@article{GuptaPathakShrivastav2022, author = {Gupta, Banshi D. and Pathak, Anisha and Shrivastav, Anand}, title = {Optical Biomedical Diagnostics Using Lab-on-Fiber Technology}, series = {Photonics : open access journal}, volume = {9}, journal = {Photonics : open access journal}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2304-6732}, doi = {10.3390/photonics9020086}, pages = {40}, year = {2022}, abstract = {Point-of-care and in-vivo bio-diagnostic tools are the current need for the present critical scenarios in the healthcare industry. The past few decades have seen a surge in research activities related to solving the challenges associated with precise on-site bio-sensing. Cutting-edge fiber optic technology enables the interaction of light with functionalized fiber surfaces at remote locations to develop a novel, miniaturized and cost-effective lab on fiber technology for bio-sensing applications. The recent remarkable developments in the field of nanotechnology provide innumerable functionalization methodologies to develop selective bio-recognition elements for label free biosensors. These exceptional methods may be easily integrated with fiber surfaces to provide highly selective light-matter interaction depending on various transduction mechanisms. In the present review, an overview of optical fiber-based biosensors has been provided with focus on physical principles used, along with the functionalization protocols for the detection of various biological analytes to diagnose the disease. The design and performance of these biosensors in terms of operating range, selectivity, response time and limit of detection have been discussed. In the concluding remarks, the challenges associated with these biosensors and the improvement required to develop handheld devices to enable direct target detection have been highlighted.}, language = {en} } @article{KogikoskiJuniorDuttaBald2021, author = {Kogikoski Junior, Sergio and Dutta, Anushree and Bald, Ilko}, title = {Spatial separation of plasmonic hot-electron generation and a hydrodehalogenation reaction center using a DNA wire}, series = {ACS nano}, volume = {15}, journal = {ACS nano}, number = {12}, publisher = {American Chemical Society}, address = {Washington}, issn = {1936-0851}, doi = {10.1021/acsnano.1c09176}, pages = {20562 -- 20573}, year = {2021}, abstract = {Using hot charge carriers far from a plasmonic nanoparticle surface is very attractive for many applications in catalysis and nanomedicine and will lead to a better understanding of plasmon-induced processes, such as hot-charge-carrier- or heat-driven chemical reactions. Herein we show that DNA is able to transfer hot electrons generated by a silver nanoparticle over several nanometers to drive a chemical reaction in a molecule nonadsorbed on the surface. For this we use 8-bromo-adenosine introduced in different positions within a double-stranded DNA oligonucleotide. The DNA is also used to assemble the nanoparticles into nanoparticles ensembles enabling the use of surface-enhanced Raman scattering to track the decomposition reaction. To prove the DNA-mediated transfer, the probe molecule was insulated from the source of charge carriers, which hindered the reaction. The results indicate that DNA can be used to study the transfer of hot electrons and the mechanisms of advanced plasmonic catalysts.}, language = {en} } @article{LiebigSarhanSchmittetal.2020, author = {Liebig, Ferenc and Sarhan, Radwan Mohamed and Schmitt, Clemens Nikolaus Zeno and Th{\"u}nemann, Andreas F. and Prietzel, Claudia Christina and Bargheer, Matias and Koetz, Joachim}, title = {Gold nanotriangles with crumble topping and their influence on catalysis and surface-enhanced raman spectroscopy}, series = {ChemPlusChem}, volume = {85}, journal = {ChemPlusChem}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2192-6506}, doi = {10.1002/cplu.201900745}, pages = {519 -- 526}, year = {2020}, abstract = {By adding hyaluronic acid (HA) to dioctyl sodium sulfosuccinate (AOT)-stabilized gold nanotriangles (AuNTs) with an average thickness of 7.5 +/- 1 nm and an edge length of about 175 +/- 17 nm, the AOT bilayer is replaced by a polymeric HA-layer leading to biocompatible nanoplatelets. The subsequent reduction process of tetrachloroauric acid in the HA-shell surrounding the AuNTs leads to the formation of spherical gold nanoparticles on the platelet surface. With increasing tetrachloroauric acid concentration, the decoration with gold nanoparticles can be tuned. SAXS measurements reveal an increase of the platelet thickness up to around 14.5 nm, twice the initial value of bare AuNTs. HRTEM micrographs show welding phenomena between densely packed particles on the platelet surface, leading to a crumble formation while preserving the original crystal structure. Crumbles crystallized on top of the platelets enhance the Raman signal by a factor of around 20, and intensify the plasmon-driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4 '-dimercaptoazobenzene in a yield of up to 50 \%. The resulting crumbled nanotriangles, with a biopolymer shell and the absorption maximum in the second window for in vivo imaging, are promising candidates for biomedical sensing.