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In s t it u t e of Ph y s ic s P u bl is h in g AbstractT h e m e a s u re m e n t o f o p tic a l e x tin c tio n is u se d to d e te rm in e th e siz e o f n e a rly sp h e ric a l g o ld n a n o p a rtic le s su s p e n d e d in so lu tio n , p ro d u c e d by a re v e rse m ic e lle s p ro c e s s. T h e c o n tra st b e tw e e n th e m a x im u m a n d th e m in im u m in th e e x tin c tio n sp e c tra a ro u n d 4 5 0 a n d 5 2 0 n m sh o w s a lin e a r d e p e n d e n c e w ith th e m e a n ra d iu s o f th e g o ld p a rtic le s le ss th a n 3 n m ; how ever, th e m e th o d c a n b e u se d to siz e p a rtic le s u p to 7 n m . E x p e rim e n ta l re s u lts for ex tin c tio n sp e c tra c a n b e fitte d b y M ie s th e o ry i f th e o p tic a l co n sta n ts fro m b u lk m a te ria l v alu es a re m o d ifie d b y in tro d u c in g th e lim ita tio n o f th e m e a n fre e p a th d u e to c o llisio n s o f c o n d u c tio n e le c tro n s w ith th e b o u n d a ry o f th e n a n o p a rtic le s.

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Malassezia furfur is lipophilic and lipid-dependent yeast, inhabitant of human skin microbiota associated with several dermal disorders. In recent years, along with the advances in nanotechnology and the incentive to find new antimicrobial drugs, there has been a growing interest in the utilization of nanoparticles for the treatment of skin microbial infections. This work aimed to study the in vitro inhibitory activity of silver nanoparticles (AgNP) against 41 M. furfur clinical isolates, visualize the interaction between AgNP- Malassezia , evaluate the synergism with ketoconazole (KTZ) and to produce an antimicrobial gel of AgNP–KTZ. The synthesized AgNP were randomly distributed around the yeast surface and showed a fungicidal action with low minimal inhibitory concentration values. AgNP showed no antagonistic effect with KTZ. The broad-spectrum antimicrobial property with fungicidal action of AgNP and its accumulation in affected areas with a sustained release profile, added to the great antifungal activity of KTZ against Malassezia infections and other superficial mycoses, allowed us to obtain a gel based on carbopol formulated with AgNP–KTZ with the potential to improve the topical therapy of superficial malasseziosis, reduce the number of applications and, also, prevent the recurrence.

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In this work we present an electrochemical method to successfully prepare silver nanoparticles using only polyethylene glycol as stabilizer and without any other reactive. Here we study the use of the polymeric stabilizer to allow the introduction of a potential tool to reinforce the control of the size and shape of the nanoparticles throughout the synthesis process. The evolution of the reactions was followed by UV-Vis spectroscopy. The electrode processes were characterized by cyclic voltammetric measurements and the final product was studied by Atomic Force Microscopy, Transmission Electron Microscopy, and X-Ray Diffraction. The influences of the current density, polymer length, and concentration media were analyzed.

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