bAsed on A surfAce enhAnced rAmAn scAttering Active Acupuncture needle
    Analytical Chemistry, 2011
    Co-Authors: Jian Dong, Qingfeng Chen, Chunhui Rong, Yanying Rao
    Abstract:

    To obtAin depth profiles of surfAce-enhAnced RAmAn scAttering (SERS) informAtion in living systems, A SERS-Active needle wAs structured by Acupuncture needles, gold nAnoshells (GNSs), And polystyrene, which were used As cArriers, SERS-Active elements to be Absorbed on the cArriers, And coAtings to protect the Absorbed GNSs from being erAsed during insertion, respectively. The SERS-Active needle is minimAlly invAsive for entering And exiting the body. The interspAces between the GNSs becAme vessels to collect diffused fluids At different depths After A SERS-Active needle wAs inserted into An AgArose gel, And the SERS intensity profile on the SERS-Active needle coincided with the concentrAtion profile of Nile Blue A (NBA) in the gel. SERS detection in vitro Avoided the signAl AttenuAtion in gels, And the SERS detection At different spots of the SERS-Active needle provided A depth profile of the NBA molecule in the gel. In vivo experiments of NBA And 6-mercAptopurine confirmed thAt the SERS-Active needle cou...

  • minimAlly invAsive surfAce enhAnced rAmAn scAttering detection with depth profiles bAsed on A surfAce enhAnced rAmAn scAttering Active Acupuncture needle
    Analytical Chemistry, 2011
    Co-Authors: Jian Dong, Qingfeng Chen, Chunhui Rong, Yanying Rao
    Abstract:

    To obtAin depth profiles of surfAce-enhAnced RAmAn scAttering (SERS) informAtion in living systems, A SERS-Active needle wAs structured by Acupuncture needles, gold nAnoshells (GNSs), And polystyrene, which were used As cArriers, SERS-Active elements to be Absorbed on the cArriers, And coAtings to protect the Absorbed GNSs from being erAsed during insertion, respectively. The SERS-Active needle is minimAlly invAsive for entering And exiting the body. The interspAces between the GNSs becAme vessels to collect diffused fluids At different depths After A SERS-Active needle wAs inserted into An AgArose gel, And the SERS intensity profile on the SERS-Active needle coincided with the concentrAtion profile of Nile Blue A (NBA) in the gel. SERS detection in vitro Avoided the signAl AttenuAtion in gels, And the SERS detection At different spots of the SERS-Active needle provided A depth profile of the NBA molecule in the gel. In vivo experiments of NBA And 6-mercAptopurine confirmed thAt the SERS-Active needle could collect fluids in living systems eAsily with minimAl invAsion And provide informAtion About depth profiles of tArget molecules in tissues.