}, language = {en} } @article{DuttaSchuermannKogikoskiJunioretal.2021, author = {Dutta, Anushree and Sch{\"u}rmann, Robin and Kogikoski Junior, Sergio and Mueller, Niclas S. and Reich, Stephanie and Bald, Ilko}, title = {Kinetics and mechanism of plasmon-driven dehalogenation reaction of brominated purine nucleobases on Ag and Au}, series = {ACS catalysis / American Chemical Society}, volume = {11}, journal = {ACS catalysis / American Chemical Society}, number = {13}, publisher = {American Chemical Society}, address = {Washington}, issn = {2155-5435}, doi = {10.1021/acscatal.1c01851}, pages = {8370 -- 8381}, year = {2021}, abstract = {Plasmon-driven photocatalysis is an emerging and promising application of noble metal nanoparticles (NPs). An understanding of the fundamental aspects of plasmon interaction with molecules and factors controlling their reaction rate in a heterogeneous system is of high importance. Therefore, the dehalogenation kinetics of 8-bromoguanine (BrGua) and 8-bromoadenine (BrAde) on aggregated surfaces of silver (Ag) and gold (Au) NPs have been studied to understand the reaction kinetics and the underlying reaction mechanism prevalent in heterogeneous reaction systems induced by plasmons monitored by surface enhanced Raman scattering (SERS). We conclude that the time-average constant concentration of hot electrons and the time scale of dissociation of transient negative ions (TNI) are crucial in defining the reaction rate law based on a proposed kinetic model. An overall higher reaction rate of dehalogenation is observed on Ag compared with Au, which is explained by the favorable hot-hole scavenging by the reaction product and the byproduct. We therefore arrive at the conclusion that insufficient hole deactivation could retard the reaction rate significantly, marking itself as rate-determining step for the overall reaction. The wavelength dependency of the reaction rate normalized to absorbed optical power indicates the nonthermal nature of the plasmon-driven reaction. The study therefore lays a general approach toward understanding the kinetics and reaction mechanism of a plasmon-driven reaction in a heterogeneous system, and furthermore, it leads to a better understanding of the reactivity of brominated purine derivatives on Ag and Au, which could in the future be exploited, for example, in plasmon-assisted cancer therapy.}, language = {en} } @article{HeckPrinzDatheetal.2017, author = {Heck, Christian and Prinz, Julia and Dathe, Andre and Merk, Virginia and Stranik, Ondrej and Fritzsche, Wolfgang and Kneipp, Janina and Bald, Ilko}, title = {Gold Nanolenses Self-Assembled by DNA Origami}, series = {ACS Photonics}, volume = {4}, journal = {ACS Photonics}, publisher = {American Chemical Society}, address = {Washington}, issn = {2330-4022}, doi = {10.1021/acsphotonics.6b00946}, pages = {1123 -- 1130}, year = {2017}, abstract = {Nanolenses are self-similar chains of metal nanoparticles, which can theoretically provide extremely high field enhancements. Yet, the complex structure renders their synthesis challenging and has hampered closer analyses so far. Here, DNA origami is used to self-assemble 10, 20, and 60 nm gold nanoparticles as plasmonic gold nanolenses (AuNLs) in solution and in billions of copies. Three different geometrical arrangements are assembled, and for each of the three designs, surface-enhanced Raman scattering (SERS) capabilities of single AuNLs are assessed. For the design which shows the best properties, SERS signals from the two different internal gaps are compared by selectively placing probe dyes. The highest Raman enhancement is found for the gap between the small and medium nanoparticle, which is indicative of a cascaded field enhancement.}, language = {en} } @article{LiebigSarhanPrietzeletal.2018, author = {Liebig, Ferenc and Sarhan, Radwan Mohamed and Prietzel, Claudia Christina and Schmitt, Clemens Nikolaus Zeno and Bargheer, Matias and Koetz, Joachim}, title = {Tuned Surface-Enhanced raman scattering performance of undulated Au@Ag triangles}, series = {ACS applied nano materials}, volume = {1}, journal = {ACS applied nano materials}, number = {4}, publisher = {American Chemical Society}, address = {Washington}, issn = {2574-0970}, doi = {10.1021/acsanm.8b00570}, pages = {1995 -- 2003}, year = {2018}, abstract = {Negatively charged ultraflat gold nanotriangles (AuNTs) stabilized by the anionic surfactant dioctyl sodium sulfosuccinate (AOT) were reloaded with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC). Because of the spontaneous formation of a catanionic AOT micelle/BDAC bilayer onto the surface of the reloaded AuNTs, a reduction of Ag+ ions leads to the formation of spherical silver nanoparticles (AgNPs). With increasing concentration of AgNPs on the AuNTs, the localized surface plasmon resonance (LSPR) is shifted stepwise from 1300 to 800 nm. The tunable LSPR enables to shift the extinction maximum to the wavelength of the excitation laser of the Raman microscope at 785 nm. Surface-enhanced Raman scattering (SERS) experiments performed under resonance conditions show an SERS enhancement factor of the analyte molecule rhodamine RG6 of 5.1 X 10(5), which can be related to the silver hot spots at the periphery of the undulated gold nanoplatelets.}, language = {en} } @article{HeckKanehiraKneippetal.2018, author = {Heck, Christian and Kanehira, Yuya and Kneipp, Janina and Bald, Ilko}, title = {Placement of Single Proteins within the SERS Hot Spots of Self-Assembled Silver Nanolenses}, series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, volume = {57}, journal = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition}, number = {25}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1433-7851}, doi = {10.1002/anie.201801748}, pages = {7444 -- 7447}, year = {2018}, abstract = {This study demonstrates the bottom-up synthesis of silver nanolenses. A robust coating protocol enabled the functionalization of differently sized silver nanoparticles with DNA single strands of orthogonal sequence. Coated particles 10nm, 20nm, and 60nm in diameter were self-assembled by DNA origami scaffolds to form silver nanolenses. Single molecules of the protein streptavidin were selectively placed in the gap of highest electric field enhancement. Streptavidin labelled with alkyne groups served as model analyte in surface-enhanced Raman scattering (SERS) experiments. By correlated Raman mapping and atomic force microscopy, SERS signals of the alkyne labels of a single streptavidin molecule, from a single silver nanolens, were detected. The discrete, self-similar aggregates of solid silver nanoparticles are promising for plasmonic applications.}, language = {en} } @article{LiebigSarhanSanderetal.2017, author = {Liebig, Ferenc and Sarhan, Radwan Mohamed and Sander, Mathias and Koopman, Wouter-Willem Adriaan and Schuetz, Roman and Bargheer, Matias and Koetz, Joachim}, title = {Deposition of Gold Nanotriangles in Large Scale Close-Packed Monolayers for X-ray-Based Temperature Calibration and SERS Monitoring of Plasmon-Driven Catalytic Reactions}, series = {ACS applied materials \& interfaces}, volume = {9}, journal = {ACS applied materials \& interfaces}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.7b07231}, pages = {20247 -- 20253}, year = {2017}, language = {en} } @article{BalderasValadezEstevezEspinozaSalazarKurietal.2018, author = {Balderas-Valadez, Ruth Fabiola and Estevez-Espinoza, J. O. and Salazar-Kuri, U. and Pacholski, Claudia and Mochan, Wolf Luis and Agarwal, Vivechana}, title = {Fabrication of ordered tubular porous silicon structures by colloidal lithography and metal assisted chemical etching}, series = {Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces}, volume = {462}, journal = {Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2018.08.120}, pages = {783 -- 790}, year = {2018}, abstract = {Fabrication of well-ordered porous silicon tubular structures using colloidal lithography and metal assisted chemical etching is reported. A continuous hexagonal hole/particle gold pattern was designed over monocrystalline silicon through deposition of polyNIPAM microspheres, followed by the surface decoration with gold nanoparticles and thermal treatment. An etching reaction with HF, ethanol and H2O2 dissolved the silicon in contact with the metal nanoparticles (NP), creating a porous tubular array in the "off-metal area". The morphological characterization revealed the formation of a cylindrical hollow porous tubular shape with external and internal diameter of approx. 900 nm and 400 nm respectively, though it can be tuned to other desired sizes by choosing an appropriate dimension for the microspheres. The porous morphology and optical properties were studied as a function of resistivity of silicon substrates. Compared to two different gold templates on cSi and nontubular porous pillar structures, porous silicon tubular framework revealed a maximum surface enhanced Raman scattering enhancement factor of 10(6) for the detection of 6-mercaptopurine (6-MP). Due to the large surface area available for any surface modification, open nanostructured platforms such as those studied here have potential applications in the field of reflection/photoluminescene and SERS based optical bio-/chemical sensors.}, language = {en} } @phdthesis{Sarhan2019, author = {Sarhan, Radwan Mohamed}, title = {Plasmon-driven photocatalytic reactions monitored by surface-enhanced Raman spectroscopy}, doi = {10.25932/publishup-43330}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-433304}, school = {Universit{\"a}t Potsdam}, year = {2019}, abstract = {Plasmonic metal nanostructures can be tuned to efficiently interact with light, converting the photons into energetic charge carriers and heat. Therefore, the plasmonic nanoparticles such as gold and silver nanoparticles act as nano-reactors, where the molecules attached to their surfaces benefit from the enhanced electromagnetic field along with the generated energetic charge carriers and heat for possible chemical transformations. Hence, plasmonic chemistry presents metal nanoparticles as a unique playground for chemical reactions on the nanoscale remotely controlled by light. However, defining the elementary concepts behind these reactions represents the main challenge for understanding their mechanism in the context of the plasmonically assisted chemistry. Surface-enhanced Raman scattering (SERS) is a powerful technique employing the plasmon-enhanced electromagnetic field, which can be used for probing the vibrational modes of molecules adsorbed on plasmonic nanoparticles. In this cumulative dissertation, I use SERS to probe the dimerization reaction of 4-nitrothiophenol (4-NTP) as a model example of plasmonic chemistry. I first demonstrate that plasmonic nanostructures such as gold nanotriangles and nanoflowers have a high SERS efficiency, as evidenced by probing the vibrations of the rhodamine dye R6G and the 4-nitrothiophenol 4-NTP. The high signal enhancement enabled the measurements of SERS spectra with a short acquisition time, which allows monitoring the kinetics of chemical reactions in real time. To get insight into the reaction mechanism, several time-dependent SERS measurements of the 4-NTP have been performed under different laser and temperature conditions. Analysis of the results within a mechanistic framework has shown that the plasmonic heating significantly enhances the reaction rate, while the reaction is probably initiated by the energetic electrons. The reaction was shown to be intensity-dependent, where a certain light intensity is required to drive the reaction. Finally, first attempts to scale up the plasmonic catalysis have been performed showing the necessity to achieve the reaction threshold intensity. Meanwhile, the induced heat needs to quickly dissipate from the reaction substrate, since otherwise the reactants and the reaction platform melt. This study might open the way for further work seeking the possibilities to quickly dissipate the plasmonic heat generated during the reaction and therefore, scaling up the plasmonic catalysis.}, language = {en} } @misc{HeckKanehiraKneippetal.2019, author = {Heck, Christian and Kanehira, Yuya and Kneipp, Janina and Bald, Ilko}, title = {Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures}, series = {Mathematisch-Naturwissenschaftliche Reihe}, journal = {Mathematisch-Naturwissenschaftliche Reihe}, number = {732}, issn = {1866-8372}, doi = {10.25932/publishup-43081}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-430812}, pages = {10}, year = {2019}, abstract = {Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates.}, language = {en} } @article{HeckKanehiraKneippetal.2019, author = {Heck, Christian and Kanehira, Yuya and Kneipp, Janina and Bald, Ilko}, title = {Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures}, series = {Molecules}, volume = {24}, journal = {Molecules}, number = {12}, publisher = {MDPI}, address = {Basel}, issn = {1420-3049}, doi = {10.3390/molecules24122324}, pages = {10}, year = {2019}, abstract = {Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates.}, language = {en} } @phdthesis{Heck2017, author = {Heck, Christian}, title = {Gold and silver nanolenses self-assembled by DNA origami}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-409002}, school = {Universit{\"a}t Potsdam}, pages = {ix, 125}, year = {2017}, abstract = {Nanolenses are linear chains of differently-sized metal nanoparticles, which can theoretically provide extremely high field enhancements. The complex structure renders their synthesis challenging and has hampered closer analyses so far. Here, the technique of DNA origami was used to self-assemble DNA-coated 10 nm, 20 nm, and 60 nm gold or silver nanoparticles into gold or silver nanolenses. Three different geometrical arrangements of gold nanolenses were assembled, and for each of the three, sets of single gold nanolenses were investigated in detail by atomic force microscopy, scanning electron microscopy, dark-field scattering and Raman spectroscopy. The surface-enhanced Raman scattering (SERS) capabilities of the single nanolenses were assessed by labelling the 10 nm gold nanoparticle selectively with dye molecules. The experimental data was complemented by finite-difference time-domain simulations. For those gold nanolenses which showed the strongest field enhancement, SERS signals from the two different internal gaps were compared by selectively placing probe dyes on the 20 nm or 60 nm gold particles. The highest enhancement was found for the gap between the 20 nm and 10 nm nanoparticle, which is indicative of a cascaded field enhancement. The protein streptavidin was labelled with alkyne groups and served as a biological model analyte, bound between the 20 nm and 10 nm particle of silver nanolenses. Thereby, a SERS signal from a single streptavidin could be detected. Background peaks observed in SERS measurements on single silver nanolenses could be attributed to amorphous carbon. It was shown that the amorphous carbon is generated in situ.}, language = {en} }